25' Alloy Build

kmorin
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25' Alloy Build

#1

Post by kmorin » Sat Apr 07, 2012 12:57 am

Since welder has so kindly created a "custom build" space here, and I'm not doing production work, I will add another thread here documenting a boat I'm building on a one off basis.

Preface

This thread is to show a boat built of the Miracle Metal by cutting and welding for those who don’t have the time or inclination to build for their own but are interested in reading about how it might be done.

There are several reasons to write a preface to this thread, most of them will likely be forgotten but boat design and building is a series of compromises which have to balance the designer’s skills and knowledge, the builder’s skills and resources with the owner’s goals and financial resources. All of these aspects have to be filtered or limited by the builder’s resources and that is very dependent on geography.

Some builders are near the mills and others are not. Some builders are near large industrial service bases and others are not. Some builders can take advantage of related businesses but in more remote locations that less viable as it's often too costly to use services that may make entire boats easier to build.

Welded aluminum boatbuilding only exists in Alaska because of the (high) cost to bring finished boats to Alaska and the cost of travel and cost of living ‘outside’ (Alaskan term for anyplace other than Alaska) to the owner while their boat is being constructed.

There are fewer skilled metal workers, almost no large forming equipment, virtually no boat building infrastructure as might be found in the Puget Sound region or the Gulf Coast region, and because there are fewer people in the entire state than one voting district in the ‘old country’: a smaller market for these products.

That doesn’t mean we don’t “build a few boats” here and there, it just means that this is not the best place to get the project done as easily as one might in many other locations.

I am not new to designing or building welded boats, but until I began this boat I was not building fulltime having moved to another business venture in 1989 from my full time building period for the previous 12 years. That venture ended in 2010 and I found myself with the time to take on a skiff build; this is a record of that build.

In the ensuing years, I’ve experienced various health related deterioration(s) that make some normal welded boatbuilding work much more difficult than they were just a few decades ago! (image that?) So there will be some work shown here that is lower quality than we might see from younger and more skilled workers in the full time builders’ fine looking skiffs posted her at AAB.com.

There are some elaborate changes in the construction and welding, compared to 'normal builders', that will be discussed as they come along in this building record. If you’re not (at least) 60 years old (?) I expect these differences may appear to be unnecessary or even wasted effort, but those who have more experience may find these fixtures, sequences and methods helpful if they consider a project like this in their future?

The boat in this thread was designed by a sort of unique process.

Cheers,
Kevin Morin
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25' Alloy Build: design concept

#2

Post by kmorin » Sat Apr 07, 2012 1:08 am

Design decisions

I tried to allow the boat owner to make the design decisions on this boat. I know that doesn't sound unreasonable, but it was more work as a design than most I've done in the past. I don’t agree with many of the decisions in this design; but my goal was to be the hands that drew- not the eye that designed.

To explain that more fully, this exercise in design was not to see if I could draw another boat; I knew that I could do that. The goal was to allow the owner’s ideas of shape and form and overall look of the boat to come out so it was not the my ‘lines’ but the owner’s.

This is pretty hard to do since I was doing the drawings. The way it worked was the owner, whom I’d known for many years as a much younger man, would take sketches of the boat back to his 2 week on job on the North Slope and review the lines, images and illustrations.

When he returned I’d try to redraw the boat incorporating his ideas and shapes to work as his ‘draftsman’ instead of his ‘Naval Architect’ so that I worked as the drafter but tried not to be the designer in every aspect. I didn't want to draw another of my ideas for someone to have I wanted to try to help a friend to realize his vision, even if he was not practiced at drawing. That may sound odd, and perhaps it is, but this was my goal as we worked back and forth for nearly a year trying to get 'his' lines and 'his' boat drawn reflecting his own experience and life on the water.

I mention this because later this came back to make my life and work on the boat very hard to build. I should not have tried to so completely listen to my owner and should have insisted on easier to build shapes that would have meant less work for me. In retrospect it would have been 'better' for me to have been more influential in the hull shape- it would have made a lot less work!

They wanted a decent V but not a deep one, so we compromised at 13 degrees in the after 6’ and warped upward to about 50 degrees in the bow. Unfortunately, for my future work on the boat, I also agreed to keep the deck line relatively flat instead of pulling the chine upward at the stem to get the V. I drew the hull with a somewhat ‘flat’ chine while keeping a relatively deep forefoot which required a great amount of twist to the bottom panels.

That would not be all that difficult to build if I had not also agreed to build the bottom of ¼” 5086 H116 alloy. Combining all these related aspects made for significantly more work than a boat bottom this size would regularly require to build.

The boat is was always open sealed deck, weather helm/doghouse for four, outboard powered and 23-25'long and 7' bottom.

so that is what I drew and the Skipper edited or marked up to get the shape and look he wanted.

