Advice on carbon mast fittimg

[ptostu]

Hello all im after some advice I have pulled my shroud plate out of my carbon mast it was riveted in whats the best way to reattach shroud plate Ihave a carbon repair kit my thoughts were to refix and then wrap with carbon cloth any ideas much appreciated
Cheers stuart

[roger]

Best bet is to ask Dan Holman. He is often on the Y&Y site and occasionally here.

[Ed]

I have just done this job on my IC mast where the gooseneck had pulled out, due to being riveted.

Basically in my humble opinion....rivets just don't work in carbon and so far I have had both my kicking strap and goosenecks fail due to rivets.

To be honest, it was quite a sod to fix and although you can fix carbon to get a very high percentage of the original strength....it is not easy. You have to really get a high carbon/epoxy ratio for it to work.

If the instructions were in a Haynes, it would give it 5stars and advise against doing it yourself.

But hey, this is the CVRDA and if you want to have a go.....I am right with you - in spirit at least!

Problem is that I just don't think that fixing with rivets again is going to work, so you have to find some way of bolting or glueing it in place.

What I did was this:

1) Dig out all the old soft carbon, that has been softened by compression the rivet pulling through or any other pressure damage, clean it up and then go gulp at size of holes, don't panic but they get worse.

2) Find a bit of mast with roughly same (or smaller ) profile. wrap it in tape and laminate a plate larger than holes. Needs to be good and strong. I used 3 layers of 300gm uni carbon tape with two layers of 150ish gm kevlar between (with carbon overlapping kevlar). This has to be well wetted out with some applied heat most probably and then all excess goo scraped out and covered in peel-ply before wrapping hard with tape. When you have done this you will have a good stiff backing plate.

3) then the hard bit. which may just be impossible on a shroud connector, I glued stainless nuts onto the back of the carbon plate that matched the fitting and glued it inside the mast, using the bolts in the fitting to pull it up into place.

4) Then filled the holes for nuts so they didn't get full of guck and cleaned up the carbon mast so that there was in effect a scarfed join for the carbon to attach to. I then filled the holes with layers of carbon uni-tape and finished off with a couple of layers of 300g cloth. the backing plate has two purposes. First it held the bolts so the fitting could be bolted in place rather than riveted in place and second it supported the carbon over the holes so I was able to tape up the carbon and get as good a chance as possible of getting as much carbon as little epoxy as possible.

5) Cleaned it all up, filled it and painted it

6) Finally bolted the gooseneck back into place.

This was not easy, and I hope this gives you some idea of the kind of job it is. Certainly not impossible, but not easy, Show me some images and I might be able to help more.

cheers

eib

[Nigel]

I believe that you need special rivets for carbon. Standard ones crush the carbon so it ends up failing.

Terry Cook at Aardvark has repaired carbon masts for me and is very reasonable on price

[ptostu]

Cheers for the info I have refitted it with some rivets and some gooie epoxy and then I have wraped through fitting and around and then over with carbon cloth and then peel ply and plastic and then squeezed tight withparcel tape and then tighter with gaffer tape , removed tape and ply looks ok and will see what its like in the morning when its hardened off will see if I can get some pics up of my first attempt with carbon
Cheers stuart

[JimC]

Damn, wish I'd seen this before.
For future reference the best way to reattach a rivetted shroud plate on carbon is: don't!
Whilst experienced pros may sometimes get away with pop rivetting fittings on carbon spars, especially if they have the right rivets, amateurs like us you should avoid them like poison. If you've got a mast that has been designed and laid up for T terminals they are fine, but they are almost certainly not suitable a retrofit. Other than that all fittings should be bonded on.
What works for me is to bond on forged shackles or D rings with unidirectional carbon. Basically take unidirectional carbon, wet it out into a bandage and wrap it through the s/s loop and then fan it out over the mast surface, v crudely like this graphic.

bond.gif

(26.12 KiB) Not downloaded yet

When its all even put a layer of cloth on the top and consolidate in exactly the way you described. If you can take a bit of mast track off to wrap the cloth right round the spar before replacing then that's much the best, but not always possible. Obviously you'll want to do all the shrouds at the same time!

[ptostu]

Thanks jimc I have done it similar to your explanation I have run strips of carbon cloth though the ring onthe stay bracket in a sort of star pattern and then gone over rhe ends and then over all sides of the bracket and then over the whole lot twice out to the mast track
Cheers stuart

[scorpion_1925]

carbon fibre has another problem, it is electrolytically reactive to aluminium and will actually corrode, or in laminate terms delaminate weakening its structure. stainless steel should be used for all parts in contact with carbon fibre

[JimC]

carbon fibre has another problem, it is electrolytically reactive to aluminium and will actually corrode, or in laminate terms delaminate weakening its structure. stainless steel should be used for all parts in contact with carbon fibre

Its the other way round: carbon erodes aluminium. But if, fo instance, someone is so unwise as to sleeve a carbon tube with alloy, then the alloy fizzes and expands into oxide which does indeed break up the carbon laminate.

[ptostu]

All my fittings are stainless , well took the boat out today and no problems the fix seams to have worked happy days
Cheers stuart

[Fantasia]

I am wondering: what do carbon fibre spars have in common with classic and vintage racing dinghies?

[ptostu]

I am wondering: what do carbon fibre spars have in common with classic and vintage racing dinghies?

Well not a lot really mine is an upgrade to the std mast and makes the boat easier to sail and I need all the help I can get but there is a wealth of good knowledge and advice off the people on here that is sometimes hard to find on other sites .
Cheers stuart

[Pat]

It's the usual cvrda cameraderie thing of helping other sailors

[Ed]

I am wondering: what do carbon fibre spars have in common with classic and vintage racing dinghies?

reckon the CVRDA is a pretty wide church and what is right for one boat in one fleet won't be right for another boat in another fleet.

We could ask the same question of the Thames A-raters.....but reckon I know what they might say.

eib

[Rupert]

Knowledge is knowledge - many on here sail other things/do other things that can be of use to others. Long may it continue.