Max Asym Spinnaker Size for VMG PHRF Racing? What is the right size Whomper?

[Slowboat]

Let's say you have an unconventional, asymmetrical boat (light (under 10klbs), carbon, long and narrow) trying to improve PHRF W/L performance in 6-11 knots of breeze.

Current large spinnaker:

Luff	54.67
ALE	45
ASF	29
AMG	26.17

Rig:

I	41
j	13.2
p	44.2
E	16.3
ISP	47.6
JSP	21.5

We are definitely underpowered going downwind deep, and need to play the angles which just isn't fast. How big a kite would you go? Looking at a J/109 (similar rig dimensions) I see the Great Lakes class goes up to a 120sqm kite, and folks have gone up to a 138 square meter - Luff=17.50/57.4 Leach=13.70/44.9 Bottom=9,23/30.23 Halfwidth=10.30/33.7

How big would you go? We have plenty of smaller kites, and with any type of reach the boat accelerates quickly and has very good boat speed. Over 12, we are very powered up and moving fast. With the current kite we just don't get the projection to go deep.

I should add that it may be possible we suck at sailing and haven't figured out the boat yet. Flip side is it sure seems like we need a bigger kite, or at least one with larger shoulders for deeper running.

 

[Marty Gingras]

Why isn't it fast to play the angles?

 

[Slowboat]

Why isn't it fast to play the angles?

Granted we are still getting the boat going, but the VMG just isn't there - sure, we cover lots of ground quickly, but we come right back to boats that are much slower. There is definitely the opportunity to get the boat going faster, deeper (I think).

 

[Marty Gingras]

Granted we are still getting the boat going, but the VMG just isn't there - sure, we cover lots of ground quickly, but we come right back to boats that are much slower. There is definitely the opportunity to get the boat going faster, deeper (I think).

If you are competitive as-is, then I'd imagine a big kite for sailing competively deeper would result in a significant rating hit. Yours is an interesting question.

 

[El Borracho]

Granted we are still getting the boat going, but the VMG just isn't there - sure, we cover lots of ground quickly, but we come right back to boats that are much slower. There is definitely the opportunity to get the boat going faster, deeper (I think).

Are you making too big of a transition between deep&slow to high&fast? Heading up just enough to establish moderate power can be the right move. Just a few degrees up. Save the high&fast for when the conditions can produce the textbook VMG advantage.

In theory, in PHRF, any boat mod that enables more speed must be reported and should produce a rating hit. Whether it is worth it is a crap shoot.

 

[sailman]

What boat? Have you checked the VPP/polars for the boat?

 

[danstanford]

Won't a bigger spin hurt you handicap wise too?

 

[167149]

max size= whatever the fuck you can hang onto

 

[eastern motors]

Are the other boats sym kites? Do you have separate W/L phrf rating?

 

[Steam Flyer]

Granted we are still getting the boat going, but the VMG just isn't there - sure, we cover lots of ground quickly, but we come right back to boats that are much slower. There is definitely the opportunity to get the boat going faster, deeper (I think).

You need a recorder. Until you know exactly what your VMG is at X wind speed, Y apparent wind, you can't really tell.

Most of the time, people head up and build apparent wind (FUN!) and then either don't bear away (because that would end the fun) or they bear away too much which kills both VMG and fun. Once you've got pressure, don't even use the helm. Have the crew hike a tiny bit and use heel to bear away 2~3 degrees. If the spin sheet is eased more than a couple inches, you've borne away too much.

Had the same problem trying to learn to sail a Rocket 22 downwind.

However, a bigger spinnaker would definitely be more fun!

 

[Hale Moana]

We had a whomper on the J130 I used to race on. It was legal measurement wise. No rating hit. The main difference was in the head panels being fuller. Not that good for reaching but allowed us to go deeper downwind.

 

[Slowboat]

We had a whomper on the J130 I used to race on. It was legal measurement wise. No rating hit. The main difference was in the head panels being fuller. Not that good for reaching but allowed us to go deeper downwind.