Image

essentially this is the boat we ended up deciding to build, it is not the exact boat that got built but it is where the original design ended when we started construction.

Cheers.
Kevin Morin
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Re: 25' Alloy Build

#3

Post by goatram » Sat Apr 07, 2012 10:43 am

As always Keven, this story with pictures will keep me coming back to see the next installment. You have a gift that I would like to have. Your writings allow me to easily follow along and understand the points of knowledge you are passing on to me the reader. Thank-you and please carry on with the build. :thumbsup:
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Re: 25' Alloy Build

#4

Post by Chaps » Sat Apr 07, 2012 11:03 am

Nice article you are setting out to post Kevin, thanks!

It will be interesting to see how you accomplish pulling those hull plates together, lots of clamping and cussing I'll bet.
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Re: 25' Alloy Build

#5

Post by S L Dave » Sat Apr 07, 2012 1:51 pm

You know...I normally don't respond to your posts, because your knowledge is generally way over my head and I simply don't have too much to offer. I do want you to know that I really appreciate your posts and I want to thank you for the time it takes to share so much info.

With that said, this boat looks BITCHIN' and look forward to it coming together.
Last edited by S L Dave on Sat Apr 07, 2012 1:56 pm, edited 1 time in total.
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25' Alloy Build:Design Decisions II

#6

Post by kmorin » Sat Apr 07, 2012 1:53 pm

chaps, goatram, sldave, thanks for the encouragement; I suspect that PNW readers/boaters will find the design choices made closer to their own ideas compared to those who live in warmer latitudes where several of the choices has less impact on year round boating?

I usually forget to mention a drawing practice of mine in these types of illustrations that is important in making sense of these posts. I make different pieces into different colors in order to make them more obviously different parts or elements of the drawing. I don't mean to imply a paint scheme, just a method to help the reader to 'see' the information in the image more easily since many of our images are going to be somewhat complex if seen in black and white or 'all gray' as in aluminum construction photographs.

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I guess we'd best go around the design cycle with the Skipper and me once or twice to make sure everyone can see the evolution of the stern? First the owner came to me for a 22-23' boat with a full bracket across the stern. That meant he'd concluded the 22-23' boat was about the ideal size for his use and budget BUT he'd also concluded that a cantilever bracket for the engine(s) [single with kicker or eventually twins or whatever combo] should #1 be a full extension of the planing surface and #2 be full width to give the maximum buoyancy and planing area compared to a 'box extension' type engine mount.

I just drew a 22'er (LOA) with a 30" extension to begin the discussions and then put the 'transom' as a vertical above that engine mount area. In another discussion we added volume to his transom so it became a hollow locker and then finally we would agree how to mount the engine(s) as the design came closer to final.

This meant the bottom itself was 21' and some from the tip of chine, at the bow stem, to the planing transom aft, so I bought longer (>20') sheet when we got the project moving, we were able to add a different stern arrangement later which 'grew' the boat to a longer LOA without changing the BOM.

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Here is a sketch or stern study we did to see if I'd correctly understood the geometry and thinking of the stern that the Skipper wanted. We did edit this area quite a few times, here the interior bulkhead is shown (pale yellow glass) in order to make the view less complex. A locker opening is blocked out in this vertical plane and shows as wide rectangle missing in the (yellow) bulkhead. This was the first look as what we would do with this stern area for stowage and filter housing.

We're also discussing the volume under the engine bracket 'deck' and deck scuppers and so on. All these discussions took a while as our mutual schedules were did not allow us to sit down and hammer these ideas out in a few days' exchange.

This is an example of the ideas I was drawing not originating, they represent the owner's very extensive boating experience and he more than held his own in these discussions about the impact on the final boat.

Image

The house or cabin is another example of our interaction. In most boats this size we'd see more cabin than just a dog house since living or at least camping aboard is an important part of using the boat. This is not true here where the owner has cabin on his own land in the area he mainly travels and only day trips on the salt water so overnight accommodations were not important.

One thing came up pretty quick was the balance of this skiff. I only had to do the numbers once to see I'd have the bow in the air if I had the fuel, batteries, kicker and main all at the stern. So I started talks to get the fuel forward, and all I could come up with was as part of a dodger forward the cabin. Even this was a compromise, since I'd have liked the wt farther forward, and still would. I wanted wing tanks along the gunwale 2/3's forward as I've used them before and even a small volume of fuel is helpful in balancing and outboard skiff- but the skipper did not care for the 'clutter' and wanted some other arrangement. Without going below decks, I had not other volume to use and the eventual tank became much smaller than my original idea.

Since the "Skipper is always Right", after much back and forth I drew a tank cut from the forward curved dodger below the windscreen. More on this later in the build, but it illustrates the kinds of details we were exchanging in order to get 'his' boat- not 'mine'.

