F147 - effects of shorter nose

[MennoB]

In the topic on F147 fins Sukhdev makes a remark on boom height on the F147, which is 6-7 cm lower than on the FV1.4 in the same conditions.

This remark got me thinking about the effects of the shorter nose on the F147.

After some thinking, I think I understand why the boom needs to be put lower, but wonder what are further consequences.

My reasoning goes like this.

General FW tuning:
-1-Higher boom = more power and lift (larger part of sail area under boom).
-2-Higher boom gets the nose of the board up.
-3-Too much lift = tailwalking. Counter that by putting mastfoot further forward.

Problem with lift is you have too little when winds are light, and too much (tailwalking) when you are really overpowered.
But you must get the planing angle right. Too flat is slow, because the board doesn't run free.

To get the nose up (planing angle) you need to lift the weight of the part of the board that is in front of the mastfoot.
The more weight, and more importantly, length ahead of the mastfoot, the more lift from your sail is needed to get the nose up.

I don't know whether there's less weight ahead of the mastfoot. But it's very clear there's less length ahead of the mastfoot.
 SO you need less lift to get the nose up to the right trim angle. This means lower boom.

Here's some expectations I have on the F147, compared to X186.
Wonder whether they match real-life experiences:
-Less nose slapping on downwind
-Less pearling on downwind
-More rider influence on trim angle

I wonder where you put your mastfoot on the F147, compared to X186?

[sukhdev]

Menno,

re your comment:
-Less nose slapping on downwind
-Less pearling on downwind
-More rider influence on trim angle

right on all counts, The gust which pulled me over completely (a long time since that happened) had no effect on the board trim, I kept pulling back against the rig till the point of no return but the board did not tail walk.

I agree with you on the short nose effect; in addition I think the lighter weight of the hull has something to do with it as well. So far its the best behaved board in high winds, though the FW1.4 comes close.

I'll measure the actual track distance I'm running, I tend to run the track very far forward.

[<Sven>]

Sukhdev,

While you are measuring the track distance maybe yoy would also measure the scoop rocker flat lenght? Every time I see the picture of the 147 you made from the side I'm puzzled about its banana shape. It looks as if it doesn't have a flat what so ever which will not be true. So what lenght does this flat area have. Would you do the same with the 1.4 pleas so these can be compared?

I'm also interested about the amount of the V the concavbes and so on and so fort but that would be a hell of a job. Thereby what would we learn more then data facts ? But the scoop rocker flat is still very much neede so if you please?

To Menno,

The AHD NT 98 also hasn't got much weight in front of the track although it is still around 260 long. The boom is sailed extremely high and the track is far forward. So it is not only the lenght but also the scoop rocker that play's it's role. The AHD is more stretched then most other boards which therby needs more height of the boom to get th board to run free. Just hope Sukdev will measure the scoop rocker flat in the fin area so we can see if that is also a different ball-game.

[sukhdev]

Sven, been meaning to really measure the rocker of several boards for some time, 147, fw1.4, 186x, ahd etc...its quite a task as you can guess. Would be kinda fun to compare all other parameters as well, volume flow, outline etc...

I'll run a measure on the flat section, I thought I'd already done it but its here somewhere..I'll post it when I find it.

[<marek>]

I notice that Starboard have shortened the mast track, taking a little from each end, tho' mostly from the rear (124.8cm-145.2cm from tail on the 147 compared to  121.0cm-146.8cm on the X186). I guess with everyone hanging on to big sails in high wind they didn't need the rear setting of the track . Mistral also fixed this on their Devil II which might have explained why the original had trouble with carrying 12.5s as the original had 138.8cm as their maximum forward position (now it is 152cm on the II).

Sukhdev, if you raise the boom on the 147 are you able to bring the mast foot back from the maximum forward setting?

[<ywy>]

Hi everyone,

Very interesting information...thank you for sharing the inside details.

On the other hand, do any of you can please help me with this one: a 12.5 is needed for a guy like me 165lb or 11.0 is just more then what I need... (ex: will be racing with F147).

thanks in advance...

[MennoB]

quote:Originally posted by <ywy>:
On the other hand, do any of you can please help me with this one: a 12.5 is needed for a guy like me 165lb or 11.0 is just more then what I need... (ex: will be racing with F147).

thanks in advance...

