Double Eagle Build

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Northeaster
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Re: Double Eagle Build

#51

Post by Northeaster » Sun Nov 23, 2014 9:02 am

Great description and illustration Kevin - clear enough to sink in for sure.

What would you say would be the minimum or decent choice for a take off strip be, as I will need it about 27' long? i.e. would a 4" wide flatbar be sufficient? Or a 6" flatbar?
I know I can only get flatbar in 20 ' lengths, but I could weld another 7 or 8 feet on the end of a 20 ft section. I could run some angle way past the joint, clamped on each side and then tack up and weld, to minimize heat distortion. Even if it were out a bit, I assume that the take off's would still be accurate, may just be skewed to one side a bit....

Widest I have now is 2" flatbar, so I can pick up what you think will work, especially if it could be useful later.

kmorin
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Re: Double Eagle Build

#52

Post by kmorin » Sun Nov 23, 2014 12:06 pm

northeaster, I'd say in a 25' hull that 6" takeoff strip would be wide enough, in scale in the illustrations I think its about a foot or so? About welding bars together, the method only requires a rigid pattern piece that cannot distort in the width direction so the lines of the frame edges and the distances of along the frames' edges to the seam points are the same on the frame and the sheet stock.

That means that if you welded the two 1/8" or 3/6" x 6" flat bars at a 10 deg angle to one another at the butt joint the method still works well, it simply requires rigidity in the narrow direction (well both X & Y but not Z where the flexibility is key). You could easily weld three pieces together as long as they were flat in one plane so they fairly represent the plane of the sheet material. If the material is rigid in both directions, then the information will not be skewed but will be accurate in taking off and laying down. This method works fine with big long arc of material, or a series of segments welded into a take off strip, the only rules are rigidity and the plane of the take off strip material laying too the framing edges of each panel- thus representing the final plate hull material faithfully.

The weld joints should be flat so some care is required in that butt joint, fit and finish. I'd sand the welds to the surface of the material and use a deadblow hammer to remove any angle point at the bars' weld. Two sided, double beveled weld being the most likely candidate for this joint.

Cheers,
Kevin Morin
Kenai, AK
kmorin

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Re: Double Eagle Build

#53

Post by Northeaster » Sun Nov 30, 2014 3:43 pm

Not at full strength yet, after an arm injury,but I did manage to get most parts of the "rotisserie" jig ends built, modeled after Kevin's "Davis" jig.
My jig already had two main beams which the frames are attached to, as opposed to one on Kevin's model. So, I have a short beam at each end joining the long ones ,with a single point coming off each of those, down and around to clear the transom and bow, then a longer piece up to and past the center of gravity point. All of this is 4" x4" box steel x 1/4" wall thickness. Then built two rolling tripods, like Kevin's, to hold the weight at each end.
Hope to finish welding and be able to flip/ rotate the boat (only frames and longitudinal stringers at this point).
Then, back to work on the boat itself.

Northeaster
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Re: Double Eagle Build

#54

Post by Northeaster » Sun Dec 07, 2014 5:52 pm

More progress on the jig / rotisserie today. All finished welding but ran out of time before being able to jack up each end to find balance point and try flipping boat on side, or over. Likely not up to shop again for a couple of weeks, but should be able to resume building at that time.

Northeaster
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Re: Double Eagle Build

#55

Post by Northeaster » Sun Dec 14, 2014 5:49 pm

2nd time typing this, so likley be brief...

Hi Kevin,

I worked for a few hours today on correcting my longs, and right or wrong, I am going with 1 1/2" x 3/16" angle near the bow, and keeping the 1 1/2" x 3/16" flatbar near the stern. I am welding the flatbar to the backside of the angle, overlapping 18", with all sides bevelled with the router, then welds ground flat, as not to interfere.
The transition / weld point will be a couple of frames from where they start to bend more, to reduce stress.

Near the stern, to midships, flatbar will remain in the slots I have cut, which are in the right spots...
Near the bow, to midships, as I had numerous extra slots cut (in wrongs spots) from my initial attempts at running the longs, and where I am using angle near the bow, it will sit in long 1 1/2" swaths I cut in the outer edgle of frames, leaving about 4" of full width at the keel, chine, and sheer.
I welded and temporarily placed two of these new combination flatbar / angle longs and I feel they sit well and now are much more aligned with the lines of the boat.

