Spinnaker Specs for My Cat

[svcattales]

I'm looking for a used spinnaker for my 37 ft Privilege and I'm technically challenged about the dimensions and cloth weight. I read the previous posts on the subject and think I want an asymetric chute designed for light to medium winds up to about 15 kts aft of the beam.

My hoist dimension (I) is 38.5 ft. What range of luff lengths will work for me? I don't want a "blind spot" forward so should I try to go shorter than 38.5 ft or will the sail rise up enough to allow for longer luff? The other dimension I'm confused about is the length along the foot. I have deck blocks on both bows to allow a "traveller-like" system to adjust the location of the chute's tack. In theory I could move the tack to windward about 7 feet from centerline to get it out of the main's wind shadow so how long should the foot-length be? I would really like a big-ole "whomper" type chute so longer would be better right? OBTW, the overall beam is 21.5' and 16' between the bows.

The last question is cloth weight. Would you recommend .75 oz or 1.5 oz?

I have zero experience with chutes on cats and very limited experience on monos, so any advice will be appreciated.

[GordMay]

You should probably talk to a sailmaker. The weight of a sail may vary, depending upon the specific sail fabric, cut, and construction chosen.

[Woods Designs]

I have a useful article on spinnakers on my website. Woods Designs Sailing Catamarans

It was originally published in both the UK Multihull Review and Australian Multihulls World. Both excellent magazines

Hope this helps

Richard Woods of Woods Designs

Woods Designs Sailing Catamarans

[svcattales]

Thanks for the help Gordo & Woods Designs. The Woods Designs article on spinnakers was very helpful. I was surprised to see the recommendation for a conventional chute for cats rather than an asymetric cruising chute. The other surprise was the recommendation for flying it without a sock. I think I would prefer to use a sock even though it may be more difficult to put it up. In my limited experience, I was always more worried about getting it down when the wind pipes up. Appreciate the help.

[Strygaldwir]

Greg;

I think you want a symetrical spinnacher. I have blocks for flying the spinnacher mounted on the bow of each hull. The lines are routed back to the cockpit. The symetrical spinnacher lets you use either side as clew or tack, you just adjust your sheets accordingly.

You really do need a sock! You can store the sail in one of your forward sail lockers and connect all the sheets/lines while it is the sock and in the locker. Once you have to sail hoisted, you can drop the sock and you're flying, pretty painless.

[svcattales]

Originally Posted by Strygaldwir

Greg;

I think you want a symetrical spinnacher. I have blocks for flying the spinnacher mounted on the bow of each hull. The lines are routed back to the cockpit. The symetrical spinnacher lets you use either side as clew or tack, you just adjust your sheets accordingly.

You really do need a sock! You can store the sail in one of your forward sail lockers and connect all the sheets/lines while it is the sock and in the locker. Once you have to sail hoisted, you can drop the sock and you're flying, pretty painless.

Keith,
Once again you have been a great help. I have those blocks on the bows with fairleads back to cockpit too. I was thinking that those were meant for a long continuous line from bow to bow and be used as kind of a traveller to move the tack of the chute back and forth. Your explanation makes a lot more sense and it sounds like it would make jibing a lot easier. Rather than gybing the chute around the front of the forestay, you just swap tack for clew and adjust the sheets. The sheets could be a bunch shorter too which is a good thing. Very clever system.

I like the sock idea too. For a short-handed crew you really need a means for one person (me) to douse the chute quickly.
Thanks again.

[gramos]

Originally Posted by svcattales

I'm looking for a used spinnaker for my 37 ft Privilege and I'm technically challenged about the dimensions and cloth weight. I read the previous posts on the subject and think I want an asymetric chute designed for light to medium winds up to about 15 kts aft of the beam.

My hoist dimension (I) is 38.5 ft. What range of luff lengths will work for me? I don't want a "blind spot" forward so should I try to go shorter than 38.5 ft or will the sail rise up enough to allow for longer luff? The other dimension I'm confused about is the length along the foot. I have deck blocks on both bows to allow a "traveller-like" system to adjust the location of the chute's tack. In theory I could move the tack to windward about 7 feet from centerline to get it out of the main's wind shadow so how long should the foot-length be? I would really like a big-ole "whomper" type chute so longer would be better right? OBTW, the overall beam is 21.5' and 16' between the bows.

The last question is cloth weight. Would you recommend .75 oz or 1.5 oz?

I have zero experience with chutes on cats and very limited experience on monos, so any advice will be appreciated.

i would certainly go for a 1.5 oz .75 oz is way too lightweight for the loads a cat will apply to it ,and result in less window of use , i.e. dousing at lower windspeed . also the tack and clew should fly "high " and not interfere with fwd visibility , there is more wind at the mast head , let it fly high .they are a great sail -you,ll be glad you went for it !

[svcattales]

Gramos, thanks for the tip on 1.5 oz cloth. I discussed my questions with a used sail dealer and he also recommended the heavier cloth on catamarans. When a mono takes a gust, the boat heels to relieve some force on the sail. In a cat, the sail has to handle the full force of the gust and should be built heavier (I assume this is true of other sails as well). The dealer also gave me some good guidance on determining foot length of the chute. On a monohull, the J dimension is measured from mast to forestay, but since I will attach the tack to each bow, I need to measure from mast to bow block. On my boat this means a distance of 15.5ft instead of 13ft to the forestay. If I calculate a 170% factor (common for chutes) I get a foot length of 26.4ft to the bow instead of 22.1ft to the forestay. That also meets the common sense test. Since tack will be moved to windward of centerline, the foot needs to be longer.

I have been pleasantly surprised about prices for symmetrical spinnakers. There seem to be many more available and prices seem lower than for asymmetrical chutes. Perhaps the windward/leeward racers trade-in the symmetricals more often than cruisers trade in their cruising chutes. I found prices on chutes for my boat in "good" condition from $400-550 and some "very good to excellent" for $600-700. Now I just need to figure out how to "rob Peter to pay Paul" and cough up the bucks for a chute and a sock.

[svcattales]

I found a nice symetrical chute with a sock for $550. It is 2.2 oz fabric in good condition with a hoist of 43' and a foot of 24'.

I was afraid it would be too big, but after using it on our cruise to Key West, the size is just right. By adjusting the guys and sheets, I can let the sail float up and visibility is better than with my genoa.

The performance was really nice since and it let us sail with lighter winds. On the return trip, we had two 60NM legs with the spinnaker and we saved lots of diesel. We had a couple of exciting take-downs when winds gusted up to 15kts. We hid the chute behind the main and dousing was fairly easy except for the sail taking off my favorite hat and dumping it in the ocean.

The sail was surprisingly close-winded and I could carry the chute with the apparent wind slightly forward of the beam.

Thank to all for the suggestion on selecting the right chute.