Best way to "fasten" board foam to aluminum?

[Landof9000lakes]

I want to provide a channel down the center of my boat using vertically placed foam boards. Then use pour foam to fill in the outsides.

What is the best way to fasten and seal the foam board to the bottom of the boat? I'll try and find/post a picture of what I had in mind since this kind of seems clear as mud.

 

[Landof9000lakes]

Re: Best way to "fasten" board foam to aluminum?



Now imagine two vertical foam boards between each stringer forming a 3-6" channel in the center. Then I want to fill the outsides with pour foam.

I'm wondering if I should just be looking at 5200 or equivalents? My two biggest concerns are that I want water that may be in the center channel to stay out of the foam, and the foam to stay in it's place when I pour it.



BTW that picture should look familiar. Hope Jas doesn't mind.

 

[Pmccraney]

Re: Best way to "fasten" board foam to aluminum?

The pour-in foam has a lot of pressure when it expands (that's why folks cut relief holes when they pour it)... I'm not an expert in this area, but the expanding pressure may knock over (break) your foam board if that's your only retention.

One option would be to pour each compartment separetely using a blocker board (or plastic sheets with PVC blocker like Trooper82 did -- I think he has a video on his thread) to keep the foam out of your middle channel. Once it cures/sets, then you glue in a vertical foam board and maybe back fill it a little with a smaller amount of foam (probably not necessary though).

Or, you can ditch the "pour-in" altogether and just stack some sheets like I did:



On the bottom of my foam cut-outs there is a oval cut-out right at the keel (see very bottom of above pic) that is sort of an open channel. That way water that runs over the deck can work its way down beneath or through the stacked foam sheets (pour in would not allow this) find its way to the center channel via gravity and then flow smoothly in the center channel back to the bilge...

Pour-in foam certainly has its merits, but structurally my boat feels very solid in the chop without it.

 

[jigngrub]

Re: Best way to "fasten" board foam to aluminum?

Do you plan to pour the foam before or after the decking goes down?

What year and make of boat? Sea Nymph, Starcraft, other?

 

[jasoutside]

Re: Best way to "fasten" board foam to aluminum?

land, that is one very ugly boat you posted up there!

PMC built out a fantastic alternative to the pour in foam. On my boat I had actually decided to go with pour in foam but after massive consideration I decided to skip it and go with noodle/foam board/foam core built stuff.

To rig the foam boards in such a way to contain the expanding foam, provide for positive drainage, and get enough foam in there would have been simply too much of a pain. And, the likely would have been blown out by the foam anyway.

It's a good thought (and might actually work in a bigger boat) but I tend to think you ought to simply use expanding foam (so long as you provide for drainage) or run foam board like PMC there ^^^.

 

[Landof9000lakes]

Re: Best way to "fasten" board foam to aluminum?

I want to go with pour in for a few reasons.
1. I want it to reduce noise. This probably sounds silly but I want it to not only reduce noise while under power but also while sitting still. I would like to add a full camp enclosure to the boat and camp on it. That sounds silly too I'm sure but that sounds absolutely awesome to me.
Even before the camp enclosure I'm going to use the boat when out of town to sleep in while away on fishing trips by myself.

2. The structural support added will IMO give the boat a more solid feel in rougher seas.

3. I eventually want to use the boat on very large waters. In this environment the pour in gives me a piece of mind that is a bit similar to a "Warranty on the box".

 

[Landof9000lakes]

Re: Best way to "fasten" board foam to aluminum?

Do you plan to pour the foam before or after the decking goes down?

What year and make of boat? Sea Nymph, Starcraft, other?

The decking is already down and I foam boarded it, but am going to pull up the decking, do the pour foam, then put the decking back down.

 

[jigngrub]

Re: Best way to "fasten" board foam to aluminum?

The decking is already down and I foam boarded it, but am going to pull up the decking, do the pour foam, then put the decking back down.

Sounds like a plan.

What kind of below deck framing do you have? Longitudnal stringers fore to aft or deep ribs port to starboard?

 

[jasoutside]

Re: Best way to "fasten" board foam to aluminum?

I want to go with pour in for a few reasons.
1. I want it to reduce noise. This probably sounds silly but I want it to not only reduce noise while under power but also while sitting still. I would like to add a full camp enclosure to the boat and camp on it. That sounds silly too I'm sure but that sounds absolutely awesome to me.
Even before the camp enclosure I'm going to use the boat when out of town to sleep in while away on fishing trips by myself.

2. The structural support added will IMO give the boat a more solid feel in rougher seas.

3. I eventually want to use the boat on very large waters. In this environment the pour in gives me a piece of mind that is a bit similar to a "Warranty on the box".

Reduce noise? Structure? Great reasons for expanding foam!

Again, just be sure you figure out drainage. Otherwise, well, it won't drain.

Sleeping on a lil boat? Well maybe a little silly but if you love it go for it! Sleepwalking would have it's drawbacks:laugh:

No doubt the best "warranty" for big water is knowledge, wisdom and experience - failing that, good gear sure helps the situation! But I bet you knew that already.

 

[jigngrub]

Re: Best way to "fasten" board foam to aluminum?

You don't have to fasten the foam board to the hull, the expanding foam will do that for you, all you have to do is figure out a way to hold the foam until you get some expanding foam against it... you could hold it by hand if you want to.

Like this:


Cut your foam board as close as you can to fit the hull (it doesn't have to be perfect), any expanding foam that oozes out into the drainway can be cut off flush with the foam board and scraped away.

When you've got your drainway done and the foam has cured go ahead and pour the rest of the foam.

The expanding foam is very sticky and self adhering, after it cures for 5 minutes you'll need a hammer to knock that foam board and expanding foam out of there.