One big questions though- I believe that I am NOT to weld or even tack weld the longs to the frames, until the sheet is on and welded, and even after the longs are welded to the sheet.....When I was only using flatbar longs in narrow slots, I had used wire to hold the longs in the slots at each station (and had planned to cut and pull the wire out when ready to weld), therefore not requiring tacks to hold the longs in place. This will still work aft, where i am still using the flatbar longs in slots. But, toward the bow, once I transition to angle longs, they just sit on the frame (to be welded later) and I cannot, or course, leave clamps holding them to the frames, when i need to place and weld the hull sheets. Is there a "normal" or accepted way of holding the longs to the frames, without tacking??
If there is not, I am thinking about drilling a small hole at each frame/ station and using some type of hook bolt to hook under the inner edge of frame, and pass through the hole on the flat side of the angle, to put a nut on and tighten down.....

I posted a pic earlier of another builder's boat, where the longs are run in long swaths cut out (per the other model Glen-L plans) but I am not sure what the reccommended way to hold the longs in place is... I belive that builder, rightly or wrongly, did weld the longs to the frames before plating, but againm not sure what other method(s) are recommended...
Darrell

kmorin
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Re: Double Eagle Build: Hull Longs sequence

#56

Post by kmorin » Sun Dec 14, 2014 8:02 pm

North, the problem that you want to avoid is heat relieving the evenly applied cold stresses of the extrusions allowing them to bend where they're softer. The stress of the extrusions in their cold state is what gives the uniform cross section material (all battens) their uniform bend the sweet shape of boats. So while there is little stress aft, the transition from bar to angle is not probably going to show a hard spot in the curvature of the final hull plating. But.. if those shape transitions, heated joints and double stiff overlapped material shapes were part of the bow's bends... I think it would be very hard to have fair curves.

As to holding the longs in their relative locations while plating the hull, I don't see that small not 2" long!-- "single dime" spot tacks will kink or overhead the extrusions? If I understand, without pictures.... :deadhorse: (!!) the gaps you've cut in the forward frames' outer edges are not well placed? Therefore the angle will be able to slide away from or toward the keel in a wider than 1-1/2" slot? That can be a problem as the angle can roll to relieve pressure when you begin to sheet the hull. At least that's what I see in my mind's eye.

I think that hull longs that ARE NOT on the buttlines (I take it yours are not?) or on the diagonals (I take it yours are not?) then I lay out these notches by laying the angles over the frames (if the frames flex fore and aft due to the pressure of these angles in the 'test' position this method will not work...) to find the correct locations along the frame edges. Then I cut notches; if your notches are combined with the flat bar notches to make 'too big' holes then I'd make a set of small frame material blocks to overlap the frame and fill in the hole so the angle extrusion will lay too the surface of the frames. These frame patches will stay in place with a few spot tacks. I'd buff them and the entire frame area like they were going to be welded solid but they can come out if they're not needed.

I think we've already reviewed the frame and long check concept? These (approx) 2" x 4" x 3/16" blocks can be used to lap the frames, covering the over-sized notches to close up the notch so the angle is held with the horizontal leg flat to the back of the notch. In some cases, and without pictures I'm blind here, you may have to put a temporary 'backer' lapping the frame to keep the notch depth max of the shape of the angle. One set of patches may have to close the sides of the notches, and a 2nd set may have to be located inside the flat leg of the angle extrusion longitudinal.

As to welding the longs, do not weld until the boat is tacked up. The reason is your framing/lofting/notching may be in question and if its welded before plating any corrections are much more work. The tacks do have to hold their wt as the plate/plank is done but in your case welding the longs will kink then as they stress relieve.

in the picture posted of the boat with the longs welded prematurely, there are major kinks, hoggs, hard spots, non-continuous curves due to out of sequence welding. That would be hard to keep the hull fair with those kinked longs. I'd prefer to see the entire boat tacked up before more than frame assembly welds were done. Well there may be some places on the keel that need joining too, if that is not one large solid piece, but leaving the entire hull and sheer clamp tacked fair before welding allows the builder to go back to any area that needs 'nudging' and push or pull to fair out the overall shapes before beginning the final welds.

cheers,
Kevin Morin
Kenai, AK
kmorin

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Re: Double Eagle Build

#57

Post by Northeaster » Fri Dec 26, 2014 12:29 pm

Kevin - I did post these pics on boatdesign.net as well, as I had originally asked for help there, and wanted to updats folks and ask for more feedback, from all of those who were helpful earlier, including yourself of course!

