How much pour foam is enough?

[Jim Walker]

I want to use total boat 2-part pour foam in my 1/8 scale. Does anyone have a proven way to figure how much to install? I want to install before I put my decks on.

 

[FloridaScaleBoater]

I want to use total boat 2-part pour foam in my 1/8 scale. Does anyone have a proven way to figure how much to install? I want to install before I put my decks on.

All I can say is BE VERY CAREFUL doing this!
Heat & humidity will make this stuff "kick" again.
Pour foam has split many a deck seams on mono hulls.
I have done it on wood hull sport boat sponsons. What I do is let it kick off. Sans the access to shape desired.... let it set, uncovered/unsealed for a couple of weeks, re-sand to shape. Seal with epoxy while laying your decks on.

 

[Don Ferrette]

I want to use total boat 2-part pour foam in my 1/8 scale. Does anyone have a proven way to figure how much to install? I want to install before I put my decks on.

In a word- DON'T. Two part pour foam is next to impossible to control well in a confined space, will absorb water and oil and is a nightmare to remove after doing so. I have also seen more than a few boats split at seam lines and/or pop a deck off when the foam continued to expand months later. Do yourself a favor, stop by your local Dollar Store and buy some pool noodles, cut them up and stuff as many as you can fit without forcing.

 

[Tom Foley]

Many years ago, 1980, I used the spray foam in my Dragn Fly 40 with decks off . I let it expand and then rough sawed raised foam
I then block sanded it flat and glued the deck on . It lasted for many years without splitting. It did add weight though

 

[RaceMechaniX]

You mentioned you want to do this before putting the top deck on so its not as dangerous compared to pouring into a sealed compartment.
I use the small dixie cups or epoxy mixing cups and fill about 2/3's full leaving some room on the top to stir and allowing the mix to aerate. Find the right mixture quantity to allow the allow the foam to mushroom out of the compartment you are filling. Let it cure for at least a day then use a loose hack saw blade to rough trim the foam before going over with a coarse sanding block to sand flush.

The 2-part foam is generally stable if you mix correctly and let it cure for at least a day. The spray in foam is junk.

Alternative is to use pool noodles or best Pink insulation foam from the box stores cut to fit.

 

[Don Ferrette]

Sounds like this is a wood build? (missed that first time) If so go with the pink foam cut to fit like Tyler suggested. Did all my wood builds that way.

 

[Mike Hughes]

Sounds like this is a wood build? (missed that first time) If so go with the pink foam cut to fit like Tyler suggested. Did all my wood builds that way.

Like the boys said. Sheet foam is the way to go. Cut it to fit in between frames and glued to bottom deck.
Easy to do and will never have an issue with it.
Mike

 

[Jim Walker]

Thanks everyone for all your input! Most helpful.

 

[john v]

Years ago I had a aeromarine conquest that I spray foamed the front section, well it absorbed water and threw the cg off and took me weeks to dig the foam back out.
Dollar store pool noodles is the only thing I use now, yeah what everyone else said!

 

[Samuel Hagan JR]

If you do decide to use it make sure you get the lightest density possible. I think 2lb is all I could find. I’ve used it in several boats with no issues. Just make sure you cure it in heat for a couple days.

 

[scottmeyers]

Pour foam is awesome when used correctly. It's in all my wood boat builds, and total boat 2lb density is the best I've found. The "kick" others are referring to is a chemical reaction between the two parts, and once mixed and done reacting, it will not move again. Be aware that it does react and expand very quickly, and will definitely blow the boat apart if you pour it into a confined space, so use it before you install the decks and you'll be fine. Additionally, it gets quite warm during the reaction and can deform thin fiberglass, so I don't recommend it for a glass boat. The biggest benefit is the added strength it provides. The stuff is crazy hard and will greatly improve your wood boat's "bumpability" (hey, racing is rough!). But yet it is very easy to carve or grind away whenever repairs are required. Second benefit is it doesn't rattle around inside the boat like foam chunks do. A mild embarrassment. Need another? It doesn't react when in contact with fuels. Blue foam chunks turn into fizzly piles of goo in nitro. Ok last thing... you need very little. Don't even think about filling the entire area as it's completely unnecessary. Plus it is made up of bubbles, right? And what do bubbles do when they get hot? They expand! This is where some make the mistake... It's not "kicking" again, it's just growing slightly with heat. Very slightly, but possibly enough to do damage if you've filled the sponson with it. So again, it's totally unnecessary to fill the whole boat with the stuff. Just tip the hull to one side and pour a bit along the sponson chine and other interior structures. In about 10 minutes it'll be set and you can tip it the other way to do the other side and you're done. Here's a video I made that may help,

 

[Flemming Breil]

The dude making the videos is hilarious yet educational! Lol

 

[Mark Anderson]

I have had pour foam pull back after several months and pull the surfaces it bonded to. I used to used a small amout in the boats that I sold. Stopped and switched to foam sheet. never any issues.

