Chris White Atlantic 47, MastFoil

Flaps

Pogo, you should find this discussion of flaps interesting:

http://www.boatdesign.net/forums/multihulls/offshore-foiling-revolution-gitana-53061-3.html#post739822

 

Are such flaps so efficient? They seem the same as the trim tabs seen on IOR yachts and Metre boats, and they dropped out of favour very quickly in IOR boats as soon as they were given a minor rating penalty. They were also used by one IRC maxi (with no penalty IIRC) but no one else has used them.

Much the same arguments apply to pivoting keels and gybing daggerboards, and practical experience seems to indicate that any benefits are very small.

 

Seems a sales pitch. A trim tab on a dagger would then send the performance edge back to the board. Not hard to do either as the Newick proa dagger rudder shows.

 

As I've said before, is it mother ocean that designs our vessels, or some rating rules

Innovation has gotten snuffed out before in our industry.

 

I just received that book, and I can not find any photo, nor dwg of that vessel you indicated would be in it.

Can you give me the particular page number?

When I look up the skippers name, Schrodt, I only get one page reference that his boat's name was Lilliam, but no other mention in the index??

 

It's normally common sense that designs our vessels via the rating rules. Fitting a trim tab means installing a shaft, pintles and gudgeons, fairing flaps and control mechanism leading all the way to the tiller or keel. They must have been extremely expensive for the very marginal performance boost.

Banning trim tabs and similar innovations was arguably an extremely smart move, unless the sport was to be priced out of existence. The benefit simply wasn't worth the cost.

Most of the guys involved in creating the rating rules are extremely well qualified and much more active in the relevant boats than their critics, while many of the critics are happy to sacrifice the truth so they can complain.

 

Good point - in fact I think the proa-style system would be a simpler, cheaper safer system (if I recall correctly) wouldn't it?

 

It sure would. You'd probably use a smaller flap than the proa version but the control shaft would go right through the board and up the trunk with no extra plumbing needed. A wind vane control could be used but it would be simple to have a hand adjustment system without complex parts or the watertight linkages a keel tab would need.

 

Rating Rules affecting Boat Design

Sorry to go off primary subject topic of this thread, but CT & I have had this running disagreement before, and I just ran across this posting by Mikko:....

 

Or putting it another way, fast efficient hulls and sailplans are not necesarily that comfortable offshore.

Very little to do with the rule stuffing up boat design.

Do you want to go fast 99% of the time or drag that hull flare, short waterline, v'd forefoot etc
around with you for that 1%.

If it wasn't for development/ racing around these rules we wouldn't know what was fast.
We would all be sailing un stayed junk rigged a-frame aftmast catamarans.

 

MastFoil
it's a V- flap, visible in Video 40 at -0.8
https://chriswhitedesigns.smugmug.com/ATLANTIC-CATAMARANS/Atlantic-47/Atlantic-47/i-V3CHvnK

Backside of rotated foil , V-flap Control
https://chriswhitedesigns.smugmug.com/ATLANTIC-CATAMARANS/Atlantic-47/Atlantic-47/i-T9hbGr2

Whole MastFoil has to be positioned after AWA , flap has One Position only ( attaching leeward Flow)
Trailing Edge of flap Radically Cut off.
very clever !!

pogo

 

There is some interesting MastFoil discussions occurring over on this page of this other subject tread.
http://www.boatdesign.net/forums/multihulls/frame-masts-54941-5.html#post765597

Pogo, please help explain this question I have. It appears to me from your posting quoted here that there is a conflict in explanations:
V-flap control, verses flap has one position?

Is the angle of the v-flap controllable, or does it flap from one side to the other?

Any idea of how this flap is attached to the aft edge of the aerofoil sleeve?

 

i have some facts , answers and some speculations, but actually no Time.
i gonna answer this evening, this Night----in a Few hours.

pogo

 

Looks like a larger flap size was utilized in the prototype cat as well
https://chriswhitedesigns.smugmug.com/Other/Prototype/i-spKxqLj

 

BTW, I ordered that book and found no such photo.
Would you please find hat photo and have it scanned by a friend or a shop? I would really like to see it.