Aluminum boat for saltwater use and foam floatation

[WendellNLA]

I am looking for some practical ideas on how best to provide flotation foam in my 18' Starcraft. The factory method was to pour foam in. But being a riveted boat that I intend to use in saltwater, I am concerned that as the boat rivets loosen up over time with use, the saltwater than enters will have no free path to the bilge and rear of the boat to be pumped or drained, and no way for fresh water to rinse it out and being trapped will cause the aluminum to corrode.

I was leaning towards pour in foam as I would think that would provide a quieter hull with more structural rigidity.
Has anyone come up with a way to use pour in and still provide some way for water to drain and possibly allow for ventilation and fresh water access for rinsing?

Thanks for any ideas you can share,

W

 

[jigngrub]

I suggest something like this:


Pour the foam before installing the decking. You can either blockout for the drainway in the middle before pouring or pour the foam solid and cut and remove the foam down the keel after it is poured.

I suggest painting the inside of your hull before pouring the foam, this will prevent galvanic corrosion if any water should become trapped below deck.

I also suggest applying your deck finish to your decking before installing it in your boat, this will allow you to install the decking with exposed fasteners so you can remove the deck later for inspection and maintenance without ruining your deck finish (carpet, vinyl, paint...)

You can look and see how I did my boat here:
http://forums.iboats.com/forum/boat...-repair/521750-97-tracker-pro-deep-v-facelift

 

[gm280]

You could always use some thick plastic sheeting and pour the foam and allow it to expand. Then cut it to fit at the top but you can also remove it and make certain there is a little passageway underneath the foam. OR, you could also buy the Lowe's brand foam sheets in different thicknesses and cut each pieces to fit in the area and build up to the floor surface and then floor over it. Either way, you will have floatation foam and air movement around the foam... IDK :noidea:

 

[WendellNLA]

jigngrub, I like the way the foam is put in your boat. The center channel being left open promotes drainage. My concern though is with water that enter from loose rivets under poured/sprayed foam. Maybe I am nitpicking too much, worrying about a relatively minor problem.

gm280's idea of using plastic to isolate the foam from the hull.... and potential loose rivets sounds like a good idea. I wonder if the boat will lose some of the rigidity as well as sound deadening being that it isnt directly attached to the floor.

Has anyone tried pour in foam with a plastic liner on each pocket over some kind of false bottom and stand offs made of a non reactive material, leaving a small space between the inside of the hull and the false bottom? The idea is to create an unrestricted path, anywhere on the inside of the hull for water to pass to the bilge accumulate or be pump out.

Or.... am I just overthinking this whole thing and expeding too much mental energy on a non issue?

I have a headache now thinking this over! lol

W

 

[Bondo]

Has anyone tried pour in foam with a plastic liner on each pocket over some kind of false bottom and stand offs made of a non reactive material, leaving a small space between the inside of the hull and the false bottom? The idea is to create an unrestricted path, anywhere on the inside of the hull for water to pass to the bilge accumulate or be pump out.

Ayuh,.... Just skip the poured foam, 'n use rigid foam board,.... Yer hull don't need the added rigidity of poured foam,.....

 

[Grandad]

Ayuh,.... Just skip the poured foam, 'n use rigid foam board,.... Yer hull don't need the added rigidity of poured foam,.....

I agree and I don't think your ride will be any quieter with poured foam anyway. It'd be hard to have the foam intimately contacting the hull to reduce noise without blocking water flow somehow. - Grandad

 

[jigngrub]

I've never seen foam board floatation float a boat like the poured foam does in this video:
https://www.youtube.com/watch?v=M30nDtZ4iys

... as a matter of fact I never seen anyone brave enough to even test their foam board floatation to see if it will even float their boat, and I'm sure some if not most will be disappointed when the time comes for the foam to do it's job in an emergency.

 

[will w.]

jigngrub, I like the way the foam is put in your boat. The center channel being left open promotes drainage. My concern though is with water that enter from loose rivets under poured/sprayed foam. Maybe I am nitpicking too much, worrying about a relatively minor problem.

gm280's idea of using plastic to isolate the foam from the hull.... and potential loose rivets sounds like a good idea. I wonder if the boat will lose some of the rigidity as well as sound deadening being that it isnt directly attached to the floor.

Has anyone tried pour in foam with a plastic liner on each pocket over some kind of false bottom and stand offs made of a non reactive material, leaving a small space between the inside of the hull and the false bottom? The idea is to create an unrestricted path, anywhere on the inside of the hull for water to pass to the bilge accumulate or be pump out.

Or.... am I just overthinking this whole thing and expeding too much mental energy on a non issue?

I have a headache now thinking this over! lol

W

My riveted starcraft isn't used in saltwater. After tearing the wet foam out and finding GV corrosion, I have been doing the same as you, trying to picture a way of allowing for drainage from under the foam. My boat has a foamless 2ft channel down the center but the foam was still waterlogged. Once wet, i dont think it will ever dry out. I personally want the poured foam back in my tin can.

I was thinking something like the above poster who suggested plastic, but instead of plastic, why not one thin (1") sheet of foam board laid on the bottom with drainage channels cut into the bottom? Scratch up those beams to give the foam something to bite on and pour foam with the floor down. Again, just something i,ve been bouncing around in my head for my boat. I also would need to drill a few drainage holes in my beams.