 

[Lay26]

Well i wouldnt say never an issue....you would'nt have issues in composite hulls
with the sheet foam....However the wood hulls........i built a backlash a few years (like 10yrs back) with that pink foam....and lesson learned.... found i had water in an area its not supposed to be...upon opening up the boat....long story short that foam absorbed the water and start rottening the hull from the inside....fast forward a few years (finished the new one 2yrs ago)...i built another backlash and put the foam in just the winglets of the backlash....i sealed off these two areas and not only is that enough...i dont have to deal with the weight gain and the boat is light and gets drainded out completely if any water gets past the drain holes(that only happens if i forgot to tape them)
the only pool noodle i use is in the rear compartment where i can remove them and squeeze out the water after running....going forward im not putting much of any foam pool noodles too in my wood boats....i'm only using very little in areas that can be sealed off..

 

[Tom Foley]

You mentioned you want to do this before putting the top deck on so its not as dangerous compared to pouring into a sealed compartment.
I use the small dixie cups or epoxy mixing cups and fill about 2/3's full leaving some room on the top to stir and allowing the mix to aerate. Find the right mixture quantity to allow the allow the foam to mushroom out of the compartment you are filling. Let it cure for at least a day then use a loose hack saw blade to rough trim the foam before going over with a coarse sanding block to sand flush.

The 2-part foam is generally stable if you mix correctly and let it cure for at least a day. The spray in foam is junk.

Alternative is to use pool noodles or best Pink insulation foam from the box stores cut to fit.

It was my first boat build ever, didn't even know what 2 part foam was lol . 1980 .

 

[Jim Walker]

Interesting info from the products data sheets. Pool noodle and pour foam have the same water absorption at 0 to 0.6 lbs/sqft.

Pink styrofoam board is 0.1% by volume max. I don’t know how to convert this to compare to the others to make an apples to apples comparison. They all take on some amount of water.

 

[scottmeyers]

Interesting info from the products data sheets. Pool noodle and pour foam have the same water absorption at 0 to 0.6 lbs/sqft.

Pink styrofoam board is 0.1% by volume max. I don’t know how to convert this to compare to the others to make an apples to apples comparison. They all take on some amount of water.

Good work Jim.
Here's the real-world-of-RC thing with "absorbing" water...
EVERYTHING absorbs water. This is why water is called the Universal Solvent. Given enough time and opportunity it'll wreck anything. We've all heard about foam in full-size boats getting water soaked, but this is due to cracks in ancient hulls allowing standing water inside the halves for decades. Most of us don't leave our boats on the bottom of a lake for years.
A brief list of pros and cons of the four methods listed in this thread so far (yup there's four...)

# We'll start with blue/pink foam;
* Easy. Cut a chunk and drop it in somewhere.
* Effective. I tested pour foam vs pool noodles vs blue/pink foam and found that by weight the insulation foam is the most buoyant. Slight, but best.
* Dries fairly quickly. The tight outer pores are very helpful in this regard. Does trap some water, but not awful.
* Terrifying. Let it contact nitro and you'll see what I mean. Fizzles and pops and melts down to a glob. Rapidly! Pretty sure I shaved a couple years off my life when I did the testing and couldn't get away quickly enough.
* Embarrassing. Those clunks when moving the hull hurt me deeply. To each their own.

# Pool noodles.
* Easy. Cut it and drop it in.
* Squeezy (technical term, try to keep up). Handy for shoving into a tight spot.
* Non-embarrasing (noise-wise). See above.
* Effective. Comes in at number two in the buoyancy test.
* Wet, wet, wet. Large, open outer pores hold a LOT of water which, as mentioned by someone earlier, will hold water against your wood boat for weeks. Or at least until all that water soaks into the wood. Remember the Universal Solvent thing? Mmm hmm.
* Embarrassing. Wait, I thought you said... But c'mon man... They're pool noodles! If I have to explain it to you, well, moving on.

# Pour foam (and we ain't talking about spray foam in a can, don't be ridiculous).
* Super fun. There's just something glorious about watching it do its thing.
* Very easy. Pour it in anywhere.
* Pretty effective. Yup it's the heaviest vs buoyant of them all, but the difference is very slight.
* Dry. Here and there you'll get an open bubble on the outer surface, but any moisture stands right on the surface and is gone very quickly. Happy wood.
* Adds strength. Don't poo-poo this until you try it for yourself. Contrary to erroneous opinion, it'll hold your seams together, not separate them (see spray foam comment).
* Expensive. Sure, but most "best" things are.
* Non-embarrassing.
* Grows dramatically during cure and will not be denied its space. In other words, don't be a dummy and pour it into a tight spot where it cannot expand without causing rapid unintentional disassembly.
* Gets very warm during cure. Don't use on very thin fiberglass, it'll wiggle it.

# Open space. Yup, somebody alluded to it earlier, and I mention it in the video.
* Easy. Do nothing.
* The true buoyancy winner. Best by weight!
* Dry. Duh.
* Zero embarrassment. Unless the boat sinks. See the following;
* Requires you to build a good boat. Good seams, good sealing, a few separate chambers

So there you go. I'm sure I missed a few of your favorites, but that about sums it up. You decide!

 

[Stephan Peterson]

 

[Stephan Peterson]

1/8 corcell encapsulated between carbon and layer of 2oz glass. Then vacuumed.

 

[Hydro Junkie]

1/8 corcell encapsulated between carbon and layer of 2oz glass. Then vacuumed.

Is that the paper based honeycomb? If so, Stephan is basically talking about building panels for aircraft since that's how it's done, less the CF