Adding additional buoyancy to an AC boat.

[OMSC]

my old cheshire cat suffers from swamping and I am thinking of adding additional buoyancy to give it a bit of a lift.

I was thinking that if I got some expanding foam, like the stuff to fill round windows etc, I could build some bouyancy stuck directly to the hull, shape it and paint it up to seal it., and protect it from the sun. this would allow me to shape bouyancy around the bags at the back, leaving a shaped channel to the transom flaps.

I know it would not support being stood on, so installing beneath and around the bags, and posibly around the mast step at the front of the boat. wherever my feet are not going to go. The thought is that it will give a few extra poinds of lift (maybe 10-20 kg) where I most need it low down, at very little cost (buying a buoyancy bag would probably double the value of the boat) and very little extra weight.

Firstly, is there anything in the rules preventing me doing this,
secondly.  has anyone tried this before?
 
I am doing a number of other things to help the problem, such as new slot gasket but the additional bouyancy will also aid bailing when we tip it in marginal conditions.
any help appreciated.

[Tim Gatti]

Most AC boats can suffer that 'swampy' feeling and don't let your Cat tell you otherwise.  Frankly, I wouldn't start gunging up the inside of the hull with adhesive foam - whatever you do it's probably likely to take up water over time - which will add a lot of weight and compound your current problem.  It will also be a nightmare to remove should you change your mind about it.
Brian Kitching made some rather neat foam buoyancy units that bolt into his vintage Chimp, instead of buoyancy bags - so if you are thinking of going down the closed-cell foam route I would give him a call. Not sure what the cost was though.
Don't know where your current bags are located but are they as low down in the hull as you can get them and are they big enough, fixed securely and fully inflated?  These four factors can all help to improve water displacement.  You might also consider a couple of small bags - one each side, under the thwart if you haven't got some there already?  They are much cheaper than the big pillow bags. 
Finally, if you haven't already done so, invest in a big bucket! See attached pic of mine - don't know if you can still get them this shape but it means you can get a lot of water out very fast if you need to.  Cheers Tim

[OMSC]

thanks for the advice tim.  Have invested in a bucket for northampton, and replaced the rubber slot gasket with a new one made from an old mainsail.
Moonshallow, are you ready to bail?
I want to try the foam bouyancy, but have adapted the plan.  I am thinking of lining the boat with plastic, probably cling film at the rear, then spray in the foam, then I can remove it when set, giving a perfect mould of the bottom of the boat, shape the top half, and seal it with a couple of layers of paint. the bouyancy should then click into place, and a couple of straps across the top should make it secure. I think the whole process can be done for about 15 quid including the paint and cling film.
 
If it does then prove to take on water, I can remove and dispose.  is it legal to have removable bouyancy so I only fit the additional when it is blowing and I am likely to dump it, and remove it in the light winds and run with minimal but legal buoyancy?
 
If not it will probably weigh as much as a wet suit so I just guess I will have to sail cold.

[angus]

Tim is that a wheely bin youve got in the back of your boat?

[angus]

Tim is that a wheely bin youve got in the back of your boat?

[angus]

whoops I seem to be getting a bit repetative

[Tim Gatti]

Don't knock it Angus - I seem to remember a few times when you'd wished you'd had a big bucket in your Crusader!

[angus]

I wasn't knocking it, I was well impressed. What I need is a skip on the other side!!

[icecreamman]

What, the outside. Surely not Angus!

[paul turner (Guest)]

Yo Gattiman! What size bags are they in the photo? I have been reviewing bouyancy for the Burton for Dolly Daydream. When I took Starfish this year and capsized off the beach we are able to recover and race (but it wasnt too lumpy) but she has two x 150lbs at the back under covers plus two x 75lbs under the side seats. Dolly doesnt have side seats so I am looking for other ways to "beef up" overall bouyancy as she only has two x 150lbs at the rear. One more in the middle at the stern would get in the way of towstraps for planing? There isnt room under the thwart. What about each side of the centreboard case? Has anyone tried this? I dont want to go with lumps of floating foam if at all possible - look horrid and add weight. Px :K)

[angus]

What, the outside. Surely not Angus!

Yes your right ICM not really blame it on depression caused by the depth of winter8)

[icecreamman]

I would have thought that you should have plenty of buoyancy with what you have described. The only worry that I would have would be that maybe the small bags under the seats may be too high up in the boat to be really useful should you decide to wash the boat out by mistake. Getting them as low down in the boat will help, it's all that clever physics stuff we learned at school devised by that Greek fellow.
Best of luck with it all however Paul.

[paul turner (Guest)]

Dear Mr Icecreamman, the 2 x 150lbs is just about ok for the river but on open water (eg when we capsized at Derwent in a blow) it wasnt enough (even though tied down low in the boat) so for the sea with proper waves we need to upgrade. Under the side seats was good for Starfish as they couldnt lift at all being trapped, but under the thwart in Dolly I agree won't work so.........? :-/

[Tim Gatti]

Hi Paul - aft bags in the pic are 36" x 12" - not sure how many pounds that is. Tim