Twin Headsails

[AlanH]

I'm planning on making my own twin-headsail rig. I have a headfoil, and the forestay on the SC27 is 32' 7".

I figure I will make the thing from materials I buy from Sailrite, and my quick-and dirty calculation suggests it's going to run me about $300. I know that my 1950's vintage singer will straight-stitch the headfoil tape, though it won't sew tape and a layer or two of Dacron. Joans Husquevarna home machine will sew a few layers of 1.5 oz. nylon, no problem.

I'm figuring on a 30.5 foot hoist, and putting the thing on an 18 inch pendant so I can sort of see out underneath it. It will be a relatively high-clew affair to keep the poles out of the water. I'd like the clews to be around 6 feet off the surface. I'm figuring on an LP of about 115%. With My spinnaker poles being the length that they are, anything larger will just wind up being more curve in the sail, and anything smaller will get stretched tight. Right now, my 100% working jib, when poled out works well, but it's pretty flat. I'm also guessing that I will have to take the thing to Rui or Synthia to get the rings pressed in, or a few bits of webbing sewn on, as my home machines aren't gonna be able to deal with that.

I'll lay it out on my churchs' fellowship hall floor (polished cement) and set up the general shape with blue striping tape on the cement. I'll lay it out and cut it out, there. I'll probably cut out all the panels for each side, first, then pin it all together. I'll broadseam it to put the maximum draft fairly far aft, and won't build in any roach. No doubt my sail shape won't win any prizes, but I strongly suspect that super-duper airfoil shape in this thing is a lot less important than it is in other sails. I have Sailrite's instruction on how to build a dacron headsail, and I figure that with some modification and thought, I can fake it and come up with something acceptable.

When it flies, the headfoil will twist around on the forestay and the grooves will face forward. I've been thinking about that, and I can't think of anything horrible that should result, though there might be abit of chafe on the pendant..

I think this will be a fun, two-weekend-long project, but we shall see. I'm hoping it will drive the boat merrily along at a great rate, with the Navik doing most of the steering.

Anybody got any brilliant insights to share?

 

[BobJ]

Well, you might want to go look at #895 and #896. They could be trimmed down and sewn together. Kame has had these for a LONG time (I looked at them in 2005) and might take a lowball offer. They were in decent shape as I recall - btw they're blue. I thought about getting them made into twins (single luff rope) but then you offered the Rainbow Coalition twins, which already fit!

http://www.pineapplesails.com/usedsail/web_jib.htm

 

[tiger beetle]

Thoughts on downwind twin headsails

The twins/butterfly sails on Beetle are sized to match a 150% jib top that I also have, which makes them huge and provides tons of power when running deep, with a lot more control than when running under spinnaker as the sails don't oscillate due to being attached down the center on the headstay furler (the two sails are sewn to a common no. 6 luff tape). The twins also work really well in super light wind despite being built of 1.5 oz nylon in a triradial panel design, as the headstay supports the weight of the sails and they will fill in 3-4 knots of wind, something a normal 1.5 kite would never do.

I asked Hood Sails to make the twins as close to a spinnaker shape as we could get, rather than being flat boards. Spinnakers develop their power by being a hi-drag shape (a sphere develops more drag that a flat board) and the twins should operate as a hi-drag shape as well. What we wound up with most resembles a giant brassiere with a very deep centers when the luff, leach, and foot are all tight. Square footage on my spinnakers is approximately 1900 square feet, the twins come in at 1600 square feet - that's a lot of cloth to generate power.

On the sewing end, don't sew nylon with a straight stitch, it should really be sewn with a 3-step zig zag which most home machines don't have. Synthia make be best able to speak to how good a compromise as 1-step zig zag is for nylon work.

For pole height, the clew should be as high as possible above the water so you don't stuff the pole end in the water when the boat rolls hugely (which it will when running deep under the twins). In my case the sails are designed such that the pole butt is at the very top of the mast track, 13 feet above the deck and therefore 17 feet above the water (this is where the pole goes when running deep under kite). I would recommend you set up your twins to have the clew set at least as high as you would when running DDW under spinnaker.