Also you may notice the lines of the cabin are not press formed; they're not straight lines? The break at the window band is not a ruled line; it is a curve. The window band top line at the brow is not a straight line either. These are all long slow curves and therefore had to be cut and welded instead of shearing and bending in order to get the look for this skiff.

In these earlier stages the cabin has no bulkhead, the owner figured to use some canvas cover, as both he and his wife were under the impression that a bulkhead was 'not possible' for this size skiff? We later learned that I was not communicating well with them in the area, and we added a bulkhead. The overhang of the cabin top was gusseted by two sweeping 'corbels' or brackets that were eventually dropped in favor of a metal bulkhead.

Image
When we built the cabin, shown here in construction, the aft bulkhead was part of the process and the overhang has no curved gussets as in the design drawing.

You can see the volume for the tank is smaller than the (first) design but in the same relative location. However the brow, lines of the side panels and the overall shaping all remained as the owner wanted it to be shaped. I would say that cabins with this amount of cutting and welding were not really going to show up on production boats (too soon) as there are many hours of time to create welds for these small finely curved seams. I'll have more on that as we go along, here I'm just discussing the implications of a design choice- labor to build these long sweeping curves compared to more straight lines.

[http://www.glen-l.com/phpBB2/viewtopic.php?f=21&t=7763 for anyone who wants to do some small 'fort' or cabin reading I posted this series on Glen-L sometime ago. The discussion goes over designing and building small welded alloy cabins or doghouses for skiffs.]

Next we'll look more at the bottom and that design cycle and what influences contributed to the final build.

Cheers,
Kevin Morin
Last edited by kmorin on Sat Apr 07, 2012 2:02 pm, edited 1 time in total.
Reason: typo's!
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25' Alloy Build: Jigs, fixtures, tools

#7

Post by kmorin » Sat Apr 07, 2012 7:35 pm

Well, I guess I was getting ahead of myself. I said in the preface that I'd make the boat a little different that the 'normal' methods to help compensate for my old carcass. Here I'll make some of those differences known so readers won't think this thread is by a complete fool. (maybe partially a fool but not completely?)

First is my back, which used to work well when I was young and bullet proof. I know that none of you reading this ever worked somewhere and said, "I'll get that," and leaned over to pick up a large weight? I did. I did it more than once. Now, my back likes to have more say in what we pick up, or how or what time of day that activity goes on.

So, I was having an online discussion with a friend in Oregon, and he suggested the Davis Jig during our talks. We were sketching and sending ideas back and forth. The image following shows the rough outline of a garvey type hull mounted to a rotisserie fixture that would allow both our back (we imaged at the time) to build skiffs without suffering so much in the evening.

Although with sufficient fermented hops beverages, it is possible to reduce the aches and pains of the 'welders' back' & neck, it seemed easier to consider a large tool to position the boat for welding.

Image

at the time (nearly 8 years now) we'd discussed powering the Davis Jig with hydraulic motor and chain gear to roll it over so that is shown but was never added to the pair of these jigs I've built.

the idea was mainly to have a fixture that allowed the boat to be rolled, in all positions allowing easier body position for welding, fitting and tool access.

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the first one I built use a 4"x6" box beam (rectangular tube) as the main support and 4" x 4" uprights to slide vertically inside 5" square tube.

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by using a long pivot pipe turning in concentric pipe friction clamps, the end frame could tilt or roll or move around without dropping the load and therefore the precision of the fixture could be low while still remaining fully serviceable for its job.

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bolt on attachment points could be located anywhere on the beam they were needed for different hulls and that would make the Davis Jig useful no matter what boat was being built.

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here is a small scale project mounted to the fixture; a rowing dory in 0.100".

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and here is the 25'er we're documenting in this thread, mounted to a similar jig and inverted.

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here the 25'er is rolled so the port chine is down showing that even an old welder could reach into the bottom and weld.

I guess the last photo does bring up another point, I decided to build this boat from the keel to the deck; then add the topsides. I know this may seem like extra work but by avoiding the topsides on the hull until the entire deck/bottom was framed finished and weld tested I avoiding having to kneel down and weld below my knees which seems to reduce my weld quality too low to be acceptable.

That means the second item on a list of what we did different is the sequence of assembly or the order of the build. We built the cabin off the boat first (not new or different). Then we built the bottom up to the deck, added the deck and all the internal hardware needed, then did a full 2.5psi air test and TIG floated the leaks. (not very commonly done) 200+ feet of seams and a hundred keyholes and I had 8 pressure leaks which would have been 200+ leaks if I'd had to kneel down and weld below my knees while crawling on the deck beams.

So the order of construction combined with the Davis Jig rolling fixture made this boat possible for me to build. I do wish for a young, capable welder but don't know if I could afford to pay what is needed to make that happen?

