Positive bouyancy

[swampthing]

I am rebuilding a small yacht (Hunter Europa) with modifications for offshore sailing. I want to install about 18cu ft of foam around the hull. Does anyone know an easy method of calculating the volumes of the odd shaped lockers etc where the foam will fit.Also, would chunks of expanded polystyrene bedded into polyurethane foam be ok?
Thanks to anyone who can offer some advice.

 

[futurama]

I presume polystyrene is bulking for the foam.
I'm no expert but polystyrene absorbs water which may not be a problem if inside foam,but it also gives off gas which may react with the foam. /forums/images/graemlins/confused.gif

 

[captainslarty]

Buy a good bilge pump and sail away from the rocks

 

[swampthing]

I have 2 good pumps. Rocks are no problem, more concerned with containers and other junk ive seen out there and some I havent seen at night.

 

[DinghyMan]

Have a look through the YBW Jester Forum as it has been discussed in detail there. As mentioned above poly is no good and you need a closed cell foam.

 

[PeteCooper]

Do a search on 'Willing Griffin' sailed by 'David Blagden' - his wasn't the Europa but the basic Hunter 19 and he crossed the Atlantic single handed so had presumably done some of the mods you are looking for.

 

[dockmaster]

How many floating containers have you seen ?

 

[bazobeleza]

why not install dinghy style inflatable bouyancy bags, that way you can remove them when you need and much more reliable than injecting foam, creating damp interfaces .

My first proper yacht was a Europa, a wonderfull boat, loved it to bits.

 

[swampthing]

2 ,in Irish sea ,2003. Plus a 45 gal oil drum. I know its unfeasable to make big boats unsinkable but with a 700kg Europa it can be done for a couple hundred quid and its a bit of extra insurance when the $h1t hits the fan.Thanks to all for advice

 

[jwilson]

I did something similar one, and not being able to afford enough polyurethane faom put in a variety of other items to pad out the expensive foam stuff. I tested polystyrene for reactions, and the PU did slightly eat into the surfaces of the PS, but it all seemed to set OK. I used some sealed hollow container (like empty milk cartons) in the bigger spaces - saved a lot of foam volume.

 

[pandos]

why not use inflatable floatation bags that can be blown up using compressed gas.

The co2 can double as an engine room extingusher.

There was an article a few years ago about making this kind of system.

 

[William_H]

My little boat in common with many small boats has seats/ berths down each side of the hull with a well in the middle to walk in. I have opted to seal the under berth area forgoing stowage under bunks.
This is an excellent place for bouyancy as it will maintain the self righting of the boat. That is if water gets into the hull and can move to the chine area of the bilge it negates the bilge area from righting.
Water in the middle of the boat however will act as water ballast.

The volume of under bunk stowage area can be calculated roughly on width of the bunk times length times depth then divided by 2 to allow for the roughly triangular cross section. In practice this triangular cross section will be bulged outward at the curved chine area so giving a lot more volume than the calculation. Perhaps closer to 2/3 rather than half.

if you fit a sealing lid then the area can be used for stowage provided you always reseal. All with the added bonus that if the hull is penetrated in the bunk area it will be isolated to that area but with some loss of self righting. olewill

 

[DownWest]

The French insurance surveyor asked if I had foam in the tanks, on me saying no, he suggested water bottles (empty!) and to change them every 3 yrs. BTW He also thought the blue costruction foam good, just more expensive. Roof Mate and WallMate are the trade names. I have read of several people chopping up closed cell and feeding it in. As said gives access if you need to fix anything. The idea of permanent foam doesn´t appeal. Don´t forget the 2-part stuff gives off very toxic fumes.
Andrew
As usual, Olewill comes up with good advice.

 

[geoffatstanpit]

Foam under the bunks might not be such a good idea for a boat where the ballast is mostly a cast-iron daggerboard which is not rigidly locked down at all times (including on the mooring). Putting permanent buoyancy so low down in the hull results in an upside-down stable situation if the cabin completely fills with water. This happened to 2 boats similar to mine on moorings, one filled through the chain locker (too short riser and big spring tide) and the other by waves over the transom and in through the washboards (tide-rode against the wind and swell). Both got thoroughly soaked inside, inverted and lost their rigs.

 

[roger]

Polysyrene foam

The white foam certainly absorbs water. It's made by expanding small beads of PS internal gassing. The beads stick together but channels run through the mass.
In the building trade they use closed cell foam of much higher quality. I only know it as "blue" foam as opposed the the cheaper "white". In fact some of the better foam is pink.
All PS has a nasty tendency to dissolve with organic solvents.
Two possible methods of fixing it. Have not tried either.
a. pint the foam with water based paint then use ordinary contact adhesive in spots.
b. use PVA - also available from builders very cheaply.

 

[swampthing]

Hi Geoff. Just to confirm, The Europa does not have a daggerboard,but a beautifull fixed fin with bulb at bottom so c of g is way down, plus a 50% balast ratio which is why these little yachts sail well. Thanks all for good tips, especially from William H.