2 part foam application

[Matrix1]

After I foam the hull back up and screw the two floor decks back down. Knowing that rain water will seep in and under the floor board along the sides of the boat where the deck meets the boat side how long will the foam last before getting water logged again? Anyone have an idea? This is in a 17' aluminum boat. I plan to use pvc pipe layed down for drainage also before foaming. But it's the floor edges that meet the side of the boat that worries me.

 

[alldodge]

If your using closed cell foam it should never soak up water

 

[oldboat1]

Allow for drainage along the keel, and install a bilge pump at the transom.

 

[gm280]

If using the quality mix and pour floatation type foam, be it the 2lb, 3lb, 4lb or which ever, you will probably never have the foam become waterlogged again in your life time. That is why so many are using the mix and pour products designed for floatation these days. The original foam was not water-proof or known to shed water. And therefore that old foam would soak up water after a few years. But this new close cell foam isn't like that old stuff. So install and happy boating. JMHO!

 

[ondarvr]

All foam used now, and what was used many years ago, is bascially the same, it is ALL closed cell to start with, it will all break down and absob water after an unpredictable period of time. The difference between the old foam and new foam is only the VOC's, the newer ones are lower due to federal regulations. There was never any open cell foam used as floation in boats.

PVC drains don't help much, the foam will block it off completely unless you do it correctly. You could use sheet foam and cut it to shape, or use two part foam poured into heavy weight plasic bags, this keeps water away from it, plus you can remove it easily at anytime in the future.

I used pour foam in one of my aluminum boats and wouldn't do it again, there are too many issues with pour foam and aluminum, I would either use sheet foam or pour foam in bags.

 

[alldodge]

Thanks ondarvr, learned me something today. Guess the stuff-it cans you get in the stores is the same stuff

 

[ondarvr]

The great stuff foam can sort of work, but it's a single part product and not as durable, or possibly fuel and oil resistant as the normal CG approved foam.

 

[fhhuber]

Thanks ondarvr, learned me something today. Guess the stuff-it cans you get in the stores is the same stuff

The spray expanding polyurethane foam in a can is open cell, not a flotation foam. It could be used as a "glue" to hold closed cell styrofoam blocks in place filling gaps, but it will degrade relatively rapidly.

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If you want the hull stiffening effect of a pour in... you can't pour it into bags because then its not bonding to the hull and framework.
Might as well cut styro blocks and drop them in (no glue)... and that would be cheaper. (and more resistant to water soaking)

The real way to minimize water logging the pour in foam is minimizing time in contact with water. when the boat is parked keep it nose up and the drain plug out. Cover the boat to keep leaves and stuff from getting in and eventually blocking the drain.

That drain hole getting blocked with leaves or other debris and the boat filling up with water then sitting and having it drip out over a period of weeks... that is what typically destroys your foam. it takes time while wet for that foam to absorb the watrer.

 

[Matrix1]

This information you guys gave me is great and what I needed to hear. Thanks!!!! I feel more confident with the decision of using the closed cell foam product now. And my plan to use the pvc down the keel and one more piece down each opposite side of the beam from windshield to transom. Just Waiting for my custom aluminum belly tank to arrive so I can get that in first. I Just finished completely rewiring the boat with a new instrument panel and accessories today. Took a couple weeks to do in between the rain storms here but it got done. Thanks everyone and Merry Christmas......

 

[alldodge]

Ondarvr is our resident expert, always great to hear his info. I was thinking it with the pvc you run, maybe drill some holes on the bottom only of the pipe. This will allow all water which comes in around the pipe to enter it and drain. This is the same method for drain tiles

 

[oldboat1]

flogging it a little more, I guess. Think there is a lot of agreement here -- including Matrix1's sense that waterproofing is tough to achieve.

I've always assumed water is going to get down below the flooring somehow, somewhere, and expect to see it collect at the lowest point -- so I try to keep the keel area drained and drainable. I think in terms of natural drain paths down the hull sides and bottom, with a way out at the transom.

With drainage in mind, I like the idea of closed cell foam cut to shape, or encased/bagged flotation, without fixing foam to the hull (not rigorously sticking it in place, anyway). Foam under the seat in an aluminum rowboat is often free floating in an aluminum envelope -- open to air and draining. Hull flotation in a 17' boat should mimic that concept, IMO. Put another way, hull drainage is what it is. Flotation is what it is. One shouldn't get in the way of the other.

I wouldn't think in terms of a complex drainage system -- would just find a way to keep the flotation foam out of the way.

 

[Scott Danforth]

After I foam the hull back up and screw the two floor decks back down. Knowing that rain water will seep in and under the floor board along the sides of the boat where the deck meets the boat side how long will the foam last before getting water logged again? Anyone have an idea? This is in a 17' aluminum boat. I plan to use pvc pipe layed down for drainage also before foaming. But it's the floor edges that meet the side of the boat that worries me.

put a good bead of 4200 along the seam if your goal is to seal the edge to keep rain water out. then make sure you store your boat nose up with drain plug removed.