- rob

 

[AlanH]

Thanks, Rob.... your poles are at the top of your track, eh? Hmmmm...maybe I'll move mine up a bit, then, and get the clew more like 8 feet off the water. I'll also take to heart your thoughts about making them very deep...can do that.

Joans Husky has a zig-zag stitch, which is what I was going to use to assemble the panels. I was just going to use the straight-stitch to fasten the nylon inside the foil tape layers. Both "halves" of the twins will be sewn to a common tape, of course.

I'm curious, how does the Beetle do with the twins up and the Monitor driving?

Bob, I checked the PS site and looked up those numbers, they're a bit big, but they'd fit an Olson 30 or your boat quite nicely if anybody is looking. 5 ounce dacron will make them bulletproof, though maybe a bit heavy.

Then again, the garish colors you got attract attention!

 

[blighbaum]

fractional rig and twins

Is there any danger of the rig falling down if you have a fractional rig and run for a long time with twins and the main furled? I discussed this with a rigger, and he said the rig wouldn't come down, but that rigging running backstays would not be a bad idea. So, has anyone rigged up running backstays in a fractional rig boat for the SHTP? - Tom Kirschbaum, Feral

 

[BobJ]

A topping lift and mainsheet/vang tension should accomplish the same thing.

If you have some spreader sweep (so the caps support the top of the rig) you should be okay. But I guess they couldn't hurt - does your mast already have sockets for runners?

 

[haulback]

For what it is worth - I have found that when running with twins it's not a bad idea to experiment with having a reefed main up at the same time.

Not only does it help dampen the 'rhythmic rolling' out somewhat, but gives you a sail up and drawing to power the boat along with during sail transition, should you want to switch to a chute at some point. I am sort of inclined to think it may even give a little more drive to the sailplan

Just measured main and both 'chutes today so am ready to apply for '08 norCal PHRF once January 1 rolls around.

Also put the lucky number '50' on the main while it was on the ground!!!

Jim/Haulback

 

[Ergo]

I've had similar results to Jim with reefing the main while flying twins. I've also had good results with only polling out the windward twin and driving up a bit while sheeting in the leeward twin a bit. It really reduces the rolling and is marginally faster than DDW.

 

[tiger beetle]

I run the downwind twins with one sail poled out to weather, the main (full hoist) to leeward and prevented off, and the leeward half of the twin sheets to the rail such that the sheet just clears the boom, and avoid running DDW - significantly faster to sail on a slight reach at say 160 AWA.

There are several extra blocks and bits I set up when running deep, under kite or twins:

a. outgragger rigged up on the spinnaker sheet, a lightweight riding block on spinnaker sheet that pulls outboard along the underside of the boom - is super for keeping the spinnaker sheet from wearing against the stainless steel lifelines, and also does double-duty at torturing the spinnaker shape when you want to depower it (outgrabber on!) and acting as a boom preventer.

b. twinger to pull the sheet down below the boom, a second lightweight riding block on the spinnaker sheet that leads to the rail forward of the shrouds, and keeps the spin and twin sheet from wearing against the underside of the boom.

c. boom preventer line, in two halves - the short section is permanently attached to the outboard end of the boom and is stored alongside the boom and attached to a bit of bungee cord at the gooseneck (this allows attaching/detaching the preventer while standing at the mast). The second part of the preventer is a line that snapshackles to the short section, and runs outboard of everything to a block set on the rail at the bow, then leads aft to the un-used (leeward) runner winch. Keeps the boom from sailing across the deck when you least expect it.

d. chicken stay, set on the mast well up the spinnaker pole track, it leads forward and to the rail midway between the headstay and shrouds, and takes some of the spinnaker pole load bearing on the mast and transfers it to the toe rail.

e. babystay, provides additional fore-aft support to the spar and helps to keep the spar from pumping in a seaway.

f. runner/checkstay, provides additional fore-aft support to the spar and helps to keep the spar from pumping in a seaway.

g. spinnaker net, set on the spare jib halyard, to prevent the spinnaker from wrapping about the headstay in light or sloppy conditions. This is a real life-saver in marginal (usually too light or too deep) spinnaker flying conditions.

