Wave-Piercing, Pitching damping or marketing?

34 Kg ?

I guess that 34 kg is for the whole platform. As you are in NZ, you probably know Murray Philpot (not sure for the spelling), 15 years ago he came to the A-Cat world with his own design and building method, light &fast.
Did you made a master shape and a mould for your hulls?
Your hull section seems thinner than current design like Flyer, is it correct ?
Did you make the design yourself, which kind of software did you used ?

I stop there, I don't want to harass you with too much question, and probably your time can be used for another purpose.

On my side I work on a morphing wing section for A-Cat, it is not easy especially with transportation issues to be addressed.

Good luck for the last steps before sailing.

Best regards

EK

 

Harassing

Hello Erwan,

I have read some of your earlier posts and would like to know absolutely as muych as possible from what you are understanding, what are your assumptions when designing the morphing wing, what are your expected benefits etc etc. All that you can possibly muster.

I do believe that when asking this I am doing so on behalf of quite many A-cat sailors.

Looking forward to reading about your project.

Best regards

Patrik

 

Hi Patrick

Thank you four your interest in my project. I focuse on a A-Cat wing primarily because I have just enough space to make the top part of the rig (above the hound: 3.50 m).
The lower part will be a copycat of the upper part but much more simple.
My assumptions are a map of reynolds numbers according to APPARENT WIND in different conditions: winward, downwind ...and with different true wind speeds.
The twist control will be similar to the Cogito system.
A control line will limit the camber, to tack will be the same than for C cat with a hinge effect in order than the wing section reverse.
I guess I will gain in maximum lift at low reynolds numbers and will have far lower drag windward at high reynolds numbers.
My main issue is to meet the measurement rules and therefore the double trailing edge must be fixed at the same point without any possibility to drift and increase sailing area at for high camber section.
As a result the problem is to allow the sail cloth to move around the leading edge fromone side to another, I dont think it is actually possible.
Also another problem is to avoid wrinkles on the sailing cloth with the twist of the underlying structure.
The wing will be a simple one, without flap.
Probably we are not at the right place for this topic, we are in the wave-piercing topic ? I am not so familiar with forum.
Regards Erwan

 

re:34kg

The 34 kg is just for the hulls and beams, the minimum weight for an A-Class is 75 kg, so once its finished we will be adding corrector weights.
Don't know many A-Class guys here, the boat was built in the USA using female frames on a jig, then strip planked with foam, then glassed internally, hull halves are then joined and the outer shape is faired using templates then glassed. The hulls are about 12% narrower than a Flyer and the LCB is more than 200mm further forward.

 

Boat looks great-one problem

You might get stopped by Homeland Security.... It looks like a couple of 2000lbs bombs strap together... Very Aerodynamic

 

That must be John out there. I was going to add to this thread that out of all of the A-Class designs that I have seen recently, the LR2 that you and Ian are building is the closest to what a wave-piercing design should be. I cannot wait to hear how the trials on the water go with Ian and Fred. Good luck and the workmanship looks great.

Tom

 

Retired Geek,

Just caught up with the rest of the thread. Realized you are not John and are not here in the US. Sorry for my presumption. If you are interested in A's there is a lot coming down the line right now. Ben hall also evidently has a new designed boat going in the water in the next couple of weeks. Also have you checked out the NZ A-class site http://a-class.org.nz/ ?

 

Hi Tom,
Im just the designer.
John says its the best A-Class he's ever sailed, Ian's not quite as sure as the helm loads up a bit in the stronger air to weather, but it appears to go fast downwind, and probably uphill as well, but they have yet to sail it against other A's to be sure. That test will come this coming weekend. The pitch damping we designed into it appears to work extra well, with no vetical motion at the bow in any chop sailed in so far (prolly 12 knots max) and no pitching with gusts up to the same....you'll have to wait and see what happens in harsher conditions.
Enjoy the attached pics
Retired Geek

 

Retired Geek,

Nice shots of the boat. Will fred's be in the water this week as well? Looking at the design, my thoughts were that the most difficult part of the boat to get comfortable with will be just how weight sensitive it will be. That is just my thought in looking at the design. Understanding just where and when to move your weight as well as how much difference even a few inches will make in the way the boat handles as well as its speed. Good luck with the project.

Tom

 

Also, maybe just change the mast rake an inch or two forward might take some of the load off.

 

Tom,
the boat shouldn't be weight sensitive at all....and at least with the range of weights that have sailed it so far that appears to be true, the same goes for where you are on the boat, other than moving too far aft...in fact both John and Ian have commented on how difficult it is to get the bow down...such a nice problem to have
As for mast rake, we want it further aft, not fwd for reasons that have nothing to do with helm load, but we think we have a solution for that now also. Like I said before....real performance is yet to be proven, but this coming weekend should give us a better idea of how well or badly we have done.
RG

 

Tom
just a few pics to show the difference between Ian's boat (red) and a Flyer (green)...pic's are a comparison at full load (i.e sailing on one hull)
RG

 

RG

Well, good luck this weekend. Where is Ian sailing it this weekend? Had they wanted another test platform, I would have let Fred keep his Boyer for another couple of weeks. I can see the loads that you are reffering to, what program is it that you are using to track, quantify and pinpoint the loads so accurately?

Tom

 

Nice boat, I like it when people go out on a limb and try something different.

I posted a link to this thread over at catsailor.com and a few people said the hull shape reminded them of a "sizzler" an aluminium catamaran from the 70's.

go to this page for a picture
http://www.thebeachcats.com/index.php?module=pictures&g2_itemId=3391&g2_imageViewsIndex=1


Hope it all goes well this weekend.

Gareth

 

grob,

I actually said the same thing to Fred Smith who is the owner of the second LR2 to hit the water.

Tom