Would a billet aluminium blades and boards work?
Would they be stronger?
Would they be lighter?

I'm gonna go out on a limb and say they'd be definitely cheaper. Once you've got the file, load up a blank in a 4 axis cnc mill and basically walk away. Plus polished boards would be frickin' cool. Or even anodized. Might want to make the top removable, a bent board could be trouble if you couldn't pull it out the top......

Snipes use aluminum dagger boards.

the amount of machining and polishing required to get a real foil shape would be massive. Otherwise, the molds they use for foils would be frequently machined from aluminum...but they use more cost effective processes even for the molds. It would still be pretty weighty too.

Yes.
No. More ductile, for sure, but not as stiff.
No. Aluminum is about 165 lb / cu ft. Carbon fiber/epoxy composite is only about 97 lbs / cu ft., but since it's almost 3 times as strong, the middle can be replaced by foam, which has a density of ~4 to 8 lbs / cu ft.

Aluminum foils are easy to make, but they're heavy and bend easily (not just flex, but bend plastically - permanently deform)

Of course, you could have figured this out on your own, but you're a lazy bastard.

Matt, you don't reach this station in life by not being a lazy bastard. It takes training, practice, and a whole mess of luck. I was actually going to figure the volume of a board by dunking it something, but then I realized I didn't have anything big enough. Then weigh it.



The machining would be nothing if it were essentially one piece. Making a female mild is a whole mess more complicated as far as machining goes.

Magnesium. 112lb per cu/ft.

Magnesium and water don't mix well. Kinda like sodium and water, if you've ever done that prank.

The Sprint 750 trimarans had aluminum extrusion boards/rudders, and there's a fair number of owners that are ridding themselves of them and going with carbon fibre

Magnesium is non-reactive in water (certainly not like sodium that will literally explode). It will corrode quickly in salt water, though. Very low on the galvanic series.

Get magnesium hot enough and it will burn with an intense white light. And you can't put the fire out. (Actually, aluminum will do the same, but you've got to get it really hot.

This is what happens when aluminum burns:

Is that on carpet?

Don't worry, Jake - the carpet won't be an issue in the next frame.

I am not sure they would be much cheaper. Your talking big and expensive pieces of aluminum, plus mucho machining time. A 1" sheet for 1 60" x8" board would cost about $300 I bet, that's before you touched it with a machine.

I'm just kicking around ideas. Its what happens when I get bored. It just seems re-goddamn-diculous what a set of daggers cost nowadays.

I wouldn't put foam in the middle. Pointless, just make them hollow, bolt the two halves together with a flat surface around the edge that can be gasket'd, or sealed, then just put a drain bolt at the top should they leak.


If you're into cars, and into building weird stuff, this is an awesome read. Larry Ellison had these guys build him a AC Cobra replica with a billet aluminum chassis. Frickin' cool stuff. The Art of Engineering


There's all sorts of strange projects I'd take on for fun if I had the means. I want to make a set of billet aluminum rudder stocks, with the.... (I can't think of the word)..... where the rudder arms are bent inwards. Its the same name as a punctuation. Anyway, make them so you can use just a straight carbon tube. It'd have to be three pieces, two halves that hold the rudder that are bolted to a piece that slides over the pintles. Maybe press in a brass bushing there too.

Then there's my want to make a carbon fibre RC flying wing. That might actually happen soon. I need to buy a new one, and make a mold of it. We'll see how horrible that goes. I know it won't survive the crashes, but it should be unreal compared to a solid foam one.

A 1" x 10" by 72" slab is about $400, (that's what it would take to get a 1st gen C2 dagger out of it.), if you're buying it retail. Which who the hell buys anything retail. Probably be cheaper if you're getting it in a 20' stick too, and you'd be able to recoup a small percentage recycling the waste.

I'm curious what the machining would cost, or more importantly how long it would take. If the machine is $100/hr, would it take six hours to do it? I kinda doubt it in a CNC, and that's what it'd take to get it up to the cost of a C2 dagger board.

I like these discussions. Way more than WtheF are we going to do with the Alter Cup.

I can't help but think about the incredible things they are doing with 3D printers nowadays. What will happen when these machines become commonplace any each boat owner can design and "print" his own boards?

6 hours is probably reasonable - it all depends on the finish you are after...how many steps the machine needs to make. I had a mold made from two chunks of aluminum for a 5lb lead bulb for r/c sailboats. The mold was about 12 inches long and it took 18 hours of machining for the two halves (I don't think the programmer really approached it correctly though).

Karl,

Aluminum foils do not survive long in salt water - no matter what the core. When the Corsair Sprint 750 appeared on the waterfront, Bob Hodges pointed out that they were subject to corrosion and fatigue.

During the 38 mile offshore race we had in 2009 for the Trimaran Nationals there were foil failures; however, they were due to the head design.

In the background, it was discovered that the rivets used in seaming the halves were becoming weak from wear, and the surface area was becoming contaminated via water absorption. The ultimate 'Fix' was to go composite, and that is what the top sailors did.

Now, let's go to curved foils for discussion... how many sailors are able to afford the cost of maintaining/replacing curved foils for an entire sailing year?

Convex machining vs concave though? I don't know for sure though. Just a wag from watching wood cnc's go at it. The feed rates in wood are faster, but there are some crazy fast metal machines too.

Our boards are never in the water though. Couple hours here and there, that's it.

Most of the boards on the Sprints are not in the water 24/7. When fully retracted they are dry inside of the daggerboard trunk.

Its hard to say, there would be a rather large amount of metal removed and that means many many passes.

Trying to build a foil from sheet metal with well designed and stout spars would be lighter and I could imagine them being strong enough, still not sure about it being much cheaper though.