CONTENTS                                                                                edited; 19th May 14
Post #  00. SHUNTING and ROLLER FURLERS                    
Post #  04.  RUDDERS
Post #  08.  about; If caught aback   &  The unlikely Accidental Jibe.
Post #  11.  RUDDER PLACEMENT
Post #  13.  SOME MODELTEST RATIO’S
Post #  28.  AMA FOIL PLACEMENT
Post #  29.  RUDDER SYSTEM DEVELOPMENT
http://proafile.com/forums/viewthread/275/ post #7 & #8 OFFSHORE in ROUGH CONDITION
Post #  35.  SAILPLAN 53ft UNAMA

Disclaimer;
It is not my intention to claim this specific setup to be the best, or the only possible solution,  but the Russell Brown designs are well proven Blue Water Pacific Proa’s and so a very solid base , to develop the Pacific Proa into a even better performing craft.
_________________________________________________________________________________________
Post #  00 Shunting and Roller Furlers

Aloha Proafans,

Coming into the shunt needs some mental preparation, this has become more and more natural the longer we sail Pacific Bee, it now a well-oiled maneuver in our family.  (If it fails the helmsman is most times to blame for sloppy steering ha,ha.)

1. See to it that you always have enough room to leeward to perform the shunt. In close quarters with a lot of other yachts around, do not expect them, to understand the “trick” you’re about to unfold, i.e. keep the initiative, and give them a wide berth,  you will have a way out though, it’s the “Panic Button”, which is dropping the sheets, so,  stopping dead in the water, till you have created enough room to leeward.

2. Douse The “Old Jib”.
Before steering into a half wind course, you douse the “old jib” .  Simply payout some Jib sheet, not all , because the clew will be in the water. Release the old jib halyard.  , down it comes , a 4mm Jib head retriever line is pulled tight to bring the jibhead to the deck.  (jibhead retriever line is a reversed 1:3 purchase , so I end up with only 1/3 of the lufflength of 4mm retriever line in the cockpit) I tried 1:4 but that’s too heavy to pull.  (the jib wants to stay down anyway, because the backstay is pointing “upwind”)

3. Dump the 1:1 mainsheet , simultaneously pulling the new mainsheet in, on the 44 Lewmar ASTL [aluminum self-tailing] [I like the self-tailing part of the winch , but when fully pulled in I have only 2 to max. 3 turns on the drum, and cleat in a vertical positioned Harken cleat, for quick release.]

4. As soon as the speed is about 0 the new rudder retriever line is released, the rudder finds its own way down.

5. Mainsheet pulled in , and picking up some speed, the “old rudder” is pulled up.

6. Dump Jib retriever line , pull up the jib, wind in both sheets , and , off he shoots.!!

Jib wells,  if you have old jibs , you could push them in there, but having a brand new set of laminate North sails, you will think twice before jumping on them. As you might have noticed Jzerro don’t have those wells, instead there are sail lockers in the bows. In a future design, I would do away with the wells. Handy barbeque stowage place though !

Sail Wardrope ; 1 mainsail w/3reefs ,  2 working jibs on SS hanks, 1 big Code-0 on a roller, 1 stormjib
Roller furlers ; I use Bartels Gmbh full SS high quality, they are virtually indestructible, and cheapest you can find.

The use of Roller Furlers on Blue Water cruisers.

-  I don’t like fixed roller furlers for working jibs because ;
A. they are in the direct vicinity of the windward trailing edge of the mainsail airflow, as such unacceptably distorting that flow .
B. they cannot easily and quickly removed offshore in a big blow, I like to keep the footprint of the total rig as small as possible, therefore I don’t like big bulky Wingmasts & Aerorigs. One day that high windage will seriously “bite” you in an offshore storm. 
C. Name of my game is , very low windage.

- I do like furlers for all free flying sails, they are great !! , those Bartels furlers have a continuous line to enable rolling, I run the furler line to the cockpit , the big code-0 is rolled away in a blink of the eye.
The Code-0 is set with a snapshackle on the very bow eye, in front of the headstay.

I might have missed a few point , so please don’t hesitate to ask, I will “add on” this article
Cheers Sven.

Aloha Sven!

Thanks so much for the detailed report.  Brilliant!

A couple of follow up questions.

Does the retriever line run inside the jib hanks or outside them? 