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I know if a builder had a crew of younger people who were still more flexible and skilled than I, that a rotisserie fixture may not be such a big deal. However, I don't have those conditions and I do have the ones I've mentioned so this 'hollow surfboard' method of construction worked fine for my purposes especially since I could roll the work to position most welds between my waist and my shoulders and almost all in the horizontal or down hand position. (nice work if you can get.)

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overhead welding? what's that?
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I could even roll the chines to angles that made each of the four chines at just the most comfortable weld height to try to give these old shaky hands their best chance to put down some decent, uniform beads.

next difference is in the weld schedule.

cheers,
Kevin Morin
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25' Alloy Build: welding details

#8

Post by kmorin » Sat Apr 07, 2012 8:33 pm

Another detour before we get back on the main road is to review welding aluminum just a little because this is still an area where there is a general lack of knowledge even among alloy boat owners who don't weld.

Aluminum is welded by two main processes TIG- 'tungsten inert gas' (or GTAW Gas;Tungsten Arc Welding) or MIG, metal inert gas or some say mechanized, inert gas or (GMAW Gas;metal arc welding) both use an electric arc to melt the metal and both use some form of added metal or filler that is added to the molten metal before it re-cools or 'freezes'. Both rely on an inert gas to cover the weld zone to prevent the parent metal and the weld from being chemically combined with oxygen.

MIG is mechanized were a wire is fed through a copper tip which has the welding power attached to that tip, so the wire is 'hot' or charged by the welding circuit when the wire gets close to the aluminum it creates and arc. By flooding the area around the 'contact tip' (the wire touches inside becoming in contact therefore 'hot') and the wire with Argon gas, which will not chemically react with the molten metal. The heat of the arc forces the aluminum to melt, and while liquid to accept the wire forming a molten alloy of the original metal and (then) to cool; all without any oxygen to chemically react with the molten aluminum.

What is most important to realize for those not familiar is that the arc is only present when there is wire being fed into the arc cone forming a puddle or bead of weld. You cannot pause for more than a heartbeat without creating welded areas that are not even, uniform and consistent using MIG welding. MIG welding is best suited for long seams and is most often applied in 'stitches' or shorter welds added together, in a very important pattern, to create the longer final continuous seam.

TIG is most often done with a torch in one hand and the filler wire/rod in the other hand.

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here is a welder without any gloves, without a welding hood and no arc, this is just an image of the TIG welder in welding position. One hand holds the torch the other hand holds the filler rod. I hope this image helps you to envision the process of 'normal' or traditional TIG welding?

Yes, this is one of the most skilled welding methods around, maybe I should say that it takes the most skill to weld this way compared to almost all other welding methods; I think you can see why.

A TIG torch is a gas covered tunsten electrode that will conduct the arc but not melt or be sprayed off into the arc into the weld zone/puddle. The torch is often lined with a water jacket to all it to be small an compact and still conduct 300 -400 amps or AC current onto the tungsten electrode in order to create and 'electric flame' that is used to focus on a point in the parent or original metal where you want to 'weld'.

Also since the 'off hand' is feeding wire by finger or hand movements into the weld puddle, the speed of travel of this weld is much slower than electric feed motor powered MIG guns that run all day and all night and 'all you do' is to point and shoot. (I'm being comparative not literal in that description, MIG still requires good skill and practice)

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what else is going on here? The rod has to be kept steady as does the torch hand and the point the rod is fed into the molten aluminum weld puddle is critical to getting a decent weld. Lots to do with your hands doing separate functions and so the result is that good TIG is an art, where the word art is being used to describe something one person seems to do much better than another. It not the same as driving between the lines with a car, and should be appreciated for the skill involved.

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here is an illustration I did to explain the sight picture one should try to imagine for newer TIG welders. The rod's position at 6:30 to 7:00 of the lead edge of the puddle and the tungsten being swung back and forth to create a uniform melted area are happening at the same time.

So... TIG has an fixed electrode that can keep the arc without filler (very good) and MIG has to have the filler /wire flowing to have an arc (good but not at handy at TIG) therefore MIG has to started and moved along pretty fast, while TIG allows you to add filler or not, and still keep the puddle molten without building up weld filler metal. But TIG, being slower, usually causes more heat contraction distortion, however, MIG, being faster, has less depth of penetration and shallower fusion of the two parts being welded.

Why do I review all this? One reason is that I TIG welded almost the entire boat in this build; but not with a hand torch.

I have mentioned before that I use a TIG GUN. I have a wire fed (mechanized feed) TIG torch that allows me to have both the speed of MIG and the bead quality of TIG.

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these are the cabin side welds done with a TIG gun allowing a high speed of travel and realtively low distortion while maintaining a proportional bead with good enough finish appearance to leave without any further surface treatment.

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The last main difference is that the amount of TIG work was not significantly different than welding this boat with MIG since I am using a motorized TIG torch that allows high speed travel and therefore the use of TIG beads not readily known to other aluminum welders who cannot explore those welds because their travel speed is too slow to allow the higher speed bead's advantages.

