flying a hull

I was flying a hull last weekend for the first time and I noticed a lot of stick pressure when I went up on 1 hull. Is this normal? I do not have very much pressure when I am on both hulls. I also noticed some humming coming from the rudders when I am going about 10 knots. I just adjusted the mask rake and have restored both rudders, and regelcoated them. I have done a lot of work on the cat and am trying to get things adjusted again.

Thanks airborne

Which way did you adjust the mast rake?

Which way is the pressure on the tiller? Wanting to round up or bear away?

Be sure to check that both rudders are raked the same (one of them may have slipped up slightly if you are using the standard pull-down system that came equipped on 5.2s). Second, check your rudder toe-in and make sure they are both pointing the same.

I raked the mast back to where a nacra dealer told me it should be. I moved it back to about4 degrees aft of vertical.

When I am on 2 hulls I have very little pressure, but when I a
am flying a hull it wants to round up.

Thanks airborne

Rake your rudders further under, but make sure to keep them even (port/stbd) else you will have different helm on each side.

I know that left rudder is raked about 3/8" fwd and the right is raked about 7/8" fwd. I was told that it should be about
1 3/8" fwd. I am not sure if I should move them when it feels right on 2 hulls. I would have to fill the bolt hole and drill a new hole to get the proper rake.

The rudders are are the same. They have "0" toe-in or toe-out.


Thanks airborne

I've never dealt with a 5.2, but the 6.0 had adjustment screws in the front of the rudder castings. We just pulled them all the way out and then removed some material on the front of the rudder where it hits the casting. That was SOP for those boats.

Bill:

My 16 and 17 both had about 1/8 inch of toe in. You need to have a little bit of weather helm even when flying hull. That way if you somehow drop the stick it will head up and drop the hull and not bear off and go over. But I am pretty sure rake should be even on both rudders. See you at WW?

Doug

I've had a 5.2, 6.0, N20, F18, and a TheMightyHobie18. None of them had the helm load change significantly when flying a hull. Something is out of alignment somewhere and it is probably the difference in your rudder rake. Some of the old Nacra castings didn't have a place for an adjustment - some have a plastic screw in the lower casting at the bottom near the hull that you could adjust the stop position of the rudder. If you don't have that, there's no reason you couldn't drill and tap a hole for a good-sized nylon screw to fit so you can set your rake to be consistent.

The fact that something changes when one hull (is it the same on both tacks) is out of the water suggests that something on one hull is not right.

You mentioned that you recently repaired your rudders ... I recently had a similar problem as you describe and after doing all the mast rake, toe-in, toe-out adjustments I learned that one of my rudders was slightly delaminated causing "flexing" once loaded-up--creating significant weather helm.

I'd check to be sure your rudders are sound before you continue on the adjustment(s) path.

and that the pivot holes are drilled the same locations in both rudders.

Yep, that was what my rudders suffered from. Was an easy repair though.

Wouter

1. Check rudder geometry
- Pivot holes are same
- Rake is same
2. Check mast rake (dealers aren't always right)
- Sounds like it needs to be moved forward a fraction.
3. If Nacra 5.2 has a jib, try powering it up some more.
- Close the leech a bit, not too much though.

Other than that, there are a lot of very obscure alternative reasons for weather helm ranging from platform setup to sailing technique.

I will have to check the pivot holes to make sure they are the same. That may be the reason for the different measurements on the rudder rake. I do have the adjustment screw holes but no screws are in them. Both rudders are against the casting.

airborne

also check that one of the rudder castings doesn't have a burr where the rudder bottoms out keeping it from going completely down - I've seen that before too.

2 suggestions...
Firstly is it definatly in relation to hull flying or is it speed?
The 5.2 had a weak pull down system on the rudder blades that caused the blade to move back when moving at high speed.
To check this lock down your blade and pull from the bottom to see how much play you get. It shouldn't move more than 1 cm if it does you might want to consider a 2:1 pull down system or some other method.

Secondly if it is hull flying causing the problem it could be a hull is out of alignment or a center board.

I have modified the pull down system and gotten rid of the bungee system. I have separate pull down line and a separate pull up line.

Next weekend I will have to try it again and check all of these things that everybody have suggested.

I will report back after next weekend.

airborne