Alternatives to foam

[Mouthfulloflake]

so you have to part the hulls to do this?

or just run a bead down the bond line?

( im defoaming sons boat next winter, its been dripping in the garage now for over a month, must be ALOT of water in it)

I am convinced it can be done. IMHO, you need to use flexible sealant (i.e., 5200) around the entire bondline, all through-hull fittings, and all threaded inserts.

 

[meatball]

It could be done, but without modifying some of the tubing (ie the coolant tubes) I think it may be difficult to get adequate inflation that fills all the necessary voids, without the need for a custom bladder. Thats just my opinion. However, if you look at FL-crackers ski with no foam, anyone ever consider using the lightweight polystyrene as a backup with drain plugs (polystrene just cut to fit with drain channels) kinda like racing sailboats have in some cases. It wouldnt provide structural integrity, but would be just in case. That said Im not sure if the voids created by cut to size pieces would be large enough in volume to take on enough water to sink the ski (depending on ski weight).

hey mouth, as far as the ski, to seal it all up doesnt require that much energy. You just run a bead along the bond line, 5200 if your not reinforcing, or foam or epoxy if you are (not sure that epoxy sticks to 5200) and 5200 the tubes and any other possible water entry points like Matt said.

 

[Matt_E]

Actually.....I like running a thick bead of 5200 along the bondline (don't forget the very back!!!), and then reinforce if you must. I wouldn't use just foam/epoxy to seal and then glass to reinforce.
The back flexes - it's best to have flexible sealant.

 

[meatball]

Oh well, whats done is done... I was going to glass over the back too, I'm cutting my flange off.

 

[Matt_E]

I hear you. I did my roundnose with just epoxy and glass last year, but this year's square got the 5200/glass treatment.

 

[meatball]

how does the glass stick to the 5200? I was worried it might not stick at all and leave that part kinda delaminated. I laid everything up at once to get a chemical bond with the bondline and laminate.

 

[onesojourner]

I still think ping pong balls are the answer. that is a good poitn about the exhaust getting hot. you could lay some pvc over it to keep the temp down. I don't think the bladder would have to fill all the space as long as it has enough air in it to keep the ski floating it should work. some one needs to take a crap ski and sink it and figure out how much of a bladder it needs to keep it floating. I would not think it would need much.

 

[Matt_E]

It's not that thick of a bead. It doesn't stick. But it's not a void, either.

The exhaust is not getting hot. That is plain nuts, and yet I hear it mentioned quite often.

 

[meatball]

I still think ping pong balls are the answer. that is a good poitn about the exhaust getting hot. you could lay some pvc over it to keep the temp down. I don't think the bladder would have to fill all the space as long as it has enough air in it to keep the ski floating it should work. some one needs to take a crap ski and sink it and figure out how much of a bladder it needs to keep it floating. I would not think it would need much.

Sure ping pong balls would work, but have you ever examined the packing efficiency? Its horrible. If there was a leak, a LOT of water could enter very quickly, and all that water between the balls would sink the ski, you get less flotation with all the air between the circular balls, a lot less. I cant recall what the exact packing efficiency is but mythbusters had it. I would crunch numbers first, figure out first hand later. Polystyrene would be the same deal, lighter weight, no strength. However if you can get a pingpong ball/foam block in there, it would eliminate the packing efficiency problem.

 

[onesojourner]

I know water would get in, but how much does it take to sink a ski?

 

[meatball]

I wouldnt think yamaha would give you much more flotation then you actually need, and ping pong balls would leave a huge gap for water to fill. As it is stock weight skis are close enough to sunk that I wouldnt want to be the test ski to find out that I need to buy a sidescanning depth finder.

EDIT: I just pulled the number, the packing efficiency is 51% with straight ping-pong balls. So if you consider the fact that you have almost half the guarenteed buoyancy in the back with only ping pong balls, would you consider that safe if your leaking in the back? With drain plugs I guess you'd notice, but the reason ping pong balls were brought up was to reduce weight and still be able to float if you sink with an entry point for water in the back. If the ping pong balls dont give enough buoyancy to begin with, why have anything at all? (enter FL-cracker). The only way around it I can see is if you mixed the balls with foam to take up for the packing inefficiency, or used another material with a good enough packing effieciency so you dont lose too much of your guarenteed buoyancy.

If you are eliminating the structural aspect of the foam in the back, then consider the only reason you are still putting materials back there is just in case for guarenteed buoyancy. If you dont have enough of that, then it would be wiser to elimnate all flotation materials alltogether, and instead install draingplugs and monitor the leaking that may occur, and follow FL-crackers example. If the ping pong balls were sqaure, it would be a different story, but then its necessary to consider how 'packed' they would become after years of rough landings, and how much the volume is then with possibly a number of crushed ping pong balls.

AGAIN, this is all speculation, and only under the fact that the cavity was filled with ONLY ping pong balls. It would be different with a different packing efficiency (foam/ping pong balls, or polysyrene packing foam cut to shape)

This was all discussed last week or whenever that discussion took place...

 

[onesojourner]

but ping pong balls are a bit lighter than foam.

 

[djkorn1]

SXR's have styrofoam. Very strange.

What about a mixture of foam and pingpongballs? :cool2:

 

[wydopen]

http://www.tireballs.com/

i dont know if you guys have seen these things but i think they would work perfect...just run alot of them w/ low psi to fill all the gaps...then just run some drain plugs...

 

[Marshj]

guys. I was thinking of this a while ago with slut. and was going to go with something different. After all the calculations, volume etc. I personally decided it wasnt worth it to run no foam. 2lb foam only adds around 5.4lbs to the hull if properly expanded. Not enough weight savings for me. just my opinion after putting a lot of though and some numbers into this

 

[Matt_E]

As I recall, this wasn't about weight savings, was it?

I thought people are tired of waterlogged foam (which gets heavy)

 

[Marshj]

not completely but i think slutty decided to leave the bottom inch or so without foam, and that way it would not hold water and could have drain holes- for me it was partially weight savings as well as keeping those buggers dry:banghead:

 

[Boris]

For me the biggest problem with foam is that you have to rip it all out to find out if it is in fact wet.

When I had my tray cut open I used 2 large tubes of 5200 to seal everything. Bond line, inserts, tubes, bulk head,........ I did it all.
However, is still fear that water will find it's way in.

I wish we could poor in styrofoam just like regular foam, add some drain plugs and live happily ever after.

 

[Matt_E]

not completely but i think slutty decided to leave the bottom inch or so without foam, and that way it would not hold water and could have drain holes- for me it was partially weight savings as well as keeping those buggers dry:banghead:

See....I am not sure that you'll really drain all the water. The foam will probably hold a lot of it. Unless it just gravity drains out of it.
That would be awesome.

I've decided to give a complete seal-job a try and cut 'er open in a couple of years.

 

[vitaly]

Latex condoms is the answer.
As an additional benefit, that will answer all the questions when your wife finds one in your pocket.