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Terho Halme's "Ping-Pong"

Page history last edited by Kevin 11 years, 9 months ago

 

 

 

Terho Halme is a Finnish boat designer and sailor.  In 2003 he completed and sailed his 7.5 meter proa Ping-Pong, and in 2005 he modified Ping-Pong with larger rudders and new beam placement.  All this and some sailing are nicely documented by Terho in messages to the proa_file group on Yahoo groups, in pictures and in some pretty videos.

 

Since I'm the contact email for the wikiproa site, I get a steady trickly of emails asking me if I know where Cheers is now (yes, try Googling, she's in France being well taken care of), if I know Russell Brown (no, I've never met him, but I'd like to), if I know where About Face is now (still in Australia, I presume), and if I know anything about Ping-Pong.  Of all of them, the questions about Ping-Pong are the hardest to answer, not due to description or pictures not existing but because they're so spread out, because Terho's Finnish Picasa albums don't show up on an english language google search, and because he's busy and doesn't have a dedicated site for the boat I can point people to.  So I emailed him, and he has kindly agreed to allow me to assemble some stuff here as reference material for people who are interested in the boat, and he uploaded some videos to Youtube for us to see, including some I don't think had been made public before.

 

I have to confess, I've always found Ping-Pong to be a unique and interesting boat.  There are precious few actual weight-to-windward proas built and sailing, and almost all of those are Rob Denny designs.  Rob's designs are beautiful, fast and ambitious, but I've wondered for a while if it wasn't possible to have a lower tech version; a plywood WTW proa with an inexpensive rig, which wouldn't be as fast as a Harryproa but would be more within the technical and financial reach of people who couldn't afford a Harry.  Well, it is possible, and Ping-Pong is the proof.

 

The following messages were assembled from conversations on the Yahoo proa_file group.  The text author is Terho Halme unless the text is preceded by the quote signs:

 

>

>

>

 

In that case the author of the quoted material is indicated at the beginning of the message.  All the messages are still available on the proa_file.

 

All text is the property of the author.  All images and video are property of Terho Halme.  Many more images of Ping-Pong can be found at Terho's albums:

 

http://picasaweb.google.fi/terhohalme

 

Enjoy!

 

Kevin O'Neill

 

 

 

Message #6589

Fri Jun 13, 2003 4:38 pm

New EQL-7 Proa

 

Hi all, While my Expess Drain is waiting for the repair of the welding machine and the revover of the welder, I just have to build a plywood proa to test my toughts. So here it is for you to judge in photos at the collection EQL-7. The structure is 6.5 mm pine plywood, stich & glue, taped with 446g/mm2 +/-45 glass and epoxy. Coated simple with white acryl house paint. The plywood sheets are already waiting for cutting and lengthening at the workshop. EQL-7 is a weekender proa for two. (It will take some time to get my wife realise that, now there is only a deep silence). For the night the haches are turned up and a canvas tent is pitched over the cockpit. His empty weight will stay under 300 kg’s. The sail area (yes, junk rig) is about 20 sqm. LOA is about 7.1 m, BOA 3.3 m, the distance of centerlines 2.5 m. The bottom of the hull is v-shaped like Wharram’s but here the shape is modified to maximise lateral force and prismatic coeffient. There will be no leeboards (before sailing test anyway). The sleeve pipes of rudders are connected by bar which changes and locks the rudder positions. The rudders are wired to a wheel in cockpit. Junk rig is used to minimise building costs. It should work well, because the sheeting system is easy to build for a wide boat like proa. Junk rig is easy to reef and it also eliminates caught abacks allowing the sail turn in freely. There are no fastened sheets on the leeward side! Perhaps he won’t be the fastest sailboat of the lakes in Finland, but here the easyness is the main target. I will add building photos of the project to the photo collection while the prosess is continued.

