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Increase your floatation by filling cross-bars with foam
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Author:  widerisbetter [ Sun Jun 06, 2010 2:15 pm ]
Post subject:  Increase your floatation by filling cross-bars with foam
Years ago it occurred to me that one reason my 16 was hard to get upright was the weight of water in the trampoline supports and cross-bars. Once I was back upright the water ran slowly but surely out of the bars. Well, as we all know, a dry boat is a fast boat so I considered putting plugs in the bars - like we have in the mast to keep water out. However, with all the rivets and attachments I figured this wouldn't work so well. Solution: Great Stuff Expanding foam. Buy a 4 foot section of clear hose that will fit over the nozzle of the Great Stuff can. Insert the hose as far as possible and draw it back as you squeeze the trigger. Do the same thing from the other end. It adds practically no weight. Honest to goodness- I was able to get my 16 over by myself after this. I currently have the cross bars off my 17 and am headed to the hardware store materials to do the same thing.

Happy sails to you :)
Author:  Nevek [ Sun Jun 06, 2010 5:50 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
West Marine and other marine stores make a similar foam that wont degrade in the water....might be a better idea for this.
Author:  Karl Brogger [ Sun Jun 06, 2010 6:00 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
Until the foam gets water logged, and then it never drains out.
Author:  MBounds [ Sun Jun 06, 2010 6:16 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
Karl Brogger wrote:
Until the foam gets water logged, and then it never drains out.


+1

Plus, you're carrying the dry weight of the foam around all the time - 2 lbs / cu. ft. Water is about 8 lbs / cu. ft. so the net is only 6 lbs/cu.ft.

But when the boat is on its side, only the one sidebar is underwater.

I don't think your ease of righting was due to the foam.
Author:  Roy [ Sun Jun 06, 2010 7:59 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
Boy we sure took the wind out of his sail right away. :oops:
Author:  JJ [ Sun Jun 06, 2010 8:40 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
Maybe he should put the foam into a sleeve or something so it can be yanked out if it does deteriorate...

Ounce of prevention is worth X lbs/cubic ft of cure. Flotation is good, eh?
Author:  wildlatin [ Mon Jun 07, 2010 7:10 am ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
I have used one-component urethane foam for repairs of my small abs-covered, styrofoam-filled Castlecraft mono-hulls for years and never seen the least indication of the set foam absorbing water. The foam degrades with long-term UV exposure- to a point where it might- but inside the cross bars shouldn't be a problem.

Note there are different formulations- some expand to less than 1/2 the density of others. Try to get the most expanding formulation available?

I sometimes note the tendency to criticize ideas as "not invented here" - or maybe "not invented by Hobie"? :roll:

I have noticed water dripping from the bars even after rains and think it's good to keep thinking about improvements.
Author:  mmiller [ Mon Jun 07, 2010 9:16 am ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
wildlatin wrote:
I sometimes note the tendency to criticize ideas as "not invented here" - or maybe "not invented by Hobie"? :roll:


Naw... I'd chalk it up to experience. Many here have been at this for a LOT of years.
Author:  Sail Revolution [ Mon Jun 07, 2010 9:37 am ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
mmiller wrote:
wildlatin wrote:
I sometimes note the tendency to criticize ideas as "not invented here" - or maybe "not invented by Hobie"? :roll:


Naw... I'd chalk it up to experience. Many here have been at this for a LOT of years.


Here's some experience for you...

I filled a Hobie 18 mast top section with expandable foam in the late 90s. It sounded like a good idea, but it turned out to be a fiasco. The foam, or pockets in the foam, collected and stored water and the mast ended up being about 100#s. Most of the weight was at the end of a 30 some-odd-foot lever, making the boat impossible to right even with a heavy crew of two- if we got to righting fast enough.. And guess what happened when I flipped that sucker, and wasn't fast? The masthead went straight to the bottom. The end of the day was loathed when the time came to lower the mast.

In your case, the frame full of water won't be a huge factor in righting your boat. The mast full of water is another matter. Make sure it's sealed and you should be fine. Air floats waaay better than foam.

I wouldn't do it.

