Aluminum floor thickness reccomendations

[Shoedawg]

Be careful foaming. High expansion rate with that foam. Far as a drain channel goes...you may want to use a pipe or conduit to act as a mold cavity to run to your drain plug. ANYWHERE you don't want foam, use lots of car wax on that surface and the foam won't stick.

Don't take this to the bank, but I think I have seen where a drop tarp, like for painting, was used to line the inside. Supposedly wax on top of it works well.

Good to know- i'll look into it. Thank you!

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I purchased some 2lb pour foam from US Composites a few months ago back (have yet to get into the pouring stage). For draining issues, underneath your floor, you can try using some aluminum flashing. They are sold in rolls of various feet and widths and very affordable.

Its pretty easy to bend, shape and cut too. Basically you would shape a conduit to run along the bottom of your boat, creating a drainage channel for water/clean up. See my second grade drawing below to understand what mean:


To keep the foam level with your floor, I would first add some plastic trash bags to the bottom of your floor first (tape it). From there, pour the foam over your choice of drainage/bottom side of boat (in my case, the alum. flashing) and QUICKLY place your floor over the foam (plastic bags down) before it starts to expand. Get some weight on the top of the floor and keep even pressure on it. Let the foam do its work, while watching for any rises/shift it may produce in the floor while it is expanding.

After the foam has cured/stopped expanding, then you can remove your floor and take off the plastic trash bags. The bags (per US Composites) shouldn't stick to the foam, thus given you a pretty even foam platform that will now support your floor and you have drainage as well.

You can then, mount your floor. I wouldn't use PVC piping for draining. The diameters (IMO) of most large piping just don't do that good of a job. Plus sticks, leaves and other crap can get stuck in them, impeding good drainage.

I am in the same boat (haha) as you are with floor thickness. I am leaning towards .090 myself. It seems most guys on this forum use that size for their floors.

 

[richg99]

I filled the two inch cavity between my "joists" with loose cut blue foam sheets. It added flotation and also firmed up the aluminum top sheet.

I cut the pieces of foam skinnier than the openings. My thought was to let water freely flow in and out. I didn't want to trap water.

I did add a vinyl covered piece in 1/4 inch ext. Plywood on top.

richg99

 

[daschmetterling]

Thanks everyone for your comments and suggestions (and even aerospace engineer calculations!).
Originally I was trying to decide between 0.90 and 0.125 aluminum sheet- and it seems like 0.090 is the way to go there. But now we are leaning toward using aluminum diamond plate, and this comes in 0.100 or 0.080 thinknesses! More to decide! Weight is pretty negligible between the two, about 16 lbs difference in a 60" x120" sheet. But 0.01 is about $50 more expensive than 0.080. In the whole scheme of things, kind of a wash. The reason we are thinking of diamond floor plate is the traction and maintenance idea. We won't need to add traction nor paint, and we figure the aluminum will get dull and dirty pretty quickly. For work we use unpainted aluminum boats all the time, so it seems normal to us!
We can always paint it it we want or need. We are trying to build a simple, cheap, durable low maintenance fishing boat, because we will use it hard, and probably not maintain it as well as we should!

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[daschmetterling]

After a lot of debate, we ended up going with rigid insulation for flotation and 0.100 aluminum floor plate.

View attachment 1
View attachment 2
View attachment 3
After riveting the floor every 8", it is really solid. If you stand between the joints it does flex, but not too the point of feeling spongy. I am glad we went with the 0.100.
You can read more details about the floor and the boat on my build thread.
Thanks everyone for your help and suggestions!

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[richg99]

Looks good. I put the same blue foam below decks on mine.


richg99

 

[daschmetterling]

Looks good. I put the same blue foam below decks on mine.


richg99

Thank you! We ended up getting a lot of foam in there, more than we calculated we needed to float the weight of the boat and motor. Hopefully, we will never need it!

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[surfman]

After a lot of debate, we ended up going with rigid insulation for flotation and 0.100 aluminum floor plate.

View attachment 1
View attachment 2
View attachment 3
After riveting the floor every 8", it is really solid. If you stand between the joints it does flex, but not too the point of feeling spongy. I am glad we went with the 0.100.
You can read more details about the floor and the boat on my build thread.
Thanks everyone for your help and suggestions!

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You will be able to float a tank with all that foam.

 

[richg99]

Unless/Until the boat fills up with water, that foam isn't doing a thing except adding some stiffness to the deck.

BUT...when you do take a big wave over the side, you will be very happy that you put it in. Ha Ha regards, richg99

 

[daschmetterling]

Here are some more pictures of the flooring installed, 0.100 aluminum riveted every 8". I am glad we went with 0.100, I don’t think I would go less than 0.090. View attachment 1View attachment 2

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