 

 

 

 

 

 

 

Message #6723

Sun Jul 6, 2003 4:59 pm

New photos of EQL-7

 

Added some new photos to EQL-7 album after three weeks of work (approx. 120 hours). Lee hull is ready to close the deck and the bridge and beams are fixed to lee hull. Mast step, guide tube for mast and partners are installed. The project is still in timetable. Launching will be at the end of July. Next week I’ll finish the main hull, then paintings, rigging and junk sail, rudders and a simple trailer.

 

 

 

 

 

 

Message #6726

Mon Jul 7, 2003 11:33 am

New photos of EQL-7

 

--- In proa_file@yahoogroups.com, “Todd” <ktsrfer@m...> wrote:

 

> Ah man I’m totally stoked for you awsome job. Seeing your progress

> really gets me fired up. One question. How high are your beams &

> bridge from your intended waterline? What was the reasoning for

> having them at that location? Where do you live can I have a ride

> when finished? Okay more than one ? >

> Todd

 

 

I used the formula of DNV (Det Norske Veritas, classification society) for necessary vertical clearance to avoid slamming. Clearance is approximately 6.5% of LWL, so in EQL-7 it is min. 0.45 m. I live in a small village Kihniö, Finland, Europe. Welcome! But do it before November, or the water will be too dense :)

 

 

 

 

Message #6841

Wed Jul 23, 2003 3:29 pm

Ping-Pong (EQL-7) on the sixth week

 

Added some new photos from this week. Named him Ping-Pong (white, small, fast, goes unexpected directions, chinese rigging and hard to handle?).

 

 

 

 

 

Message #6896

Wed Aug 6, 2003 2:59 pm

EQL-7 (Ping-Pong)

 

Added some new photos on the eighth building week. I have worked so far 380 hours. My target launching date will delay about two weeks.

We had uncommon hot wheather in July here in Finland. Yeah, just an excuse...

 

About expensies, my first guestimate was about $1000. But as always, the final costs can have when multiply the fist guess costs by pi (3.14).

 

 

 

 

 

 

 

 

Message #6954

Sat Aug 23, 2003 9:03 am

EQL-7 ready to launch

 

EQL-7 (Ping-Pong) is ready to launch, watch the photos. The day is tomorrow, Sunday 24 of August (if the lorry driver is able to do it).

It took 10 weeks and 450 hours to build him. The last two weeks I spend with the rudders. They were the only ones which I didn’t design properly at advance...

 

 

 

 

 

Message #6958

Tue Aug 26, 2003 10:52 am

EQL-7 Sailed!

 

The first sail on Sunday 24 August. Crew: three nervous men. Motoring (Yamaha 4 hp/4) was very easy, though using rudder pin took some minutes to get used to. Speed with motor max 7,2 knots. The wind was from North 10 to 12 knots, waves about 0,5 m high. Three panels of junk sail up and go. Junk sail worked well, it is quite balanced so the sheeting force was low. Speed about 5 knots and we sailed across lake Toisvesi. First shunt, we got in irons, damn. Well, two men backwards on board and then waiting that the wind turns the new bow of the wind. Next try to sheet, easy in... and when we have about 3 knots the rudder bites again and there we go. The whole sail up, Yahoo! 6 to 7 knots to side wind. After few legs we sailed downwind and get our maximum 8.6 knots. The second sail on Tuesday with good friends. Wind from North 4 to 8 knots. We didn’t measure speeds, but realised that the boat goes up to wind nicely. Much more relaxing sail this time. What to do: The rudders must change by one bar only, now there is to much to do while shunting. The sheeting system need still some tuning. The balance is a problem only, if the boat don’t stop for the shunt exact to side wind. When the speed is over 3 knots there is no balance problem at all. Now I am very pleased with my new boat. Some tuning and he will be superb. Terho ps. Sorry, no sailing photos yet. It was far too exiting. Some motoring photos still.

 

 

 

 

Message #6970

Thu Aug 28, 2003 11:51 am

EQL-7 Sailed!

 

--- In proa_file@yahoogroups.com, “Todd” <ktsrfer@m...> wrote:

 

> Your boat looks AAAAAAWSOME. Great job. I love the concept and over

> all look. Whats the sq.footage you put up for sail? I would love to

> know how he sails in winds around 15 to 25 knots with a 3 foot chop.