The main differences here are that I could roll the boat to get decent weld position for both MIG and TIG and that I could use TIG for welds that would not be cost effective without mechanized feed TIG and that I made the boat keel to deck first, then added the topsides & transom making all the work of getting in and out unnecessary.

Hope this makes sense? If not; please let me know so I can clear up what confusion I've caused as we move along.

Cheers,
Kevin Morin
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Re: 25' Alloy Build

#9

Post by edwardn » Tue Apr 17, 2012 12:10 pm

Hi Kevin

Thanks for posting your build and explaining the processes, I have a question regarding your tig gun, from the gun do you have a control box for it and what kind of power source do or can you connect the controller to? Does it matter if it is 1 or 3 phase power supply.

Thanks
EDD

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25' Alloy Build:Tig Gun Power

#10

Post by kmorin » Tue Apr 17, 2012 12:34 pm

EDD, the OTC Tig Gun has a controller, essentially a set of transformers that control the DC for the wire speed control, the on/off contactor for the power supply - and I've added the remote control for the amperage from the TIG power supply to the handle of the torch so I have on/off (trigger) then a pot to roll up for wire speed and one to roll for amperage.

This arrangement frees me from a foot pedal welding power control that is not really agile enough for boat building applications- typically.

I power my TIG gun from a Miller Dynasty 300 DX that provides up to 300 A of welding power and I'm connected to single phase 220VAC in this location. I have run this power supply on 3Phase before but its fine with single phase power. I had run the TIG gun on a Lincoln 300/300 TIG power supply for 20 years and things were fine, but this newer power supply has many arc control features that allow weld control not possible with a transformer power supply.

The OTC controller has several functions I don't use, one is a crater fill feature, I do that with the control knobs on the handle. I mainly use the controller to power the DC motor and interposing relay for the contactor in the Dynasty.

Cheers,
Kevin Morin
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25' Alloy Build:Tig Gun Power

#11

Post by kmorin » Tue Apr 17, 2012 12:34 pm

EDD, the OTC Tig Gun has a controller, essentially a set of transformers that control the DC for the wire speed control, the on/off contactor for the power supply - and I've added the remote control for the amperage from the TIG power supply to the handle of the torch so I have on/off (trigger) then a pot to roll up for wire speed and one to roll for amperage.

This arrangement frees me from a foot pedal welding power control that is not really agile enough for boat building applications- typically.

I power my TIG gun from a Miller Dynasty 300 DX that provides up to 300 A of welding power and I'm connected to single phase 220VAC in this location. I have run this power supply on 3Phase before but its fine with single phase power. I had run the TIG gun on a Lincoln 300/300 TIG power supply for 20 years and things were fine, but this newer power supply has many arc control features that allow weld control not possible with a transformer power supply.

The OTC controller has several functions I don't use, one is a crater fill feature, I do that with the control knobs on the handle. I mainly use the controller to power the DC motor and interposing relay for the contactor in the Dynasty.

Cheers,
Kevin Morin
kmorin

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Re: 25' Alloy Build

#12

Post by edwardn » Thu Apr 19, 2012 10:28 pm

Thanks Kevin

I found a OTC tig gun and controller on-line the other day and ended up buying it so unless I was scammed it will be delivered in a week or so. I am still along ways off from starting a build and need a unit to power the tig but slowly I am gathering what I think I'll need for when the time comes but once I get this gun operational i'd like to see how you bypassed the foot control etal. Getting back to your build, is it possible for you to go into more detail about the hulls interior framing and the steps you took to put it all together.

Regards
EDD

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ARGHHHH!!!! I missed a TIG Gun!!!

#13

Post by kmorin » Thu Apr 19, 2012 10:52 pm

EDD, I have been looking for another TIG gun for months and haven't found (another) one!!!! :banghead:

Please write with any questions and I will try to create an explanation for every single detail of the gun; if you did find one (?) and please see if they have another one?

I will continue with the build sequence post, and try to give building detail photo post(s) as we go along.

Cheers,
Kevin Morin
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25' Alloy Build; bottom- layout and cutting

#14

Post by kmorin » Thu Apr 19, 2012 11:17 pm

EDD, I used Defltship Pro to create the model and do the developed plate shapes, but I used to do these takeoff from plate models that Randy/netman will be doing on the adjacent thread where he's getting ready to build a net skiff.

The outlines of the panel shapes, keel and various other hull shapes were printed to CAD files from Delfship Pro and then measured in the flat form to create X,Y coordinates along the curves using the factory/mill cut sheet as the base line for the grid.

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the grid lines are laid out and the X points are where the batten is being held with vise grips and clamps to the sheet. The beauty of this method is there is no unfairness as the batten corrects even the tiniest error in PC 'fairing routines' or in measurements or CAD unit rounding errors if you forget to set the value to 1/64" or a tiny fraction of a mm when you do the curve layout and offset table.

