Hi Rob,
I don’t think of it as a trailer sailer, more of a fast voyager, that when I am home based I can park it , I won’t be towing it to the Whitsundays for instance, rather sail it up stay for 3 mths then come home and park it till the next trip. About 30k’s will be the furthest it goes by road, you are right it would be a hassle to tow it around in general.

When you say 2 hatchways do you mean drop in type from above? I will keep thinking about the options there and the length, thanks.

Jo

Jo - 20 February 2014 09:15 PM

Hi Rob,

When you say 2 hatchways do you mean drop in type from above?

Half and half.

PM me.

Rob

Jo - 20 February 2014 03:50 AM

It appears that there is a good case for having the mast further to windward regarding minimising rudder load ...

I want to get the balance right, an unbalanced helm destroys any sailing craft, have been there and not keen to go back!

Perhaps the second of the rigs I suggested in another thread might appeal to you: http://proafile.com/forums/viewthread/94/.  Or set up the rig like Fritz Roth, who uses a jib both at the bow and on the windward shroud.  You can see that at http://www.proadesign.com/ if you scroll a little less than halfway down.  Roth’s rig is what gave me the idea for the biplane sloop, by simplifying his rig.  But if you want something more like the Russel Brown rig, you could do it like Roth and add just a small boomed jib to windward to get the centre of effort to where you want it laterally.

Regards

Robert Biegler

Robert
thanks for the links, I feel like I am possibly getting too deep into it,

Does anyone think that the Jester class will have a helm imbalance due to that mast position?

I appreciate the points re staying base and close coupling as it is a racer. I have re read through the posts and can’t see anyone has explained why they are able to move the mast position that much in comparison to Jzerro, (maybe I missed it)

Or maybe it is the case that if Jzerro’s mast was shifted to a similar spot it wouldn’t affect the helm much either.

I don’t want to have to add an extra sail for balance, nor do I want to try and be a pioneer myself, I am happy to follow in the footsteps of those with proven designs, adding my own touch here and there. I need to nut this point out before my design moves on.

Does anyone have real life contact with Russel to ask him? re mast position and rudder balance of the 2 designs.

Thanks
Jo

Jo - 21 February 2014 09:07 PM

I have re read through the posts and can’t see anyone has explained why they are able to move the mast position that much in comparison to Jzerro

Perhaps the ama is expected to be less lightly loaded.  If it is mostly just skimming along, total drag moves leewards.  For cruising, you’d want more reserve stability than for racing.

Regards

Robert Biegler

Thanks for that Robert,
That is what I was thinking and had inferred in an earlier post, glad to have some consensus, I think I can move on from that aspect now, but the type of sail plan is another matter now that my eyes have been opened to other possibilities by you and the other Proa boffins.

And thanks to Mal, Rob, Bill and anyone I have forgotten.

Regards

Jo R.

I’m sorry I haven’t been involved in this discussion. I missed it and have also been traveling for a few weeks. As I see it, there are no right answers to any of these questions though, except that the helm is not going to be affected much by moving the rig to leeward a bit. My boats have always had a touch of lee helm when going to windward which is always balanced out by dropping the forward rudder a bit. Moving the rig to leeward will help a bit to eliminate the lee helm, but dropping the forward rudder a bit is not a bad thing. Dropping it enough to create weather helm really helps the boat point.
As far as me knowing the best approach, I really don’t. I follow my hunches, but they don’t always work out and I have spent a lot of time modifying things.
Proa’s have a very long list of compromises and no one knows all the answers. I’m sure that’s why they are so interesting, but at this point the only way to learn about them is to build them and sail them and share the experience.
Hopefully better typers than I will learn a lot and share their experiences.
Russell

Thanks for chiming in, Russell.  Its always great to hear from you on this forum.

I have a quick question.  How do you know if the lee helm you’re experiencing is because of the position of the rig windward vs. leeward, or the position or the center of effort fore vs. aft? 

Thanks!
Chris

Hi Russel,

glad to hear from you, nothing like the knowledge of someone who is actually doing it. You have answered any remaining questions I had and I can now happily detail the hull to suit.  Cheers.

Chris, if Russel doesn’t get back here again, I think that the majority of Lee helm will be due to the lack of underwater appendages fwd of CE.  As Russel said “the helm is not going to be affected much by moving the rig to leeward a bit”
That is why helm balance is achieved by dropping the front board a bit. All of this is most relevant to the Bermudan rig, Any proa design with similar proportions to Jzerro or Jester I think we can safely say will carry a little lee helm to windward.

Jo

Thanks, Jo.  But that was not quite my question.

I was asking if there was a way to discern the effect of ww/lw placement from fore/aft placement of the rig.  Both are remedied by the same method; moving the CLR of the hull (in this case forward by lowering the front rudder).

Make sense?  Thanks.
Chris

Luomanen - 08 March 2014 09:18 AM

I was asking if there was a way to discern the effect of ww/lw placement from fore/aft placement of the rig.  Both are remedied by the same method; moving the CLR of the hull (in this case forward by lowering the front rudder).

Chris,

Fiddly and very guestimated but it might help:  Use a deck plan and plot the vertical/plan positions of centres of effort of all the sails, approximate thrust / lift direction and the vertical/plan CLR position (which will be the nett of the lee side of the hull(s), rudder(s) and the centreboard / foil, wherever they are located). Then take moment arms of each sail CE’s around the CLR, multiplied by each sail area. you will end up with a nett turning moment, similar to righting moment.

You can then work out how much and where you have to shift CLR or CE to get the balance you are aiming for by recalculating with different moment arms..

As a general rule, for the same rig (whatever it may be) and CLR the further out you move the rig to windward, the more lee helm / less weather helm it will have due to the forward component of sail thrust. / lift. Biplane rigs canting rigs and windward staysails can be very interesting…...

Rob