Hoping to get some feedback after my attempt at correcting my improper running of longitudinal stringers, especially nearing the bow.
For right or wrong, as I had numerous extra slots cut in my forward 4 frames, I decided to use 1 1/2" x 3/16"angle forward of midships and keep the flatbar in slots, aft of midships, as I believe it is Ok there.
I beveled backsides of flatbar and angle and welded them back to back, overlapping about 18", which falls around midships, where there is little curvature.
I cut 1 1/2" swaths for the angle to sit in and I am able to adjust the position of the stringers somewhat - but I am hoping the the experienced folks here will think that they look better than before..... Foward, they definitely don't sweep in nearly as much toward the stem / keel but rather ( I believe) follow more the lines of the chine and sheer.

I have only done one side, so I am hoping for input, so here's a bunch of pics.
I did not "correct" the wavy flatbar stringer nearest the keel/ stem yet!!!
The chine flatbar is only temporary - just to see how the stringers look with the chine there as well.
DSCN2033.JPG
Attachments
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kmorin
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Re: Double Eagle Build

#58

Post by kmorin » Fri Dec 26, 2014 12:52 pm

North, the test for framing to be fair and ready for sheeting, as noted above, is to lay a piece of plate diagonally over the frames and longs, and see? Does the 6" or 12' wide piece of hull plate lay to the framing?

I do see the method used to allow the forward longs to move and lay fair. I think your idea of drilling two small holes and wiring the angle/longs to the frames until the hull plate is on will work fine. This could be tacks on the back/upper flat of the long to as long as they were single to double dimes and did not relieve the tension and bend the long/angle. To be sure and safe the cold wire method will give plenty of room to correct and still hold the longs out of the way of plating/tacking hull bottom panel onto the frame.

one other method is with short sticks of metal along side the vertical or hull leg of the longs, laying from the long to the frame surface, these would keep the angles/longs from rolling where the wire may not? Once the plate is on, rolling in this sort of wide space may be a factor in getting a good tack to the hull, even when tacked the longs may tend to roll, so having these sticks along side the vertical/hull leg may help keep them more 'normal' to the hull?

Then once the fair outline panel is on, you can release the longs and allow them to lay to the inside of the hull bottom panel's surfaces and tack, that may involve moving then inboard if they're too proud/above of the surface, and outboard if they're too shallow/shy of the surface.

I see the wide are of the frame edge you've removed to allow the longs room to be places in a wider area without being kinked or unfair. Your previous remarks make a clear picture of the term 'slot' where I'd been mistakenly thinking of a 2" to 2-1/2" wide rectangle not a entire frame edge opening the depth of the longs. My only remark about this is that the back or inner edge of the frame's reduction; would have to be a curve following the original frame's outer edge curve.

So this slot can't be cut along a line but along the outer curve off set evenly the depth of the angle/longs.

Thanks for pictures, they're very informative.

Hope I've answered what is being asked?

cheers,
Kevin Morin
Kenai, AK
kmorin

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Re: Double Eagle Build

#59

Post by Northeaster » Fri Dec 26, 2014 3:02 pm

Hi Kevin - thanks for the quick reply! I will re-read and digest a bit further later- just have a few minutes right now.
Just wanted to answer your concern re: how I cut out the large "swaths" - you are correct, I did not follow a straight line. I set a block up to have a leg with a depth of just over 1 1/2" and simply ran this along the outer edge of the frame, with a marker at the bottom of the leg. So this gace me a true removal of 1 1/2" of material from the outer edge, as I went along with the jig saw.

I experiimented with hook bolts and you can likely see some in the stringers nearest the floor. Just got back from removing more clamps, and drilling one hole per attachment point, and using hook bolts. I quickly used a piece of 1/8" plywood, 4' x 4' and it appeared to lay very well to both the longs and the frames.
Darrell

kmorin
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Re: Double Eagle Build

#60

Post by kmorin » Sat Dec 27, 2014 9:09 pm

North, some notes to help your overall understanding of others' remarks in context.

IF you cut aluminum with a jig saw you naturally leave a jagged edge with saw marks, so do you with chainsaws, table saws... and so on. BUT in aluminum that jagged edge CAN/may/might/could form small corrosion lines in the cut irregularities of the reciprocating saw. These small corrosion sites may, then, eat into the edge of the aluminum so... a frame that was not cleaned using a carbide cutting at high (>15k rpm) speeds and 'dressed to a mirror edge' could form future deterioration that may weaken that cut line's adjoining structural element. If, however, you dress these regions of the reciprocating saw cut remnants with a high speed carbide bit; it will result in a fine surface that is relatively immune to the corrosion that is often supported/created/allowed by overlapping jig saw strokes and their resulting 'dross' or scrap leftover cut material that still adheres to the cut area's edges.

