Foam in the boat

[Mity]

Hi, I am new in sailing and I just bought the V25 made in 1976. I noticed that the owner removed all the foam of the boat thinking it had no use and was taking place......i need to replace it now. Can I replace it with any type of foam? how much should I add in?

I also noticed some water is coming i, only when I sail....he said it is from the keel movement, i doubt it....i'll have to check this when it is out of the water...any ideas?

Thanks for your help everyone.

Mike

 

[MrMikey64]

As far as foam is concerned, you can use just about anything. Many people are now leaning towards using those foam insulatiion boards you can get from Home Depot and such down here. As for amount, I discovered 27 cubic feet of foam placed throughout the boat when I dissected my 1981 Mac 25.
On the water issue, check the rubber washers/seals on your pivot bolt and keel lockdown bolt. If there worn or damaged, you will get water in through there. Also, check the tube where the keel cable comes through the hull. Damaged or deteriorated tubing also a good source for leaks.

 

[rgranger]

I've used the pink foam boards. They are very easy to cut and work with, they don't crumble much so they are also less messy to work with. Leaks on my boat come from the keel bolts. You can make new rubber washers but if you want a quick and easy fix, just smash some plumber's putty over the bolt heads while underway.

On my boat (V22) the keel cable hole will "spit" water when I'm sailing fast into a chop. So stuff a rag into it or a sponge and you will stop that also.

 

[Faris]

Yeah, what everyone else said ...

... except for foam volume. I did calculations for a V22 once, and to provide positive bouyancy with a loaded boat with an outboard, the volume of foam came to quite a bit more than 27 cubic feet. I don't remember the volume, but I do recall that I wasn't willing to give up that much space. Somewhere I have the spreadsheet I made to calculate. I'll try to dig it up and post it when I get back on dry land.

It also depends on the density of the foam. Pink (or blue) insulation foam such as was mentioned is not bad since it has a relatively low density, but it is not as buoyant as some. The trade off with low-density foam is that it is more buoyant for the same volume and less expensive, but more prone to damage.

I would like to make an appeal to the boating community in general and ask that you never use bead-type polystyrene. It WILL make a mess, and that mess WILL make its way into the water eventually where it will remain for a very long time.

I've considered making very lightweight fiberglass compartments that can be removed. I need to do the math, though, to see if this could result in reduced volume. My hunch is that it would be a wash.

 

[MrMikey64]

Yeah, what everyone else said ...

... except for foam volume. I did calculations for a V22 once, and to provide positive bouyancy with a loaded boat with an outboard, the volume of foam came to quite a bit more than 27 cubic feet.

No way I'm gong to argue the science here, if the numbers prove otherwise.
My results were based purely upon removing the blocks and stacking them. The resulting stack, after all the pieces were put together, was 3 feet x 3 feet by 3 feet high.

 

[Phyrexii]

Foam calculations

One thing you need to remember is that everything displaces water, and the weight of a submerged object is less than what it would be on land. The USCG Boat builder's handbook has a more thorough explanation of this:
http://www.uscgboating.org/regulations/boatbuilder_s_handbook/flotation_part1_e.aspx

As a crude example, my V25 weighs approx 2100#. To grossly simplify things, let's assume that weight is divided up as my keel, @ 630#, and the fiberglass hull is the remaining 1470#. 630# of cast iron displaces 1.24 cubic feet of water, at 64# per cubic foot. So, the submerged weight of the keel=630-78, or 552#.

1470# of fiberglass displaces 15.4 cu ft of water, which weighs 985#. So, the hull only weighs 485# submerged. Therefore, the total combined submerged weight of the boat is only 1037#, requiring only 16 cubic ft of flotation to remain neutrally buoyant. The 27 cubic feet of foam that was originally in the boat would give an additional 700# of reserve buoyancy.

This is only a super crude example, and does not consider anything else in the boat, including gear and passengers.

 

[Mity]

Thanks to everyone for your answers. I'll check the pivot bolt and cable guide next week. For the foam, I found some information on how to calculate the quantity require. (www.glen-l.com/weblettr/webletters-7/wl55-flotation.html). as for the type of foam, i will get out of the bead-type polystyrene....too messy and not environment frendly.

Thanks again.

Mike