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the battens' have to be selected so the cross section will allow the bend but not deform the angle and small 'trip blocks' are added to the sheet being battened to keep the angle from rolling when the curves get tighter.

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once the curve is sighted and all the points are 'averaged' so the curve and the batten are 'fair' to the eye then the line is marked with a black felt tip pen and then a tungsten scribe to make a very shiny and narrow cut line in the black background. Then the line is cut with either a 'skill saw' or a jig saw depending on the radius of the curves and the sizes of the blades in the tools.

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and this jig saw cut the two bottom panels, net 1/2", without pause or effort; I use Pam or generic frying pan spray as blade lube and it has worked fine for a long time.

Note: the (Computer Numerical Control) cut files for a single one off boat are a non-trivial effort. If the design will be built more than once, or will be large enough to justify effort for NC cutting, the I'd have done this work in that manner. In AK there is no full service (marine) NC cutting that is really reliable and the cost to have this done elsewhere is high compared to the 16 hours of shop labor to layout, cut and prepare these pieces for tack up. [Most cut files are justified by repetitive builds or larger hulls.]

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the two bottom panels ready to be tacked to the vertical keel- note the very tight forefoot which will haunt me for weeks!

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and the easy part, tacking the bottom panels to the keel on the Davis Jig with some formers to give the bottom deadrise and forward some temporary wood formers to hold the bottom while its being prepared to tack.

This skiff only has 13 degrees at the transom, and the keel is straight for the last 2/3's the hull so this stage of tackup is just a matter of aligning the inner edges of the bottom and the outer edges of the keel.

Cheers,
Kevin Morin
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25' Alloy Build; bottom tack up and framing

#15

Post by kmorin » Thu Apr 19, 2012 11:30 pm

EDD, I was going to explain why the bottom is shaped like it is, but that can wait, I'll post a few more shots of the build and get to the shape ideas as we go along.

I want to make a note about the keel seam, for those who are considering becoming aluminum boat builders, because this joint is critical but lots of times you won't hear about details that make the welding easier and higher quality.

If two 1/4" sheets are angled to 13 degrees above horizontal and only separated by a 0.160" (5/32") keel bar they form a weld groove that is 'too tight' to produced good fusion. Therefore, we beveled the keel seam of the bottom panels for their after 16 feet as the weld seam will become more and more open as the V increases forward.

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just used a bevel bit of about 15 degrees in a standard plunge router to make the cut.
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result is a long smooth bevel that is uniform and cut with carbide leaving a fine welding surface without more than acetone cleaning to degrease the cut zone, and of course the SS hand brush immediately before the welds were put on.
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so this cut allowed the keel seam to groove to be wider at the bottom side so the arc didn't 'jump' to the sides of a too deep weld and make the weld cold lap instead of root penetrate into the inside back weld.

Just cutting the shoulder off the weld groove side allows that arc to 'ground' to the bottom of the weld zone or the keel bar's lower edge and avoid the wander to the two sides. That detail provides for easier access to the root of the keel weld than if the sheets' edges were left in tact.

Cheers,
Kevin Morin
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25' Alloy Build; bottom tack up and framing

#16

Post by kmorin » Thu Apr 19, 2012 11:51 pm

EDD,
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the keel is going to be flexible in this design, for a while. So we have a set of temporary flat bars on one side to keep it fair until we get to the stage where we can add the permanent stiffener to hold the deck frames.

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starting with a few nylon straps to pull up the bottom sides we're tacking the last of the straight part of the keel to bottom seam. temporary blocks are to keep the nylon sliding side to side at the keel- but we'll need alot more pull and fairing to keep pulling these two 1/4" 5086 H-116 panels to their final shape.

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so lets add some more pull and keep inching along the keel seam pulling the two bottom pieces toward the keel and where one side is 'above or below' the other side we'd tap down along the keel and pull up at the chine with more tension at the nylon straps. The tension is added in 'passes' or 'lifts' where you tighten a few 'clicks' on one then the next and so on... moving forward.

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eventually we had to put a bunch of these on the boat to keep the bottom pulling together- the vise grips keep the strap ends from sliding forward and loosing tension at the (inner) chine edges.

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eventually we turned the bottom over, using the Davis Jig, and worked down hand working the seam along the keel bar.

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the tension on the tacks at this point was pretty impressive so I began to put a TIG root pass into the keel as we progressed up the forefoot (quick reminder that "up" [the keel's forefoot] is down in this photo!)

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At this distance forward the V of the bottom panels and the keel seam is wide enough to allow good weld fusion inside the keel and this area was 'triple TIG welded' because a single passe would be to 'hot' to fill the entire seam and with the TIG gun this work is about as fast as MIG.