I hope this helps you understand why a pro, might find fault, legitimately with irregular reciprocating saw cuts that are not router speed cuts resulting in very fine shiny and smooth refined edges of frames, shapes and parts for aluminum boats?

Next, if a naval architect were asked for the level of tolerance of their design they would reply with a figure of three of sometime four decimals. Glen-L designs have been over engineered to a one or two decimals. So that implies a small boat with a 3/16" or 1/4" hull plate is not in the same engineering ratio as a 40' boat with the same hull plate thickness! Let's look at that for a few lines?

if a boat that weighs 5,000 with an engine and fuel has a 0.187" hull panel there's a few ratios you could assume by dividing one way or the other. But what if that same plate is used on a boat that has a 50,000 lb, displacement? Well then the level of engineering becomes somewhat more exact doesn't it? I mean the factor of safety for the second boat is not even in the same world as the factor of safety for the first skiff- is it?

So when you have remarks about safety and hull strength one factor that you as a new builder may not be fully aware of is; there is no linear proportionality in this scantling discussion, A'Hoc knows this, but is not going to spend the dozen of hours of typing to explain it. I'm taking a few minutes to make it clear to you that when either Glen Witt or Ken Hakenson (sp? I never get Ken's name right) drew the Double Eagle, they used bullet proof plating to make sure the home builder would be pretty safe!

Last but not least another point not made but I will; ANY TIME two aluminum surfaces, or for that matter many other materials, are held close (touching) aluminum and this interface area can become wet.... bad things can come from this.

Please take the time to use the Search Function here and research the many posts we have here regarding crevice corrosion, poultice corrosion, and see if you can become familiar with why someone would argue against mating un-sealed surfaces of aluminum together. Essentially this creates a thin film of water; thin films of water against alum ALL become acidic; acid corrodes alum; even dew and humidity can keep this 'cell' going and propagating and so... A'Hoc was just slapping his fore head when you told him you'd lapped longs in the bilge... but he didn't take time to say why.

Hope this helps a little with some 'salt for others' remarks' in regards your quest to do the best job you can in your build.

To the FORUM: North has posted on more generic marine forms about his build and I'm answering those reply posts, really giving context because the remarks are legitimate but the perspective is missing for North as he's not an experienced builder and may have some concern because he's not as fully informed why a naval architect would say some things. This post was to give North, a member here, context for the remarks he received, which may be distressing if they were not taken in that context. What North was told was spot on! but more reflective of a much larger build's more critical specs.

Cheers,
Kevin Morin
Kenai, AK
kmorin

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Re: Double Eagle Build

#61

Post by Northeaster » Sun Dec 28, 2014 1:38 pm

Thanks Kevin for providing great context and real world experience in the small/ med boat construction.
I certainly do not want to discount any (obviously well founded and knowledgable) advice, but I do want to worry more (and attempt to correct) the issues which are more likely to be of greater importance pertaining specifically to my (small) build. It's good to at least know and ackowledge what sins you are performing, and reasoning behind them, even if you choose to continue!

I know we have discussed hull sheet size choice previously, and as a general rule I agree that larger / longer sheets would be best, and I want to eliminate as many hull butt welds as possible. If I were building an 18' boat, I would certainly opt for the 20' sheets!
But in my real world example, with a hull of 25' loa, and I believe a distance along the chine of about 27', I am going to be into a butt weld, even with 20' sheets. Of course, this weld could be located near the bow, so the distance of the weld, from chine to keel for example, would be about 2.5' as opposed to about 4' if it were located in the aft section. I have previously talked about the additional charges we are faced with here (roll change charges) when ordering long sheets - this makes it more costly to order 3/16" sheets for the bottom and 1/8" sheets for the topsides, for example - as I am hit woth two roll change charges instead of only one if all teh same thickness.

As I am faced with a butt weld anyway, should I consider just going with stock 5' x 12' sheets (not subject to the expensive roll change charges) and therefore I could order 3/16" or 5/32" (.160") for the bottom and 5/32" or 1/8" for the topsides? I am not specifically asking what thickness you recommend here, but rather would you support the idea of going with 12' sheets inctead of 20' sheets, which still require a butt weld? I guess the 12' sheets would really result in a long butt weld near midships, and another shorter one very close to the bow.

kmorin
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Re: Double Eagle Build

#62

Post by kmorin » Sun Dec 28, 2014 4:13 pm

Northeaster, I haven't reviewed the thread to be up to speed on the relative costs to buy the 20's sheets over the 12'ers. I'd use a 'what's it worth' question to answer that question? What's it worth to skip those butt seams versus the cost of the added sheet length?

