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Old 10-04-2019, 01:26 PM   #1
Dr Hook
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Default flotation foam and Al boat, best practices?

Last month while on the ocean alone, I hit a deadhead when running back from fishing. No damage, but it shook me up. It got me thinking about that Alumaweld earlier in the year that took a wave over the bow and immediately sunk, leaving the crew of 6 bobbing in the bar. ...boy, it'd sure be nice if my boat would have some basic flotation... even the bow above water to grab onto! Or the guy out of Newport last weekend who was found with his lifejacket on, but likely died of hypothermia before anyone could find him... if there was only something that you could up on to get out of the water. I've been looking into the pro's/con's of flotation foam, mostly the negatives have been discussed: it takes up storage space, eventually gets wet, holds water close to the Al skin causing premature corrosion, bilge area is a hostile environment (fish blood, fuel, oil) and a PITA to remove.


Now the bow of my boat already has a layer of sprayfoam along the bottom half for sound deadening. It avoids the deepest part of the "v" (continuous with the bilge). So any more foam that I added here would be unlikely to get wet. And, I thought why not simply provide for proper drainage for the foam sprayed into the bilge area? I thought of using a dimple board, akin to the drainage fabric you use in basement/home construction. It's durable and resistant to fuel/oil. http://www.centralconstructionsupply...CABEgLyRfD_BwE


I called up my boats manufacturer and they suggested that I use a froth-pak: https://www.lowes.com/pd/Dow-FROTH-P...Kit/1000015591 This is the same closed cell urethane spray in foam that is used in a marine setting. It's resistant to fuel/oil and most bilge cleaners (TSP) and it is fire rated.


So far I've got all of the materials but am just waiting to strip off the decking to evaluate the specifics. I'm pretty sure it'll float (basic flotation), as the calculations are pretty easy. I'm not sure that this is the best idea for the longevity of the boat structure and I wonder how hard it will be to keep fresh/clean (tuna blood, etc)... I mean, I've still got a few years before it's paid off. Any experience or comments? Thx

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Old 10-06-2019, 01:36 PM   #2
LGB
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Default Re: flotation foam and Al boat, best practices?

So your Weldcraft 202 is over the 20' size that is required to have flotation per Coast Guard Regs. Adding it is probably a good idea. Smaller boats are required to float level so keep that in mind when distributing the flotation foam. You transom with the motor(s) will be the heaviest part of the boat.

However, you mentioned the fellow who died in his life preserver from exposure so even if the boat floats you may be in trouble. So It might also be a good idea to have a exposure floatation suit if you are going in the ocean. Not to mention a portable VHF radio with GPS and DCS emergency location broadcasting and some form of signal flares or signal light that floats (http://www.weems-plath.com/SOS-Distr...nic-Flare.html). I would go for these items before worrying about keeping my boat afloat.
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Old 11-08-2019, 11:18 AM   #3
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Default Re: flotation foam and Al boat, best practices?




Project float your boat is now underway! I couldn't get the pics to load upright... so it'll take a little imagination.





The basic calculation for reserve buoyancy (ISO-12217) says that my boat needs 37 cubic feet of foam to float 971kg of dry weight and 236Kg of motors. That is actually a lot of foam!


I did use an expanding insulation ("Dow 210 froth-pak") to fill in much of the void in the bow. I was careful not to get it too low, as to keep it clear of bilge water. I did provide a pathway for water to drain from the top. The Froth pak was easy to use, but the expansion is very temperature dependent.



In looking at the underfloor, I'm rethinking the idea of expanding foam laid over dimple board... the shapes are just too irregular to ensure complete drainage once the foam was poured. I did a test with loosely packed pool noodles, which did easily drain water past them. These dried out completely after a few hours of draining after flooding the bilge. These are also polyurethane and shouldn't soak easily. I doubt that they are fuel or fire resistant. They would be easy to remove should they become moldy/stinking or if this turns out to be a bad idea otherwise. The foam volume of a standard 2 1/2" x 60" solid core noodle is .174 cubic foot. I can easily access to the two boxed-in frame rails which should hold 20 loose packed noodles each. (7 cubic feet).



There are also a couple of large spaces that would accommodate polyurethane foam board. A typical 2" x 48" x 96" sheet = 5.33 cubic feet of foam. Again the sheet would be easily removed if found to be problematic. I think I can stow 2, maybe 3 sheets under the floor. (16 cubic feet).
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Last edited by Dr Hook; 11-08-2019 at 03:06 PM.
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Old 11-09-2019, 08:17 AM   #4
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Default Re: flotation foam and Al boat, best practices?