Hope that helps.
Author:  wildlatin [ Mon Jun 07, 2010 11:07 am ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
Surf City Catamarans wrote:
mmiller wrote:
wildlatin wrote:
I sometimes note the tendency to criticize ideas as "not invented here" - or maybe "not invented by Hobie"? :roll:


Naw... I'd chalk it up to experience. Many here have been at this for a LOT of years.


Here's some experience for you...

I filled a Hobie 18 mast top section with expandable foam in the late 90s. It sounded like a good idea, but it turned out to be a fiasco. The foam, or pockets in the foam, collected and stored water and the mast ended up being about 100#s. ... I wouldn't do it.

Hope that helps.


With appreciation for those who have experienced fiascos, etc. in this submitted concept- filling cavities with urethane foam- I submit that the failures are in the application. Also, that an effective installation may be difficult for non-professionals.

Both ASTM and ISO have standard test methods for 'Water Absorption of Rigid Cellular Plastics' and indicate industry 'acceptable' results in the range of just 4% water absorption after immersion. This should be readily attainable with polyurethane foam. Such foams can be produced in densities as low as 0.5 to 6.0 lb/ft3 - vs water at 62 lb !

I agree that pneumatically sealing is much simpler- even as simple as installing some reliable air bladder inside these structures to prevent water intrusion. Maybe a good use for all that bubble wrap :wink:

Anyway, I'm not about to tear into my crossbeams right now- I'd rather go sailing! I admit I have a lot to learn and benefit greatly from the comments on this forum...

Will in Latrobe, PA
H14 & H14T
Author:  widerisbetter [ Mon Jun 07, 2010 1:21 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
thanks Matt Miller for the cred :wink: a LOT of years indeed. I sailed my first 16 about 40 years ago at age 17. Been sailing other things since the ripe young age of about 10.

I used expanded foam for years on hydroplanes that I built from about age 12 to 18 (one of which is still in service). It is a non-absorbant polyurethane that is not bio-degradeable. I have also used it in buildings, basements, for creating stage-props and to add a little more floatation to older aluminum canoes. It is probably the same thing as sold by West Marine except it doesn't say "Marine" and thus probably 1/3 of the price. :)

One really funny side effect is that the foam extrudes itself in the exact shape of the cross-bar until it is done expanding. Until I figured it out I had about 3 feet of extrusion on each end of the bar. One not so funny side effect is DO NOT get it in your hair unless you're really down with "liberty spikes" that will last shower after shower :lol:

It did make it easier to get the 16 over, not because of the floatation of one bar in the water but because I was not trying to lift about 30 - 40 lbs of water 4 bars @ approx 10lbs h2o per bar. Since those days I have gained enough weight to right a small tug-boat so it doesn't matter any more ... >;D

to Will in Latrobe - can you get those little pony-cans of RR down there? I haven't seen them in years!

for more info here's the technical stuff: http://greatstuff.dow.com/literature/index.htm
Author:  Karl Brogger [ Mon Jun 07, 2010 7:53 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
JJ wrote:
Maybe he should put the foam into a sleeve or something so it can be yanked out if it does deteriorate...

Ounce of prevention is worth X lbs/cubic ft of cure. Flotation is good, eh?



I like bulk heads, after digging waterlogged foam outta the FXone. The new boat doesn't have any positive flotation, but the front half of the hull is sealed off from the rear half. No drain plugs to forget either.

Worked for the Titanic........
Author:  nicolas92 [ Tue Jun 08, 2010 1:30 am ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
Instead of filling the cross-bars with foam or other urethane fill, you might try putting ping pong balls...these have a very good floatation, small & convenient size, very light and doesn't fill with water...
Author:  widerisbetter [ Tue Jun 08, 2010 8:52 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
nicolas - from the category of "things that work" you might have just come up with a good one. I like it.

It has occurred to me that some people don't understand the difference between styrofoam and polyurathane foam. The hulls of Hobies are filled with styrofoam blocks. Styro is more "spongey" and can trap and absorb water. Poly is, as I said, not absorbant and (for better or worse) not even bio-degradable.
Author:  JJ [ Tue Jun 08, 2010 9:21 pm ]
Post subject:  Re: Increase your floatation by filling cross-bars with foam
There's an idea to bounce around... (rimshot)
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