If you're going to have to pay the re-roll charge for the 20's it seems like that could be rolled to 25' or whatever the LOA of the sheet for the bottom and topsides called for? I'm not dealing in that market so I'm uniformed just speculating.

Back to butt seams, they're not that big a deal if you're making savings that pay wages to have you butt weld the seams then planking the project with 12' sheets is a good choice. The reason to pay the extra money is your 'fear'/skill/potential impact of welding those seams. I may have mentioned there are two schools of thought, #1 To weld when cut to fit, tacked on, and in place and; #2 Weld the sheets into final large pieces before any cutting. In the latter if you have wrinkles they get mechanically flattened by hammering out the contractions before using the plates.

I'll call them before and after, and state that you can learn to do either weld method, and if you plan, practice and patiently execute; there's no final detriment to your finished boat. The concern for transverse hull plate seams are the results of those who have done these seams incorrectly. Cross panel welds are done on all larger boats/ships/yachts so its not like these welds are some risk. They're just more touchy than a self supporting chine seam because they can, if done poorly and not in full control, produce large dents/bulges in the hull where these would be very visible.

Not sure if I'm helping any? but I'm not facing a cost shift either, 20' is a stock size on this coast as far as I'm aware?

Cheers,
Kevin Morin
Kenai, AK
kmorin

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Re: Double Eagle Build

#63

Post by Northeaster » Sun Dec 28, 2014 5:30 pm

Hi Kevin - I did inquire previsouly about 25' sheets here locally (Halifax,Nova Scotia), but was told, by at least one local supplier,that they could not get that size (from their distributor, likely in Montreal). It may have been more due to them not wanting to have the ship, unload and handle the larger sheets (supported on a large protective pallets).
I will inquire again. The roll change charges are substantial (i.e. maybe $400 so if you get one sheet thats $400 divided by one - if you get 4 sheets of the same thickness, at least it's only $100 / sheet extra.)
Out here, where aluminum welded boats are rare, 20' sizes are not stock. I woudl have to drive about 10 hours t obe at a distributor who stocks 20' sizes, and that would be in New Hampshire. Shipping would be difficult and would involve duty at border, or i could rent a large trailer and pick it up, but most cost savings would be lost to travel costs, so I am trying to buy locally.

I will likley bring in the experienced local aluminum welder, who stopped by to help me earlier, in order to get a good start on hull sheet welding,

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Re: Double Eagle Build

#64

Post by Northeaster » Sun Jan 25, 2015 4:06 pm

No pics today, but made some good progress this weekend, after receiving four 6' x 20' sheets of 3/16" 5083 h116 aluminum last week.
Cut out both port and starboard bottom sections and port topside section. Actual sections are about 25 - 26' long, so I had to butt weld small pieces onto the 20' sections to be long enough. (ordering 25' sheets would have added about $1500 to the project, and although not having butt welds would be nice, not at that price).
Butt welds went very well (from my amateur view), after tacking and tacking on a piece of angle next to the joint, as a stiffener, to help prevent warp from the heat.
I clamped a long brass bar, about 3" wide by 1/2" thick, under the joint to act as a temporary backing plate and heat sink.
There seems to be two 'camps" of builders when it comes to aluminum welding for boats. Those who prefer short (2"- 3") welds, to help minimize heat input (with proper cutting out of craters/ends in each short weld, to allow new weld to penetrate fully next to previous welds) and those who prefer as long of welds as possible (hit it quick and get done before the heat builds up too much and avoid the potential cold starts associated with numerous starts and stops).
After practicing more and getting email advice, I decided to try the latter approach and was very pleased with the results.
Butt welds were about 3 ft long and I was able to do each side in one continous pass (I did have to increase travel speed as I went) and was able to put my hand on the aluminum, next to (not directly on) the weld only a couple of minutes after the weld pass. I had experienced much more heat buildup when practicing with shorter welds, but admittedly, I did not wait long between weld sections in praticing.

