Rudder Issues

[noemar]

I could not remember how to send the info on the centerboard to the forum, so I sent copy to Chad and Kevin and asked them to forward it.
It's still cold here in Ma and I guess I'm getting brain freeze.
Noel

[Chad]

http://www.ebay.com/itm/251507403258

..if you're interested. Pretty thin, works out to 7% thickness. Might be prone to detach flow when things are interesting...

[Tim Ford]

I want to order my rudder attachment hardware today. Six of one and half dozen of another question:

Assuming my rudder is going to be super-buoyant, which should I attach to the transom: pintles or gudgeons? Is it harder to stick a pintle on a floating rudder into a gudgeon that is fixed to the transom? Or is it easier to loop the gudgeons on to a fixed pintle? I suspect it doesn't make much difference. The hardware comes both ways, but I prefer the gudgeon on the rudder.

[Kevin]

I went with pintles on the transom with my first rudder. And the bottom pintle I used had a taller pin then the upper one so you hooked on the bottom first, then positioned to catch the top one. This is all pre-cassette as I now have 1 big pin with gudgeons on the transom.
k.

[Tim Ford]

Hey, what do you think of this as a safety issue? See photo. When the rudder is installed, it will stick up above that spikey pintle. But when the rudder is off, the spike is there. I guess I could stick a tennis ball or something on it. I dunno. Does anyone see any issues here that might come along? I could always lower it, but I wanted max. separation between the two pieces of hardware.

bigSpike.jpg

[micah202]

Hey, what do you think of this as a safety issue? See photo. When the rudder is installed, it will stick up above that spikey pintle. But when the rudder is off, the spike is there. I guess I could stick a tennis ball or something on it. I dunno. Does anyone see any issues here that might come along? I could always lower it, but I wanted max. separation between the two pieces of hardware.

...you know murphy's 8th law?...once a concern is brought up,,,the chance of it happening increases 4fold!!



....always hate it when someone asks if I'm worried about getting a speeding ticket

[Tim Ford]

Thanks for that reminder, michah!

I dry fit the rudder yesterday and think the pintle placement is going to be OK. I can even hollow out a little hole on the tiller, if the pin is in the way of the lowered tiller, as that's the pivot point. I overdrilled the holes for the six bolts that hold the gudgeons and filled them with what is essentially a rod of epoxy. I'll drill through those epoxy rods to hold the smaller dimension through bolts. The only issue I had was, the carbon fiber gets hot and the epoxy I poured into the drill holes cooked off and exo-thermed a lot of gas holes into the structure. I hope it's OK...I'll drill some pilot holes to check the integrity of the "rods." If they are crap, I'll drill them out and try it again on a cooler day, using slow hardener.

RuddDryFit1.jpg

[12to6]

Has anyone considered the VX One rudder cassette style for the i550? Below is a link to a picture which seems like an elegant aluminum extrusion cassette design: kick-up capability with line to snug rudder tightly in place. Your thoughts on the load capabilities of the gudgeon spacing is much appreciated, as a continuation of the clever calculations Chad posted a few years ago, quoted below.

http://sphotos-b.ak.fbcdn.net/hphotos-a ... 6580_o.jpg

Loads on the upper gudgeon get reduced by the difference in lever arm- twice as much separation means half the load to the upper gudgeon. The bottom gudgeon sees the full load of the foil added to the load going to the upper gudgeon. So increasing the lever arm doesn't have the same proportional load reduction to the lower gudgeon- there will be a point of diminishing returns.

Here's a look at the difference between 10" gudgeon spacing and 13" gudgeon spacing using the same rudder specs posted further up the thread:

10inch.jpg

13inch.jpg

One observation is that gudgeon spacing doesn't change the bending load that the rudder sees, just the compression load applied to the side of the foil by the strap assembly. From this I would think about making sure that the area under the lower straps is made of high compressive strength material, or make sure the straps distribute the compressive load to a large area of the core and sheathing.

[Chad]

Had my first "rudder issue" yesterday...

bad square corners.jpg

It held together through the day, and I think it'll be a quick fix.

I'm planning to grind away the paint in the area outlined by the tape, radius the square corners (the problem in the first place), and just wrap a couple of layers of carbon over the loose area.

Had a hoot of a day though. A lake tour distance race, we were 3 minutes late for the start having had a D1 pop out of the mast (just had to reinsert the t-ball, no idea how it happened). We returned to a dock, leaned the boat over, stuck it back in, started and chased the fleet. We got half of them by the first mark, 3/4 by the second mark, and all but three by the finish. It was another 12-15 building to 15-20 kind of day, we sailed with three, and the boat was working pretty well. The kite is super tough on these narrow lakes- when the puffs come from the side (which they almost aways do!) there's just no room to run off and stay under the kite. We put it up on a few legs, but it seemed to put us on our ear more than get us down the course.

...and Rocky, with three up, I'd say the big top main is good until maybe 18. It rags a little above that, but I could keep it driving off the leach pretty consistently.

Next weekend is Sail Oklahoma, near Eufala. A bunch of small boat kooks, self-built stuff, some small boat designers giving talks, and people generally showing and seeing what everybody brings. I think this will be the cruiser set mostly, but there's at least one i550 plan-holder attending, and a bunch for whom the i550 is on the radar. Could be interesting!

[noemar]

Chad ,I have been meaning to ask where did you get your GNAV?
Noel

[Chad]

Built it!
I used a gooseneck for the top of the strut, same spec as my boom gooseneck.

Then either a track and car on top of the boom, or follow this plan (since done by one of our intrepid builders) for a Vx-One style slider:

i550_GNAV_1.pdf

i550_GNAV_2.pdf

i550_GNAV_3.pdf

i550_GNAV_4.pdf

i550_GNAV_5.pdf

[Chad]

And the strut:

Strut complete.pdf

(I've got a bunch of 1.25"Ø X 42" long foam blanks, if anybody would like one to use for the core of a gnav strut.)

[Chad]

Rudder fixed.
Grind off paint:

image.jpg

Glue on a few layers:

image.jpg

All set!

[Kevin]

And the strut:

Strut complete.pdf

(I've got a bunch of 1.25"Ø X 42" long foam blanks, if anybody would like one to use for the core of a gnav strut.)

I have one issue with my gnav pole. The top leading edge runs into the mast bracket when I have it hard on (so I run out of vang purchase when I really need it). Maybe my "gooseneck" is too thick, but I plan to move the hole much closer to the leading edge (currently centered) to solve that problem.

k.