making some fibre glass joints for aluminium

[mmmboats]

hi hope you guys and girls can help me, at the moment my holidays are coming up and i thought i would make up some shorter wings for my b14 out of snapped laser top sections and put some trapezes on the boat ala i14(make her 2m wide).
ive got what i think i need fibreglass/ epoxy/ sections but how do you think i should make the joins? how many layers of lightish cloth would i need to stop the joints ripping apart? was thinking of rapping cloth around each peice of ulum builing up the join with strips of glass, say 20 mm thick then wrappin another layer of fibre glass around the whole joint to hold it together, then once done should i wrap it with peel ply (is that nylon) or grey tape which i have rolls of.
thanks any help would be nice n i needa make a new centre board as well but im not up to that yet

phil stevo i noticed you post on this site and since i got the idea from you building a plywood moth i hope you can help me-this has also been posted in boat building but i thought i might get more help from this place

[Phil Stevo]

We have done a few of these on cheap moth projects.

You will find that sqaure weave cloth does not go around the compound shape very well. I have used chopped matt with success, you need a few layers. I have tried kevlar cloth but its no good if you need tosand toshape afterwards to get a good finish.

If you want to dismantle the boat you need to make some sleaves to slide over the latterals, alloy or glass it des not matter.

Start by wrapping all of the tube where you do not want any glue, because you will be handling them with sticky gloves which will make a big mess.

Then shape the ends of the sleaves and the longitudinals to a good fit, and glue them together on the boat with some epoxy/fibre bog. Put some release on the latterals so you do not glue it all together. This ensures you get everything at the right length and angles.

Remove the longitudinals and sleaves from the boat to apply the CSM to the joints.

Clean the joint areas of the tubes with sand paper dry, and then sand again just before laminating with sandpaper and epoxy, this appearently prevents the alloy oxidising and assists in the bond.

Lay on three or more layers of CSM, wrap with peel ply. You can use tape on the cylindrical parts but it will not go around the corner. If you use tape wrap it sticky side out so it will peel of the epoxy easier.

[mmmboats]

thanks for your help thats could stop me from making a couple of big mistakes. just quickly when you say CSM doe that stand for chopped strand matt?
and lastly where could i get some peel ply is this nylon? or shoold i go to a boatbuilders and ask them for some?
thanks again

[Phil Stevo]

CSM = Chopped Strand matt. lighter weights are easier to use in this application.
Peel ply is a synthetic woven material like curtain material. It is a made frm stuff which does not stick to epoxy or polyester. You can probably buy it in a haberdashery if you know what it is but it is dirt cheat at big fibreglass and carbon suppliers so why bother.

If you're going to use chopped strand mat +epoxy make sure to get the epoxy compatible version! You might consider using 6K carbon tow(in combination with the CSM) to reinforce the corner. 6k tow has 6000 very fine filaments per strand and comes on a roll. Its easy to work and will add strength to the joint without causing finishing problems. You can get way more than you need for about $54.00 from www.aircraftspruce.com or you may be able to talk a boat company out of enough for your job.
Mat has very little strength but makes getting around the corner easier; reinforcing it is a good idea. You can substitute S-glass Roving Filaments if you can find it in small quantities.
Good Luck!

[Phil Stevo]

Carbon and aluminium must be isolated from each other to prevent electrolytic corroson of the aluminium.
I have tried using carbon over glass over aluminium but those tiny electrons always seem to find a way through. FIZZ and Bubble, aluminum gone very fast.

[mmmboats]

thanks guys need to start shaping the ends of the aluminium then and hopefully will have it ready to go by midweek