Foam Layout Project

D

Dave Williams

Member
Well, I needed a Summer project, and thought I'd blow some money and attempt a foam layout for no particular reason. It started out with some scaled plans, buying the "way expensive" 2" foam from Home Depot, and cutting out the bottom pieces.
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Next was cutting out the plywood base. I went with 3/8" for stability, but after getting everything together, next time I would go with 1/4" for weight reduction, and I think it would be plenty strong. I Thompson water sealed both sides.
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I then epoxied the plywood to the foam, also used 3 inch drywall screws to keep it from sliding while drying.
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I then painted the inside of the foam and floor before adding the final top piece that comes about 2/3rds the way back to the front. I added aluminum bar stock under the top piece for support (i had it on hand or would have used wood) Then started shaping.
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I shaped the entire boat with a 4 inch grinder with a 60 grit sanding disk, and it took not time at all, but a little messy.
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I then added some rounded corners in the cockpit for aesthetic purposes, and coated the entire outside with epoxy. The forward rounded corners will be shaped down to flow with the boat.
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I need to add some tie downs forward and aft for the anchors somehow, and then I'll paint the entire boat. I know it won't be very tough, but I'm not planning on glassing the top of the boat for weight savings. I need to get it done so it can be tested before the water gets cold. Anyhow, the boat is 8 feet long, 4 feet wide (due to the foam sheets) and the cockpit is 6 feet long and 30 inches wide. Max height from waterline is about 7 1/2". My buddy and I calculated it will take about 280 pounds to sink it down the the first top piece. More pics to come of finished boat.
 
No, but it kind of works out, as a few buddies weigh 225-250, add their gear and it should work for them, I'll just need some ballast when I'm in it.
 
Have always thought about doing something like that for a layout. Can't wait to see the finished boat on the water.
 
Dave

Very clever. I'm impressed with the simplicity. You mentioned you were not going to glass the boat. I take it this type of foam will not absorb water? You might consider using a 2 oz cloth just to give it some durability without adding much weight.

Thanks for sharing your build. I think everyone wants to see the finished product.

Eric
 
The boat looks great, I would glass it with a light weight fiberglass. Just be careful you need epoxy resin so it does not eat up the foam.

Chris D
 
Thanks Guys.......I may add the 2oz cloth at a later date, since it wouldn't be a big deal even after a season, just some sanding, but for now I'm going to try just the epoxy layer without glass, then multiple coats of paint. I'm sure without the glass, I'll have plenty of dings and dents. I'll be interested to see what the final weight is, for now I can pick it up and carry it around with no real problems, the size is just awkward.

Erik, as for the foam, it is what is used for insulating foundations, and states on the foam it is water resistant (to what level, I don't know), but with epoxy and paint, I'm hoping it'll be ok, we'll see.

I'm painting the base coat tonight, so more pics to come!!
 
Extruded polystyrene is fairly water resistant as long as you don't let it sit in water for months on end.

Without a very heavy layer of glass, say 10oz, you will get lots of dings and those sharp corners will be rounded over on day one. My foamer marsh boat has 6oz and is really torn up.

My one concern about the wings out past the body box is that without cloth enforcement on both sides of that joint it will pull apart with little effort. This type of foam has very little shear strength and even if your face to face joint between layers is built with quality glue/epoxy the foam itself will tear with little effort. Since EXP is not a structural foam you need to build structural support into the design. The EXP just ends up being a form to build your FG system over. You have cloth on just one side of that wing and once loaded to where the wing us holding the weight of the hunters it will fold up at the corner.

Your cover piece will be split in two the first time a hunter sets his gun down roughly or tries to sit up using it as a brace. If the hunter puts any weight on that cover while climbing in it will snap in two. That piece will need to be glassed with heavy cloth on both sides to last more than a few minutes of use.

When building my foamer I experimented with a couple of different weights of cloth and decided I could risk the project to 6oz knowing that it would not last for long unless I handled the boat very carefully.
 
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Thanks for the input Ray, very good info. Again this is my first attempt at foam, so very experimental on my part. I am trying to get a better understanding of your concern with the wings and how they are supported. I glassed the entire bottom over the box and out across the bottom of the wings, then filleted the joint with flour epoxy. Water pressure will be trying to push the wings up, and therefore it would have to tear the fiberglass for the force to even see the joint where the layers were put together. Maybe I'm missing something, but like I said, that is why I want to get it done soon and try it before the water gets cold, lol. I do undertsand the fragility of the top piece, but it is supported underneath, and again, I may have to go back and glass the top, but that will be fairly easy, just some sanding. Just a note....before I started shaping the top piece and put the supports underneath, I actually sat on the front edge and middle of the foam with all of my weight (160lbs), and it bowed, but didn't break.
 
I am trying to get a better understanding of your concern with the wings and how they are supported. I glassed the entire bottom over the box and out across the bottom of the wings, then filleted the joint with flour epoxy. Water pressure will be trying to push the wings up, and therefore it would have to tear the fiberglass for the force to even see the joint where the layers were put together.
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Without a top strand of fiberglass the EXP foam will crush and shear with very little force. Once crushed the foam will no longer provide support for the fiberglass and it will start flexing. The EXP has a crush rating of around 6psi or less meaning that it has no real strength. You have to think of any composite panel construction as a something like an "I" beam. If you take one of the flat strands away the I beam fails. Your boat has a lot of surface area that may be in contact with the water depending on the load and that may reduce the forces effecting the boat by spreading them out.
 
I had thought of doing that but was conserned about strenth. I was thinking about doing the burlaping to it just like foam decoys. I don't know if that would work or not.
 
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