Adding foam floor to small boat

[DocTide]

So I am getting a 12ft Skiff pretty soon. This boat does not come with a foam floor, only positive foam in the gunnels. I like to mount things to the floor, and plan on adding a small center console so I would like to add a thin layer of foam and fiberglass a deck on the floor. I understand that adding to the floor of a small boat might increase "tippyness" but that really doesn't concern me as I stand and cast from a kayak. I am not looking to add a great deal, just something to give some more positive flotation and provide some structure to mount a center console. Also- since I frequently fish around oyster bars, and dock up on sandbars I don't want anything to puncture the bottom and not have some kind of extra protection. I know this might be an odd request- but is something like this a good/bad idea?

I was thinking of buying the pink/green insulation closed cell foam sheets from home depot, about 1/2 to 3/4 thick, stacking two of them, and simply fiberglassing them to the floor of the boat. Leaving the drain canal and possibly the sides for cable routing purposes. I was a little unsure if I should put a hard material flooring on top of the foam and wanted some advise.

For reference- here are pics of the ideas I was thinking, starting first with the boat itself:

Let me know your thoughts on whether this is a dumb idea, or if it is do-able. Having had this boat, and boating around much larger boats, I think it is useful to have deck flotation as I have swallowed plenty of wakes over the bow, this time around I want more flotation, and 1 electric/ 1 manual bilge pumps set up. Let me know please.

 

[Woodonglass]

Depending on how deep the sides of your boat are I don't see how this could hurt. I'd prolly use construction adhesive to adhere the sheets to the hull and to them selves and then do an over lay with 1/8" luan plywood and then a couple of layers of 1708 glass. I think it's a good plan. Wha'ts the beam width?

 

[gm280]

DocTide What you're asking actually happens a lot on these forums. So yes, you can install a floor with floatation underneath. However, understand the lower you make your floor the better stability it will provide. So I would install a floor and keep it basically straight across with the side flat areas and then trim it to fit in the front. And since this is a fiberglass hull, I would use 1/2" exterior plywood covered with polyester and CSM (Chopped Strand Mat) to waterproof it before installation. I suggest reading a few boat projects to get an idea how to proceed. Some great reading on here... JMHO!

 

[DocTide]

No Title

Ok great, I planned to keep it as low as possible, perhaps with that 1/2 foam sheets (maybe 2 for a total of 1in height). I want to keep the center line for drainage, the sides of the boat are about 24" tall in the back of the boat, the front has about 18". IS this image what you were referring to gm280: uploaded below. would the two "stringers" even be necessary?

@woodonglass: the boat has a beam around 52in. I was considering either plywood, or divinycell for the rigid structure on the deck.

Is the foam sheets I mentioned from HD a good idea for this project? Glue two together, glue them to the bottom and shave to create a flat surface, then lay wood and fiberglass the bottom?

Thanks for quick replies, I have been searching all morning and am pretty excited.

 

[Woodonglass]

Yup, the Pink or Blue Slab foam works Great. You can lay it flat but you might want to check this out and consider doing it like this member did...http://forums.iboats.com/forum/boat...r/9265964-save-the-manatee/page23#post9971857 It'll give you more strength. It's a bit more of a hassle but a better install IMHO. but since it's only 2" deep it might be easier to do it on the flat. 1/2" Plywood tabbed to the sides of the hull will give you a very solid deck but... will add a lot more weight. How big of a motor will you be using? Since you're overlaying ontop of solid foam you won't have much "Give to the wood and the glass with stiffen it up quite a bit. 1/4" would prolly be plenty but that's up to you. My original thinking about 1/8" is prolly not enuf!!!

 

[Woodonglass]

Deleted

 

[DocTide]

No Title

I plan on using a 15hp 2stroke (about 85lbs). In the future though, I wanted to upgrade to either a 15hp 4stroke or 9.9hp (120lbs). I read somewhere that 2 sheets of the foam can add 650lbs of positive flotation. Now I know this will probably increase my draft, but the boat weights about 230lbs stock and it floats in 3-4in of water. The idea for the foam floor is just to add some flotation for piece of mind.

I would like to keep it as lightweight as possible, and since it is only a 2 person capacity boat I feel like there wont be much stress on the floors weight wise. Would a thin layer of divinycell work as an overlay? The 1/8th plywood was my original plan but have no problem trying to spend a little extra to make it lighter? If I did go with plywood how much weight do you think this might add?

For simplicity, I would like to just lay it flat. The boat actually is flat in the stern which would be easier. Attached is a image of the idea. Does this make sense without using the wooden strips as stringers, just fiberglassing the wood on top of the foam to the sides of the boat? I can add a stiffer product or "stringer" to help the wood rest on, maybe a PVC pipe for running wires would help? Just thinking out loud.

