For the F20c, there is a definite "twist" to the boards. It's not a straight curve...
Not all curved foils were born equal.
Symetrical section curved foils with different angles of incidence along their span on the F20C, compared to asymetrical section curved foils with fixed angle of incidence along their span on the french maxitris.
It will take a while to fine tune curved foils in cats. And never forget the "S" foils that were barely tested.
Source? Some say the foil is symmetric, some say asymmetric on the F20c. What is on the new F17?
You can get by with 2 mold halves if twist is 0. Otherwise, forget about it. Doubt they are doing that in a production environment anyway, I am sure there are 4 mold halves at an easy $40k for the set.
If you have twist, which is one method of getting elliptical lift distribution, things get complicated really fast. For starters, simply modelling the foil in CAD becomes a nightmare-try 100+ hours of CAD work for the plug and then another 40 or so hours for the molds themselves.
I also realized the broken Nacra foils I own have Rohacell or similar high density foam cores. If the curved boards are similar, you would need to machine this core prior to putting it in the molds. That's probably $200 worth of machine time per core if you own the machine.
One way to look at this is by cost, and surely a foil that costs 30% more isn't going to make your boat 30% faster, hence its not worth it. IMO, $1300 is already a lot of money for a daggerboard, why not just pay the extra $400/board for a curved foil? Its a 3% increase in cost on a brand new F18, for example.
I think the Nacra curved foils actually have rib/spar construction inside.
I spoke to Peter Vink today to check what I already new and can confirm the F20 Carbon foils are symmetrical with a linear curve and NO twist. They have 2 main ribs with a number of stringers/spars combined with a foam core.
Maybe the first ones that had the problems(per David Lennard- F-20c sailor) had twist and that was the problem. Mike Krantz said they had twist per post #243870 a couple pages back, and he's had to see a few. So maybe it's quality control instead of engineering genius.
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For the F20c, there is a definite "twist" to the boards. It's not a straight curve...
"I said, now, I said ,pay attention boy!"
The cure for anything is salt water - sweat, tears, or the sea Isak Dinesen If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most. E. B. White
All the UK boats have a linear curve with no twist-spoke to Peter Vink today who confirmed this...
Our boards definately don't have any twist. Notice how they lay on each other perfectly in the picture. The other F20C here had first gen boards (the fragile type) and they where also not twisted - we fit them in our trunks
Opher Nacra F20C ISR1 F18 Cirrus ISR2 Sdot Yam, ISRAEL
Re: New Nacra 17
[Re: Opher]
#244069 02/15/1203:36 PM02/15/1203:36 PM
All the UK boats have a linear curve with no twist-spoke to Peter Vink today who confirmed this...
Our boards definately don't have any twist. Notice how they lay on each other perfectly in the picture. The other F20C here had first gen boards (the fragile type) and they where also not twisted - we fit them in our trunks
Thank you Opher for confirming the facts about the boards...
I took a look at a set of f20c foils that we have here in Pensacola. And the do NOT appear to have any twist in them. Maybe people are seeing twist due to an optical illusion? we have 2 sets and they don't have any twist.
wouldn't the dagger slots have to have a little slop built in to accomodate that, when you raise and lower them?
Dude ,It's a NACRA, slop comes standard.
"I said, now, I said ,pay attention boy!"
The cure for anything is salt water - sweat, tears, or the sea Isak Dinesen If a man is to be obsessed by something.... I suppose a boat is as good as anything... perhaps a bit better than most. E. B. White
