Bridle Vane on a Nacra 6.0na

I've got a Davis Telo-Cat vane mounted on top of my foil. It's mounted with an adapter that's rivited to the top of the foil. I had to bend the rod that the vane is attached to more than 90 degrees in order to level the vane. The vane rides a little higher than the foil. No complaints about how it works.

Alec,

Hey big guy, getting the itch yet? Looks like we get to host the Ice Breaker this year - should be a blast!

I would hold off on drilling the foil. I don't know what the stress points are on the foil. Don't they make the vanes that clamp onto a shackle or a wire.

See ya at the Fleet Party!

Ballast

There are vanes on the market designed to clamp to the forestay. With the N6.0, however, the bridle rides ahead of the tack and doesn't allow anything to be mounted to the stay.

You may be able to mount it on the post. As for drilling the foil, the adapter I have on mine is mounted near the leading edge of the foil with two rivets.

While I'm no engineer, I don't see the mount as creating a stress point any more than the mount for the striker post. (Mine's been in place for six years.)

Kevin, Thanks for the advice, and as they say, a picture is worth a thousand words.

When I had a 6.0, I riveted the telocat clip to the bottom of the foil and then bent the post upward. Also drilled a retainer clip hole in the rod to secure the rod and wind indicator. After I put a spinnaker pole on the boat I had to remove the clip for the pole would go under the foil.

So in hindsight I would go with a top mount clip. But ... I am no longer comfortable with drilling additional holes in the center of the foil. I have seen 4 or 5 of these foils fail. Typically they fail because of a fitting or dolphin striker rod issue but I recall seeing a foil folding. This is not pretty.

Good luck.

I would suspect that a folding foil would most likely be caused by an improperly set pre-bend, allowing the foil to bend in a downward direction under load.

Mr. Meis is right. Although drilling holes in the foil won't add stress, it is taking away strength from the very centre of the foil, where the most stress occurs.

I've seen foils fold, it's not pretty. The mast comes down at the very least. And I'd hazard a guess that if you had a big load on the foil at collapse, you might even break bows as they're pulled inward.

There are clips available, or you could fabricate something, or even duct tape, but for me, I wouldn't drill my foil...

sea ya
tami

Presuming you don't use a furler, Murrays sells a long bridal fly for a Hobie 17. It is about 15 inches long and has a red plastic vane. this one easily attatches to the front chain plate on the foil and can be bent 90 deg and then 90 degrees back such that it clears the foil post. If you buy the shorter one it wont clear the post and still be able to rotate.

I would advise against drilling into the foil. Performance catamarans has beefed up tangs for the foils that they will give to you (although I am still waiting for mine to arive). I broke 2 foils in about 1 1/2 years when tangs broke.
both foils were properly prebent.

Eric anderson

Hi Eric,

On foils that you've seen that have folded in the middle, was there an indication of what caused the failure?

The pelican stryker(bridle foil) is functioning similar to the dolphin stryker (except there is a very ecentric load).
You may have seen some boats which use a cable for the dolphin stryker, similar to the Nacra bridle foil.
The bridle foil assembly is a truss with two loaded triangles.
In a loaded triangle, one or two members are subject to compression loading and the other one or two are subjected to tension loading.
The forestay loads the double triangle with very large forces.
The foil extrusion is subject to large compression forces due to the pull (though skewed) of the forestay.
The rod is subject to large tension forces. So large that the rod stretches enough to lose several inches of pre-bend.
I have never heard of a foil collapsing from compression, only from the tension member (rod) failing.
Drilling holes into the foil near the post would slightly weaken the foils bending strength.
The holes, with stainless srews, could stimulate galvanic corrosion inside of the foil.
Why not get a small verticle flange welded onto the front of the post? Stainless on stainless is usually safe.

how about holding it in place with one of those worm drive hose clamps?

Sam,

OK, but now another question. How is drilling a couple of small holes in the foil different than drilling holes in the beam to mount cleats, etc.? Aren't the forces similar?

