Solid foam buoyancy

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Ed
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Re: Solid foam buoyancy

Post by Ed » Thu Jul 31, 2008 2:30 pm

The problem with putting bouyancy too high under inwhales is that it only really works when the boat is on its side and does next to nothing when boat is right way up.

It does however make the boat pretty stable when flooded, which is no bad thing, but does not help you get going again.

Merlin Sailors are the absolute experts at sailing & self-draining flooded boats. I used to be worried because on Rozzer MR999 the transom was pretty much water level when flooded. I went to Merlin Inlands without buoyancy certificate suspecting it would not be given. But they were happy to only check the strength of straps (picking the stern of boat up by straps - tough test!). I explained my worries about lack of stern buoyancy and they said not to worry - they were pretty much all like that - which was true. But they did give me some lessons in how to empty it, which were very helpful. After that (and a fair bit of practice) I was pretty much able to sail the water out as long as there was enough wind and room to do it, but it certainly is a bit of knack.

cheers

eib
Ed Bremner
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STEVEB
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Re: Solid foam buoyancy

Post by STEVEB » Thu Jul 31, 2008 7:48 pm

Hi,
would a centreboard gasket help slow down the incoming water enough to let you bale it out quicker?
Steve
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Ed
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Re: Solid foam buoyancy

Post by Ed » Thu Jul 31, 2008 8:28 pm

Well I am sure it would help!

But very few gaskets stay in good enough condition for long and most have a little cut-out at the back to encourage the water to drain out.

So I don't think it would replace the rag or whatever.

cheers

eib
Ed Bremner
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Jollyboat J3
Firefly F2942
IC GBR314 ex S51 - 1970 Slurp
MR 638 - Please come and take it away
Phelps Scull
Bathurst Whiff - looking for someone to love it

andrew
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Re: Solid foam buoyancy

Post by andrew » Thu Jul 31, 2008 9:23 pm

Thankyou all.
I was very close to buying resin and cloth today.
Having had a very interesting discussion at the excellant Porter brothers in Emsworth.
Glad I waited and read todays postings.
Of course more efficient bag buoyancy and a towelling scarf is the way to go.
I had planned roof insulating polystyrene cut and wire brushed into shape covered in parcel tape.
The parcel tape to keep the resin from dissolving the foam.
2 layers of 450 g chopped strand mat and lots of gloss paint.
Polyester foam is available and can be glassed directly without the tape but is apparently more expensive.
It was all beginning to look a very messy and smelly job.
Who does custom buoyancy bags ?

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Ed
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Re: Solid foam buoyancy

Post by Ed » Thu Jul 31, 2008 11:37 pm

Custom Buoyancy Bags are made by a few people.....

Mine were made if I remember by a company called Haymoor Leisure or something like that.

But they go to all (well most) of the boat jumbles, selling a range of goods made from plastic sheet from prop-covers to seats and boat covers.

but I have come across others, I will try and dig something up

cheers

eib
Ed Bremner
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Michael Brigg
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Re: Solid foam buoyancy

Post by Michael Brigg » Fri Aug 01, 2008 2:17 pm

There are numerous inflatable dinghys out there with inflatable floors. If you could canabilise a couple of these and batten them down you could have a jolly boat that doubled as a bouncy castle! Who said they couldn't persuade the children on board?

I am actually being fairly serious! I presume you want a solution that is easily removed when you want to show the boat in its "Classic" condition, but need to feel that you are not in peril on the water. Weight of course is a bit of an issue. The advantage of an "inflatable floor" is that it could be started under the deck and extended perhaps down to the turn of the bilge.

Which reminds me...

Headteacher of the inflatable school to boy with pin....

"You've let yourself down, and you've let your class down, but worst of all....

You've let the whole school down!"
Michael Brigg

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Re: Solid foam buoyancy

Post by Ed » Sat Aug 02, 2008 10:06 am

Now, first of all, I should say that I am not being in the slightest serious here.....but.....

Jollyboat class rules specify that all bouyancy should lie underneath the plan of the deck surfaces, which pretty much outlaws any kind of false floor.

Not that this worries me much about your plans....go ahead and do it.

It is one of the rules (there are a few) that I would really like to convene an 'Owners Association' again to study and change or revoke.