Gybing the rig in the middle of the night with all the extra spaghetti in the air adds to the excitement!

- rob/beetle

 

[brianb]

Hi Alan,

I have often wondered about headfoils and will they blow up if the loads applied are different than the design load ?

Brian

 

[AlanH]

Hi Alan,

I have often wondered about headfoils and will they blow up if the loads applied are different than the design load ?

Brian

OK, so here' s my thought on that.... It's a twin-groove headfoil, yes? So I can hoist two headsails at a time, one in each groove. I can then pole them out and go wing-and wing that way. But if I do that, the loads on the two headsails are trying to pry open the headfoil, and I'd be concerned that it'd come off of the forestay.

But with this rig...two 1.5 ounce nylon sails sewed to a single luff tape, there are no forces trying to pry open the headfoil, so I *think* it should be OK.

BTW, I had intended to fly all this with 1) twin chicken stays (basically just a line with a bit of purchase on it that will take, say 500 lbs load or something) from the mast track rings to the toerails, and not use a spinnaker net. However, if I'm gonna move the rings way up on the mast, the angle that the chicken stays work at becomes less advantageous. However, they're so easy to rig, that I figure I'll just do them anyway.

i was also going to do all this with the main up, with a reef in it, as well. Then again, I've never tried it, so what do I know?

 

[sleddog]

Just a reminder that in most situations with twin jibs/poles, it is desireable to locate the mast attachment points for the poles with about a foot or more of separation. This helps avoid damaging the poles when bringing them onto centerline..

For those with twin poles affixed to sliders at the inboard end, the mast track undergoes extreme sideways loading, and will often work it's way loose, especially if the track attachment machine screws are just tapped into the thin aluminum wall of the mast.

At minimum, it is best to use extra machine screws to secure the mast track to the mast. Stainless inserts are also available that can be used to strengthen threaded holes in aluminum mast wall.

~sleddog

 

[tiger beetle]

I have often wondered about headfoils and will they blow up if the loads applied are different than the design load ?

This has not happened to me using a metal foil of the Harken and Schaefer roller furlers. I can't speak to what would happen with a plastic tuff-luff headfoil.

- rob/beetle

 

[WBChristie]

The twins/butterfly sails on Beetle are sized to match a 150% jib top that I also have, which makes them huge and provides tons of power when running deep, with a lot more control than when running under spinnaker as the sails don't oscillate due to being attached down the center on the headstay furler (the two sails are sewn to a common no. 6 luff tape). The twins also work really well in super light wind despite being built of 1.5 oz nylon in a triradial panel design, as the headstay supports the weight of the sails and they will fill in 3-4 knots of wind, something a normal 1.5 kite would never do.

I asked Hood Sails to make the twins as close to a spinnaker shape as we could get, rather than being flat boards. Spinnakers develop their power by being a hi-drag shape (a sphere develops more drag that a flat board) and the twins should operate as a hi-drag shape as well. What we wound up with most resembles a giant brassiere with a very deep centers when the luff, leach, and foot are all tight. Square footage on my spinnakers is approximately 1900 square feet, the twins come in at 1600 square feet - that's a lot of cloth to generate power.

On the sewing end, don't sew nylon with a straight stitch, it should really be sewn with a 3-step zig zag which most home machines don't have. Synthia make be best able to speak to how good a compromise as 1-step zig zag is for nylon work.

For pole height, the clew should be as high as possible above the water so you don't stuff the pole end in the water when the boat rolls hugely (which it will when running deep under the twins). In my case the sails are designed such that the pole butt is at the very top of the mast track, 13 feet above the deck and therefore 17 feet above the water (this is where the pole goes when running deep under kite). I would recommend you set up your twins to have the clew set at least as high as you would when running DDW under spinnaker.

- rob

Sorry to drag up this very old thread, but I'm very interested in how this setup worked for you Rob. I'm would like to have a similar set built, that is more of a spinnaker shaped sail. Is it still possible to tie the clews together... or does the "brassiere" shape preclude that option? What sort of apparent wind did you use this in? Were they "reefable"?
Thanks for any input.