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Old 08-10-2018, 03:57 AM   #1
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The foamed dinghy argument...

I found this interesting and thought it was a good idea. Apparently the people in the comments are quite offended.

What say you?

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Old 08-10-2018, 06:06 AM   #2
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He wrecked the boat in my opinion.

The foam only adds weight, not bouyancy, making the boat even more overweight.

The foam is not waterproof as far as I know and the can foam I experimented with actually acted like a sponge if water made it past the harder outer coating.

The push in plastic caps are probabky not watertight so water will probably get to the foam.

If you are going to do it, use pour in foam made for flotation.....but remember it will not increase basic bouyancy, just increases rigidity and unsinkability.
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Old 08-10-2018, 06:12 AM   #3
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How can foam reduce buoyancy when it’s used in large blocks for floating piers? All those are, are big blocks of foam encased in plastic.
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Old 08-10-2018, 07:04 AM   #4
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Read what bouyancy really is.

Its about the volume of water displaced. Don't change the volume, add weight and the boat sinks deeper. They would have had to spray the foam on the outside of the hull to increase the volume with a lighter than water material to increase bouyancy.

The foam under the dock theory is probably what the two wannabe naval architects in the video thought too.
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Old 08-10-2018, 12:21 PM   #5
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Probably.

I really don’t care one way or the other. I just posted it for discussions sake.
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Old 08-10-2018, 12:28 PM   #6
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Plenty of boats use foam for positive flotation, however I don't think that increases load. It only prevents it from sinking when swamped. What they've done is possible reinventing what Boston Whaler did decades ago, but not actually solve their problem at hand.

Adding positive floatation will not increase freeboard, allow the vessel to plane easier or increase capacity or load.
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Old 08-10-2018, 12:46 PM   #7
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When Iím thinking about flotation i use 60 pounds of floatation per cubic foot of trapped air. I think itís actually a little more. If the space is filled with foam, you have to reduce the bouancy by the weight of the foam. Flotation foam seems to run between 2 and 4 pounds per cubic foot.

You must use closed cell foam or it will absorb water and become useless. I think all spray can foams are open cell foam. If anybody knows of a closed cell spray can foam, please let me know.
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Old 08-10-2018, 01:52 PM   #8
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Well, I just learned something new.

That's another way to ruin a boat!
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Old 08-10-2018, 02:55 PM   #9
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The scary part is the two wannabes actually sound like they know what they are talking about.

Enough that others would folllow their very flawed reasoning and procedures.
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Old 08-10-2018, 03:04 PM   #10
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Quote:
Originally Posted by psneeld View Post
Read what bouyancy really is.

Here:

Stability of Boats and Ships


(It's imaginary)
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Old 08-10-2018, 03:38 PM   #11
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I've been using closed cell expanding foam in voids for 40+ years. Available as a spray or mix and pour. It doesn't absorb water, bonds itself to materials it's in contact with, can be easily shaped and comes in different weights per cubic foot. I most commonly used it in spaces under floors in fiberglass I/O drive boats. I normally us 2lb/cu.ft mix. It quiets the boat, stiffens the floor and provides a space that can't be flooded. Hull full of water still floats. When a bottom is damaged, any water is stopped within inches of any opening. It also makes repairs easier.
I carry a 16' Bayliner I/O, open bow with a foamed in bilge. I don't think the foam added 50 pounds. The boat is quieter, especially in pounding waves, the hull stiffer, and the new floor is supported.
I also used it in new steel commercial boat construction for insulating and sound deadening. A foot thick or more around fish holds and 4"-6" thick around crew areas. In a completed hull, in the galley (over the engineroom), with several diesels running, no engine noise except the outside dry exhaust. Easy to maintain crew area comfort levels and -20įF in the holds.
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Old 08-10-2018, 03:46 PM   #12
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Fresh water weighs 63 pounds per cubic foot.
Salt water weighs 64 pounds per cubic foot.
Air has the buoyancy of the water it displaces minus .08 pounds per cubic foot (weight of air).
Basically there are 2 types of foam, open cell and closed cell. Open cell absorbs water; closed cell doesn't. Open cell foamed boats will continue to increase in weight over their life as they absorb moisture from the air. Moisture will find it's way past the plugs.

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Old 08-10-2018, 04:06 PM   #13
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Somehow those guys remind me of the old Sven and Ole jokes. This one comes to mind:

Ole and Sven went fishing one day in a rented boat and were catching fish like crazy. Ole said, "We better mark dis spot so
ve can come back tomorrow and catch more fish."
Sven then proceeded to mark the bottom of the boat with a large 'X'. Ole asked him what he was doing, and Sven told him
he was marking the spot so they could come back to catch more fish.
Ole said, " Ya big dummy, how do ya know ve are going ta get da same boat tomorrow?"
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Old 08-10-2018, 07:15 PM   #14
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Foam filled boats? What about Boston Whalers? They seem to make it work to the point where they're "The Unsinkable Legend".
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Old 08-10-2018, 08:41 PM   #15
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Foam is often a good thing, but filling a hull with it doesn't increase bouyancy until you go from normal conditions to some level of flooding.

BWs included.....
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Old 08-10-2018, 09:05 PM   #16
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I didn't notice them saying anything about making the boat more buoyant. The goal is just to make it more rigid, which they seem to have accomplished. The long term question will be whether the spray foam pulverizes from use and the boat reverts to its original flexing.
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Old 08-10-2018, 09:49 PM   #17
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They're fishing in the rain with silicone seals on holes to open cell foam. The water will enter and be retained by the foam and the boat will become heavier and heavier.

It's not a matter of IF it will happen. It's more of an issue of WHEN.
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Old 08-11-2018, 12:02 AM   #18
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Double skin plastic/poly dinghies are popular here as tenders for hire/charter boats. I used to use the marinas spare ones occasionally,though no idea if they were foam filled. But many definitely held water between the skins, to a greater or lesser degree,and they rowed like it, directionally unstable. Often felt way heavier than a 10ft dinghy.
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Old 08-11-2018, 07:52 AM   #19
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Quote:
Originally Posted by ssobol View Post
I didn't notice them saying anything about making the boat more buoyant. The goal is just to make it more rigid, which they seem to have accomplished. The long term question will be whether the spray foam pulverizes from use and the boat reverts to its original flexing.
At the very beggining, he discusses too much weight to carry and it being a problem. He says he is looking for a little more bouyancy......then at minute 9:14 I am pretty sure the second guy says the bouyancy is better than before after specifically being asked hows the bouyancy.

While it may not have been the only objective, both guys lack the badic understanding of it and are going out on a limb modifying boats without it...or even the most basic concept of the right materials for the job.
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Old 08-11-2018, 10:13 AM   #20
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Quote:
Originally Posted by psneeld View Post
.

While it may not have been the only objective, both guys lack the badic understanding of it and are going out on a limb modifying boats without it...or even the most basic concept of the right materials for the job.
I find it interesting that you have attacked THEM more than the idea.
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