The album of Ariel #422

[ebb]

I may need enlightenment.

Believe the .89 figure is not right and could be inverted.

If I have a 6000# boat and I use the 58# reserve bouyancy per 100# I come up with 103 cu ft of foam needed to suspend the boat in water. I would need more than that to float it with the decks awash. And more than that even to have the boat floating high enough to try to repair it.

Maybe the .89 should be 1.11 as a minimum.


I, of course, agree with Baldwin on everything he says.
Open top bulkheads like the one for the head will not float the boat if water goes over them. If that incident where he was holed by a fishingboat had been below the waterline, we might be reading another story.

[CapnK]

Hmm, OK, this is how I understand it:

Take something which weighs 1# out of the water. When you submerge it in water it weighs less, and just how much less is a function of its relative density.

This difference is its "reserve buoyancy".

I am going to do some number-rounding here for ease - since math makes my head hurt.

According to the Skene's chart on Baldwins site, 700#'s of lead (one cubic foot) weighs only 636#'s in the water - a ratio of .908 (or: 636 divided by 700). So the 2300# ballast in an Ariel would weigh 2,088#'s submerged, right?

An empty Ariel displaces 5120#'s of water, so that is it's weight. Subtract that 2300#'s of lead ballast, and that leaves 2,820#'s of miscellaneous other materials, the largest majority of which is fiberglass.

According to Skene's, a cubic foot of fiberglass weighs 96#'s, yet underwater the same cubic foot only weighs 32#'s - exactly 1/3, or .333. Fiberglass is denser than most everything on the boat, so for simplicity's sake lets just say that the whole rest of the boat weight is fiberglass. Underwater this mass of fiberglass would weigh 940#'s (2,820 x .333)

Add the 940 to the 2,088, and you have 3,028#'s, which would be the amount of flotation you would need to provide in order to suspend the boat in the water, just at/below the surface.

Right?

3028 divided by 58 (the flotation of a cubic foot of polyurethane foam, from Skene's) equals 52.206, the amount of cubic feet of foam needed to barely float an empty Ariel.

(~8 more cubic feet of foam (to make it an even 60 cu/ft) would provide for an additional 464#'s of flotation - which is more than 464#'s of stuff, taking into account that that stuff would weigh less in the water...)

Note how close this is to the "1 cu/ft per 100#'s of displacement" guesstimate - neato.

So - Am I figuring this right, even though loosely?

If I am, I will be amazed.

[mbd]

You'll know for sure when you "test sink" your boat!

[CapnK]

You'll know for sure when you "test sink" your boat!

LOL, ain't that the truth.

I put some foam into the boat last night, and found (as usual) that it'll be a learning process. My first attempt was using 1 large piece of foam - approx 18" x 6'4" - up against the hull, in the area under the stringer, down to the level of the original vberth. This taught me that it will be easier to do this with smaller panels - say 2' max dimension. It also taught me to cut the foam outside of the boat, in the daytime - little tiny pieces of foam get *everywhere* when cutting, even with a razor knife. For this "exploratory foaming", I am using 'Cellofoam' brand panels - 3/4" thick EPS, it has a mylar radiant heat barrier on one side, and is only US$10 for a 4'x8' sheet. I'm using 4 sheets to make a first run at the process. This foam will probably all be removed in favor of pink/blue foam for the end product.

I also made a small test panel of my "foamboard plywood" concept (pink foam sheathed with wood) to see how strong that combo is likely to be, and have to say I am *very* pleasantly surprised. I recommend that anybody adding structure into their boat consider this as a light, strong alternative to conventional plywood. I sandwiched the foam using Luaun door skin material - it comes in 1/8"x3'x7' - and it is very light and very stiff. The door skin material can be cut with a razor knife, too, which really cuts down on dust and noise. I think another advantage is that I will be able to use it like and instead of cardboard for laying out the size and shape of the bulkheads inside. Cut the Luaun to the right size, and I have 1 skin which is also the pattern for the other skin as well as the foam core...