Bottom sections are roughly in place (Boat is upside down), but require a bit of shaving, to achieve an acceptable fitup / joint at the keel line before tacking.
Then I will prop up the topside and do some more tweaking / shaving of material until the chine seem is ready to be tacked.
I allowed a bit of extra material, over my plywood templates, as I was told that the alunimun would bend differently than the ply. The bottom section did pull down nice around the more rounded bow section, and overall I am very pleased with the fairness thus far. I will have to let some stringers out a bit, to come into contact with the hull sheet, before welding - but that is a ways off.

Qusetion though- if a stringer ( 1 1/2" angle) sits 1/4" away from the hull, would it be acceptable to let it out 1/8" so there is then an 1/8" gap between the stringer and the hull (to be welded) and as well, between the stringer and the frame. Would this be an acceptable gap to have the weld filler material fill?

here's a couple of pics with the ply templates on a couple of weeks ago.
Attachments
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kmorin
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Fairing Seams

#65

Post by kmorin » Sun Jan 25, 2015 9:45 pm

North, I see some pretty major hoggs in the seams?? The chine just forward the stern is hogged rather significantly, are you using battens to fair these seams?

If so, I suggest the batten cross section be increased as they're not fair, and if not I suggest the batten would assist in cleaning up the major hoggs shown in the photos.

Cheers,
Kevin Morin
Kenai, AK
kmorin

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Re: Double Eagle Build

#66

Post by Northeaster » Mon Jan 26, 2015 1:13 pm

Hi Kevin - you are correct. I have not gone through a lot of effort, in trying to make the plywood templates fair. I wanted to err on the side of caution, not knowing how much differently the aluminum sheet would bend / fit vs the ply templates -so \I just left about 1/2" extra material on the aluminum sections, when cutting them out from the templates.
I know that you had written on how to do the take off measurements, but in the end, I chose to make (rough) ply templates so I could actually see how they hng on the boat, as well as being able to move them around on my large aluminum sheets, for nesting efforts. I realize that one could make ply templates from take off measurements.
I now have the two bottom sections and ne topside section cut out of aluminum, albeit a bit large. The two bottom sections are roughly in place, and only require a bit of shaving to have them fit well at the keel line. Then, I plan to tack at the keel line, and just prop up my topside section to see how far off the sheer is - i.e. how much material needs to be shaved off to allow the topside to meet the bottom section nicely at the sheer.

I realize that this is not the way professional do it, and of course I am I open to advice - It should be apparent however, that my level of fit and finish will not be anywhere near your level of expectation, after you have built hundreds of boats. I want a solid, decent looking functional boat, but not a showpiece.

I have to decide soon on how deep of a keel to use, and proceed with that aspect.
Thanks,
Darrell

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Re: Double Eagle Build

#67

Post by Northeaster » Fri Feb 13, 2015 5:29 pm

Making some progress on the bottom sections. Tacked about 3/4 of the keel seam tonight.
Have to do some shaving near the bow to get them to fit better before tacking there. Largest gap in pics will get smaller as I trim and pulls sections closer and down to the frames.
Then, start work on the chine / topside fitup.
Topside panel on ground next to boat is upside down, if anyone wonders how it will fit....
Attachments
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Re: Double Eagle Build

#68

Post by Northeaster » Fri Feb 13, 2015 5:34 pm

a few more pics
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Northeaster
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Re: Double Eagle Build

#69

Post by Northeaster » Sat Feb 14, 2015 11:38 am

pics after keel seam tacked and straps removed.
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Northeaster
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Joined: Mon Mar 31, 2014 3:33 pm

Re: Double Eagle Build

#70

Post by Northeaster » Wed Feb 25, 2015 7:25 pm

Hi Kevin (and all)- Hope you have just been busy, and haven't lost interest in this amateur build.
Although I have not followed all of your advice thus far, I do really appreciate your experience and input!

I am hoping to have the topsides tacked on in the next month or so (I have a 2 1/2 year old and a 5 month old, so build time is about 3 days a month right now.)

The next big step will be (hopefully) flipping the boat, to weld up the keel and chine seams on the inside, and then flip back upside down again to backcut and weld the outside of the same seams. And, build and install a box keel, if that's the way I decide to go.....

I was pretty much set on a traditional inboard shaft drive install, but have recently been considering (at least somewhat) following in another aluminum Glen-L Double Eagle builders footsteps and installing a home-made Surface drive / shaft through the transom setup, with little or no keel.
I have not been able to get many details from him, as he has not been on the Glen-L forum frequently, and I hope he doens't mind me attaching a pic of his boat (which was on the Glen-L picture Blog/gallery) to illustrate the surface drive.
He reported getting about 22kts with a 130hp engine, and was planning on prop changes to better that on his 28' Double Eagle. I have a 150 hp Diesel for my 25' boat, and would be satisfied with roughly similar numbers.