 

[gm280]

Matrix1, seem you are looking for that same situation that every boater that is rebuilding their boats back to usable again is looking for. Everybody wants a quality close cell foam for floatation but also ways to allow water out. And we all try to figure out ways to accomplish that. But honestly, nobody has actually come up with a perfect answer to both mix and pour foam AND drainage capability that is known to work. At least I haven't seen any myself.

A lot of boater, self included, thought of the PVC pipe with holes in it to allow water to drain. But the mix and pour foam will close those holes up when poured. Then others thought about using screen mesh over the PVC hole to keep the expanding form out of the PCV pipe. Again the expanding foam will close over that idea as well. So haven't read of any really correct idea to give the best of both worlds myself. So the best you can do is mix and pour the foam and seal the flooring areas to shed the water into the transom area and hope for the best. If the water is draining with a raised bow, then nothing should rot. JMHO!

 

[ondarvr]

Great Stuff (Dow) makes several versions of the product, they are closed cell, but lower in quality than 2 part products and make no claims to be a boat building or repair product. Technically it could work, but it's not a CG approved product and isn't going to hold up for long if used as a typical floatation foam, but, if used in a place where there was no stress, water or UV contact involved it could last and provide floatation. This doesn't mean I'm recomending it, far from it, I'm just saying that in some very limited applications it could possibly work.

Alumuinum boats don't use pour foam as a structural component, it's just for floatation, so not bonding to the surfaces when using it in a bag is a plus. I'm not making any comment on the cost of either method, cutting sheets and pouring 2 part into bags both work, but the pour foam is actually CG approved if someone sees that as important.

Trying to seal water out of any location in a boat is a losing effort, water will find it's way into every part of a boat, so just plan for it to happen and let it get out easily.

When spray foam is used directly on aluminum it tends to trap moisture and corrode the alumnum rather quickly, we have many aluminum boat builders in this region and spray foamed hulls can be a huge issue just a few years down the road. The bag method works well and some people use it, and I would use it in my next aluminum boat and wish I had in my current one (did it 15 years ago). If I didn't have pour foam on hand, or just didn't want to use it, cutting sheets would be fine, I don't really have a preferance either way, but there are pros and cons for each method.

 

[Scott Danforth]

I use great stuff for adhering wire chases under the gunwals. I also used it to quiet down the sound of water slapping the underside of my swim platform.

 

[ondarvr]

I use great stuff for adhering wire chases under the gunwals. I also used it to quiet down the sound of water slapping the underside of my swim platform.

I have some in one of my boats too, it works well in some applications. I wasn't going to offer that up at first, but you did, so what the heck.

 

[Matrix1]

If one was to drill some holes in the pvc pipe and line the holes up facing down and towards the joint of the beam so to say. I am thinking that maybe one could mix and pour a little bit at a time, working your way down the pvc with several small pours to just cover it lightly. Then when it expands its not trying to force its self under the pvc pipe or lift it up when it expands and cures. It will cover it and hold it down in place. Then wait 15 or 20 minutes and finish with the final pour. Just thinking....

 

[64osby]

Alumuinum boats don't use pour foam as a structural component,..

When spray foam is used directly on aluminum it tends to trap moisture and corrode the alumnum rather quickly, we have many aluminum boat builders in this region and spray foamed hulls can be a huge issue just a few years down the road......

My Lone Star is one of the very few Aluminum hull that did use foam as a structural component, Mirrorcraft also had a few models.

I do have several small areas of corrosion that need to be addressed but it is also a 1965 hull.

For hulls that don't need structural foam I would use sheet foam. My .02

 

[ondarvr]

64
I'm near saltwater, this is where it shows up first, freshwater can be quick, slow or never.

Matrix1
The foam is liquid when you pour it, so it will flow under the pipe almost immediatly and block off the holes. Leave the center of the hull empty with no foam, make a dam on each making a channel about 8-10" wide to keep the foam from flowing into the center area. This leaves an area for water to collect and travel to stern without comming in much contact with any foam.

 

[JASinIL2006]

If one was to drill some holes in the pvc pipe and line the holes up facing down and towards the joint of the beam so to say. I am thinking that maybe one could mix and pour a little bit at a time, working your way down the pvc with several small pours to just cover it lightly. Then when it expands its not trying to force its self under the pvc pipe or lift it up when it expands and cures. It will cover it and hold it down in place. Then wait 15 or 20 minutes and finish with the final pour. Just thinking....

To me, this sort of approach always seems more likely to give water a path into the foam than an exit route.