Strengthen aluminum mast?

[opie]

Despite being careful I've bent my third mast since October.  Both Takuma and Naish.  I have one straight mast left.  I'm not buying anymore.   

They always bend in the first 4 or 5 inches below the plate.

Can I wrap it with carbon to add strength? Will epoxy bond with aluminum?  Does it need to? 

What if I poured a liquid mix of epoxy and 1/4th inch chopped carbon fiber down the middle, filling it up?

Thanks for any help.
 

[surfcowboy]

Man, that sucks.

You can get milled fiber by the bag cheap and it'll make a bog really strong and if you mix in some cabosil or something you could make it lighter but it's still going to be heavy.

I'm curious to see what people think about the external reinforcement idea. That seems to make more sense to me if you could get it to bond.

[PonoBill]

Filling the inside won't add much strength--you need beam strength, which comes from the periphery of the structure. Aluminum is an odd metal, it's structure lets it yield because it's ductile, but when it bends it work hardens a lot, so it's a bitch to straighten. To do it right you have to anneal it first, straighten the part as well as possible, and then heat treat it to harden it.

Since the masts are formed by extrusion the aluminum is likely 6063 or 6061 and you could try hardening it. If it's 1000 or 3000 series then it's not hardenable, the part is crap, and you're screwed. Even if it's 6000 series the extrusion may not be hardened other than quenching it as it comes out of the die. Doing real heat treating generally distorts the part, especially if the solution step is done after forming which heats parts to near melting and then a quench. Nothing you can do at home. Instead, you might try just doing the aging part of heat treating, assuming that some high-temperature quenching was done during fabrication. Stick your mast in an oven at 400F for 4-5 hours and then turn off the oven and open the door. Let the part cool in the oven. If all goes well and the assumptions are valid it will be somewhere close to T5 instead of the T2 it is when it comes out of the die. Your anodizing and any lacquer will be gone, and the kitchen will smell like hell for a few hours, so do this when the wife is gone for the day.

You can certainly wrap the mast with carbon, but the result may not be all that great unless you use enough carbon to replace all the strength of the aluminum. Dissimilar materials can be engineered to have great strength, but that requires a lot of analysis and design to have complementary properties. Just the difference in thermal expansion between aluminum (lots) and carbon (not much) might cause problems.

[TallDude]

It makes sense where they're bending. From the wing up, the aluminum mast will flex pretty evenly. As it gets closer to the base plate or T-box it will flex less. The bulk of that stress is taken up by the stiff base plate. The plate reinforcement distributes the lever force away from the base plate and down the mast. That first 4 or 5 inches down are taking up more of the force than the rest of the mast. This is the problem with the in board Tuttle boxes. They put the brunt of the force (fulcrum) directly on the aluminum shaft. The base plate mounts take a lot of the stress off of the mast at the critical point. They could make the base sleeves even longer to reduce the stress on the aluminum masts. The longer the mast, the longer the lever, the more likely the mast is to bend.

[Bean]

Will epoxy bond with aluminum?

Not a chemical bond, but it will provide a very strong mechanical bond if the surface is keyed down to 60-80 grit.





 

[TallDude]

You could add a pair of struts or braces on either side attaching to the base plate the mast further down. These struts could be flat plates maybe 3/16" thick by 2" wide and 10" or 12" long, mechanically attached with rivets or screws. The mount at the base plate might have to be inline with fin base plate bolts. Maybe utilize the base plate bolts? I don't think you'd feel that much extra drag from the added flat plates.

[opie]

After reading your replies I had an epiphany on the way to work this morning.  I'm going to sell the Takuma  while I still have a straight mast and buy a go foil.
Thanks.

[Bean]

And, if the GoFoil is not stiff enough, (I hear) you can always bond some aluminum plate to it.

[surfcowboy]

Opie, good call. Don't hack something you can sell and upgrade.

[PonoBill]

After reading your replies I had an epiphany on the way to work this morning.  I'm going to sell the Takuma  while I still have a straight mast and buy a go foil.
Thanks.

Now you're talking. I think there are a lot of good foils out there, but they seem to be about two steps behind GoFoil for foil surfing. You can buy a three-foil combo GoFoil with three wings and two tails that suits your weight for everything from high-speed big waves to downwinding. I see people in Maui using them for kiting, windsurfing, downwinding, and surfing. I've banged mine into rocks while I'm at full speed and all I did was chip the paint. I think this sport has a long way to go as far as gear goes, but right now, it's kind of GoFoil and everyone else.