Do you have to go forward and bungee down the jib?  It seems like even if the luff were compressed with the retriever line, and the foot had some tension with the sheet, the rest of the sail would still be trying to go overboard—or at least flapping around.

I love the reverse advantage on the retriever line, smart!  Have you ever thought about using a retriever line that gathers up the leech as well?

With regard to the rudders; are you saying that you have an uphaul but they just fall down when that is eased?  Or is there a downhaul too?

Again, great explanations!

Thanks,
Chris

Hi Chris,

Luomanen - 06 November 2011 01:08 PM

Aloha Sven!

Thanks so much for the detailed report.  Brilliant!

A couple of follow up questions.

Does the retriever line run inside the jib hanks or outside them? 

Outside the hanks, attached to the 3th hank from the top.

Do you have to go forward and bungee down the jib? 
No, never , unless it starts to really blow,  but then I Park the proa, and walk up to tie it down., most likely I have to reef anyway by than.
It seems like even if the luff were compressed with the retriever line, and the foot had some tension with the sheet, the rest of the sail would still be trying to go overboard—or at least flapping around.
To leeward is a net -outward and up a bit , so nothing goes over the side, it blows tight into the net.

I love the reverse advantage on the retriever line, smart!  Have you ever thought about using a retriever line that gathers up the leech as well?

No , as for now this system is working OK.  [because of the net ] But for some proas without a net that would be a good idear.

With regard to the rudders; are you saying that you have an uphaul but they just fall down when that is eased?  Or is there a downhaul too?

yip, thats that green line in the picture, 9 out of 10 times the rudder sets without having to pull the downhaul,
Cheers Sven

Again, great explanations!

Thanks,
Chris

Aloha Sven,

This is all super helpful.  I have another question about rudders.

It looks like all of the Russ Brown proas have rudders that are more or less rectangular in cross section where they come up through the deck.  Is the opening in the bottom of the boat, and the foil that protrudes below it foil shaped in cross section, while the majority of the rudder that’s in the daggerboard case is rectangular in cross section?  Are there any softish bearing surfaces (plastic?), or is the contact fiberglassed wood against fiberglassed wood?  Also, about how much clearance is there around the boards inside the cases?

Thanks again,
Chris

Post #  04 RUDDERS

Hi Chris here self explaining pics ,

The case is rectangular , the through hull shape , is according to the blade shape.

Foam crush block, during its 25 years of sailing ,  only one, was ever crushed , when hitting a shallow on the Great Bahama Bank at considerable speed.  The rudder was pulled and the foamblock replaced by a spare , with only modest tools.

Proving that this is a trustworthy system,  capable of withstanding big blows without structural damage.

Cheers Sven

Thanks for the detail on the rudder construction Sven.  that’s probably the single most difficult thing to come up with for a proa design.

Tom

WOW!  That’s a nice piece of engineering!  I’ve seen crush blocks in dagger board cases, but not the boards themselves!  Brilliant.  And that’s why the cases are rectangular.  Makes perfect sense.

Thanks for that, Sven,
Chris

yes, I’m impressed with the thinking with the crush block too. Very very neat!

Post #  08.  about; If caught aback   &  The unlikely Accidental Jibe.

Aloha Proafans,

There seems to be a lot of gossip going around this “getting caught aback” on Russell’s proa’s, let me address that for a couple of minutes to put it back in its right perspective.

During the time I spend sailing around, it NEVER happened to Pacific BEE by accident yet, and a lot of people with very average sailing qualifications have helmed that pacific proa.
The thing is that before I go out , I tend to explain proa newbie’s what would be the situation if caught aback, and what we would have to do next. It’s not difficult, and neither would the mast fall over the side.

Sequence is;
-Release the jib halyard , leave the jib as is.
-Release the big Spinlock main halyard stopper on the mast.
-Let the main down.
-The proa will now turn ama to the wind naturally, by way of design concept.
-Hoist the main and jib , continue sailing.

Note; I designed the new mainsail details in such way, that, the batten pockets at the leech are completely smooth, the battens pockets are open at the front , to fit and mechanically tension them.

This enables the mainsail to glide easily , furthermore I fitted Harken sliders [no balls] and track, the system is so smooth now that it really “falls” down , so you have to slip it down on the winch.