First of all, the bridal fly is forward of where you are when sailing downwind -- and sailing downwind is why you use a bridal fly, right?
So, forget the bridal fly and tie a piece of 8-TrackTape (easy to find cheap at any yard sale) to the sidestay. That way you can actually tell if it is 90-degrees, aft of that, or forward of that.Much easier to read when it is reading from where you are sitting. Much easier to read and significantly less expensive.
Interestingly, When I fly a spinnaker I have a tape on the end of the pole, one on the bridal fly and one on the side stay. Guess what! They all read a different apparent wind direction.
The one at the end of the pole is almost 90-degrees, the one on the bridal is more aft, and the one on the sidestay looks as if I am on a close reach.
Use it all.
Rick

Oh, c'mon Rick,
devils advocate here:

You mean you can get the same thing accomplished, with just a cassette tape? (I use an old VHS tape, kinda like the 8 track )

You're saying, you don't have to spent 20+ dollars, drill standing rigged parts of boats, and use a simple tape somewhere that basically does the same thing? c'mon now!

Actually a rarely use the tape either, just feel in the hairs of my forearms, and the tell-tales on the sails, my spin has tell tales too. Drives my crew crazy sometimes. I'll probably start using the tape more though, sometimes, the old hair on the forearam technique isn't quite as accurate on the true wind 8*)

Now we are really getting into the hi-tech part of this. Actually, cassette tape is too light and dances too much to read properly. Sort of flitters around while it should be settling down and doing a good job.
That is why I use the heavier, 8-Track Tape. But, if you can't find 8-Track anymore, you can buy some reel-to-reel tape at Radio Shack. Tim Johnson told me they are both 1.25, or something like that.
But I still like my 8-Track.
Using some really fast stuff now: Abba

Rick

rick, i'm not quite as old as you (have only seen 8 track tapes in museums). i do have some old vinyl records. in particular, i have a 12" of the first abba album. do you think that will work, or should i use my copy of waterloo on 7 inch?

For me, it's still my VHS copy of some

'Star Trek' episodes! Now that's what I call 'high tech'!

Kevin,
There are differences and similarities.
Yes, the FORCES are very similar with bending and compression.
The big differences are the EFFECTS due to the dissimilar shapes of the two extrusions.
Resistance to bending forces is directly related to the structural shape of the element, as well as the composition of the material.
The foil is an almost flat wing shaped tube. Unsupported it has very little strength in the flat direction.
A crossbar is generally a round or square tube. This shape has the highest shape related structural strength in multiple directions.
Holes reduce the cross-sectional area of the foil shape by a higher percentage than the tube shape.
I don't believe the holes ALONE reduce the strength of either extrusion by enough to impair their performance.
The difference that I see and the potential problem, is the effect of galvanic corrosion, particularly in the foil due to the closed ends.
There is always some GC when stainless hardware and aluminum in contact.
In extrusions that are ventilated or get rinsed regularly, the damage is minimal.
The foil very small and GC COULD eat away a critical percentage of its strength.
A NACRA crossbar is very large and often ventilated or rinsed regularly.
BUT, even a crossbar can corrode enough to fail.
At the Old Spice - Wide Open, Open Regatta, on Pamlico Sound, I saw a Hobie 16 front crossbar snap approxmately halfway between the mast and end casting. Upon examination, we could see that the break occurred at the location of one of the jib track pop rivets. There was no outward sign of corrosion but on the inside you could see how the corrosion had eaten a ring around the tube.
I would be concerned that something similar could happen to a foil.
The hose clamp idea is the easiest solution.

not really, the analog tape is the easiest solution.

We are discussing how to mount a bridle vane on the foil of a NACRA 6.0.
I don't think the videotape will hold it very well.

Sam,

Sounds logical, but what about the rivets that are used on the striker post? Wouldn't they be subject to the same galvanic corrosion?

Sam,

The point was made that the thicker analog tape, (video, 8-track, etc.) will work as good or better than any store bought vane, but you know that right?

We've been talking about compromising the strength of the bridal foil, by drilling holes, and/or by galvanic corrosion. It would seem to me that if I filled those holes with aluminum pop rivets I would have solved both problems due to the fact that aluminum on aluminum would not cause the GC problem, and the rivet filling in the whole should restrenghten the area. Am I missing something obvious?

Alec,

That is exactly how mine is set up. No problems evident after six years.

Alec,

congrats on the 6.0! I too had the same question and after trying tons of different things, I am planning to order a larger (15") masthead wind indicator - should be in relatively clean air up there (if my eyesight holds). I've tried taping other indicators and all sorts of stuff everywhere on the boat but could never get a good read. The foil is just too close to the hulls and the sails to get any undisturbed air.

P.S. - go to Blockbuster video and ask if they have any trashed VHS cassett tapes - chances are they do and will give them to you for free. Use that stuff for wind indicators.