> Think he could be made to to wind speed or better? >

> Todd

 

 

Thanks Todd. The sail area is 22.8 sqm approx. 245 sq.feet. I don’t think he could be made to to wind speed, the deep-V hulls have too much of wetted surface area. I am too waiting for stronger winds, but these below 10 knots are wery good for study him.

 

 

 

Message #6974

 

Fri Aug 29, 2003 10:29 am
EQL-7 Sailed!

 

 

 

--- In proa_file@yahoogroups.com, “fghmurcia” <fgh@m...> wrote:

 

> To Terho:

>

> Congratulations! Indeed an excellent and fast work. You can be very

> proud. I look forward to see your pictures, and I am particularly

> interested on how you have solved the sheeting of the sail.

>

> Regards.

>

> Fulgencio

 

 

Thanks for your kindness! Look at photos, there are some new sailing photos to show the sheeting system. I’ll try to sketch a principle of junk sail sheeting in Ping-Pong proa.

 

 

 

Message #7007

Wed Sep 3, 2003 2:42 pm

More Ping-Pong sailing

 

Sailed today against Lightning (http://www.lightningclass.org/), wind 4 to 8 knots and shifting a lot. Downwind Ping-Pong was clearly faster, boatspeed 1-2 knots better than Lightning. Downwind speed 6 to 8 knots.

 

Upwind boatspeeds and angles almost equal, but Ping-Pong lost while shunting and Lightning was far more faster to tack. However, our shunting weren’t too poor. Upwind speed 5 to 6 knots. Going upwind there was very little need to steer, just controlling the sheet and the upwind angle was OK.

 

I had a feeling that there sould have been more wind to beat those busters. The wind was enough for them to reach the upwind hull speed.

Did I say that Ping-Pong is not a racer?

 

 

 

Message #7017

Sat Sep 6, 2003 2:11 pm

Re: More Ping-Pong sailing

 

Here is a short video of Ping-Pong (6.9.2003):

YouTube plugin error

 

(The original video is no longer on Terho's site, this is the Youtube copy.  Ed)

 

Happy sailing

 

Terho

 

 

 

Message #7030

Tue Sep 9, 2003 5:47 am

More Ping-Pong sailing

 

--- In proa_file@yahoogroups.com, “Janusz Ostrowski” <janusz_o@h...> wrote:

 

> Terho

>

> Thank you for this film.

> Really happy,smooth and quick sailing.

> Probably speed is even better on left tack, when mast is to windwward from

> sail.

 

 

Actually I didn’t find any difference during five hour sailing session. Need a VMG instrument to find the difference, I only have GPS. I also became confirmed, that going upwind there is no need to steer at all, I just turned him to the right direction and the balance of the slim hulls and junk sail took care for the last. Amazing! He also took nicely small shiftings. The position of sheeting determined the angle and speed. The best feeling was with shunting angle about 100 degrees. This was with wind speeds some 3 to 8 knots.

 

 

> You have plenty of sail on PingPong, for a reason ;) > and that seams so easy to handle..

> Like on modern light 60’s you will need to reef early, > but what’s the problem with junk sail :))

 

 

The best thing is that the reefing of junk sail is not a problem at all :)

 

 

 

Message #7037

Wed Sep 10, 2003 12:20 pm

More Ping-Pong sailing

 

--- In proa_file@yahoogroups.com, “bradwoodbr” <bradlina@o...> wrote:

 

> Thanks for helping to view this video.I was able to see your proa in action.

> The wake of the boat is impressively small. Will you angle the bottom end

> of the rudders away from vertical to give less water turbulence or is the

> amount seen in the video > acceptable?

 

 

Tilting the dudder does not change the resistance of it. There is no way to lose the wave resistance of rudder while it is separated from the hull (well, I have none, yet). From the performance point of view the rudders should be under the hull, but this was difficult to design for easy anf fast changeable while shunting. I take the turbulence as a cost of safety.