I have heard from another Double Eagle builder, who has been on similar boats with no keel and full keel (which he said stayed too upright for his liking during turns) so he advocates for a short keel as in the outboard version.

The appeal, to me, of the surface drive is the perception, at least, that the shaft through the transom, allowing the strut to hang below the swim platform, may be easier to install in that the struts supports would not pierce the hull as they would with a traditional shaft drive (with a short keel) or have as much complexity as as a shaft log through a full (box ) keel.
I have read that surface drives normally provide performance gains on the top end. I will be boating in (island) protected and unprotected Atlantic Ocean conditions (10 - 20kt winds and 2- 4 ft chop would be typical) so I would think that even with a top speed of 20+ kts, I may be limited to around 12- 15 kts often, to maintain a comfortable ride - but I have little power boat experience - I normally sail at 4- 6 kts.......

I would appreciate thoughts from those with experience on similar boats, or general knowledge!
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kmorin
Donator 08','09,'10,'11,'12,'13,'14,'15,'16,'17,'18'
Posts: 1363
Joined: Mon Aug 18, 2008 1:37 am
Location: Kenai, Alaska

Re: Double Eagle Build

#71

Post by kmorin » Thu Feb 26, 2015 12:50 pm

North, the Dbl-E's designer is probably best to ask these questions since he would have more insight as to the various versions?

I see that rising butt lines aft and think the bow will squat if pushed more than 20ish, the engine position in parallel butt lines boats can be an advantage at the stern of even aft the stern. The engine fuel mass farther forward as this design's primary intent is to create a slower (by today's standards) speed boat with a performance of slower boats. Less pitch by the bow, less impact, and more 'ride' by slowing the pitching moment with the main load over the center of buoyancy near the center of gravity about amidships.

The keel's main job in this type of hull is to keep her head in a following sea and allow the hull to have less helm input while keeping a nice track. The keel doesn't have near as much to do with heel as does the chine in plan view. The keel also protects the running gear which is desirable for commercial fishing boats, and that is where this hull shape originates. The exposed shaft and wheel, with a spade rudder as shown is so vulnerable that it is not often accepted by the people who primarily use this hull shape.

IT would be difficult to sell in Alaska due to the large amount of floating wood in our coastal waters- that, if hit with this arrangement, would cause more damage than other drive designs.

So the original hull's intent is not to go fast, to begin to discuss how fast it will- go top end; then to agree to an average cruise of 1/2 that is too confusing for me to understand? Clearly the bow will pitch drastically by comparison between the engine located aft versus forward. Clearly the full forefoot and descending keel line, in profile, and rising butts were not intended to provide a classic planing hull where this designer knows full well that a parallel keel and chine will give drastically better planing performance for the same power to wt ratio.

So the design is intended to travel (efficiently) at 12-15 knots (probably gets great mileage in the 8knt range?) and misunderstanding it to the extent of an aft engine and pushing it to plane will result in bow up 5-8 degrees more than needed, and lacking a keel the boat will be a complete work out in a following overtaking sea. The boat shown in the photos will have a marked inclination to slew about in a following sea- the combination of deep forefoot and no lateral plane aft is not a sea boat. As a lake boat it shouldn't face conditions that make this a problem.

I have no experience with this particular design, but I have built in the type though much larger, so my opinion is speculative at best.

cheers,
Kevin Morin
Kenai, AK
kmorin

Northeaster
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Re: Double Eagle Build

#72

Post by Northeaster » Mon Mar 09, 2015 8:13 pm

Hi Kevin,

I do appreciate you thoughts on the design, and impacts of changing it, even if it is only speculative... it is based on alot more knowledge and experience than i possess - so thanks!
I will likely stay with the plan of a tradtional shaft and full or shallow keel - I do like the protection of the full keel, but this design also has options to outboard or I/O power, which would still run a higher risk of prop/drivelline damage. Is there a way to have a more shallow keel, but then somehow go deep enough suddenly before the prop to provide a skeg to the rudder?

I worked most of the weekend on the boat - Aligned and tweaked the topside to better fit at chine, and then made a copy for the other side, including butt welding a 76" scrap piece onto my last 20' sheet, to make it long enough for complete topside. Finished tacking most of the first topside, and removing straps. Still have to tack the aft end, and try to mitigate bends a bit near butt weld as I tack the chine.... Butt weld on 2nd topside has less warpage as I used 4 temporary strongbacks lengthwise instead of 2, as on the one shown in the pics..
I realize that yourself and other pros would not likely be happy with the results I am settling for, but I know the chine is good enough for me to get a solid weld, and I am happy, thus far, with the look or the boat - for my first one.

