25' Skiff

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Yofish
Posts: 8
Joined: Thu Jun 12, 2014 10:37 pm

25' Skiff

#1

Post by Yofish » Fri Jul 24, 2015 12:38 am

Here is lines view of the skiff I'm building now. 25'x8' 6", 15* at the stern, has a cabin, self-bailing deck. 3/16" sides, 1/4" bottom. It's an iteration of a design I've been working on for awhile. Surface modeling done in ProSurf. Major parts cut CNC plaz by Alaska Steel, Anchorage, AK. I'm quite down the road from the 1st pic I posted and will post some more soon.
Attachments
25_LINES.jpg

kmorin
Doator '08, '09, '10, '11, '12, '13, '14, '15, '16, '17
Posts: 1302
Joined: Mon Aug 18, 2008 1:37 am
Location: Kenai, Alaska

Re: 25' Skiff

#2

Post by kmorin » Fri Jul 24, 2015 1:36 pm

Yofish,
When time allows it would be nice to see the Body Plan View with the station sections so the forefoot's V can be seen as it progresses aft.

She's very full forward, her work boat heavy load heritage showing? and she has the T bottom aft where the engine mount's lowers are the bottom plane extended. On the 20'er's did this bottom work so well you've gone to that configuration as your solution to the outboard stern arrangement?

In regarding trimming this design for different loads and sea states @ different speeds; would you use a DoleFin-like appendage mounted to the cav plate ()?) or... trim planes under the two sides of the bottom flanking the outboard mount/bottom extension? This size boat can haul a pretty big load, people or gear, so trim at different speeds can become a running battle so I was curious how your other hulls have influenced your ideas about trimming this scaled up version?

It will be interesting to see which cabin type and deck arrangement will fill out the design? Forward cabin with trunk and after open deck (not sure if we can call that traditional) versus a walk around or dog house with an open foredeck?

[Another check in on the plans vs NC cuts and the cost of the AK/Stl services versus value?] How was the cut package to build? Are there any adjustments to the cut files from the plans? If I recall, the ProSurf application was making the chine to keel camber adjustments to the transverse frames (an area of work I've had constant work to adjust in my own designs) ? How did those convex sections in the frames work out for 1/4" material compared to the 20'er's last year? I think I recall the 20'er's were 3/16" bottoms?

So the material (1/16" increased over 3/16"- could be called 33% increase of previous design) is thicker, and with a relatively small beam increase (inner chine BOA of 72" to 76" or there about? ) not actually in direct proportion to the increase in thickness of material- how did the ProSurf predicted bulge or convex curve (outward) of the bottom plate from the keel to the inner chine- turn out when you built with pre-cut frames produced by that software's output?

What is your deck to waterline distance? I'm trying to focus on your design decision about the displacement you used to figure the deck above at rest waterline. I've used lots of load conditions before (to locate the deck above the waterline) and it seems that some skippers just haul more than I'd have figured and needed to plug the scuppers/clearing ports when they turned their skiffs into freighters. So I was looking for some reply about your rule of thumb for deck line versus waterline in Profile View of the design.

Looks nice on paper, I like the hollow sheer, and look forward to learning about the bottom's entry (sections) and what the cabin arrangement will contribute. I'd guess this is an client driven build? not a spec boat?

Cheers,
Kevin Morin
Kenai, AK
kmorin

Yofish
Posts: 8
Joined: Thu Jun 12, 2014 10:37 pm

Re: 25' Skiff

#3

Post by Yofish » Fri Aug 07, 2015 9:32 pm

Kevin,

Body plan attached.

kmorin's quote: She's very full forward, her work boat heavy load heritage showing? and she has the T bottom aft where the engine mount's lowers are the bottom plane extended. On the 20'er's did this bottom work so well you've gone to that configuration as your solution to the outboard stern arrangement?

Yes, I'm very happy with this arrangement for several reasons: it makes the boat narrower (aspect ratio), provides a damn nice dam when you're getting your BACK SIDE pushed up on Glacier Spit by a rowdy SW, and makes engine servicing a dream. It also provides a chance to get back aboard if having fallen overboard alone, something that people laugh at unless you know someone that that happened to. Of course, the first two points are the only interesting design points as the transom could be full across and still aid in the engine access but having the surf boil under the swim platform does make a difference. Bayweld likes the so-called 'off shore' bracket that kicks up aft. I don't because reverse doesn't work as well for the froth that boils up as it does not produce as much thrust directly under the boat. It also does not provide the same amount of floatation. They do have the benefit of providing clearer water to the prop but I reject that over my order of importance.

I'm afraid I'll never let go of the workboat platform until I build a panga. Back to Glacier Spit, when you have 850 lbs of humans clamoring about in the bow, it is never full enough.


kmorin's quote: In regarding trimming this design for different loads and sea states @ different speeds; would you use a DoleFin-like appendage mounted to the cav plate ()?) or... trim planes under the two sides of the bottom flanking the outboard mount/bottom extension? This size boat can haul a pretty big load, people or gear, so trim at different speeds can become a running battle so I was curious how your other hulls have influenced your ideas about trimming this scaled up version?