Cheers,
Kevin Morin
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25' Alloy Build; bottom tack up and framing

#17

Post by kmorin » Fri Apr 20, 2012 12:09 am

EDD, that d*mned 1/4" bottom was a bear to pull in, as anyone who's done this could have predicted and I should have too! But the Skipper is always right (sort of corollary of the "Customer is Always Right" for boat builders) so 1/4" it is.

I will point out that those with a fine eye will not the chine is all but 'flat' in profile, therefore the bottom's shape is much (much) harder to form since most hulls chines rise and therefore the V is raised upward at this point instead of being 'kept down' as I drew this hull.

I would advise against this since it was a lot of work. But what do I have to do but pull on the bottom some more?

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finally to close the keel gap of the bottom we had to pull the sides' inner edges together with clamps on temporary tacked on angles that allowed the furniture clamps to pull together while the chines were pulled in at the same time.

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closer and closer.... until the entire forefoot is closed and the boat rolled back to add the chine flat

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at this point I've found most of my sailor like language and the blue streak was wafting out the vent fan. But by pulling and pounding and finally tacking some 'closures' (like butterfly bandages) we did get the keel seam to conform to my drawings.

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next we need a chine flat or two to make the bottom shape complete.

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the reverse chine or chine flat helps in several aspects of this type of hull and is somewhat standard in many builder's work. I've used them on most planing hulls of this class for lots of reasons and they were laid out and cut from the Delftship output and shown above in the cutting sequence.

Cheers,
Kevin Morin
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25' Alloy Build; bottom tack up and framing

#18

Post by kmorin » Fri Apr 20, 2012 12:26 am

EDD, I discussed above the idea that the boat would not have full ht sides.
I've crawled over more than my share of skiffs and after climbing in, then I've knelt down to work either at or below my knees and I have also confessed that those days are gone- passed tense- ain't happen' now.

So the boat will not have full height sides until I get done with the bottom as a hollow surf board. So the the chine flats will need short or 'lower topsides'.

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once the chines are on the lower topsides were added to both sides.

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they're put on by just tacking at the bow and working the seam to a knife edge as we move aft. The guy here is mostly responsible for building the whole boat- all I've done is bellyache and sit on my kiester until he had another fit ready to tack :thumbsup:

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Eventually the lower topsides are added to the outer chine flat edge and tacked ready for some preliminary welds.

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the after end of the lower topside is being lifted and lowered and clamped and pushed and pulled to get the inner, lower edge of the piece to the outer upper edge of the chine flat so there is a knife edge intersection and then that fit is tacked about 3" to 4" OC.

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Eventually it all comes together and fits into a shape that may float?

Cheers,
Kevin Morin
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Re: 25' Alloy Build

#19

Post by goatram » Fri Apr 20, 2012 12:35 am

Kevin Thanks again for your insight it will help in the near future. Definitively the harder way of building the boat having to do your own layout and cutting.

The Pam Spray works to Lube the blade of the jigsaw? Good to know that. What to you spray the Blade or the plate to be cut?

The Tig Gun is a uncommon item? Will a Miller 200 weld with it or do I need to step up to a Miller Syncrowave 300 as well? I am planning on a 350 pulsed Mig machine to do the welding with the Push Pull add on device. Name of the add on escape me now.

Lastly your rotisserie looks cool with multable uses

Please continue
John Risser aka goatram
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2015 Ford F350 Dually
Master of R&D aka Ripoff and Duplicate

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25' Alloy Build: tools and methods

#20

Post by kmorin » Fri Apr 20, 2012 12:53 am

John,
I use the 1.90$ (US)/can generic food spray from the local pallet stacked warehouse food supply, and it works good because it will keep the build up off the saw blade which is where I spray it. Then, if the acetone misses some when you clean up, it vaporizes at a lower temperature than any petroleum product so the weld zone is not 'totally' contaminated by the lube.

I use it on all the sanding discs but not on grinding discs, I use it on the three or four band saws, skill saw, the jig saw and the various carbide cutter bits and always on the router bits. But, that is the one place I generally spray the metal that is when I'm using a router bit to form and edge; not always and I still spray the bit too.

Yes the TIG Gun by OTC (Osaka Transformer Co. or Daihen America) is no longer made, and it hard to find, I'd buy another if the opportunity arose. What are you going to weld? The little 200 is not really a 'boat building' power supply but if you're doing small scale modifications in thinner material it will work. Aluminum needs lost of heat so if your work will be 0.187"/3/16" or larger then the 200 will be working hard. I use the 300 amp power supply and need the power regularly.

350 Amp pulsed MIG is good for building even larger vessels and the Miller push pull or the Lincoln are just copies of the MK Products guns which are better than either Miller or Lincoln's native push pull systems.

