BBC's Flotation Foam.... Which one can you walk on...?

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Capt UB
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BBC's Flotation Foam.... Which one can you walk on...?

Post by Capt UB » Mon Nov 13, 2017 7:21 am

FS14

Installing a floor/sole in my FS14.

Need to go as lite as possible on the marine plywood 1/4" or 3/8" and foam the space under it.

Which one of BBC's foams is dense and strong enough to work or should I use something else?


I'm always lost when building a boat, it's when the boat is in the water, I know my way.

1970? 13' Canvas on frame canoe
2017 Bateau FS14, starting build Oct 2017.
2017 Bateau NC16, starting soon.

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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by Jaysen » Mon Nov 13, 2017 7:31 am

On my Lil Bit, I used the standard stuff they suggest for the v12 under the rear seat. That is covered with 3/8. You can't deflect the seat. At all. And I'm not small. I don't have my plans on hand, but if I recall, the seat is 34x20something. Granted the seat didn't deflect much without the foam, but now it's like walking on concrete.

That's the standard closed cell stuff they list with the pre-sized kits.

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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by Capt UB » Mon Nov 13, 2017 9:06 am

Jaysen wrote:
Mon Nov 13, 2017 7:31 am
On my Lil Bit, I used the standard stuff they suggest for the v12 under the rear seat. That is covered with 3/8. You can't deflect the seat. At all. And I'm not small. I don't have my plans on hand, but if I recall, the seat is 34x20something. Granted the seat didn't deflect much without the foam, but now it's like walking on concrete.

That's the standard closed cell stuff they list with the pre-sized kits.
Thanks.

The sole will have more frames under it, leftover 3/8 Okoume. Do you think a floor with that and foam will be OK with 1/4 (6mm) Meranti BS6566 on top epoxy down?
I'm always lost when building a boat, it's when the boat is in the water, I know my way.

1970? 13' Canvas on frame canoe
2017 Bateau FS14, starting build Oct 2017.
2017 Bateau NC16, starting soon.

Jaysen
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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by Jaysen » Mon Nov 13, 2017 9:38 am

First, I'm an idiot. Just ask my wife. So I wouldn't take anything I suggest without thinking about it a bit...

I don't see why not. The one thing though is that the foam will break down from the stress. Not right away, but over time. Even though it seems really stiff, the cell walls (closed cell) with flex. Eventually they will crack and no longer be closed. Once they are not closed then they will lose the advantage of internal pressure which will make them bend more (as well as allow water into the cell). This will compound over time to full failure.

That said, 1/4" over the foam isn't the worst thing you could do. ;)

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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by cape man » Mon Nov 13, 2017 4:10 pm

I would go with 3/8" on the deck. 1/4" is 2 plies less than the 3/8".

As to the foam, the standard sold here is a 2 lb foam, not structural, but for flotation. You need to go to a 6 lb or even better an 8 lb foam before it can stand a load.
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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by Aripeka Angler » Tue Nov 14, 2017 3:39 pm

My fs18 has 2 pound foam flushed with the top of the deck framing.
The deck is 1/4" plywood with 6 ounce woven on top. The ply rests on the framing and the foam.
I feels pretty damn solid when you stand on it. Like a rock...
Richard
Completed boats...XF20 "Red Alert", Aripeka Angler's Strip Canoe
Currently building...PY12 Kayak and FS18 "Bare Bones"
If there is magic on this planet, it is contained in water. - Loren Eiseley

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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by cape man » Tue Nov 14, 2017 4:39 pm

Well there you go... learn something every day.
The world always seems brighter when you've just made something that wasn't there before - Neil Gaiman

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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by Capt UB » Wed Nov 22, 2017 7:41 pm

Need a little help.

Two part flotation foam (50:50), 2 gals. (A&B) makes 8 cubic feet.

I need to pour 10 pockets size

3" x 16" x 16" = 768 cubic inches

1728 cubic inches = 1 cubic feet

1 cubic feet is 1/4 gal. = 32 oz.

1728 cubic inches = 32 oz.

864 cubic inches = 16 oz.

So, less then 8 oz. of A and B each.

Should fill a 3" x 16" x 16" pocket.

Does that sound right?
I'm always lost when building a boat, it's when the boat is in the water, I know my way.

1970? 13' Canvas on frame canoe
2017 Bateau FS14, starting build Oct 2017.
2017 Bateau NC16, starting soon.

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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by pee wee » Thu Nov 23, 2017 9:35 am

I didn't check your math, but the way the foam works often doesn't follow the math, either. The warmer it is the more it expands, and the bigger the volume you pour the better. Lots of builders end up having to order more foam because they didn't get the expansion they calculated; it's not that their calculations were necessarily incorrect, but that the foam can be so variable in the way it behaves.
If you are thinking of walking on a foam-filled compartment, then practically speaking you will need to overfill that compartment and cut off the "muffin top" to get a perfectly flush surface. That means your cubic inch calculations are a guideline but not a bottom line. A 3" deep compartment will fill easily, but it won't produce the same expanding efforts that a 12" deep compartment would. How much foam will you need? More than your volume to fill. Heat the compartments before pouring, if you can. It's chilly now, and I believe you're working in a carport (?), so you won't get the maximum. Order extra, or be prepared to order more.
Hank

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Re: BBC's Flotation Foam.... Which one can you walk on...?

Post by seaslug » Thu Nov 23, 2017 10:50 am

My FS18 also has the same foam as Richards with 1/4" ply and 6oz. cloth, and is as solid as walking on a sidewalk. I was careful when cutting off the "muffin tops" to not cut down too low, using a combination of a long board and long Stanley Surform tool for sanding the foam flush with the floor frames. Load that sucker up with thickened epoxy, weigh it down really good, and you'll have a floor more solid than any production boat sold.....This may be a stupid question, but: Since a lot of builders are concerned with added weight, how much weight does the foam loose, if any, to evaporation / out gassing, or whatever is the proper term, as it expands and cures? Mike

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