Rivets or welds on aluminum?

Yes, and when the manufacturer has hundreds of engineers dedicated to these joints, extensive lab testing, controlled factory environments and procedures, decades of real-world experience, and a regular and rigorous inspection regimen, confidence is justified.

However, using "off-the-shelf" products, minimal personal and anecdotal testing, backyard environment and skill-sets, and very low production runs (think: 1) caution is appropriate. Particularly in an evironment every bit as risky as flying. When I am out with my family in colder water conditions, a major seam failure below the waterline would mean near-certain death.

Again, if anyone has real information or experience, please share it!

Sal's Dad

 

Fred
Vastly different situations - your analogy is poor.

Planes are built to rigorous standards. The longest flight for any passenger jet is about 15 hours - nearest airport usually less than a couple of hours away. They are generally in a dry, low corrosive environment. The only real load the hull experiences is during take off and landing. And some thermal cycling once a flight.

By comparison boats are typically built to much less rigorous standards - certainly most leisure craft. They are continuously exposed to the most corrosive environment. They could be on a voyage for many months with the nearest land weeks away. They could be exposed to high stress cyclic loading for days on end.

I fly most weeks but each take off I still wonder if it will be the last - so maybe I am a pessimist. I fly for my paid work. These are the things I think about because I have seen the way cracks are controlled in plane structures. Irrespective I still would have much greater concern setting out to cross an ocean in an aluminium boat relying solely on glue for its structural integrity.

Rick W.

 

I have used a 3M epoxy several years ago to glue aluminum together - not for a boat, but for some electronics. I remember testing several epoxies to see which was stronger. I prepped the surfaces by rough sanding (prob 80 grit) and acetone wash. The 3M beat the other epoxies, I remember. I recall that I had to damn near chisel the pieces apart.

Epoxy does lose strength with temperature - same as epoxy resin in a fiberglass hull. at 160 deg. F (easy to get on a dark surface in the sun) I think epoxy has about 1/3 or 1/2 it's strength -don't remember for certain off hand, but it is really substantial loss.

I remember this from composite aircraft construction - that's why composite airplanes are usually painted white, and a good reason to have a white fiberglass boat. Of course boats can be water cooled - but the top deck isn't unless you crash thru some waves....

just my rambling thoughts...

 

Oh, the 3M epoxy was an industrial product. 3M makes dozens of different epoxies.

 

Here's a interesting article on the Lotus Elise's chassis.

http://www.sandsmuseum.com/cars/elise/information/technical/asauto.html

 

14 gauge or thinner material it's best to rivet, 12 gauge or thicker, weld. My Kestrel design for an aluminum ketch used 12 gauge for this reason.