Sleeving broken ali mast

G'day I've picked up a Aluminium Taipan 5.7 mast thats broken about 3ft from the base and I want to repair it as a spare to keep at the club. I have mast section to sleeve it with and I have cut the twisted pieces of. My plan is to put a new section on the base then internal sleeve followed by an external sleeve to be welded.
My question is what length would be right for the internal sleeve?
What length for the external sleeve?

Hi Jeff, I know it's against the rules, but I make a sleeve out of glass and carbon fiber, then cut the parts to be connected straight, then epoxy the sleeve in place.
( first dry fit everything and make some jigs to hold the mast in alignment) Once the sleeve is done I prep the outside of the joint and tape up the mast track with "flash tape" ( http://avtcomposites.com/order.php3?i=91 ) not (http://www.herroom.com/braza-1009-flash-tape.shtml ) and vacuum bag on a few (5+) layers of carbon.
I have done this more then a few time and never had a problem. (yet!!)


Best of luck.
les

Thanks for your reply, I've already got the ali parts to sleeve it but using resin to put it together is a new idea to me and appeals to me more than welding. Could I use vinyl ester to glue the sleeves in place? How long are the sleeves you use?

I would use epoxy (not five min.) and you should sand off any anodizing and use a surface prep. ie. acid wash.
If you weld you will lose a lot of the strength in the mast.
The sleeve I have used are about ten inches long.

I agree. I would not weld a mast unless the builder agreed.

Keep in mind there is a lot of compression load on the mast at this point. Make sure the external splice to mast joints are square. The parts will be pressing against each other with 100's to 1000's of lbs of force.

I once saw a 18 square mast with a splice like you are talking about. The splice kept breaking so the owner kept beefing up the splice. Finally he had a 3 ft internal splice and it held. I looked at it a couple of years later and the metal at the splice had deformed where it was pressing.

Never weld alloy...it will take the stength down about 2/3rd's that of the original tempered material.

My first T boat I sailed on when I was a kid had a spliced mast. Dad put it together from two damaged sections laying around the SailCraft of Canada factory.

Had an internal sleeve section and an array of large (1/4"?) Monel rivets. That beast held together for decades. I believe the splice was beteween the hounds & spreaders.
Had to keep a low profile/avert eyes/ /etc. at a class meeting during the CORK regatta as a teenager one summer when they starting talking about a vote to ban "compound" masts that top guys were experimenting with to design in differenential flex charactistics between top & bottom sections...

Thanks for the info guys it sounds like epoxy is the go as it will spread the compression load if it adheres to the ali all the way up inside and out.
regards

jeff, i have sleeved plenty of masts before, always an internal sleeve 600mm to 1000mm. using about a dozen 3/16 inch stainless rivets was enough. using some epoxy glue to take up any voids. never had to use external sleeve or to use cloth on it. i have heard of carbon going straight on to alloy and the alloy is completely eaten out in about 6 months. but make sure you cut the existing bits with a drop saw or similar so that the both ends are perfect.
cheers.

Thanks Brian, I've trimmed the ends perfect with my drop saw. The Taipan section has irregular reinforcing inside and its really a bitch to sleeve. I have to make a fore and aft sleeve to slide in seperately. Then there are 3 thicker wall areas on the section so I cant really slide a neat outer wall on.

I am going to change my mind about epoxy bonding aluminum.

I just went through a similar issue, 3000 psi bond of 2 aluminum sheets. To get a reliable bond you need to sand, 2 part etch and then use a pressure and temperature cure epoxy. The curing requires the 2 plates to be pressed together at 5 psi or more and cured at 250F. A no pressure room temp cure will have a lot lower bond strength, 100 psi(?). The larger gap of a no pressure cure also makes the bond easier to break (don't ask me how I know).

The reason we have gotten away with this in the past, is the loads are mostly compression and if the fit at the joints is good, most of the load is taken up mechanically. Just as a guess, to handle the load with bond only, you will need about 200 sq inches in each mast segment. Consider the 3rd segment as just a spacer.

If I ever have to do this again, I am going to use epoxy and add a couple of monel rivets

how does one make the internal sleeve?

I'm cutting up mast section to a snug fit then plan to knock it in tight.

I take a mast section and clean up the inside.
Then wax it ( 5 times) than put on pva.
With the section on its side layup ten layers of glass (with epoxy) on the bottom, when it is mostly cured (still sticky) rotate the section and do the other side. Do this most the way round, I leave a gap at the mast track area. When it is fully cured use wood shims to pry it loose.