Using foam to reinforce things....

chewy · 17 November 2008, 19:48

I want to fit some knees to my transon as the original stainless ones are missing.

Will any of the following foams be suitable:

http://www.cfsnet.co.uk/acatalog/CFS...RIALS_129.html

Is it the wood in the knees and transom that give it strength or the fibreglass that covers them?

Dirk Diggler · 18 November 2008, 07:08

It's a combination of both, although with enough glass the wood or foam don't matter.

Foam is easier to work with, but wood is easier to laminate to.

9D280 · 18 November 2008, 12:34

Wouldn't it be quicker & easier to get a couple of lengths of stainless tube, then 20 mins use of a large hammer & a 10 (I think) mm drill & you replace the original braces? Alternatively even quicker (but probably 10 times the price) do Avon or an aftemarket place sell them as "bolt on" spares?

If you do use foam, don't do a "Dell Quay" and end up with the heaviest set of knees ever created. (i.e. Make sure you use closed cell / non absorbent foam!). Also the key with any bracing is to make sure it's properly attatched - if you're going down the knees route that means make sure it's properly bonded to floor and transom or you might as well not bother.

Having once used a "'glass knee" reinforced SR4 I really missed the braces at the stern for mooring alongside, towing, tieing fuel tanks down........ Personally, I'd just replace the stainless braces, but that's just me!

Searider · 18 November 2008, 13:28

I replaced the ones in my 5.4 as they had been replaced with a horrible frame for mounting tanks in. Got them from a local Avon dealer. About £80 for the pair if I remember correctly. (6 or 7 years ago).

If the studs that are embedded in the sole of the boat are in good condition and secure then, although not the cheapest way, this would be the simplest solution.

Be careful of the nut size / thread pitch for the stud. Nothing metric that my chandlery had would fit my 1978 boat - fortunately I kept the ones I took off and could re-use them.

chewy · 18 November 2008, 14:33

What size pipe should it be and whats the wall thickness?

I think I'll still go down the glassed in knee route as it looks tidier.

codprawn · 18 November 2008, 20:15

i would use wood for the knees - liberally soaked in epoxy first. I would also put long dowels right through from the transom - also liberally soaked in epoxy.

chewy · 18 November 2008, 20:34

Cheers for that, never thought of the dowels.

Dirk Diggler · 19 November 2008, 09:25

Quote:

Originally Posted by codprawn

liberally soaked in epoxy first. I would also put long dowels right through from the transom - also liberally soaked in epoxy.

Why?

codprawn · 19 November 2008, 12:47

Quote:

Originally Posted by Dirk Diggler

Why?

To give extra strength and reduce the possibility of water ingress - thought it would be obvious really............

Jono · 19 November 2008, 13:09

Quote:

Originally Posted by codprawn

To give extra strength and reduce the possibility of water ingress - thought it would be obvious to a know-nothing, idle boat builder..really............

.............

I'm assuming Codders means to "plug" the holes left by removal of the bracing bars ......

Downhilldai · 19 November 2008, 13:11

I'm not convinced that he did mean that.....

chewy · 19 November 2008, 14:08

Will have a look when I get home, stainless pipes could be easier although the deck end might need glassing in if I use larger pipe.

bedajim · 19 November 2008, 14:15

Quote:

Originally Posted by chewy

Will have a look when I get home, stainless pipes could be easier although the deck end might need glassing in if I use larger pipe.

Have you got a picture of the transom etc ?

chewy · 19 November 2008, 14:19

http://rib.net/forum/showthread.php?t=27218

See post 4 on the above thread.

bedajim · 19 November 2008, 14:29

Quote:

Originally Posted by chewy

http://rib.net/forum/showthread.php?t=27218

See post 4 on the above thread.

I'd do it with stainless brackets and tube you could make the fixing plates on the transom larger to spread the load and double up as part of the anchor point for the Aframe

chewy · 19 November 2008, 16:31

I'm going down this route now. If anyone knows how long each strut/stay needs to be can you let me know please?

floater · 19 November 2008, 17:17

Hi

just a quick thought is that another potential concern is that you need to ensure that both sides of the brace's can drain in to the bilge pump area to stop water gathering and going manky .

or am i wrong ?

Andy

doggypaddle · 19 November 2008, 17:20

each strut tube is approx 630mm long with a plate tig welded on the ends.
thats the longest side of the tube measured, i cant measure the shorter underside.
if you want any more measurements like the height on the transom or the distance from the transom to the anchor bolt let me know. boat is in driveway so easy to get at.

chewy · 19 November 2008, 18:27

Stainless it is, I would prefer glassed in knees but the pipe is easier.

What diameter is the pipe?

Thanks

Phill

Downhilldai · 19 November 2008, 18:50

Quote:

Originally Posted by floater

Hi

just a quick thought is that another potential concern is that you need to ensure that both sides of the brace's can drain in to the bilge pump area to stop water gathering and going manky .

or am i wrong ?

Andy

Yes - there's no bilge pump well in a Searider.
He's using stainless struts now anyway, just as Avon designed them to be.