Moth Tuning

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alexshaw48
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Moth Tuning

Post by alexshaw48 » Mon Jul 22, 2013 6:42 pm

Hi all,

I recently bought a lowrider Moth, number 3936 and am getting to the stage where I am just about finishing races.
The main thing I have noticed is that it does not point upwind very well at all!
I have searched around but because very few people sail lowriders any more I haven't really found much. I have no idea about where the mast rake should be set, or how much rig tension should be on.

Also, during the race the spreaders move up and down the shrouds so one ends up much higher than the other one. I have tried tape but it just ripped it off and they moved anyway. Does anyone have any suggestions?

I believe the design is 'gentleman Jim' and I am using a Bolt rope sail on an aluminium mast.

Thanks
Alex

JimC
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Re: Moth Tuning

Post by JimC » Mon Jul 22, 2013 9:17 pm

I think the main option to locate the spreders is more tape, although you could try stainless steel locking wire as well.

If the mast tip is more or less above the rear of the daggerboard with max downhaul on the sail you're probably more or less right.

I have a Moth rig of that sort of vintage and I found it needed a phenomenal amount of prebend below the hounds to get the sail setting half decently in lighter conditions, a real contrast to the skiff style rigs I'm used to where the lower mast is kept straight.

Spiderman
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Re: Moth Tuning

Post by Spiderman » Mon Jul 22, 2013 10:55 pm

Hi Alex,
I'm surprised to hear that you can't get the Moth to point very high upwind as Moths generally point quite well. As Jim points out you do need to be fairly firm with the sail controls to get the sail to set properly and induce a certain amount of mast bend. It is also very important to sit well forward on the wingbars when going upwind to dig the bow in and increase the lateral resistance. One problem could be that you are trying to point before building enough speed causing the daggerboard to stall and lose grip. Long Narrow high aspect ratio foils are prone to this compared to shorter wider foils like on a Laser. As for the prodder/ spreader ends moving on the rigging it may be that you haven't got enough rig tension on. If the lee shroud is going slack and flopping around when you crank everything on upwind then it is probably too loose. As for mast rake I would'nt rake back too far unless you have a second clew cringle allowing you to shorten the leech in high winds otherwise you might get stuck under the boom. If you post some pics of your rig set up as you would for going to windward it will be easier to identify any problems you might have. Welcome to the world of Moths anyway and keep us posted as to any progress you make.
Regards
Ian M

alexshaw48
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Re: Moth Tuning

Post by alexshaw48 » Tue Jul 23, 2013 10:11 am

Thanks for the advice, from what both of you have said it sounds like I'm being a bit soft on the controls. It feels very fragile so I've been a bit scared to start hauling on control lines!

Here us a couple of pictures of it sailing upwind:
https://fbcdn-sphotos-b-a.akamaihd.net/ ... 9845_n.jpg
https://fbcdn-sphotos-d-a.akamaihd.net/ ... 9230_n.jpg

Since these were taken I have put a better kicker on the boat and raked the mast back a bit as it looked very upright when I looked at the pics. You can also see the spreaders pointing at random angles from the mast which can't help upwind performance!

The point you made about trying to point before getting speed probably is correct as I have been sailing a laser for the past year and a half.

Alex

Rupert
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Re: Moth Tuning

Post by Rupert » Tue Jul 23, 2013 1:09 pm

Lee told me he had passed the boat on to you, Alex - I suspect the learning curve was a bit steep for him?

I have one of its centreboards here - Lee gave me a snapped one to try and fix. I'll get it to you one day, somehow, but no promises it won't just snap again - there wasn't much to work with!
Rupert

alexshaw48
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Re: Moth Tuning

Post by alexshaw48 » Tue Jul 23, 2013 3:16 pm

Lee did mention the centreboard, there's no rush as I have got one I can use, as well as another broken one which my dad fancies a go at fixing at some point. And the 'no promises it wont just snap again' just makes it like the rest of the boat :)

Spiderman
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Re: Moth Tuning

Post by Spiderman » Tue Jul 23, 2013 7:54 pm

Hi Alex,
Having looked at the photos you posted there are a couple of things I noticed.
Firstly a big plus point is that in both pics you are keeping the boat beautifully flat which as all Mothists know is not easy in itself.
Secondly, as you suspected yourself, the cunningham needs to be a fair bit tighter which will induce some mast bend and flatten the sail. This would then need to be backed up with a bit of kicker to maintain leech tension and bend the mast a bit more. Because you have the sail so full it looks as though the leech may be hooked to windward, possibly exaggerated due to too much mainsheet tension in an attempt to point higher. High aspect fully battened sails are potentially very powerful and aerodynamically efficient, but like daggerboards will stall more easily than low aspect Laser style rigs.

