cracker39

I finally found some blue foam at a Lowes, but only in 1/2" thick sheets. I'll have to cut and laminate 5-6 pieces to make my airboat. That's good in one way as I can cut out the electronics and engine mount areas in some pieces before laminating and not have to dig out those areas as I would from a solid block of foam. I also plan on laminating in some pieces of 1/4" plywood to secure the engine mounts.

I've searched posts for info on glueing foam. I don't want to use gorilla glue as it expands a lot. I read posts where builders used white glue or 3M77 spray glue. Are either of these good for boat building. I have some Titebond II on hand that is highly water resistant. I also plan on painting the foam boat with latex paint when it'd finished. That should help waperproof the seams as well.

Any other suggestions?

Dan S

we use Epoxy (not Lepage) I use 30 Minutes Epoxy.

Dan.

thevirginian

cracker39'
Don't use Titebond or any of the "white" glues. Because the foam is a closed cell foam there will be no air to get to the glue joint, thus a thourogh and fast curing is prefented, due to the lack of oxygen. You need a glue that does not attack foam and cures chemically. 30 min epoxy is good for small glue joint only not good for large areas. There is a foam "cement" made by Henkel (Germany) called UHU-Styropor or close to that. I used it in it works great. Works like "Contact Cement" I bought it in Europe on my last trip over there. But search the web, you might find it here in the States as well.

Dan S

My appologies,

I tought he was building a wood over foam.

Dan.

cracker39

I am testing some glues now before I read the last posts. I glued some 2" x 3" pieces together. One pair with Titebond II and another pair with some spray contact adhesive I had around...It's 3M 77. It doesn't say it's meant for foam, but it didn't melt the foam either. I'll give these until tomorrow morning to set up and them immerse them in water for several hours to see if they come apart or not. It the glue holds up, I'll decide which to use. I know epoxy would work, so it wasn't in the test. Bassed on the comment above, I suppose the 3M spray contact cement would be better.

This is an all foam boat made by laminating the 1/2" sheets together, except for a piece of plywood that will be laminated in between layers 4 and 5 (from the bottom up) to secure the engine mount. The plywood is cut in a U shape with two narrow pieces extending forward to the front of the electronics compartment just to provide strength and rigidity. The hull thickness is 3" except for the 5" x 9" or 10" at the rear, where it will be only 2" thick as shown below. The overall dimensions are now 22"l by 12"w. I'm also considering painting it with latex enamel paint for more protection and to give the hull some gloss to reduce water drag.

Umi_Ryuzuki

I use a lot of that super77, but to laminate my
SDM tug hull pieces, I used 30 minute epoxy.

I fiberglassed the hull, using epoxy resin, for a nice finish.

cracker39

Is your hull coated with thinned 30 minute epoxy? if not, where do you get the epoxy resin. All I have on hand id Bondo brand fiberglass resin I use on wood and it eats up foam.

Umi_Ryuzuki

Should be someplace local that retails West systems...
http://westsystem.com/

or maybe place an online order for epoxy resin.
http://www.tapplastics.com/

cracker39

We have a West Marine store about 6 miles from me. I'll check it out. Thanks.

Ron Olson

My Feedback: (1)

We use 3M 77 at work and somehow a can of it followed me home. I think that it would work fine for laminating sheets of foam. Some other stuff that we use at the shop is a double-sided tape, really thin and sticky that I've used to bond lite ply to foam. For extra measure I CA around the joints. It's kind of like carpet tape but better.

thevirginian

cracker;
I bought epoxy plus all my fiberglass stuff from www.raka.com in FL. Great prices and fast deliveries. Check their website. Don't use polyester resins like Bondo. Bad idea.

cracker39

Thanks, Virginian. I'm in Florida...I'll see where they're located.

My glue test results. Both the titebond and 3M 77 pieces were in water for over an hour. Neither showed any signs of coming unglued. The titebond piece actually looked better than the 3M 77 piece as the edges were glue-filled. I could pull the edges of the 3M 77 piece slightly apart. I'm going with the Titebond II. I'll cover the foam with paint of epoxy to seal it.

I got started cutting and glueing my foam pieces together. This blue foam really sands beautifully. I just ordered a radio set, so I'll have to wait for that to arrive so I can set up the parts to balance the boat and see where to install the engine. I decided on making it pull rather than push...less complications.

Already, the plans have evolved. The hull has gotten a half inch thinner, the engine turned around, and more shaping of angles to curves. I'm undecided about putting a skeg on the bottom until I see how it performs. A true airboat is flat bottomed so it will slite...that's what makes them fun. It will be a week or so until it gets asembled and then I'll post a build thread.

cracker39

I found that I have the solution for the finish on my boat. I have a couple of quart size "bar top" two-part epoxy kits that I bought well over ten years ago. I'm amazed that it still works as the shelf life for this stuff is under a year I believe. It does set up slowly, over a day to set and a couple of days to get hard enough to handle, but it does set up and that's what's important. I just covered the cabin/electronics cover with it as a final test. I'm con sidering laminating 3/32" balsa sheet to the bottom first though.


The bar top epoxy is working out OK. I put a 2nd coat on the cabin/electronics cover and it's pretty tough and takes spray enamel paint very well. The only problem is that it's not very thick and runs easily. It's meant to pour on, spresd and let it run down the sides and drip off. But that leaves drops of epoxy that is easily sanded off wood, but not off of foam. So, I have to trush sides and try to keep runs from happening. I did the bottom and sides and only a little formed near the top from runs. After I coat the top and top part of the sides, I may be able to sand down the raised "bubbles".

As I'm working on it during the 4th of July weekend, I decided on red, white and blue for a color scheme.