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Old Jul 14, 2015, 01:21 AM
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Build Log
Yankee Dolphin 24

Since I didn't do any kind of build log on my first two boats (Archimedes schooner and Brando footy), I thought I'd at least make a go of it with my third boat here. I wanted a simpler boat, or at least simpler rigging, so I wanted to do a Marconi sloop.

As much as I enjoyed building to the plans of the Brando, I enjoyed the complete scratch build of the Archimedes more, so I decided to do something from big boat plans again. I own several real sailboats and my favorite is a Dolphin 24. Just a perfect-sized boat. Not so big you can't single hand it even in a pinch, not so small that you can't take a couple friends out without bumping into each other. And classic lines. So I decided I would do an exact (within reason) replica of my own boat, Yanqui. I got ahold of the plans for the boat and made a mediocre copy.

I also decided I wanted to try doing it in fiberglass. As such, this build log might end very abruptly. I have worked with fiberglass some in the past (mostly repairs), but it's a messy affair and a lot less certain than wood. But I'm 99% certain that I couldn't reproduce the lines of a fiberglass boat with wood.

The first thing to do is make the plug, using the sandwich method. I started out with the plans in a PDF. I'm going to use 2" foam pieces in between the pieces of bread (plywood) and each piece of ply is 1/8", so the first thing I had to do was scale the plans so that there was 2 1/8" in between each station. That meant printing out that plans at 112% scale.

Next I took the 12 printouts and I scribed a vertical line down the center (since they're drawn as half sections), then folded them. I cut along the lines for each station, then unfolded and had paper cutouts for each station.

I sprayed 3M adhesive (and got it everywhere, of course) on the paper stations and glued them on the 1/8" plywood.

Tomorrow, when the kids aren't asleep, I'll put it on the scroll saw and cut out each station. On the plans, there are a couple prominent dots drawn along the centerline. I plan to drill 1/4" holes in these and running a couple rods the length of the plug to keep the stations and the foam aligned. I had thought about leaving the sheer line totally flat so that it could be set resting on it's top, but then I'd end up having to cut the actual sheer into the fiberglass. I'll know whether this was a good idea or not pretty soon.
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Old Jul 16, 2015, 12:37 AM
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That didn't work

Not even a little. It appears that the main challenge of this method is keeping all the sections aligned while the foam is being cut and sculpted. Even with glue, the foam was wiggling around on the plywood sections enough that it wasn't going to stay straight and aligned all through the process.

So plan B will be to mount the sections on a temporary "spine" to keep the shape, then plank the frame in 1/16" balsa. I'll fair that out, then lay the fiberglass right over it. Then I'll remove most of the sections, leaving a couple for strength. The actual boat has balsa cored fiberglass, so it ought to work.
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Old Jul 29, 2015, 12:41 AM
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minor progress

Got a little closer to something that actually looks like a hull. Had a couple of hiccups, particularly with the foam. I started out using some of the white, common styrofoam that I had around. Not nearly dense enough, and it wriggled around impossibly. So I went with the pink stuff. Much better. I cut the stations on the keel board very tightly so that once the stations are in, the gaps in between are a tiny bit less than the 2"thickness of the foam. As a result, the stuff is really in there tightly and doesn't move around at all. Now I'm cutting it with a fine tooth Japanese saw and 60 grit sandpaper. What a mess.
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Old Dec 18, 2015, 05:17 PM
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Progress

I finally got back around to this boat project. I was stalled with a hull form that was good in the body, but lacking a bow, a stern and the keel.

I found that it was nearly impossible to keep the keel aligned, so that once I got the foam sanded down to the hull forms, I found that the keel curved off to one side badly. I messed around with it quite a bit before giving up and cutting the entire keel (forms and all) off.

I then attached a new built up block of foam in the keel area, along with blocks at the bow and stern. I ran into the same problem of finding an adhesive that worked with the foam. I tried several and finally used double sided tape.

I shaped the keel pretty much by eye (I have the actual boat parked next to the garage now) and fudged a lot on the stern. The plans aren't extremely specific about the transom and say to just shape it according to the lines of the boat. I'll have to do some more shaping, as well as glassing in a piece of thin plywood.

Then I covered the entire hull in packing tape. This was, obviously, difficult to do smoothly. I considered another release agent of some kind, but I also needed something that I could stick tape to while keeping the fiberglass cloth on.