I'm big on 'fins' because they work. Interestingly, the two 21's don't seem to 'want' trim plates but my guess is this one will. The client weighs 270lbs and I'm sure his 3 buddies aren't far behind. The cabin is aft of amidships and the fuel forward so we'll see! There are accommodations for tabs provided.


kmorin's quote: It will be interesting to see which cabin type and deck arrangement will fill out the design? Forward cabin with trunk and after open deck (not sure if we can call that traditional) versus a walk around or dog house with an open foredeck?

More or less amidships and belly-rub walk around. Not my choice, the client dictated certain aspects despite my recommendations.


kmorin's quote: Another check in on the plans vs NC cuts and the cost of the AK/Stl services versus value?] How was the cut package to build? Are there any adjustments to the cut files from the plans? If I recall, the ProSurf application was making the chine to keel camber adjustments to the transverse frames (an area of work I've had constant work to adjust in my own designs) ? How did those convex sections in the frames work out for 1/4" material compared to the 20'er's last year? I think I recall the 20'er's were 3/16" bottoms?

Still happy with AK Steel. Other than their table is too short (20'), they have done me good. Piecing is a pain and ugly on the sides but hey, that's the way we had to do it before custom lengths were available. The scribed lines are perfect and much better than felt pen, for the obvious reasons, as when going with the router cut. There is an issue with heat. The longer the piece is to it's width can be really affected by distortion, like the 'flats' but it's all been workable for me and much better than paper plot transfers which have their own problems.

kmorin's quote: So the material (1/16" increased over 3/16"- could be called 33% increase of previous design) is thicker, and with a relatively small beam increase (inner chine BOA of 72" to 76" or there about? ) not actually in direct proportion to the increase in thickness of material- how did the ProSurf predicted bulge or convex curve (outward) of the bottom plate from the keel to the inner chine- turn out when you built with pre-cut frames produced by that software's output?

The inner chine is still around 6', the flats are quite wider. The biggest reason for the 1/4"bottom is I DO NOT KNOW THE CLIENT! If I was building it for me I would have used 3/16". This guy is not a mariner and I don't ever want it back in my shop again. The whole forward 1/2 of the skiff has 2-1/2" x 3/16" mini-frames that split the mainframe/longs distance in half so the 'pounding' surface is divided so that it is supported by framing not less than 18"x 12" of area . If intuited correctly, he's the kind of guy that will pound his liver into pat'e in order to get to Pogibshi to go halibut fishing two hours AFTER the day breeze starts.

I think ProSurf does a good job of predicting plate curvature but it has no inputs for what resistances differing thicknesses would present. I don't know of a surface modeling program that does so. It 'just' aids in making a developable surface no matter what. My guess is that it is purely mathematical in this approach, adjusting curvature in two directions for the best fit. Put another way, I'm really happy with the results I've achieved using the software. It's always remarkable to me when everything pulls to the shape designed. Mind you, there are still strange things that happen and they all happen up in the last 30" of the bow!

kmorin's quote: What is your deck to waterline distance? I'm trying to focus on your design decision about the displacement you used to figure the deck above at rest waterline. I've used lots of load conditions before (to locate the deck above the waterline) and it seems that some skippers just haul more than I'd have figured and needed to plug the scuppers/clearing ports when they turned their skiffs into freighters. So I was looking for some reply about your rule of thumb for deck line versus waterline in Profile View of the design.

Hooboy! I'll work at an answer but this has been a 'seat of the pants' thing for me even though ProSurf has tools to aid. All I'll say for the moment is, because of the 'skipper factor' you mention, I always make the ports from pipe that can be plugged - what else can you do, design a little skiff that has a bailing deck that stays dry with 900 lbs of beer on the stern? Unpossible! I don't need to tell you that when the deck is too low it sucks, really bad. When the deck is to high, it sucks but not as bad because Billy's tennis shoes are still dry and you're hoping he is not affected by the less obvious unpleasantries of a too high deck. Whoever said a boat is a series if compromises should have added that the smaller the boat is the bigger are the.......
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Last edited by kmorin on Sat Aug 08, 2015 11:22 pm, edited 2 times in total.
Reason: added quote labels KM

Yofish
Posts: 8
Joined: Thu Jun 12, 2014 10:37 pm

Re: 25' Skiff

#4

Post by Yofish » Sat Aug 08, 2015 10:59 pm

In the end, there may be only two things that viewers may find useful from my efforts. The first is to download AddBlock and use it to wipe out those irritating and awful smilies that crawl around like blowflies on a moose carcass to the right of the text box. I've never used them and never will and now that they are eliminated, feel more like posting.

