Lightest dinghy rig

[Wardi]

Originally Posted by CT249

A sailboard rig is as light as a Moths (?) and the wishbone means that there is no vang load and a very light mainsheet load. Whack some stays to the boom like Kovesi (?) did and voila!

Here is a photo of my swing rig for a Moth being used in current Moth foiler testing. It uses a 2Kg carbon mast from Furya in Japan, extended to 6.0m, supporting a high aspect 8.0sqm sail with 1.5m foot length. The boom is 32x1.2mm dia aluminium tube, but could be much lighter and stiffer in carbon. The wishbone allows the sail luff to extend to the deck. As the boom extends forward of the mast and has a stay to the mast hounds, no boom vang loads are taken by the mast at all. This means a very light mast can be used and it can be very easily over rotated if required.

As all loads are self contained, there is no need for the hull to take mainsheet or vang loads. It is the traveller in an A-class cat and the hull structure and wing tubes in Moths which are uncounted weight to support their rigs.

By comparison with a sailboard, the wishbone does not need to take the load of the crew directly and is much lighter, and as the wishbone does not touch the mast, it does not have to be as heavily constructed as a sailboard mast which must take heavy bending loads.

I would therefore contend that this is in fact the lightest total rig arrangement!

[grob]

Originally Posted by CT249

A sailboard rig is as light as a Moths (?) and the wishbone means that there is no vang load and a very light mainsheet load. Whack some stays to the boom like Kovesi (?) did and voila!

Cheers, thats exactly what I've done , except that I've used two rigs!, the really great thing about the windsurfing rigs is thier price/weight ratio. Probably due mainly to the vast numbers they are sold in.

Gareth
www.fourhulls.com

[National3434]

Wardi,
I guess this is the same rig as shown in your foiling photo at http://www.moth-sailing.org/pictures...iler_large.jpg.
I like the concept alot and am thinking of doing something like it on my foiler.
For ref, this type of rig (but not so light or elegant) is standard on the UK Catapult catamaran (has inflatable hulls) www.catapultcats.com.

A few Qs come to mind.
Using a wisbone type double boom, you can not square out when running down wind as much as with a conventional boom, before the boom hits the shroud wire. How do you overcome this problem or with the foiler do you never need to square away?

You seem to have some extra 'knitting' in the foiler picture under the sail foot. Is this additional vang control or just something to hang the mainsheet off? Any reason for centre sheeting or is it just what you prefer?

You mention over-rotating the mast. How do you control this and are there useful forces to push the mast around (since there are no vang/boom thrust forces).

The sail looks realy nice but seems to be too high in aspect for a measuring moth sail and I can see it seems to be a cut down NS14 main. I gather you 'extended' the luff to 6 m to compensate for the narrow foot to get 8sqm?

Sorry this refers to your posting of a few months ago. I only just found this thread!

Cheers

Tom E

[Wardi]

Hello Tom,
Yes you are correct, I am trialling many things using the one test platform.The Scow Moth is not really intended to be the final solution but it offers a lot of advantages being cheap, light, simple to launch and handle, easy to get back to the beach when something breaks etc. A big improvement over my narrow skiff Moth at just 250mm waterline width!

I am using a wisbone type double boom, but it is not nearly so wide as for a windsurfer arrangement as I am not hanging off it and do not need use it to get my weight out to weather. Downwind I ease the outhaul and the sail is then just touching the inside of the leeward wishbone which sits hard against the stays. It is in practice very little different to a normal boom, so I have not experienced any limitations running square.

Even with a foiler, in light winds, it is necessary to run square, so this is still important. Maybe if it was a boat with large sail area and spinaker, then it would not be an issue.

"You seem to have some extra 'knitting' in the foiler picture under the sail foot. Is this additional vang control or just something to hang the mainsheet off? Any reason for centre sheeting or is it just what you prefer?"

I am using central sheeting off the vang wire and have a small cord up to the boom to provide extra stiffness. This works OK and I personally prefer this because it is how I have always sailed Scows, but end boom sheeting would be technically better as it puts no bending moment on the boom.

Have also tried using the boom itself as a vang lever by letting it run freely up and down on the forward stay. A cord is then used to pull it down, This provides a very effective vang lever and gets rid of a lot of rope and purchases in the cockpit and around the foot of the sail.

"

You mention over-rotating the mast. How do you control this and are there useful forces to push the mast around (since there are no vang/boom thrust forces).

"

I am currently using a round mast but have previously experimented with overrotating masts, as they offer good light wind performance.The thing with over rotating masts is to remove all bending loads from the vang etc so that they are easy to rotate.

"The sail looks realy nice but seems to be too high in aspect for a measuring moth sail and I can see it seems to be a cut down NS14 main. I gather you 'extended' the luff to 6 m to compensate for the narrow foot to get 8sqm?"

Yes you are absolutely correct! The area is 8.0sqm and it is an extended lightweight Landenberger NS14 mainsail. It is set on a 2.2Kg Furya carbon mast. It works well but does not currently measure as a Moth sail, although if I cut the foot round with a very large curve, shortening the luff to 5.185m it will comply due to a quirk of the class rules...which really ought to be fixed! :-)

My experience is that the tall rig is definitely more efficient and actually works well and feels good, but it really requires a stiffer mast. That is why I use spreaders. The only downside is that it contributes a greater pitching moment than a standard rig, which makes it even more difficult to maintain height & pitch control while foiling. It is the height and pitch control which is the greatest technical problem for Moth foiling.

I have had many ideas on how to solve this pitch and height control problem and am still working to achieve a really good, simple solution...
Any ideas on this are most welcome!!

[National3434]

Wardy
Thanks for your clear answers.

Here is one more. Do you use a haryard to get your sail up or do you tip the boat over and pull /push by hand? I much prefer hauling a sail up the mast (it is often muddy where I sail) and a halyard running in the mast with a lock that works would be ideal. Any ideas? Anyone?

Your Q in the foiling pitch problem prompted me to write down some rambling thoughts which I will post on the hydrofoil thread.

Cheers

[Wardi]

Tom,
I have a halyard but do not use it. We are pretty spoilt downunder with grassed rigging area beside golden sand beach. I have no cradle, rig on the grass, tip it over to pull the sail up and carry the boat on its side perhaps 3m down the sand by myself and sit it upright in the water. Wade out 30m in warm shallow clear water with a sandy bottom..too easy!

Another idea for you..
I do not have a continuous boltrope on the sail. It is about 200mm long at each batten end. This was originally intended to make recutting the luff round very simple and cheap. Just take off the batten ends, unpick 200mm luff tape and sew it bakc on in another position!

Another benefit is I can attach the entire sail before hoisting it. This is the same as for a yacht with slides on the mainsail. It is easy to attach it and then pull it up on ones own, without the need to feed it into the track. It also all stays neatly bunched together on the mast when lowered and does not blow overboard.

All of these are simple innovations to make it easy to handle on my own.

[National3434]

Thanks Wardi,

Some really interesting ideas. I first read 'not continuos boltrope' as '..continuous halyard' which prompted an idea for the halyard (problem of where to stow the tail).

The fact that England is a 'green and pleasant land' means that there ia usually mud not far beneath your feet. Unless it has been capped by concrete. My launch is from muddy grass over a seaweed covered shingle 'hard'. Stray off the hard and you have good smelly mud. But the water is still the same stuff!

Cheers

[Wardi]

I notice that the Tornado cats run the free end of the halyard back up the track with the head of the sail, tucked beside the boltrope. Very neat!!