However, as theory without practice is a bad mix, I deliberately steered Pacific Bee through the wind, and did the above sequence.
The one thing you don’t want is the battens get stuck above and against the backstay, I found the mainsail to
come down easily , and with a bit of pulling helped the big lower battens along the backstay. Not a big deal.

Typically, when does a caught aback occur? That’s when you are falling asleep because there isn’t much wind anyway. [ beter let the autopilot do that kind of steering, and enjoy your coffee and the famous French butter cake.]

If its blowing you are likely reefed 1 or 2 times. , if you make a unluckily mistake now, you wouldn’t have a problem either, because the mainsail is below the hounds, and as such can hardly tough the backstay.
Again release of the main halyard gets the main to the deck in seconds.
So for the very odd one out, you have to have your game plan set.

Losing the mast .
Technically it is not even possible to lose your mast that way, because the way its set up.
The mast is stayed way to leeward with the forestays, and to the ama well to windward.
Due to the flat shroud angles the mast compression load is very low, hence the mast can be a very thin section.

The forestays are 6mm 1 X 19 SS DYFORM rigging, they will stretch way less than conventional wire , they are of predetermined length, you CANNOT change their length, no turnbuckles here , just pin to pin fixed length.

As such they are too short , and you will not be able to pull the mast to windward against the forestays, neither will the proa structure “bend”  to allow this.

Tensioning of the rig , to do away with headsail sag, will be done by way of pulling the purchase of the windward stay. Sometimes I play a bit with this tension , but generally is very taut.  To get a fuller headsail I release the halyard a bit to get the max draft a bit aft.
Furthermore I carry intermediate Vectran stays to control the prebend of the mast.

Breaking your beams
The beams are designed to take the full load of the vaka into the air. That situation will not occur, ever, because there is barely any sail pressure in such a situation.

Sinking the ama
The old ama has about some 60% of reserve flotation , plenty to counteract that little bit of sail pressure [see above]. The new ama has even 100% , this to take the higher waterballast load into account.

Mast Lean
I have the proa setup at about 2.5 degrees of windward mastlean, so the rig is about upright at best skimming angle, while the foresails are designed for 7 degrees of windward lean. this gave the best speed upwind, [ but we need more real life data to make this into a final “confirmative”]
in the new ama this will be even a bit more at 3 to 4 degrees.
This was basically a call from our North sail designer, I believe he is right in this, but have yet no prove of it.

Accidental Jibing and Yawing

First of all I never ever sail straight downwind, I always sail angles (board up).
Why; because;
—your sailing angles homework properly done , the VMG is way higher like this.
—only gentle corrections necessary, higher average speeds make steering easier.
—the Autohelm barely correcting.
—As such it will never come near to accidental jibing.

Downwind Yawing in a heavy seaway ; I never fight that motion let the waves take their cause, you likely to find yourself in the original path, ones the wave cycle has passed , and without aggressively having to correct.
I find a daggerboard to only work against the easy vaka ama movement, more precisely it can bite and send you specifically into the direction you not intending to go. i.e. you get an easier motion without daggerboard,
besides the long narrow vaka/ama has plenty directional stability without that daggerboard.

Cheers Sven
Last edited 7 jan 13

RUDDER & FOIL

Sven,
thanks for your very informative posts.

Much thought is given to ‘improve’ on rudders and foils, yet when I read & see yours, it does make me think it is going to be hard to improve on anything that simple and robust. 

One point I note is that the original on Cheers had a large foil with a smaller steering tab which was only for the top half. So very much a dagger board with rudder added.

Yours is the opposite, more a rudder with skeg, that also works as dagger board. 

Questions:
Does the tiller ever become highly loaded due to the large size?
Could the rudder part be smaller, which would give more strength to the skeg?
Does the shaft give support or just for turning?
Does the dagger board in the outrigger relieve the load?  (Cheers did not have one).
How much lift do the hull(s) contribute compared to the boards (ie leeway prevention).

Just love the foam block.  When forced back, does the rudder hit the underside of the hull?  It does appear from the photo that there is a gap between the top of the rudder and the hull.  Obviously this will help, but not give the best water flow?

Thanks
Mark

The foam block configuration is new to me and is simply elegant! May have to reconsider rudder placement.

cheers,
Skip

Hi Mark,
Post #11.  RUDDER PLACEMENT

Sven,
thanks for your very informative posts.
 