The Davis Jig makes welded aluminum boatbuilding 'still' possible for me. Today I did some welds that were 'out of position' and just rolled the entire hull to get those welds at my shirt pockets and put down decent beads where I'd have been stumped without the jig.

Image

Cheers,
Kevin Morin
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25' Alloy Build; bottom framing

#21

Post by kmorin » Fri Apr 20, 2012 1:32 am

John, EDD, we'll need some framing to keep the shape but the lower topsides and chine flats to create some shape rigidity that allows the interior framing something to weld too.

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first some prelimiary beads along the long seams and to do that, turn her keel up and weld down hand! not overhead or crawling around on a creeper on the floor- enough of that.

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the outside fillet of the outer chine is at one heat setting and the inner chine another. Both seams are being stitched to avoid more than 'normal' sheet contraction.

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reaching into the keel from either side is realistic for even a 'fatboy' like me, as long as I can use the Davis Jig to make the work position welds that I can reach flat footed on the shop floor.

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to clear the chine at the floor the end uprights needed to be lifted and lowered prior to some of the rolls that is why they are drilled on 6" centers to five pivot points of different offset from the center pivot.

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when back upright the skiff hull is too high because of the clearance of the chine to floor but then we just lowered the end uprights to get back to working height.

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we fit a bulkhead at about 1/4 the waterline to allow for two different sets of framing. The bow is conic (developed surface) so there are straight line radians to be had - these bars are all either sheet edge off cuts or flat bars and they all lay to the cone's surface so there is no fitting/cutting/layout or any work to install them but to dress the ends slightly to the keel plate and the bulkhead.

lots of designers will frame this section with cut longitudinals that are either diagonals or butt lines or waterlines. I find that is great but more work than small skiffs need and since I wasn't using NC cut parts the flat edges worked easier and I think will prove more than strong enough. The inner most frame is only 1/4"x 4" in a 28" run (!) and the next 9" outboard is 6" deep in a 4"' run- the outer most frame element, just inside the chine is 9"deep in a 6' run.

yes (!) there is a 1/4" thick "breast hook" (dead plant boat building term) that creates a horizontal 'gusset' at the inner chine and covers the forward end of the longest bow conic surface frame element.

Image

Getting a little closer to the bow framing, the span of each radian of the conic surface is normal or 90 to the bottom so with the short spans and the relatively deep 1/4" framing elements this type of framing is pretty fast for the result. The jig allowed me to weld these horizontally, including the stitches not shown that are under the 'lean' of the bars.

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looking aft at the bow framing as they fit to the bulkhead, and all ends are fully welded both sides but the inboard sides are not visible here. We are beginning to install the first (inner most) longitudinal which is a 1/4" x 4" flat bar transom to bulkhead.

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A permanent 3" x 2" x 1/4 angle has been fit to the top of the keel as the main edge stiffener that both fairs the keel bar, keeping it in vertical plane and seats the deck cross beams that will come later.

next post we'll need another view or two of the after long's to clarify their installation.

Cheers,
Kevin Morin
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Re: 25' Alloy Build

#22

Post by Chaps » Fri Apr 20, 2012 9:23 am

Chaps wrote:Nice article you are setting out to post Kevin, thanks!

It will be interesting to see how you accomplish pulling those hull plates together, lots of clamping and cussing I'll bet.
as I predicted!

It's all downhill from here, great post! :beer:


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25' Alloy Build: pulling in the bottom

#23

Post by kmorin » Fri Apr 20, 2012 10:56 am

Chaps, you're right, it was a bear and the rest has been pretty simple; by comparison. The topsides panel cuts were quite full in the forward five feet and since I don't/didn't use frames they went on without the full amount of final cone. Therefore putting the guard deck on was pretty Olympic too.

But nothing was as much effort for as small an area of the build as that forefoot! good call, and one that most sane skiff builders would have avoided; guess that says things about me? (The Jettywolf will please refrain from agreeing too loudly.)

Cheers,
Kevin Morin
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Re: 25' Alloy Build

#24

Post by edwardn » Fri Apr 20, 2012 1:46 pm

Hi Kevin

Again great posts and explanations, a question for when you weld the lower topsides to the chine how do know or control the angle they come off at so when the time comes to weld deck plate on the width matches up , do you measure from the center keel line out to the lower topside pieces or is it the shape of the lower topside peice that gives it a natural angle or flair off the chine?

Regards
EDD

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25' Alloy Build: two topsides, lower and upper

#25

Post by kmorin » Fri Apr 20, 2012 8:09 pm

EDD, yes the two topsides plates, one a strip about 25' long the other the full 'sides' of the boat were both shaped by the output of the D'shipPro application to create the developed surfaces.

When the lower topsides strip was tacked edge to edge to the outer edge of the chine flat the two shapes formed the correct lean at any given point and when the deck was joined then topped by the full topside that shape was as drawn in the software.

Cheers,
Kevin Morin
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