Aluminum boat floor (two part adhesives)

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Tim F

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Hi everybody. I have a odd question for you guys. I have a few leaky rivets that I have bucked to tighten back up. To get to these rivets, I removed a lot of closed cell flotation foam. The foam was there for flotation (of course) but as a secondary function, it would dampen sound. I don’t want to pour any two part foam back into the bottom of the boat, i plan on using rigid foam in its place. But I’d still like to coat the inner hull to dampen sound and add some thickness to the hull. I have 3 pails of two part epoxy adhesives left over from a flooring job I did and was wondering what would happen if I used it in the bottom of the boat as a potting compound. If the adhesives are indoor/outdoor, do you think this would work, or would this just end up coming off in a full sheet the first time the boat hit a bump or froze and thawed. I will include pictures of the two types that I have.

Thanks in advance.

tim

i have 1 pail of 96 plus and two pails of eco-grip
 

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JPfloor

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Aside from the fact that I wouldn’t trust it to adhere to aluminum the whole freeze thaw thing will almost certainly result in failure.

There are plenty of aluminum epoxies on the market.
 
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Tile Tom

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I think I would be tempted to give it a good scuff and then a few layers of hydro-ban.
Boats aren't my specialty so not sure if it would work but if it were mine that's the route I would take.
 

JPfloor

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If you’re just looking to deaden the sound I would consider some of that spray foam “Great Stuff”. Cheap, light, will stick to anything, and if I’m not mistaken will probably add a little flotation. Be careful, it expands quite a bit.

Epoxy might be adding more weight to a tin boat than you want and won’t help much with deadening the sound.
 
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First, these adhesives are not designed to be used in a thick application. Most trowel notching is going to be at most 1/8" thick. I would say that is going to give you little-to-no amount of sound deadening and in general, they are going to be problematic more than helpful. Keep in mind that epoxies generate a large amount of heat when mixed and this could be a potential fire hazard if you pour a bunch of it in the bottom of a boat. They will literally start smoking if you leave them in the container when mixing them. Most flooring guys will pour them out on a sheet of cardboard or plastic to keep them from getting too hot because of this.


If you're going to use them to adhere something in the boat, then...

So, from the picture you've got 1 urethane adhesive and 1 epoxy adhesive. While many times they are used for similar purposes there are some subtle differences that really make a difference in your application. They both should adhere to a clean metal substrate just fine.

The biggest difference is that a two-part urethane is typically much more resistant to temperature change than an epoxy. Urethanes stay more flexible at lower temperatures than epoxies unless they are specifically formulated for low temps. Epoxies can become brittle and sheer off if they get flexed or stressed.

With two-part urethanes you MUST mix the entire unit for the adhesive to work properly. With an epoxy, they can typically be "ratio'ed" out. In other words, you can mix less than the unit as long as you maintain the proper ratio of part A to part B.

While they aren't using it to attach anything to a boats hull, I have a boat manufacturer that uses one of our two-part urethane products in their boats because of the broader temperature range. Been using it for years and so far, I've had zero complaints.

Last, I'm not sure how old those are but most two-part adhesives only have about a 1 year shelf life when stored correctly. If those have been exposed to potential hot and cold cycling for a period of time, I would not trust them to work as expected. Since this could be a very expensive failure if things go south, if it were me, I'd purchase fresh adhesive.

I wish you the best with your project and hope this info helps!
 

JPfloor

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Another good option would be Flexseal. I’ve used it on a number of projects and it works. I know you’re just looking to use up some stuff you have laying around your garage but a floor covering adhesive is not you best choice for bonding to aluminum. Aluminum expands and contracts A LOT when exposed to varying temperatures.

 

Tim F

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Thanks for the replies everyone. Sounds like i should just forget about the idea. I will take all the advice and continue on my boat project without adding any of the adhesives….
 

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