I'm curious. How significant is the aerodynamic drag(and possibly hydrodynamic drag in chop) from the mid-pole snuffer when an F16 is going upwind? It seems that racing this boat in light air solo against sloop rigged non-spin boats might be a disadvantage.

There is some drag there, no doubt, but what would you do instead, launch the spin off the tramp like in the dark ages? That would be a tuff snuff if you were racing solo!

There are a few thoughts to this:

Testing the TAIPAN 4.9 with and without the spinnaker (snuffer) it has been noticed to be slower up wind with a snuffer. However this was at the upper end of the wind range, and the testing had it's limitations.

A much more accurate test was done in the US on the Tornado's. Back when they where testing to figure out the best position to place the snuffer, there was extensive testing done to see whether the drag on the snuffer was a major disadvantage. The result was there was drag but it was so minimal they would be better focusing on other improvements.

Those "case studies'" aside the physical of the problem is:

The drag force is much higher at higher wind speeds. For the mathematically minded - the drag raises to the square power relative to wind velocity. This means that there is more drag in higher wind ranges, but then you have more power to over come this.

I would be very surprised if you're losses up wind where more than your gains down wind. If you are loosing out around the course, I would say it it something else apart from the snuffer.

I have been told that an open mouthed snuffer (The opening facing more toward the tack than the head)compared to a closed mouth snuffer (opening pointing towards the head of the kite when set) is equivalent to carrying an extra 3kgs or 6.6lbs due to the additional drag.

That would depend on the windspeed of course. Would be very interesting to know how somebody calculated that, even if outside the topic.

Hi Rolf
I used the term "drag" in the post above and this probably isn't strictly correct. Wind resistance could have been more accurate. How this ex World Champ, Engineer and Foil manufacturer amongst other things came up with 3kgs is beyond my comprehension but I still have no reason to doubt him. However, I have yet to amend the angle of my snuffer mouth to reduce wind resistance but that doesn't mean to say it wont stay on my 'to do list'.
Every time I look at my avatar photo it reminds me

Hakan did some work in this; I think he said he wored out he lost about 2.5% going upwidn with his snail-house for thre Spi.

But you gain so much more down wind :-)

It has been suggested to me that the weight of the spinnaker, snuffer and pole when wet has an affect on the boat pitching more when sailing upwind in a chop. the pitching slows the boat down.. but how would you measure that???

Increased windage is a factor, all testing and calculations indicates so. In the beginning (2001) the classic Tornado was still faster than the new rig Tornado upwind with the top Tornado teams sailing both boats. This was at the multihull evaluation event arranged by ISAF at the time and removed sailor skill quite well from the equation.

I just stalled a bit on the 3kg number as there must be a lot of intermittent steps between increased windage and calculated weight on the boat. That was all that was behind my question and it was not intended as a loaded question.

Dazz, only way I can see to do that would be two boat testing or some creative numbers games and a calculator. I guess it is more a question of feel and we certainly agreed when we switched from the classic to the modern Tornado. Going out on double trapeeze and trapeezing downwind more than made up for it in sailing pleasure we thought.


Greg, you are sailing under a yardstick system I guess. To stop people from removing their spi gear the day of the regatta everybody here have to declare at the time of signing up for the event wether they will sail with or without spi. If they dont say anything, it is assumed that they will sail with their boat set up like it is for the boats measurement certificate. This is enforced and if you race without spi, you are still scored as if you used the spi. I think that is a good system.
Even in light winds I much prefer sailing downwind with a spi compared to without

C'mon guys - 6lbs of additional weight?
Not that I am disagreeing about there being some VERY minor efect from windage, but most of it has to come from your head if is is noticable.

The hoop and sock on these boats is in line with the water and moved down to be close in plane with the tramp and beams. Those would be hard to remove from a boat and provide aerodynamic drag anyway. Most drag effects, like this do not become mathmaticaly significant untill the wind is high. And the advantages of the spin off the wind are undeniably significant.

The general concensus seems to be that additional volume and freeboard are good things, but both of these have a pretty significant negative effect on the windage drag also. In a solo application with light air and flat water, the current F16 designs are far from being optimal, as they have to be able to do 2-up and rough conditions equally.

I've lost twice that and it doesn't seem to matter!

As a heads up, this issue is not covered by the F16 class rules and therefore must be in the NOR or SI's to be binding. Gentlemen's agreements are well and good but we all know people are people and regardless of an agreement reached on the beach if a rule hasn't been broken a gentlemens agreement really doesn't mean much for some people. Besides, if it's formalized you don't run the risk of souring an otherwise very pleasant weekend.

Just my 2 cents, I'm leaving now.

David,

this is just how things are done under the national handicapping system, it have no reference to the F16 class or any other classes. But those racing under the system know that these are the rules, and it is specified in the NOR for larger events. For the wednesday night races, it is usually not specified but people are so used to it that nobody ever complain about it.

F16 clas rules state what an F16 is.

AS long as the boat conforms tio the class rules, it's an F16. Exactly the same is true of an F18 i'd expect, unless your class rules are different from the norm.

If this is NOT the case then the boat is not an F16.

No issues with class rules within the F16's.

Okay before this goes off on a tanget that was not intended, my response to Rolf was created with the assumption that teams would be pulling off their spin kit during the regatta which was CLEARLY NOT what he was saying (my bad).

The events where this could be an issue it is handled by the NOR and SI's. It's all good.

Crap! I just made a big bag of popcorn.

If you enter an event as an "F16" or "F18" or "Tornado" or Hobie 16, if your boat starts the regatta conforming to the class rules under which you entered and then mid regatta you change something that takes the boat out-of-class, you should get protested and DSQ.

Class rules simply define what boats of common name "look" like.

This is more like it. I didn't know you guys ate popcorn.

IMHO Tikipete was responsible for a lot of the windage around here. :-p

I have this theory that windage is more important than what we think as the speeds of the F16's and others such as the F18's are becoming nearer the 20knot mark than the 10 knot mark. The higher the speed the greater the effect becomes, the faster we go in the boat the faster the apparant wind.

Certainly in other sports such as gliding, wire struts and anything superficially that sticks out has long been done away with, certainly as speeds have risen.

Yes we do need to consider windage, not only the F16's but all boats with snuffers. I think Swell Catamarans have spent many an hour thinking about this and looking at their boats they are always very clean and aerodynamic compared to other manufacturers. The Shadow a prime example and part of why it does so well on handicap.