 

[Grandad]

I've never seen foam board floatation float a boat like the poured foam does in this video:
https://www.youtube.com/watch?v=M30nDtZ4iys

... as a matter of fact I never seen anyone brave enough to even test their foam board floatation to see if it will even float their boat, and I'm sure some if not most will be disappointed when the time comes for the foam to do it's job in an emergency.

Hi jig. I think both rigid and poured foam placed in the same quantities and in the same area will provide equivalent flotation. Lund may have found the sweet spot for the right amount in the right place. Good for them. Only manufacturers have pockets deep enough to experiment like this until it works. And when they do succeed, they publish dramatic videos for us to distribute and promote for them. I'm mathematically sure the rigid foam I've placed in my boat will keep it from sinking to the bottom, but I also readily admit that it won't likely stay upright like the Lund. But poured or rigid won't make the difference. We can only do the best we can with the boat designs we have. - Grandad

 

[WendellNLA]

On a riveted aluminum boat, I think we all agree water WILL makes its way to the inside of the hull, either through condensation, water intrusion from the topside or water intrusion from the seams/trivets. I guess what it comes down to, is it better to isolate and exclude or drain and ventilate?

Isolate the pour in or sheet foam by encasing in plastic sheeting and exclude by coating the inside of the hull with gluvit or some other sealant.

Or....

Use pour in foam or sheet foam that is kept off the bottom of the bilge area, allowing the free flow of water that accumulate to reach the drain or pumps and some how allow air to circulate to promote a dry bilge.

Im no engineer, but I do understand that designing anything to be perfect is nearly impossible, as there are always conflicting needs to be considered as well as compromises that need to be made.

I am really enjoying the discussion and appreciate the ideas that have been put forth. Thanks,

W

 

[will w.]

After reading some Djpeters 79 22' Super sport thread, it appears the idea of laying sheet foam down before pouring the expandable has already been discussed somewhere. They didn't go into detail but it sounds like sheet foam may squeak when placed against the aluminum hull. I wonder if strips of 5200 could help mitigate the movement. I like the idea of routering drain channels in one face of sheet foam, then laying the channels face down in each framing compartment maybe fastened with 5200 to prevent the squeak. A barrier of some sort (caulk or plastic) could be applied around top edges to prevent expanding foam from seeping down and filling the intended drainage channels. Caulk sounds like a better option as it might help keep movement to a minimum, but if it didn't.

 

[Grandad]

I haven't heard any squeaks from my install of rigid foam. I wasn't aware of a potential problem with squeaks, so I never took any special precautions during the install. If someone has squeaks, perhaps they could comment. I never wedged any foam. I wonder if that's the cause of squeaks, if there are some. - Grandad

 

[djpeters]

After reading some Djpeters 79 22' Super sport thread, it appears the idea of laying sheet foam down before pouring the expandable has already been discussed somewhere. They didn't go into detail but it sounds like sheet foam may squeak when placed against the aluminum hull. I wonder if strips of 5200 could help mitigate the movement. I like the idea of routering drain channels in one face of sheet foam, then laying the channels face down in each framing compartment maybe fastened with 5200 to prevent the squeak. A barrier of some sort (caulk or plastic) could be applied around top edges to prevent expanding foam from seeping down and filling the intended drainage channels. Caulk sounds like a better option as it might help keep movement to a minimum, but if it didn't.

Hey! Yeah, my idea was to lay sheet foam down on the ribs and then pour the foam on top. I started doing that up front, but, when you dump that pour in foam in, it is thin...like water thin before it kicks. So any little gap it is going to find and end up in the bottom of the boat anyway. My boat has four stringers, so I filled in the outside and left the very center open all the way from bow to stern.

I agree with what Jig said....pour in foam will get you the most foam in. Period. I did all my pours under ideal conditions so I know I got the expansion advertised. I do not wonder if I have enough foam in my boat.

As far as your saltwater use, how long do you plan on this boat lasting? Chances are it will be a long time no matter what you do.

 

[WendellNLA]

Hey! Yeah, my idea was to lay sheet foam down on the ribs and then pour the foam on top. I started doing that up front, but, when you dump that pour in foam in, it is thin...like water thin before it kicks. So any little gap it is going to find and end up in the bottom of the boat anyway. My boat has four stringers, so I filled in the outside and left the very center open all the way from bow to stern.

I kinda like the idea of pouring foam over sheet to get it away from the hull and potentily leaky rivets. Im thinking pour foam over foam board, using plastic stand offs to elevate the foam board off the hull to allow drainage and some air flow( at least enough to avoid an anerobic environment) with plastic sheeting lining each cel, to keep pour in foam from running into unwanted ares, isolate the foam from any water intrusion as well as make removal in the future less painful.


As far as your saltwater use, how long do you plan on this boat lasting? Chances are it will be a long time no matter what you do.

If a long time is 20 years, I would be happy with that! Heck if it 10, I guess I cant complain. II just am trying to make sure I dont have a disater that is very hard to fix in 3 or 4 years. From what I have read of others experiences concerning pour in foam removal, I dont think I want to do it more then once if I can at all avoid it.

W