Would a modern 20 ft cat, like my Inter-20 , be faster if I added more more sail area to it, and made wings that extended 30 inches from each side of the hull? The sail area would be via a bigger jib and bigger spinnaker.. the wings would weight 15-18lbs each side ..I'm trying to decide if the added sail area would offset the added weight/windage and make the boat faster in most conditions. Whatcha think, is it worth it?

If you wanted to supercharge your boat, I would increase beam before adding wings........ More efficient use of righting momentum.

Thanks for the feedback Tornado Alive.. I did think about that option as well. I like the wing option because I can unbolt the wings in a couple minutes, use the standard sails and race I-20 class.

I checked out the factory wings the Performance offered at one time, and they do not look like the right design..when I called the factory they did not seem interested in selling them, so the option would be to make them.. I'll be honest , part of reason is for cruising around , wings are kinda cool...

In summary,

In high winds you'll want the same sailarea or less with preferably more righting moments. So don't add sail area here. If anything add righting moment = wings

In light winds you'll want more sail area high in the mast. This won't happen with the jib and the I-20 spi is already very large. This means that its area is relatively bit in relation to its luff length. Luff length is more important performance wise then area in a spi. Afterall the 350 sq. ft. Nacra 60 NE spi is not faster then the standard 270 sq. mtr. I-20 spi. So you'll be making costs for hardly any gains. Not smart.


30 inches = 0.76 mtr.
18 lbs = 8 kg => 16 kg in total

Basic I-20 righting moment 150 kg crew = 787 kgm
With wings = 922 kgm = 117 %

With this increase I would just keep the current sailplan and just add wings if you really want that. I big winds you may expect some 5% more speed if the wings don't hit the water etc. Mostly when beating to weather. On downwind legs you won't win much at all.

Wouter

Based on experience with the 18 Magnum, 18SX and a Winged Experimental, I don't think you will go much faster. You will gain some comfort and stability, especially in heavy seas. If you keep pushing it, you will just pitchpole before you flip.

theres a thread in the F20 forums about a 10' wide I20 conversion. So far I don't think anyone has picked up the torch on it.

Some of the old open-class Worrell boats had wings that could flip up on the downwind side so they didn't touch the water. Adds complexity and weight though, I'm sure.

By using wings you can handle more wind while the boat will power up earlier.. I like the idea of reasonable wings, especially wings that extend back of the boat so you can really drive it hard downwind.

Thanks everyone for responses and feedback... I'll send along my wing design once completed.. Agree with Rolf, have them extend back for downwind work.. Also think that having wings might enable me to carry the spinnaker at a closer angle to the wind in moderate and heavy air, without being overpowered.

Adding larger wings may work best ,this was the approach taken by several earlier 1000 mile race entries .

If the basic math is taken into account a 400 lb crew moved out 2 ft provides an added 800 ft Lbs of righting moment to help hold the boat down as wind increases .

Move them out 10 ft and the ft Lbs becomes 4,000 --wow .

The I-20 has wide flat large volume forward sections so it can handle some of the added forces from a 10 ft wing without pitchpoling ---right away . <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />

The other corespondng modification might be smaller forward placed hydrafoils

http://www.foils.org/sailfoil.htm

and these could aslo act to balance the spin set on a longer spin pole --say 15 ft .

this increases spin luff angle and also creates added lift .

Check out Aussie 18 skiffs for examples of spin luff angle and lift .

http://jameswebb.ca/gallery/Aussie18Crashes

It would also be a good idea to lengthen the forstay a little and rake the mast back more .

There is a speed trials on San Fran Bay in June ,--this would be a great craft to enter .

Having sailed a Hobie 21, I must agree that wings ARE comfortable.
If I were you, I'd just buy from Hobie the wing model that best fits the specific boat, instead of making a new design and going through the trouble of building it.
Less worry about things going wrong, less suppliers, more time to cruise, spares available...

Hello All,

Go to the Hobie FX-1 site in France.

One has to do a little 'hunting', but there are pictures of
'racks' for the FX-1

They are quite innovative, not the 'passenger' models,..rather, the 'race' versions.

I remember 3 models.

One was a 'short' extension, maybe 8 inches out from the hull.

The next was 20-24 inches out. Made to hike off of.

The last was the largest extension and set up to sit on.

My needs for my I-17 was the 2nd model[heavy weather], but I do not need any material [ other than support] forward of the d-board well [ just d-board back to say, 1 foot behind rear x beam]

Throw a couple footstraps on,...and bam,..you are ready to fly!

regards,

Bruce
USVI <img src="http://www.catsailor.com/forums/images/graemlins/cool.gif" alt="" />