I looked at all the adhesives at Lowes and Home Despot trying to find one compatible with the foam. For right now, I don't want a permanent solution, so I eventually went with "Duro All-Purpose Spray Adhesive" which claimed that it would work with foam board. It does, but only if you spray it very lightly and quickly - otherwise some ingredient in the stuff literally eats the foam up. When I put the foam in for good, I am thinking that I will just use 4200, spread with a squeegee/trowel...

[ebb]

Kurt,
Thanks for the conversation and your math.
I will probably find out what the specific gravity of fudge is
and apply it to a decent flotation fudge factor for 338.

It's patently obvious that this respondant enjoys detailed information and experiences on our classic plastic sailboat refurbishing. So, I hope you continue to regale us with your discoveries.
I hope also that this panel invention of yours works out. You may indeed have something for us whole boat remodelers.

Weldwood (UPC# 25330, pint) has a 'professional grade' NO SOLVENT, LOW ODOR neoprene contact cement. It's nonflammable, low odor. waterborne. Has a half hour + dry time and a 2 1/2 to 3 hr assembly/open time! "Resistant to the effects of water" and the "bonds become stronger and more resistant as they age." It can be applied with a short nap roller (or spray). Work has to be above 65degrees. No clamping is needed but pressure is by using a J-roller. Normal. After bonding you can cut the panel. I'm taking this off a Tech Bulletin. You might find more info at www.dap.com


Ofcourse, if you make up these panels in a ventilated place you can use regular cement. But the solvents, as you point out, may melt the styrene.

I'm getting me some of that goo, and may follow you on your panel invention. Attachments to the panel will require glueing, with some thru fastening possible with backing plates/cleats. But you will be building in reserve bouyancy!

Assuming you'll be testing the panels, I'll be very interested on what permanent glue you come up with. 4200 sounds expensive, and difficult, I imagine, using it to make up whole panels. Onward!
__________________________________________________ _________________________________________________
Just been reading Practical Sailors old review of caulking and sealants. Complaints about 5200 include that it's too runny and takes too long to skin over. Sounds good to me! Except for the $$$$$ - and the possibility that you unwittingly can buy tubes too long on the shelves and the product has become too stiff!
[Will try an experiment with 1/2" flexible ensolite that is intended to line the inside of the hull above the waterline on 338 - using this Weldwood stuff.
The Tech Bulletin has a help number that may be useful followup. Most of the uses for contact cement are for laminates, veneers and plywood over core panels - and also paper and cloth and cloth-backed vinyl.]

[CapnK]

Kurt,
Thanks for the conversation and your math.
I will probably find out what the specific gravity of fudge is
and apply it to a decent flotation fudge factor for 338.

Ay, and for beer and/or rum, too!

Does the math seem right?

Thx for the heads up on the DAP product, it sounds just right.

Hadn't thought of it, but attachments to the foamply would follow the same process as attachments to the deck. Without the complication of potential leaking when it rains...

[Howard]

Kurt,
Go out and get a cheap "hot" knife if you are going to cut alot of foam. No pieces little whatsoever and the heat seals the foam a little. I use alot of foam in making GFRC monuments. Also, if you are going to make some high cubic sizes you can leave a void inside your block if you plan on sealing the luan with glass.
The air pocket would be more buouyant than the foam.

[mrgnstrn]

Ay, and for beer and/or rum, too!

Nope, they float by them selves!

In fact, they will likely float away......

And, since it is rare to have a full bottle of liquor on any sailboat (based on my extensive crewing on other people's boats), you could statistically figure out how empty your collection of hooch is likley to be, and count on the air in the bottles as flotation, in addition to your foam.

And I just thought of this, if you are basically lining the inside of the whole hull with foam, when you are done, you should glass it all in. This way you will not only have flotation, but a double hull (ala freighters and russian submarines....)