Along with:

Free shape/design of rudder
Allow full length top batten
Allow higher mast as suggested by meeting at last convened Jollyboat AGM

There might be a couple of others too.

cheers

eib
Ed Bremner
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IC GBR314 ex S51 - 1970 Slurp
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Michael Brigg
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Re: Solid foam buoyancy

Post by Michael Brigg » Sun Aug 03, 2008 5:56 pm

Dunno if this helps; It's how I fix my bags in onder covers and in my opinion is the best way to keep the bags really firmly fixed in and held firmly down where you want them. Its also easy to remove the bags when you need to.

I'll add explanatory note to the pics in a day or two.

http://s225.photobucket.com/albums/dd31 ... 20fitting/
Michael Brigg

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Re: Solid foam buoyancy

Post by Ed » Sun Aug 03, 2008 6:36 pm

Pretty much exactly what I do also,

although I just have a batten on bottom edge and hold it at either end.

In fact I have a batten on the Jollyboat, but not on the Firefly,

Michael's way of holding bottom is better, I guess, but I havn't lost a bag yet and although it is a bit dodgy, it is just fine on the Jollyboat.

The tops are identical.

cheers

eib
Ed Bremner
CVRDA


Jollyboat J3
Firefly F2942
IC GBR314 ex S51 - 1970 Slurp
MR 638 - Please come and take it away
Phelps Scull
Bathurst Whiff - looking for someone to love it

Michael Brigg
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Re: Solid foam buoyancy

Post by Michael Brigg » Mon Aug 04, 2008 8:13 pm

Ed said...
but I havn't lost a bag yet
Not what you told me! I thought you had one wriggle out from under the cover on the way home. Deflated to reduce pressure in the hot mid day sun, it shrunk further still in the cool of the evening and having escaped it's promethean bondage leapt joyfully into the path of a pursuing juggernaut!

Which of course is also the problem with a capsize. The cool (or bloody freezing) water may cause the bag to shrink ( Physics:- Charles law; Gas volume = Gas constant x Temparature) by as much as 30% or more. More than enough to make a tight binding very loose. I think Houdini had a similar technique of expanding his wrists when he was tied up.

All the more reason for securing the bottom in several places. (Only two secure points also leaves you vunerable if one point comws undone.)

The particular nicety of my method is that the coers are easily removed for cleaning or maintenance, by simply sliding the top batten out through the hole in the front Knee.

The arrangement is like hanging a Roman Blind. I've added explanations to all the pictures now.

http://s225.photobucket.com/albums/dd31 ... =slideshow

For this to work in the Jolly boat I would envisage it would need a stringer along the line of the bilge to attach the lower line of attachment but nothing that would seriously alter the originality of the boat, and might if anything improve the stiffness of this part of the hull which from what you describe might otherwise benefit from a Monocoque stiffening effect of a built in tank.
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Re: Solid foam buoyancy

Post by Ed » Mon Aug 04, 2008 10:44 pm

Yup,

You are absolutely right!!!

I totally forgot that in the rush writing that post. Of course what I meant, at least in my head was I had never lost one in a capsize.

As I said, I have no doubt that your method would certainly be better.

With the jollyboat, now I think more about it, I have a batten holding the bottom edge and then straps that go right around the bag and up to connect to the inwhale. There is not much room, here and the bags bulge out anyway, so they can't really be any lower....or higher....just held in place and certainly I have never had one of these move...in the water, or on the road, even when half inflated, they wouldn't go anywhere.

cheers

eib
Ed Bremner
CVRDA


Jollyboat J3
Firefly F2942
IC GBR314 ex S51 - 1970 Slurp
MR 638 - Please come and take it away
Phelps Scull
Bathurst Whiff - looking for someone to love it

ACB
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Re: Solid foam buoyancy

Post by ACB » Wed Aug 13, 2008 9:49 pm

I have seen solid foam bouyancy done properly.

Some years ago I bought an ex-RNLI boarding boat (16ft larch clinker rowing boat) built at the IBBTC in Lowestoft which, with a bit of tweaking and a Yanmar 1GM10, became a launch and then gained a standing gaff rig - I sold her a couple of years ago on the grounds that Three Boats are Enough and Four Is a Crowd. She came with, and still retains, blocks of foam cut to fit under the thwarts - here is the clever bit - wrapped in cling film to keep the solvents off the foam and then wrapped with thin glass cloth and epoxy and painted to match the rest of the boat.

Very durable.

F 3163 "Aquarius",
IC K229 nameless for the time being
I14 K377 "Mercury" - long term rebuild project

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