 

[Woodonglass]

If you do as shown in the pic, and coat the Luan Plywood with 3-4 coats of epoxy my Guess-ti-mate of added weight to your boat would be aprox. 25 lbs. It might flex just a bit when walking on it but that's the beauty of Epoxy, It remains flexible when fully cured. If you want to remove the flex you could go to 1/2" ply and that would add about 60 additional pounds including the foam

 

[DocTide]

Is luan plywood the wood of choice for this type of work? Any input on epoxy brand/type aswell as fiberglass brand/type? I really appreciate you taking the time to help me out by the way!

 

[Woodonglass]

Any ext. grade plywood will suffice. It all uses 100% waterproof glue in the laminations. Some use better quality woods for their plys in the laminations. Fewer voids means better quality. U S C O M P O S I T E S . C O M is a good source for epoxy. The Medium 635 is what most people use.

 

[sphelps]

Just remember polyester resin will melt the ridged foam .. Not sure about epoxy ..

 

[DocTide]

Interesting. I might have to try with each and see what happens, the cheapo bondo stuff at HD is a poly yes?

My material list would consist of the following:

Medium 635 Epoxy (after test to make sure it doesnt melt the foam) - or - Poly

Luan Wood 1/8 thickness

Fiberglass: 6oz plain weave glass for the floor overlay on the Luan wood. +8oz for attaching to gunnels

MY questions now are: How many layers should I do overlay on the Luan? Also, I planned to do a gelcoat, but read it might not stick well to epoxy, what is a good "paint or roll on" product I can use to help keep the epoxy safe from UV?

Thanks

 

[Woodonglass]

Epoxy won't eat the foam. 2 layers of the 6oz should be plenty. Gelcoat does not adhere well to epoxy but Oil Based paint will. Rustoleum Pro with the added Hardener will yield a high gloss very durable finish..Paint Your Boat with Tractor Paint...Say What!!!

 

[DocTide]

Thank you! So the epoxy when dried/cured will need to be primed for paint? The Rustoleum Pro with hardener is an enamel paint?

EDIT: I actually planned to add hydroturf deck for some color and grip on my casting decks, could I theoretically just put this all along the floor? Would this be sufficient for covering the epoxy deck?

 

[Woodonglass]

Yup, As long as it's not exposed to direct sunlight you're good to go.

 

[DocTide]

I might be over thinking this, and I apologize for the silly questions.

Is there a way to just lay a fiberglass/resin over the top of a product instead of the wood/epoxy? I have been reading, and know that epoxy is a great material for decks, in particular wood laminating. However, I personally like the idea of poly for the cost and the easier finishing with gelcoat or awlgrip. I have looked into Nida Core, which I assume could replace the home depot foam and the wood. It apparently provides a some buoyancy and strength tot he floor and then poly ontop of that. Or perhaps use the Nida-Core instead of the Luan. Do you know anything about this product or am I thinking too much?

 

[Woodonglass]

Nida Core will provide minimal buoyancy if any at all!!! Awlgrip can be applied quite readily over just about any surface. Nidacore is a good product but quite pricey. A 3/8" 4x8' sheet is appox. $250 + shipping. It's basically honeycomb fiberglass sheeting. Based on what you are trying to accomplish I don't think it's what you are thinking it is. IMHO, you are WAY overthinking this but...It's your boat/project and you're free to do as you see fit. It could be used as a substitute for the plywood.

 

[DocTide]

Lol. Okay thanks. I just keep reading, it seems like the plywood is what I want, but the painting epoxy seems a little more extensive than what I originally planned. So I can just paint the non skid awlgrip over the epoxy? No primer needed? I have read about blushing as well and am pretty new to these terms.

 

[Woodonglass]

If the humidity is high or the temps are low then epoxy can develop an Amine Blush during cure. All that's required to remove this blush is a quick washing with hot soapy water and a scrub brush. Do this BEFORE you do any sanding to avoid driving the waxy blush down into the pores of the epoxy. Normally if you use a good quality epoxy and the humidity isn't bad this blush won't be a problem. You can paint with good ole' Rustoleum Oil Based and sprinkle some sand on it and get Excellent results too!!! LOTS of the members have used it with GREAT results, including me. Or Roll on some gelcoat using polyresin and then use plain ole screen door screen material to get a textured look like this member did...http://forums.iboats.com/forum/boat-...ld#post9988743 You can paint the foam first to keep the poly resin from "Eating" it or cover it with Clear Packing tape. But if you're putting plywood down over it then you don't have to worry about the resin Eating it cuz you won't be coating it with resin, only the plywood and then you can coat the plywood with gelcoat. But if you use gelcoat you're gunna want it to be stiff enuf not to flex cuz gelcoat will crack if it flexes to much.

 

[DocTide]

Thanks, humididty is a HUGE concern for me here in south Florida. I am sure I am going to run into this blush then. Do you just spray/roll apply the Oil based paint without a primer?

Assuming that I will get it, Wash with warm soapy water - Sand epoxy - (Primer?) - Paint

Sounds right?