Hi Jim
It’s an IOM. The root cause I think is probably that the mast/fin are too far aft, 520mm from bow to front of mast. Obviously mahjor surgery to change that. I am really hoping someone will come up with something simple like move the adjuster weight (250gm) currently forward of the mast.
Regards, Tony
and
… If you could rake the mast further back to compensate the deeper bow?
(but it looks extreme right now)
What about a smaller rudder?
Is the jib sheeted too tight?
What about more draft at the main (more sag at the main’s foot, less backstay tension)?
I have already trimmed a bit off the rudder as well as raking it forward, and I feel as though I’ve lost a little manoeuvrability because of it.
I have to tune the jib boom wider than ideal and the main sheeted close to combat the lee helm…
Interesting suggestions about the main - so more power aft. I will try those tweaks. Thanks. I suppose by the same token flattening the jib might also help.
But there-in lies the problem: tuning for helm not VMG.
What about the weight distribution? Will moving the adjuster weight forward more (or aft) help?
Tony
If you rotate your picture to put the boat on its waterline and strike a vertical (perpendicular), you will see that you have a tremendous amount of aft rake in the rig and a little forward rake in the fin. I do not see any possible way that this boat could have lee helm. It should have a tremendous amount of weather helm. Forgive me for asking, but are you sure that you are not confusing lee and weather helm?
No, its definitely lee: wants to turn away from the wind. The more I think about it (and look at your overlaid photo) the more perplexing it becomes.
Mast/fin too far aft, max draught about 30mm forward of the fin, I agree, all that submerged hull forward plus all the raking and I’d expect to have severe weather helm…
Any takers?
Try this —
Unhook your jib boom at the rear of the jib (from the fixed jib boom) and just let the boom and jib swing free and see what happens. Naturally it will be a bit more sensitive to tack, but by letting the jib swing, you are sailing under mainsail alone and there is no “input” from the jib.
I would “expect” a huge amount of weather helm from the main. If the lee helm seems to go away, reattach the swinging part of the jib boom, but start with slow adjustments as you begin to bring the leech of the jib back in line with your beginning setting. Somewhere in there you may see the return of your lee helm - and then you can go from there with necessary adjustments or changes.
Boat i [/i]balance should come before helm i[/i] balance otherwise you find going literally in circles trying to balance the boat out on the water.
If it is of any help this is how I [u]balance my boats[/u], starts at post # 15
Cheers Alan
Thanks K1, I will shift the adjuster weight progressively forward. I pretty well tried everything else except open heart surgery. The hydrodynamic balance of my boat was arrived at with a wood saw and a couple of beers. I carved a foam block into a male plug. I did have plan and profile drawn on the block but it was more art than science.
This boat just need to last me till #3 gets built, which has been designed on Freeship, no more shaping by eye.
Jeez, while I’m at it here is the data from Freeship. I’m totally open to suggestions.
Tony
[i]Hello Tony,
How does the boat sit int the water?
Jim.[/i]
Right on it’s lines actually. I am going to move the 260gm of adjuster weight forward about 75mm for tomorrow’s race and see what happens to the helm. Yeah, if might be slightly bow down but if it sails straight…
I think that the poverty pack was designed by Steve Arthur in South Australia. He sailed his with swing ifs with good success.
He’d be a good starting point to tune your M. Just google SA Sails to contact him. Steve is a good guy.
Dingo,
The boat doesn’t look THAT radical in terms of shape. Yes the keel is a little aft, but nothing outrageous, maybe 10mm…
I’m thinking it must be a rig problem. Can you put up some pics showing your tune on the rig?
Does the amount of lee helm get better or worse in gusts? The answer to this may be telling in my opinion. If there is too much jib boom tension, to boat will go bow down in a gust. The rake shown on the B rig is decent, but won’t contribute to your problem.
If you believe it is hull/fin, simply take fold some clear plastic, and carefully tape it to the front of the keel, thereby extending it maybe 15mm further forward. Yes I know it adds drag etc, but may alter the balance of the boat, and give you an idea. It cheap and easy to do!!!
Excellent idea Pat I will try that.
She wants to round up in a gust.
So lee helm to weather helm in a gust???
would be intresting at which heeling angle she turns from lee helm to weather helm.
Sorry, let me clarify that: “round up” is not correct: stop bearing away, is a better way of putting it. As the gust passes, she will turn her bow away again.
Hmmmm, that’s a weird one!
So you’ve had others at the lake take a look at it?
Yeah, past Qld Champ who is a tuning whiz but not a builder. I haven’t had a chance to try your fin extension idea, but I will I am curious to see its effect. I am fast coming to the conclusion that the mast/fin was positioned just too far aft. It’s 520mm from bow to mast centre and it seems that pushing the corrector weight further forward is going to be its only hope- aside from tuning the lee helm out which is exactly what I am trying to avoid having to do.
Ah, I thought the keel was 520mm back. If its the mast, well yeah it’s aft. 485-500mm would be the norm I’d say. It’s a bugger, but you could cut out the mast tube and fincase, or mould a new hull.
Theory says the CE of the sails needs to be further forward of the boats CLR, thecdifferencecis termed the lead…
Maybe contact Jeff Byerley, or Peter Kampe, they may be able to help.