NP are big into promoting their boom cut out concept and many other brands have adopted it. Is it a gimmick or benefit????.
I use Pryde sails and the set up seems to work well but it's hard to quantify the level of benefit from this feature alone.

I had a 9m NP RS1 sitting in the garage because I couldn't justify the cost of buying a big carbon boom for it's occasional use. So I went to a sail maker and had the boom cut out, in by 15cm, like my newer Pryde sails.

Did it make a difference?? Well my existing carbon boom now fits nicely.
I used the sail the other day and it felt very different (could be partly my imagination as I have only used the sail twice before on a new board).

The sail felt a little gutless (its probably lost 0.1m under the boom) and I couldn't drive the board upwind. After a bit of fiddling with boom height and mast track I found a setting that worked quite well. However I felt that the sail still didn't seem to be as powerful as before the mod, but I probably need to find the new correct outhaul setting. Overall I was surprised that I needed significant re tuning of the set up.

So what do the experts think about boom cutouts and it's effect on sail performance.

The new Evo11 Race sails look like the clew is cut in at least 30cm.

It would good if you could post a few pics, rigged of course... From the head and foot to highlight the twist and across the leading edge to see the depth vs height profile.

I've used Aerotech VMG's & Naish stealths with the cutouts- I'm now back on longer boomed slalom sails. I do like the handling the shorter boom gives however i've found its easier to oversheet and yes it is very easy to kill the power... with the adjustable outhaul it requires about half as much tension to have the same effect as with a longer boomed sail.

How much your sailmaker charge for doing the cutout btw?

That's not a clew cutout...





THAT'S A CLEW CUTOUT

Some pics of my modified sail. I think the RS1 was designed as a high wind formula sail and it's certainly got some range. I sailed it all afternoon in a solid 20 knots gusting to 25 and it was very well behaved. Maybe the cut out helped.

The did a nice job !!!!
Try setting it in the top ferrule.

Regards Martin

Your boom is still pretty maxed out...

Adriatic Blu said...

Hey guys,

Well, it would interesting to know why the cut out.

Sails with cut out are,
Ka
Gaastra
Neil Pryde
North to name a few

Sail without are
Ezzy
Maui
Goya
Loft

I guess there is a mixed bag out there which might indicated that it could be only a concept rather them real benefit.

Regards
Adriatic Blu

Loft do have a small cut out, I was playing with a Loft Blade today. Some of the others you mention are more into wave & freeride sails, I think, which don't use cut outs. Maui Sails still don't, but I think Barry Spanier who used to work for N Pryde, doesn't want to be seen as following Pryde.

Personally I think the cut out works, apart from better twist and shorter boom / swing weight, using my boom on a smaller setting (15cm less) also reduces boom flex.

I'll be keen to try out the new Pryde RS sails in January, they've increased the size of the cutout.

I was reading this thread only because I was filling in time @ work then something grabbed my attention! Waiting4wind, would it be possible to see more photos of the lady holding the rig? I would contribute something more constructive but I don't have a clew!

Having had a bit more time on my modified sail I thought I'd give you an update. Had a light wind session yesterday and discovered a huge bottom end after a bit of time spent tuning.

I mentioned in my earlier post that the sail felt a little gutless and I thought that this may have been as a result of the boom cut out. Using just a little less downhaul made a big difference and also made the sail a lot more tunable on the water with an adjustable outhaul. This sail was designed around a really stiff mast (NP CK100), but the X6 I'm using is considerably softer, so I suspect its easy to kill the power with too much DH.

Overall I'm now quite impressed with the modified sail and I would recommend the upgrade. Having used it in 20 knots and still manageable and yesterday planing comfortably in 10 knots (Isonic 111) I can't complain about the range.

I put the question re boom cut outs recently to Barry Spanier on the Mauisails forum here: http://www.mauisails.com/forum/viewtopic.php?pid=11355#p11355 (post #4); Barry's response is in post #5.

chris

mathew said...

A cutout might be a good/useful idea, but the Neil Pryde description appears to be just marketing:

http://www.neilpryde.com/sails-2009/sail-technology/dynamic-compact-clew.html

The example shows the clew/leech section twisting off by an amount approaching the radius of the deepest part of the foil.... how? Specifically, there is far more skin tension in the first 30% of sail (including lots of extra cloth to fill that curve), than with the trailing edge - how can the back end of a rod-batten twist by that much?

I should be able to let you know how well it works soon, I plan to replace my 7.8m Mk11 with the new (bigger cut out) Mk111.

"Dynamic compact clew" - gotta love the buzzwords