I don’t think there’s anything wrong with using pool noodles. I’ve used them on 2 boats now and haven’t been unhappy. On any of the noodles that I’ve tested they were definitely closed foam and didn’t gradually take on water and they did not dissolve in petroleum products (i.e. any spilled gas).

You’re wise to keep the floatation as high up as you can to try to minimize having the hull turn turtle in the event of a catastrophe. In my first boat I was able to hide the noodles up along the sides, but in the boat shown above that just wasn’t possible.


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Old 11-09-2019, 12:11 PM   #5
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Default Re: flotation foam and Al boat, best practices?

Totally agree with Dave b above in my testing. I think he did everything right in the above picture except he should have used more green and blue for a better color pallette
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Old 11-15-2019, 08:32 AM   #6
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Default Re: flotation foam and Al boat, best practices?



I've finished my float your boat project. It took (2) Dow 210 Froth pak's to fill the bow. I was able to fit (2) 2x4x8 foam board sheets under the floor and able to stuff 50 solid core pool noodles into the wishbone rails.


I got a much better expansion rate of the Froth-pac by first warming the tanks and warming the area prior to spraying. I would think that this project would be best saved for an 80 degree summer day and not a cold November day. Still, I was pretty much able to maintain my forward storage area. I was pleasantly surprised that there was very little over-spray mess to clean up afterward.



This project gave me some awareness of how hard it is to provide enough foam to float a 20' + boat. Maybe that's why floatation is only required in smaller boats. Still, I think it'll float bow up. Hope to never test that theory.



The actual calculation for my (Aluminum 0.62) boat @(971kg) and motors (236kg) reserve buoyancy is:


1.2 x (( 971kg x 0.62) +236 kg) divided by 1000-35 = 1.04 cubic meters of floatation foam.
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Old 11-15-2019, 11:02 AM   #7
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Default Re: flotation foam and Al boat, best practices?

I read an article once on the foam requirement coming about from the boom in small boat ownership in the 60's and early 70's drawing the Coast Guard's attention to the number of drownings that were occurring in cap sizes/accidents. Some not very well thought out or built boats were on the market then, and when they capsized from negligence or a failure, they sank like a rock leaving boaters in pre-PFD days with a serious problem.

A lot of the safety things we have today (hull weight/HP ratings posted on the boat, foam in boats under 20', bilge ventilation and blower requirements on inboards, etc...) come from that era.

I think you are spot on about the 20' cut off being more about the practicality of trying to float larger hulls than anything else. Short of going to a more expensive double-hulled design (Boston Whaler, Arima) or a chambered design (Stabicraft, Zodiac) it isn't really practical.
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Old 11-16-2019, 03:49 PM   #8
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Default Re: flotation foam and Al boat, best practices?

So, I am taking out the soaked up foam from my 2013 Alumaweld. Click image for larger version

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Its a tough job, but the worst part is getting the foam out of the box stringers. There are only some eggs shaped holes and I cant figure out any reasonable way of getting that foam out. Any ideas?

Alumaweld will not return my calls. Boat kept in the garage.Click image for larger version

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Old 11-16-2019, 06:04 PM   #9
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Default Re: flotation foam and Al boat, best practices?

Quote:
Originally Posted by gregsalmon View Post
So, I am taking out the soaked up foam from my 2013 Alumaweld. Attachment 734243



Its a tough job, but the worst part is getting the foam out of the box stringers. There are only some eggs shaped holes and I cant figure out any reasonable way of getting that foam out. Any ideas?



Alumaweld will not return my calls. Boat kept in the garage.Attachment 734243
Enlarge those couple holes on top and make a couple more spaced out as needed. Just leave a lip at least an inch next the the edge to keep the strength and it won't affect your boat strength at all. Still a little pain to get out. Easier to cut the whole top off and clean out and then weld it back together though.
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Old 11-16-2019, 06:59 PM   #10
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Default Re: flotation foam and Al boat, best practices?

Quote:
Originally Posted by Quiet Riot View Post
Enlarge those couple holes on top and make a couple more spaced out as needed. Just leave a lip at least an inch next the the edge to keep the strength and it won't affect your boat strength at all. Still a little pain to get out. Easier to cut the whole top off and clean out and then weld it back together though.
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Old 11-16-2019, 07:00 PM   #11
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Default Re: flotation foam and Al boat, best practices?

Thanks! Kinda what I was thinking. I don't understand why this had to happen....
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Old 11-17-2019, 09:19 AM   #12
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Default Re: flotation foam and Al boat, best practices?

Is the foam completely waterlogged or jus wet.


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