I admit before acquiring Pacific Bee (Cimba) back in 2008,  I designed quit a few other systems, but each time I finished the engineering part of such a system, I found it to be too risky to use it in a heavier seaway, further comparing it againt the Dick Newick and Russell systems , I discarded my plans again.  I can’t seem to come up with a simpler system for now.
Loose hinged kickup rudder blades I consider prone to damage.
These systems, outside and to weather of the the vaka, might be fine for inshore cruising, no good for Blue Water stuff,  they are way too vulnerable in a heavy seaway in that position, capable of receiving major blows by oncoming waves and breakers.  Besides the well documented hydrodynamic in- efficiency of surface operated foils.

Questions:  Does the tiller ever become highly loaded due to the large size?

No never , weather helm is however always found whenever I loaded the ama too much, In that case I do something about the weight distribution by shifting it back to leeward again, that will correct the unwanted weather helm at an instant. 
Proper sailing Pacific Proa’s should always be sailed with lightly loaded ama’s any proa with too much weight to windward is a “pig” to steer, you see them often carrying massive rudders to counteract that bad behavior.
WTW is very bad for proper motion of any proas in a seaway,  essentially it becomes a catamaran, only a very bad one as most times the ama is designed too short to sail it like a displacement hull.

Ama L/B ratio
L/B ratios must be higher , this was extensively tested with towing tank models back in 2005 , the funny thing was that that tests, where confirmed by the way Pacific Bee behaved in a seaway. Beware that any figure given has to be seen in the light of the whole Pacific Proa design, so I tend to be careful not to state to much figures as they will not tell you anything for your own platform configuration. Rule of thumb derived from those tests were that the minimum the L/B ratio needed to be higher was 1.5* the vaka L/B ratio , this would give Pacific Bee an ama L/B ratio of about 1:20 , and this for all drafts of that ama hull while sailing.
Now this is speed we are talking about, the motion and behavior in a seaway is another close watched aspect ,as you Never want too much area exposed to the elements on the weather side, if you do design to much surface area out there, one day a bad breaker will smash it to bits, because ama is essentially “parked” at that moment by the deep V vaka, as it is some distance from the rolling breaker, it will not move aside yet,  I had this a few times, that is dangerous. So making a big condo all the way out to windward is a design Nono,  again this, if you are facing the elements, cruising inshore you can get your condo in save haven .Did we veer of course too much? No, Its still about steering.

Could the rudder part be smaller, which would give more strength to the skeg?

Well, might at speed at sea, but rather not, as sometimes in very confined places , it can start to be a little hectic to sail the proa around, we start to get used to that , slow maneuvering is done by 2 rudders, as very sharp turns can be made.

Does the shaft give support or just for turning?

The rudder consists of a massive build wooden rudderstock w/glass UD on its sides, with a rudder shaft incorporating at the back end of the stock, its properly hinged , so I guess you could say the stock and shaft help each other., given the massive blow it received , one could say that it is almost indestructible,
Another beauty is , that if you have damaged you rudder and you need to remain going in that direction, you simple swap your other rudder for that wounded one, till you find the time to repair it, so essentially you are out there with a spare rudder.

Does the dagger board in the outrigger relieve the load?

No , I found the daggerboard to be a nuisance on all courses except close hauled.  Round bodied more modern shapes need those daggerboard to fight upwind, Pacific Bee can be sailed almost without, due to its V vaka shape.

How much lift do the hull(s) contribute compared to the boards ?

Edited 6march13; for clarity; the hulls generate no lift , rather deep V shape reduces the amount of leeway .

For Pacific Bee the above situation , clearly suggest that its very vaka shape related, how much I could honestly not tell you at the moment, might be a nice separate test next year, but let me say that I don’t bother too much about the leeway, going upwind together with a reasonable good sailed monohull, I can keep the same height. If I walk over to the ama ,but the board down, I normally point some 4 to 5 degrees higher than them, without the speed dropping.

Just love the foam block.  When forced back, does the rudder hit the underside of the hull?

Don’t know, don’t think so , besides the hull is very V shape and very very strong at that point,so I would think if you hit something, the blade shoots either on leeward or windward up along the hull, again that major blow on the Great Bahama Bank, didn’t any damage to either hull or blade.

It does appear from the photo that there is a gap between the top of the rudder and the hull.  Obviously this will help, but not give the best water flow? 