I guess I'm old school, but I always appreciated the big kites on the original J/Boats (J/120, J/130, etc.) Big huge shoulders that would rotate around letting you go deep for max VMG.

 

[IMR]

You might want to look at building a vmg running kite at the current max size of your inventory as to not impact your rating. This kite would have a ton of luff projection so much that sailing above 150 twa is nearly impossible.

 

[Steam Flyer]

We had a whomper on the J130 I used to race on. It was legal measurement wise. No rating hit. The main difference was in the head panels being fuller. Not that good for reaching but allowed us to go deeper downwind.

Fuller top, or even just a harder leech in the upper sections, will help the A-sail rotate out to windward too.

 

[BoksNoRox]

With your JSP of 21.5', you should be able to get a much wider spinnaker. Your mid girth could be up to 38' possibly without a rating hit. If you are using normal PHRF rules. On a J-80 the difference between class legal, and PHRF legal asymms is huge.

 

[Olsonist]

 

[Slowboat]

I only have a Nexus .nxp polar file now (working on translating it out to a more common format - if anyone has any tips that would be great!)

I believe these are the target speeds out of the polars:

Wind Speed	OptUW S	OptUw A	OptDwS	OptDwA
5.54	4.81	49	4.32	144
7.39	5.57	48	5.2	149
9.23	6.25	48	6.06	151
11.08	6.55	46	6.67	156
14.77	6.8	45	7.5	171
18.47	6.88	45	8.29	175
22.16	6.87	46	8.97	175

I think this shows that under 11 knots, we are sailing hot angles with pretty poor downwind VMG. Please correct me if I'm wrong!

 

[Livia]

Buy a pole and a symmetric on those numbers
Then learn to dip pole gybe

 

[FlyingCircus2]

You need a recorder. Until you know exactly what your VMG is at X wind speed, Y apparent wind, you can't really tell.

Most of the time, people head up and build apparent wind (FUN!) and then either don't bear away (because that would end the fun) or they bear away too much which kills both VMG and fun. Once you've got pressure, don't even use the helm. Have the crew hike a tiny bit and use heel to bear away 2~3 degrees. If the spin sheet is eased more than a couple inches, you've borne away too much.

Had the same problem trying to learn to sail a Rocket 22 downwind.

However, a bigger spinnaker would definitely be more fun!

I...umm... Agree with steam flyer.

If you look at your line sailed, it should be squiggly downwind, somewhere between 5 and 10 degrees of squiggle if the breeze is constant.

Your spin trimmer may be over trimming, too. Most of them do: it's an obvious, spectacular failure when the kite collapses, so a lot of trimmers hedge on the sneaky subtle failure of choking the kite. The trimmer should be able to handle the kite without a grinder in 10 it's of tws, maybe 13 if they are strong. If they can't hold it with two wraps, you are sailing too hot or the kite is in too far.

How old is your kite? I have one from 1996 and one from 2010 and they are radically different. The 96 has an S curve to the luff that takes out a ton of the power and compels me to sail really hot angles. The '10 has a c curve, and it's much faster.

If your gut tells you to get a new, bigger kite, probably trust it.

 

[FlyingCircus2]

I only have a Nexus .nxp polar file now (working on translating it out to a more common format - if anyone has any tips that would be great!)

I believe these are the target speeds out of the polars:

Wind Speed	OptUW S	OptUw A	OptDwS	OptDwA
5.54	4.81	49	4.32	144
7.39	5.57	48	5.2	149
9.23	6.25	48	6.06	151
11.08	6.55	46	6.67	156
14.77	6.8	45	7.5	171
18.47	6.88	45	8.29	175
22.16	6.87	46	8.97	175

I think this shows that under 11 knots, we are sailing hot angles with pretty poor downwind VMG. Please correct me if I'm wrong!

The optima downwind angles seem off to me. 175 downwind in 20 kts is borderline suicidal.

I'd subtract 20 degrees from those optimal and see where it goes. On a 109, our optimal *apparent* wind angle at 6-10 true is between 100 and 110.