[Rhodes22-list] Hull strengthening
jfn302 at yahoo.com
Sat Dec 21 12:29:56 EST 2013
I'm certain the foam I found was original because it was in areas of the boat that could not have been gotten to without either cutting out the inside liner as I did or pulling the deck off, then pulling the liner out from above, and neither of these things had been done before I got the boat. And you are right, some of it was water logged and had turned into big blocks of ice when I was pulling it out.
The area that I took the foam from is roughly triangular and the v-berth was roughly 6ft give or take a few inches in length and about 4ft wide. So overall cubic area would be 12cf if the shape was perfect, minus 2cf from that for the battery box that was in the V-Berth. So it had a little under 10cf of floatation under the v-berth, which would give the boat about 600 lbs of positive buoyancy.
So it looks like I am going back with a little under half of what was there. So, if I went with a full inch instead of 1/2" then I would be right where I started.
The foam I am planning on using is the blue sheets that have the higher R value. It says it is water resistant, but doesn't say if it is close celled or open.
I had thought about the spray in foam, but it would be hard to make sure I filled the area behind the liner sufficiently. Which is why I decided on the foam sheets. I could pull the liner away from the wall where it is tight and slide the sheet up to the top. Also the blue version of the foam is more flexible than the pink (or white) so it would handle the flexing and pushing required to get it up behind the liner better than the other foams I looked at.
I am thinking I might be able to regain my positive floatation completely now that I have done the calculations, and still gain the extra storage because I'm spreading the foam out over the entire inside of the hull rather then just below the v-berth. I get the added benefit of about R 6.6 insulation throughout the hull as well to help keep the interior comfortable in the cold waters of the northwest.
From: Graham Stewart<gstewart8 at cogeco.ca>
Sent: Sat, Dec 21, 2013 at 10:35 AM
To: 'The Rhodes 22 Email List' <rhodes22-list at rhodes22.org>
Subject: Re: [Rhodes22-list] Hull strengthening
James:Interesting. I am wondering whether 240 lbs of flotation would be adequategiven the weight of the boat - I have no idea what the weight would be whensubmerged to the gunnels. I have not been able to see under the cockpit tojudge how much flotation there is there but I assume it cannot be very much.If the original flotation is adequate to keep the boat from sinkingpresumably if you replace the flotation with an equivalent volume of newflotation, that should be adequate. I do think, however, that white beadflotation would be questionable and I wonder whether what you found wasactually the work of a previous owner. I would want closed-cell flotation asthe white bead stuff can become waterlogged and if that were to occur, forwhatever reason, would need to be replaced- or worse. I think thathigh-density foam is closed-cell or close enough but I would want to checkthat out. Is it the same as the pink flotation blocks that Home Depot sells?If not, you
might be better to cut up the flotation blocks to fill the spaceor use foam-in-place.I just found the following excellent article on the subject on the Glen-Lsite that takes much of my guess work out f this discussion:http://www.glen-l.com/weblettr/webletters-7/wl55-flotation.html Graham
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