 

 

 

Message #7040

Wed Sep 10, 2003 12:50 pm

ping pong Video

 

--- In proa_file@yahoogroups.com, “Todd” <ktsrfer@m...> wrote:

 

> Nice video. Sweet boat, really awsome. When can we see it in some

> stronger wind and waves. 15-20 knots 3’ chop. Would it fly the

> weather hull? How did you come up with the design for the junk rig?

>

> Todd

 

 

I can tell you, I am as impatient as you to test him in a real weather. Normally there is lot of wind and cool weather this time of year, but now we are having an Indian summer. But the winds will come before ice and snow...

 

Flying weather hull is not an issue, but if it will fly, the skipper has done something wrong (and mayby having fun and fright).

 

Junk rig is cheap (under $400 with mast, sail, battens, blocks, ropes), low stresses everywere, low sheeting force, the easiest rig to reef, all controls in cockpit, safe caught abacks and so on. After I realised how to adapt modern performance of a sail to an old junk rig idea I simply had no alternatives left.

 

 

 

Message #7052

Thu Sep 11, 2003 4:09 am

ping pong Video

 

--- In proa_file@yahoogroups.com, “Todd” <ktsrfer@m...> wrote:

 

> Okay, so how did you come up the demensions for the sail?

 

 

First I calculated the wetted surface of the loaded boat. Then having enough power for light air I multiplied WS area by tree to get the sail area, so the SA/WS = 3. Then I checked the static stability by calculating the wind to flying windward hull. Methods are universal yacht design stuff. Look at Harvey’s Multihulls for Cruising and Racing and Larsson’s Principles of Yacht Design. Then a decision to have aspect ratio of 1.5 and number of panels 5 at the sail. I designed luff and leech elliptical to maximise performance.

 

 

> What style of junk is that?

 

 

Just my own, mixing of the principle of junk sail by van Loan’s Chinese Sailing Rig and modern aerodynamics.

 

 

> Did you make it your self?

 

 

Yes, designed panels for camber by Rhino3D. Cut panels from white polytarp, taped panels together at the places of battens by carpet tape, taped rope round the sail and sewed rope seams. Making it took about one workday.

 

 

> How did you attach the battens ? I want to scale yours down to 100 sqft for a test sail of my own.

 

 

Battens are two strips about 15 mm x 50 mm screwed together through the sail.

 

 

Terho

 

ps. To get this point, took about 45 years of interest to boats, about ten years of self studying yacht design books, changing my trade to boat business, numbers of boats designed and few built, four year of full time study of boat manufacturing and tree last year a strong dream about proa.

 

There are more than twenty pages of different calculations made by excel and mathcad for this proa. Don’t wait for too “how to” and simple answers. Though it would be fun to write a book about “How to Design an EQL-proa with Junk Sail”. Have to think about …

 

 

 

Message #7075

Mon Sep 15, 2003 2:42 am

Ping-Pong and choppy lake

 

Sailed yesterday in very choppy conditions. Picture this: There are tree big fans, one in West, one in SW and one in SWW. Then someone switch them on and of in random periods of 1 to 5 seconds. The wind was from 0 up to 20 knots and direction impossible to read from waves. Also the wind direction and force changed in different high levels of the sail. This can be normal on the lake, but I’ve used to be lived on the sea coast and this was a new experience.

 

Get maximum speed of 13.5 knots and several times over 12 knots.

Didn’t try to fly the ama, but get near to capsize once. My backbone released the sheet. The whole sail have static stability up to 17 knots and there was a lot more in the gust. Upwind speed about 6 to

6.5 knots. Reefig a junk sail was a pleasure.

 

There was steep waves up to half meter and the boat took them nicely, not too much pitching. Some sprays to kockpit too to keep the skipper awake. Sorry no photos, I was too busy.

 

And then the bad news.

 

The rudder has a tendency to ventilate and stall when the going gets fun. To the side wind above 9 knots and downwind above 12 knots. It acts like a hand brake. Have to redesign the rudders. They will go under the lee hull to slots. Have to turn back to my original idea.