The second is the 'hog trough', a simple device that aids old hands and poor eyes to run lots of corner welds very quickly without arm strain or frying those expensive Miller gloves too soon. The first pic shows one of the swim deck pans welded out. The second and third show the outside sheer weld at beginning and end, welded out with the trough. It took 16 minutes to do it, about 25 lin ft. One stop about 3/4's through to stick the gun barrel (Miller 30A) in a can of water to cool it. Usually it so hot that the water evaps almost instantly. Poor man's water cooled Miller gun. The geometry is such that it works around gentle inside and outside curvatures. Now, this is not a critical weld as it gets covered over with a gunwale trim so one can just walk it. It really earns its keep with fuel tanks, though. The only important thing is the piece of UHMW pipe that allows the gun barrel to smoothly glide along. This one does 20" at stretch, which I can do without moving my body.
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kmorin
Doator '08, '09, '10, '11, '12, '13, '14, '15, '16, '17
Posts: 1302
Joined: Mon Aug 18, 2008 1:37 am
Location: Kenai, Alaska

Re: 25' Skiff

#5

Post by kmorin » Sat Aug 08, 2015 11:47 pm

Yofish, I'm glad you got the flies off your page display and feel more like posting! I will have to dispute a bit though, I don't think the Forum will only find two take away items in your posts, I'd say every post will have countless useful info, you just might not see the value since you already know it.

Wow, she went from tack up of the bottom to welding out the sheer in one post? That's fast work, do you happen to have some progress shots of the steps in between these stages?

I noticed there's a flat bar down from the guard deck at the sheer, inside, does this shape have future/other structural parts added to this? Will it be free from the topsides or will it have some tie-in back to the sides?

The rod shelf is on but looks longer than in proportion to the 21'ers of this design? Is that the pics, or is there a difference to that inside side stiffener?
There's a shelf on the transom, is that a temporary or permanent bar on the inside?

On the welding fixture 'hog trough' does the gun lay with the case on the outside (right side in posted pic) and the barrel just hanging over the blue plastic slide pipe? The 30A gun has a fairly large front of case panel if I recall (?) so the gun is kept the exact distance from the weld as it travels OR do you just rest downward and hold the gun's gas cup in and out to suit the weld?

I'm trying to get a little more info for the non-welders here that might not see immediately how the gun fits onto the guide/hog trough. It would be great, if time provided, to have a one handed picture of the gun laying on the fixture?

I've posted the panga derivative shape on our old panga thread so- Please drop by and post your thoughts for the entire Forum to read there too.

Cheers,
Kevin Morin
Kenai, AK
kmorin

Yofish
Posts: 8
Joined: Thu Jun 12, 2014 10:37 pm

Re: 25' Skiff

#6

Post by Yofish » Thu Aug 13, 2015 9:44 pm

kmorin wrote:On the welding fixture 'hog trough' does the gun lay with the case on the outside (right side in posted pic) and the barrel just hanging over the blue plastic slide pipe? The 30A gun has a fairly large front of case panel if I recall (?) so the gun is kept the exact distance from the weld as it travels OR do you just rest downward and hold the gun's gas cup in and out to suit the weld?

I'm trying to get a little more info for the non-welders here that might not see immediately how the gun fits onto the guide/hog trough. It would be great, if time provided, to have a one handed picture of the gun laying on the fixture?
Kevin, I'll answer your post first with a pic of the Hog Trough. Depending on which gun one has, the distance between the 3/4" PEX pipe glide and the work point which would need to be considered, as well as the angle of incidence. The 30A Miller has a pretty long NON ALLOY barrel and is the only gun I use. Also, I use a little more radical forward angle than most would use as I find it works better (cleaner brighter welds) with this apparatus (see the lead angles incorporated in the trough). If you have good fit up you can just run a straight bead with no weave like automatic mig. Sometimes it's scary how good the weld looks. I maintain the same distance from the cup to the work and probably closer than most would; I get loaded with boogers pretty fast but that has the best effect. These pics are of working the outside chine. With practice, one can get nice root penetration which is important for building tanks.

So someone please tell me when I type f.i.b.e.r.g.l.a.s.s., as what the barrel of a 30A is made of, some idiotic, and automatic substitute words NON ALLOY shows in its place? That has got to be about the stupidest thing I've ever encountered on a board! I understand swear words but sheesh, c'mon guys.
Attachments
gun (Medium).JPG

Yofish
Posts: 8
Joined: Thu Jun 12, 2014 10:37 pm

Re: 25' Skiff

#7

Post by Yofish » Thu Aug 13, 2015 10:08 pm

At the end of my career, I work alone for the most part or try to as much as I can. One of the most daunting things to do by self is to flip the thing over and back. For me, my method is a work in progress. I have an overhead track down the center of a modest size shop with two chainfalls. I've built extensions with adjustable pivot points to my build-on dolly in order to rotate the skiff by strapping it down. Ive been thinking of ways to eliminate the dolly. To that end I built a pivot point that uses the 1/2" holes for the outboard mounting as 1/2 of the equation. All made from stuff laying around. So far so good as it worked fine this time. I have ideas about the bow by using the painter eye, which is close to the CG, and some struts thus using the body of the skiff as the main structure. It would also make it so that the thing could be rotated to work on without a bunch of meltable straps in the way.
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