Need to buy a 4' x 8' sheet for the transom as my offcuts are not large enough, and I don't want a horizontal weld across the transom - I do have 4 offcuts measuring about 20' x 2.5' so they should provide most of my cabin floor/sole.

May not get to work on it next weekend, but a couple more days to tack on the other topside and transom and then hope to flip it over in the next few weeks, to begin welding inside keel and chine seams. May lower engine roughly in place at that time to check angles, clearances and perhaps mock up engine girders.

Then, hopefully flip upside down again to backcut and weld outside of keel and chine seams, and potentially start on keel.
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Northeaster
Posts: 39
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Re: Double Eagle Build

#73

Post by Northeaster » Tue Mar 24, 2015 5:45 am

Progress report - finished flipping boat right side up using jig based on Kevin's "Davis Jig" pictures. Worked well and I lucked out and was very close to center of gravity on first try, as it turned by hand (with long board as a lever)- with safety lift line in place in case it wan't well balanced.
Now will weld inside of keel and chine seams then flip back upside down to backcut and weld outside of same seams.

It will likely be back upside down in a week or two, so I would like to start looking more closely at box keel design.

I had planned on lowering the engine to mock up/ rough fit it, and get a first hand view of how it fits in there, shaft coupler position ,etc.
I have this drawn out on large paper, but really would like to see it in the boat, and mock up some cardboard engine girder templates, and know how much of my frame 4 or so I will have to butcher to fit it in best.

But, it would be difficult to get it in right now as I can't move the boat ( I had castors on one of the jig tripods, and had planned to add them to the other, but it did not feel as stable). And the chain falls are not in a good location - cannot lift engine beside boat and also get it in proper position - no trolley / set moving hoist setup...
In about a month we will take the 5th wheel trailer and sailboat out of the shop, so I should be able to lift the engine in with the backhoe, if I want to flip it again before adding keel.
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Northeaster
Posts: 39
Joined: Mon Mar 31, 2014 3:33 pm

Re: Double Eagle Build

#74

Post by Northeaster » Tue Mar 31, 2015 6:23 pm

Have inside of keel seam welded up and most of inside chines done. Have not noticed any significant distortion.

I will finish the inside chines this comiong weekend, and lilley flip the boat back over to backgouge and start welding the outside or same seams.

Kevin - I do have a question re: transom - I have read that some leave it off for better access and this certainly aids my efforts. Is it Ok to wait and add transom after outside keel and chines seams are done? Waht about even after stringers to hull and stringer to frame welding?

Northeaster
Posts: 39
Joined: Mon Mar 31, 2014 3:33 pm

Re: Double Eagle Build

#75

Post by Northeaster » Sat Apr 04, 2015 5:38 pm

Finished welding the inside seams of keel and chines ,and took about an hour to flip the boat back upside down working alone.

I will start on backchipping the outside of same seams tomorrow and welding them up, starting with the keel, then chines ,working from midships towards ends.

Also, while right-side up I placed the transmission in it's rough place, going from my full size drawing/ sketch of hull, frames ,CB of boat and CG of engine/gearbox.
Then drilled small hole through keel seam for prop shaft mockup and tacked temp brackets to hold the mockup shaft in place at transmission coupler and at strut / cutlass bearing location. I only used a couple of 1/8" tig welding rods end to end for the mock-up shaft for now.
I didn't want to enlarge the hole in the hull until the gear and engine are more mocked up for real, in case I am able to modify frames or location slightly and get the engine even lower in the hull.

I am still debating between a full keel, per plans with a skeg bar to the bottom of rudder post or a partial / lower keel (as in outboard version) and then a more exposed strut, prop and rudder. One member told me he would go with a small keel, as the full keep version stayed very upright (no lean) during turns and he thought a small keel would be a good compromise, although it would be difficult or impossible to have a skeg bar, unless the small keel took a deep dive with a piece of flatbar for example, just before the prop.....
The plans had called for a single plate keel but Kevin talked me out of that, dues to multiple repairs he has made in the past on plate keel boats, and he advocated a box keel. So, that is the route I will likely go, incorporating the shaft tube/ cutlass into the aft end of the box keel, rather than requiring a separate strut to hold the cutlass bearings.
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