 

The leeward hull should be larger. In a proa of this size the distribution of empy weight is about fifty/fifty and the underwater hulls should be equal. Now afterwards I have to think about what made me to design this too narrow and low leeward hull. Was I thinking the costs or the looks... surely not naval arhitecture. Perhaps the hurry and exitement to get it done clouded my brains. Luckily this is quite easy to improve. Just glue a 50 mm foam round the float sides and bottom and coat it by glass.

 

Well, the errors are our knowledge :)

 

 

 

Message #7097

Tue Sep 16, 2003 11:07 am

Ping-Pong and choppy lake

 

--- In proa_file@yahoogroups.com, “briancady413” <briancady413@y...> wrote:

 

> Terho, could a shelf partway down the rudder’s windward surface halt

> ventilation from getting too far down?

>

> Brian Cady

 

 

I was thinking about that and they are in my models. Too hurry to get him to water...

 

First I’ll try to tilt them slightly backwards like in RC-30, because it is easy to test.

 

 

 

Message #7099

Tue Sep 16, 2003 11:16 am

Ping-Pong and choppy lake

 

--- In proa_file@yahoogroups.com, “Tom Speer” <me@t...> wrote:

 

> I would think the lee hull should have at least 200% buoyancy. When flying

> the ama, the lee hull has to take 100% of the weight, plus any down load

> from the sail. But the buoyancy isn’t distributed evenly along the length

> because of waves and the pitching moment from the sail. So you have to have

> well over 100% buoyancy in the lee hull so as to have 100% in the right

> place when you need it.

>

> Cheers,

>

> Tom Speer

> F-24 MkI Ama Deus

> me@t...

> http://www.tspeer.com

 

 

The buoyancy reserve is OK (quite near 200%). The broblem is the drag from beams and nets when the heeling force increases. A’ll make the ama deeper for next spring and raise the nets up to level of ama’s sheer line.

 

 

 

Message #7135

Fri Sep 19, 2003 3:55 am

Ping-Pong and choppy lake

 

--- In proa_file@yahoogroups.com, “proajunk” <laburnumho@s...> wrote:

 

> Dear Tehro, your boat is great, I to have bean thinking along such

> lines, but got no where near a real sailing boat.

> Are you a member of the Junk Rig Association, if not you will find

> many ideas for rig improvement.

 

 

Not yet. I just don’t see what improvements you mean. There is some, sure. Last spring I did about two months very active study in the internet to find all valuable information of junk rigs. Dadadata and arne’s junk sail are greate. I purchesed van Loan’s Chinese Sailing Rig and that was very informative. Unfortunately from my point of view there was too much traditional admiration and depat in the internet and too little scientific stuff. I have sailed on quite a many sailtypes and I feel this junk is an effective one compared to western sails.

 

 

> The present thinking is to give some shape to the sail, either by

> cutting shape in the cloth between battens, or by hinged battens.

> yours seems to have some of the former, though perhaps to little. It

> should be about 6% curve, interstingly, from the Junk rig group (I

> think Yahoo also) I discovered the centre of curve is not too

> critical, in the middle seems to work fine.

 

 

Yes, I do agree. Well, my sail has cut for a 6% camber at 45% of batten length. Hinged battens are to complicated for this construction. I designed the profile of sail luff and leach elliptical to minimise losses of upwash-downwash phenomenon.

 

Though polytarp is cheap, it is also laminated and doesn’t set up as nicely as thin dacron which is more elastic in 45 degree direction of fibers (from corners). I’d like to test a new sail with more camber, about 10 %. Arne’s sail seems to have more camber than mine.

 

 

> I note your sail is well back on the mast, all JR advice it to move

> to about 10% back when going up wind.

 

 

True, I put it at the place of dynamic pressure centre, which is about at 25% of batten length to minimise sheeting force. That seems to work fine and I have had no problems going upwind. On what is this “all JR” based on? For an opinion of an author or some real research? The general figure of aerodynamics (25%) works fine to me.

For simplicity I did reduct luff control.

