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teknologika

Member Since 23 May 2007
Offline Last Active Yesterday, 08:50 PM
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Posts I've Made

In Topic: Team NZ

12 January 2017 - 03:14 AM

 

We are talking VMG during a foiling tack versus a non foiling tack.

There id no doubt fouling is faster between tacks.

If you watch a foiling tack from above you will see the helmsman drive the boat quite deep to get the speed to maintain foiling thru the tack. Also the speed in an out of the tack is not that much better for the extra distance, time, and angle, away from th top mark, they sail.

It could be a close thing.


I don't agrree. the main reason is that if you don't foil tack you have to lose a huge amount of vmg to get up on foils after the tack,especially in light airs; or at least this is what really makes the difference in moths;it's not the speed difference during the manouvre, but he vmg loss to get back up on foil if u crash down.

 

 

 

So I once worked out based on GPS traces a couple of years ago that I was loosing 70-100M per tack (land, turn then get flying again) to our pace setter who sailed the whole race "dry". That translated to ~1/4 - 1/3 of a windward leg each lap. You then change your tactical thinking that it is better to minimise the loss and say, sail on a knock and loose 30 instead if tacking and loosing 80.

 

In the moth fleet, (outside the top 20%) your tacking ability is the main factor in your finishing position in most races. We are only doing 15-18 knots upwind, the AC boats last time out in low mode were doing 24s so the gain will be much bigger for them.

 

When you compare a "touch and go" tack to a fully flying one, the difference is much smaller, but still very obvious.


In Topic: Moth rig evolution & conclusions?

10 January 2017 - 11:27 PM

There have already been smaller super high modulus smaller masts (I have 35mm diameter one). To go smaller the wall thickness has to go up, and stiffness becomes a trade off. 40mm seems to be the weight / stiffness / cost / diameter sweet spot. I have gone back up to a stiffer 40mm mast and gone faster.

In Topic: Moth rig evolution & conclusions?

07 January 2017 - 08:23 PM

It is more about mast sail combination than diameter. There are many many different mast types and each has different bend characteristics. These are then matched to the sails desired fullness, luff round and skipper weight.

For example, the Lennon A3M is designed to be used with a CST Elite 22, or 23 depending on skipper weight and how hard you are prepared to pull on the vang and cunningham.

Any 50mm moth mast will be at least 5 years old, probably more and won't work with much beyond a MSL 12 (the bladerider X8 sail )

In Topic: Interesting moth design

21 December 2016 - 10:22 PM

Everything has been so refined aerodynamically, why can't we get rid of the spreaders already? I know it has been tried many times. What seems to be the biggest issue?


Everything is a cost vs weight vs drag issue. Remove the spreaders, you need to increase the weight and/or size of the mast. At this stage, at least based on the experiments that I know of it is a net loss not a gain to do it.

In Topic: F101

12 December 2016 - 09:11 PM

Thanks-so would that result in different flight altitudes on each tack?


Not if you know what you are doing. There are some wand geometry tricks to sort out that problem.