Your right, however at the speed the blade is shooting through the water,  a bit of pressure lose is not a big deal I think.  At least its way better to operate a blade well below the surface , than having it operating at the surface ,on the very disturbed and turbulent weather side of the vaka, that’s for sure.

Cheers Sven

Thanks for this detailed information to Mark’s questions, Sven. The part that caught my interest particularly was the ama L/B ratio was best at 1.5 times that of the vaka for best speed from the tank testing. Could you talk a little more about what those tank tests revealed?

Post # 13

TESTING WITH MODELS

Aloha James, Hmmm, I had already been digging in those old test file data a while ago, and posting them in full would not reveal any further useful data without all the background intentions known. it validity after 6,5 to 11 years must be considered in some areas aged   some parts even surpassed. However I compiled a short version of what we found, and what I still render valid today,  and this mixed with what I know now from Pacific Bee. 

Both 15 meter designs were made in January 1999 , The reason for testing in 2005, ; was to see how much “fatness” the windward side of a pacific proa needed to have ( see below models), to counteract the ama induced weatherhelm.  I spare you the results, as I now firmly believe that it is not worth bothering about making the vaka A-symmetrical at all, ( unless for the purists, who seek to unveil the historic Pacific Proa’s true nature ) 
Why, because the A-symmetrical behaviour of a Vaka hull is largely depended on speed.  The quicker the Vaka travels, the more force is generated to bear away to leeward.

Now ,the faster you travel the less weather helm “correcting “ force is needed, as the ama is scimming now anyway, generating barely any resistance to the platform.  See also Russell’s Sept 2011 video at 7min.
It should be; the quicker you go , the less force you need to have to bear away to leeward. Matter of fact , the quicker you travel , the less force you want anywhere, its directional balance you seek, and minimal steering corrections. 
Note; Pacific Bee most times sails with Autohelm 2000 , and it barely needs to correct the path of intended travel. 
So that A-symmetrical test route was back then considered busted, that Vaka model discarded.

Platform width ratio cl-cl
Next we experimented with the symmetrical hull with different ama length, starting with the shortest having a B/L ratio of 1:10 , as is logical we ended up with a narrow platform width setup , it had less “arm” to pull the vaka to windward,  or let the ama fall back due to resistance, however you want to explain the problem.

We could not make it too narrow because you have no Rm arm left, to play with.
Related to the vaka cwl length , the platform cl-cl width we ended up is 0,42 * vaka cwl. Leaving you with enough width to sort out the Rm-var via waterballast.

Ama B/L length
With this platform width we continued testing the ama B/L ratio’s we tried 1:10, 1:20 and 1:30.
1:10   too short ,too much drag, too slow in displacement mode , discarded model.
1:30   too long , but very quick , no noticeable weather helm, tracking very good, but too long in real life , difficult to construct, a disaster in heavy wave conditions, as it would “send” the ama skywards when hit.

1:20 (1,5 * vaka B/L ratio) the compromise, quick enough to have no serious weather helm in displacement mode, yet short enough to be able to engineer , construct and attach safely to the beams.  I expect it to take the oncoming bigger waves well   cwl Vaka hull   to   cwl Ama Hull 1 : 0,68

Disclaimer,  these ratios are what I design to with now, they are for the total platform setup, where I can I incorporate it in Pacific Bee, ( hence the shortening of the beams ) next will be the 2012 1:20 sleek wave piercing ama. 

1. Drawing A-symmetrical   50-footer ( testbed.scraped)
2. Same hull but now symmetrical.  drawn,  w/ 1:10 ama   ( testbed.scraped)
3. General shape of 2012 new ama.

Thanks very much, Sven, for that detailed reply. You have answered many questions there! The reasoning behind dropping the asymmetrical vaka makes a lot of sense. I think Russell commented that the asymmetrical hull on Jzerro was not worth the effort.

And thanks for sharing the information behind those ratios. Good luck with your new ama next year.

I remember you saying that you shortened Pacific Bee’s beams to reduce RM and now i see you did it to conform to the optimal overall beam that the tank testing indicated. A good real world test for for the experimental data. Did the shortening of the beams live up to all your expectations?

Aloha James,  Allow me to redirect your question to ; 

Topic   ; PACIFIC BEE STABILITY   Post   # 04 Handling the Variable Righting Moment Rm-var

Cheers Sven