To answer your question, please indicate:
-What type of spot do you sail(most common windstrengths, flat or choppy)
-What board and sail is your largest now
-Is the fleet you're going to race in, also equipped with "big stuf"?

Advantage of 12.5 over 11.0:
-VMG downwind (average speed, and deeper angle)
-Angle upwind in sub-9-knots

[sukhdev]

Hi YWY,

at 165lbs (75kg) I would say stay with the 11. You can go larger but then your wind range with a 12 or 12.5 becomes very small. Bear in mind there is some development going on with the 11s due to the Youth Formula class limit; this might result in 11s which have a good range, though its early to tell yet.

If you are in Singapore a good quiver for you might be 11, 9.8, 8.3. If you can get a chance try a big rig out, one problem with going too big is pumping becomes a nightmare.

[<ywy>]

Thank you both for the input...

MennoB, you are right about the Advantage of 12.5 over 11.0:
-VMG downwind (average speed, and deeper angle)
-Angle upwind in sub-9-knots

I got smoked at last race because of this, the 12.5 turnned the corner and went down deep and he was gone...I was on a 11.0 couldn't match his angle downwind...

Sukhdev, you are also right about the new 11.0...

so now all come down to the board... F147 which will be the one that I will be racing this year... will F147 help me to get down faster and deeper to catch up the 12.5 guy with the 11.0?

this is a great forum ... thanks Sukhdev

[P.J.]

I send a post in Gastra :

Dear Phil
For a 70Kg sailors for light wind 5knots up. What do use suggest for the biggest sail. Is it 11.0,11.5 or 12m

GO TO THE 12M. IT'S A BEAUT. - Phil

But I need to convince myseld to do it. Every year I increase my sail size by 10% and feel could handle bigger. Will try to make a mistake once for going too big.

[sukhdev]

Hi YWY,

I had an interesting discussion with Robbie Radis during the AWT Kuantan about sail sizes. The biggest he had was 9.8, same for Kookiat. I had a 10.4 but never used it (unrigged it after 1st day). Ok it was windy but we sort of agreed on a couple of things..

- going bigger may not make you faster if you are light. You may end up having to overdownhaul in which case you are no longer optimal, the sail is creating drag after a certain point.

Robbie pointed out he noticed this most in Japan where 75kg sailors were trying to hang on to 11s in about 17 to 20 knots. In order to do so they had downhauled the sail till it looked like an elephants ear. He won the event on a 9.8, pointing out to the amateurs that they would have been faster on an optimal sail (Robbie is 80kg).

My own experience with 12.5NX2, 11Yes etc is that the larger I go the narrow the wind band I cover.

Bear in mind Meng (who is not small by Asian standards) did extremely well in very light wind in Singapore open with "only" a 10.5 NX2.

If the assumption is made that the sailor is super fit then yes, you can handle much larger sizes; but other than those who train full time hardly any amateurs approach this level of fitness.

If you really can't decide then just wait, I'll have a 12 and 10.4 for test; Meng will have an 11 so you can try the sails out.

Re downwind, Kookiat was doing extremely well with the 147, taking it at a crazy angle. I don't think the board will hold you back in any way.

Kuantan was reaching and downwind racing - this gave a huge reality test to being oversized. Given the strong and gusty winds, sail choice was critical, get it wrong and the sailors came back with cramped forearms looking like Popeye's arms..very painful.

PS - I raced on a GTX 2003 9.3 in Kuantan, very  happy with this "budget" sail. I broke my 490 so ended up having to use a 520 on the 9.3 and it worked very well..one lesson here that I'll try out is it might make sense to go smaller in sail size but use a stiffer mast..don't know yet..but will test the idea out for sure.

[<ywy>]

Thank you very much Sukhdev for sharing your experience with me and this great forum and your site.

You have been so detailed and patient sharing all the information about the races and equipments with us... you are A+... so far no one in this windsurfing world is spending the efforts and willingness like you to show us the pictures of the new boards (on top of all you always get them before the rest of the world)...

I really appreciate your time and whish you all the best with 2003...

I am from Canada and it is cold like hell right now, until April...hope one day I have a chance to visit you and your place...

I will stay with 11.0 and play with the fins..

Thank you

[sukhdev]

YWY, thanks for you nice words. Let us know how your experience goes, hope to see you in our warm waters one day (I don't even want to guess how cold it is in Canada right now).