Once all taped up, I cut pieces of cloth to size. I ran them longitudinally to minimize the number of doubled up areas. I tried to double up in key areas like the bow. I attached them with double sided tape. Then I slathered on the epoxy.

West System epoxy has worked really well for me in the past, but it relies on a precise mixture of resin and hardener. That's provided by a pump on each can. The hardener pump suddenly wasn't working, though, so I ended up having to estimate the amount of hardener. Not optimal. I'm not sure if it's going to set up correctly.

At this point, if you're thinking that this is all more of a pain in the rear than it's worth, we're in the same (ahem) boat. This is my third model boat. The first I built out of wood from full size plans, the second was balsa from model plans, and now this one. It's an interesting experiment, but it's confirming for me why there isn't a big fiberglass model boat building scene.

The smart way to get to the same place would have been to build a frame model planked with balsa, fair it, then glass it with light cloth.

I'm probably at the make or break moment here. I have no sentimental attachment to this hull and if it doesn't come out pretty impressively I'll 86 it and this thread can hopefully serve as a warning to others.
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Old Dec 19, 2015, 12:24 AM
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Ah, so its THIS again. . .
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I like the process your going through. I have considered doing the same thing for my favorite Schooner. But only if others were interested in the boat as well and I could help other people get their hands on a 50" Schooner hull.

But I dont know how much interest there is in that.
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Old Dec 20, 2015, 03:30 PM
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Post Mortem

TL;DR:

Don't try this, it isn't worth it.

Full Post Mortem:

I'm sticking a fork in this project, it's done. The epoxy set reasonably well, but it's clear that the hull will need at least another layer of cloth to achieve enough rigidity to maintain the form. As well as plenty of bolstering within.

Is it all possible? Sure. The layup of the hull needs to be many layers of very light cloth, I think. Two layers of 6 oz, which is what I'm using, leaves too many folds and deformities that would need a lot of fairing.

All in all, here are the lessons I'm taking away:

1) The plug needs to be made much more solidly, like of balsa. The foam shapes very easily, but it's really hard to get it glued to the plywood sections in such a way that it's a solid mass. Thus it twists around.

2) The sections need to be secured against twisting by all having the same tops, not the sheer line. Meaning if they are cut square on the top and mounted on a board, they can't twist and bring the keel out of centerline.

3) Speaking of the shortcomings of the foam, it makes a God-awful mess of pink dust. Horrendous.

4) The fiberglass layup needs to be multiple layers of very light cloth. Using large strips of heavy cloth inevitably results in folds and creases that are impossible to fully get out when the resin is wet, and will be a pain once it's set.

5) The hull will still need plenty of structure, including at least a couple of frames and longitudinals. Those probably ought to be planned in advance and built into the plug so that they come away with the epoxied hull. (Like the transom, stiffeners in the keel, etc.)

And most of all,

6) If you plan on making a dozen of the exact same hull, and thus can justify really putting a lot of time and effort into the plug, this might be worth it. If you're trying to recreate a fiberglass boat hull (and, thus, some of the angles that wood planks can't be tortured into), I think the way to go is shaping balsa and then glassing that.

So, if I was going to do this project again, I would take the sections that I cut out of plywood and instead make them negative reliefs. Then I'd glue up a block of balsa with a hollow core (maybe glue it up surrounding a block of pine that can then be removed). Then I'd sand the hull to form, using the reliefs to confirm the hull shape. Any mistakes I would correct with some thickened epoxy.

Once I had the hull made out of balsa, I'd router/scoop/dig out as much space inside as I thought consistent with hull integrity, and probably add back in a plywood bulkhead amidships and a plywood transom.

Finally, I'd fiberglass the outside of the hull using really light cloth.

Overall, I'm confident that would produce a much better boat. Probably more expensive, with the blocks of balsa instead of a bunch of cheap foam, but maybe not if you added up all the time spent.

And most of most of all, this project wasn't fun. There are no books written on the magic of working with insulation foam. There is no Foamenboat Magazine. You don't look at a pile of foam scraps and think, "I wonder what I can make with these." Your wife absolutely will not brush pink foam dust off of your shirt when you come inside and tell you that you smell good.

I just downloaded the plans to Presto and with be using it for cathartic purposes.
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