The prodder going to the forestay needs to be pointing upwards slightly (not quite as high as in the photo) so it looks more like an arrow on a bowstring with a similar angle to the forestay above and below. Having achieved that first then pull the spreaders so that the outer ends are at the same height then with the rig tensioned tape it all in place. If it still slides around too much then as Jim suggests use some thin stainless steel seizing wire (0.025 -0.032") through small holes drilled in the spreaders and wrapped in a few turns around the shrouds above and below the spreader end before twisting the ends together.
Finally, why do all your sail numbers appear to be on the same side and where are you sailing your boat. It is always nice to know which clubs people sail from as it may then be possible to link up sometime.

Regards

Ian M

alexshaw48
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Re: Moth Tuning

Post by alexshaw48 » Tue Jul 23, 2013 8:46 pm

Thanks, I will try it all out next time I sail it, the cunningham is pretty good on the boat and I should be able to pull a good amount on to get a bit of mast bend. Too much mainsheet tension makes sense, as later that day the rope holding the mainsheet pulleys to the boom snapped.

I'll have another go with the tape around the shrouds and forestay and see if it holds, hopefully with more rig tension as well that should work fine :)

I hadn't even noticed the sail numbers until I read your post, very odd!

I sail at Manor Park SC, about 10 minutes down the road from Blithfield.

Andy P
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Re: Moth Tuning

Post by Andy P » Tue Jul 23, 2013 11:14 pm

More downhaul required - moths don't do the wrinkly luff thing. The sail looks much too full - more downhaul!
The mast looks like it needs more rake.
I have used copper plumbing tube, flattened and cut into strips ~ 2mm x 5mm, and compressed around the shrouds with pliers to locate the prodder ( but squeeze carefully - don't nick the shrouds! )
The rig tension should be enough so the lee shroud doesn't quite go slack ( and more importantly the forestay doesn't go all wobbly and loose in a nose-down bear away )

bornagainmothie
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Re: Moth Tuning

Post by bornagainmothie » Wed Jul 24, 2013 11:52 am

I agree with all suggestions so far, a bit more rake, tighter downhaul, induce some bend in the mast etc.
As a puddle sailor mothie myself, I consider tell- tales and a burgee essential for survival, but I can't see them on your photos. 2 or 3 pairs of tell-tales near the luff (about 30% back) will allow you to see the flow upwind and keep on the shifty edge. They also give you that split second warning of the 45degree header that catches us out! Another set near the leech by the second batten down will show if kicker adjustment is correct.
Burgee is a must for downwind ( keep away from dead downwind as its slow and very wobbly) and to give you a rough idea on reaches, but it has to be on top of the mast to avoid interference from rig and other boats, and you have to hold the boat steady before you believe the reading. Waving the mast around is no good, but of course thats the tricky bit. Capsizing and digging it in the mud is expensive in burgees, so more incentive not to fall in.

PtoStu and I sail our Moths at Greensforge which is very close to you. Come over and see us, we can set up a practice session sometime.

Lyndon

alexshaw48
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Re: Moth Tuning

Post by alexshaw48 » Wed Jul 24, 2013 1:16 pm

Those 45 degree headers sound very familiar!! I have a little hawk burgee that straps around the bottom of the mast but I will put one on top as well along with some tell tales on the sail. I think there may be some tell tales along the leech of the sail but I haven't really used them so far. I don't have the mud problem as theres loads of depth in the main sailing area :)

Would love to meet up, however I don't have a road trailer with the boat so transporting it would be a problem

Alex

bornagainmothie
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Re: Moth Tuning

Post by bornagainmothie » Wed Jul 24, 2013 4:09 pm

45 degree headers are the ones you might see coming, anything more is a guaranteed swim!

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Nessa
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Re: Moth Tuning

Post by Nessa » Wed Jul 24, 2013 8:26 pm

All of this is useful to me too. I wonder if I slit open a ferrule and swaged it onto the wire, that would do the same as Andy suggests to stop the prodder waglling about. I will also try more downhaul. I learned about deaddownwind the hard way.

We need a dedicated lowrider meeting somewhere central. I am at Hunts with the magnum five and the mystery moth.
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ptostu
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Re: Moth Tuning

Post by ptostu » Thu Jul 25, 2013 8:20 pm

Im up for a gathering meet up or training and a session on not breaking things lol :D
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bornagainmothie
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Re: Moth Tuning

Post by bornagainmothie » Fri Jul 26, 2013 7:34 pm

We would organise a day at Greensforge, but its difficult Moth conditions at the best of times. surrounded by trees and only 17 acres. Still, if you can sail one here you can manage anywhere!

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