 

 

> Pictures and movie very informative, though more tech details would

> be of interest. How do you prevent leeway, if it is just the rudders

> I see why you are having problems.

 

 

The hulls have a deep-V body and an elliptical profile. In fact they are low aspect foils and they work fine to me upwind. A 100 degree angle of shunts is acceptable and as you see from wake pictures there isn’t too much leeway.

 

I have thought a lot the problems I have with my rudders. When does the aerating appears? There was always a high pressure and high drive force at the sail and the stern has been arisen. Then the pressure centre of hulls moves forward and the rudder needs to make more lift to keep the balance. Then the rudder stalls and sucks air in the water and the rudder lose holding and creates only high drag and funny noise. So, I finally have a balance problem, not when going upwind but going downwind. Moving weight backwards would raise the speed on which the aerating accurs. Need more crew to have fun or to go slower...

 

 

 

Message #7149

Sat Sep 20, 2003 7:36 am

Ping-Pong and choppy lake

 

--- In proa_file@yahoogroups.com, Malcolm Smith <mal@c...> wrote:

 

> You might consider simply making the rudders deeper. I’m not sure how

> deep they are at the moment. The rudder for this type of boat, I

> believe, should be significantly larger than that for a conventional

> boat of similar size. Proportionally, it should perhaps be in the

> order of the size of the centreboard of a similar sized conventional

> boat.

 

Well, that could be the right answer, the rudders are about 0.8 m deep and 0.3 m of chord length, their area is 0.19 m2, which is under 1% of sail area (22 m2). Anyway, have to leave testing to the next spring, we are going to have winter soon and the boats in my home marina will be picked up next Saturday :-(

 

But, I have the whole wintertime to design him better...

 

> P.S. Terho, I re read your Cruising proa Concepts analysis

>(http://kotisivu.mtv3.fi/terho.halme/cpc/Cruising_proa_concepts.htm)

> and you should be commended on on your concise and logical work. It

> would be great if you could extend it to include conventional

> monohull, catamaran and trimaran configurations:-).

 

I am starting a new job next week (hopefully over a two year project in wooden boat production). If I needed some brainstorm against it...

shall see.

 

 

 

Message #7179

Wed Sep 24, 2003 4:30 pm

Re: ping pong

 

--- In proa_file@yahoogroups.com, “Mark Thomasson” <laburnumho@s...> wrote:

 

> Dear Tehro,

> thanks for your very informed reply, I think you know more than me! Though I

> am always pleased to learn. I did find that the Junk rigg groupsite was very much intersted in

> traditional design, with little on cutting edge design.

> The 10% mast postion is, I guess, from the bendy batten designs, to induce

> some curve. Though I suppose it would help with your sail on the sail to

> windward of the mast.

> My questionon your rudder is, are you using it to prevent leeway at all,

> I.e. is the boat fully balance with the rudder left free? If not, or in any

> case would a board help to balance the boat leaving rudder only for low

> force fine steerage.

>

> Regards Mark.

 

 

Mark, no day without study!

 

Next spring I’ll continue to test junk sail more. I also think, the battens now are too bendy. So more camber to panels, more rigid battens and controlled twist over the sail is the way to go.

 

Yes, the boat is fully balanced when clouse hauled. It also takes small shifts by oneself. On harder open winds the wind pressure starts to rise sterns and the balance is lost. Then the rudder should act like a board but when it is too small and stalls it just sucks air into the water and slows down the speed.

 

I will resist the centerboad in ping-pong as long as possible (because it was the main reason for hull shapes) and find an other functional solution. At this moment the bigger rudders seem obvious.

Sailing hour today confirmed me that, the rudders should have more holding power.

 

 

 

Message #7469

Tue Oct 14, 2003 2:13 pm

Ping-Pong sailing photo

 

--- In proa_file@yahoogroups.com, “Todd” <ktsrfer@m...> wrote:

 

> Terho , Whats the helm balance like on your boat? In the picture it

> looks like you have a lot of sail aft. What do you do to compensate

> having the CE aft if any?

>

> Todd

 

Upwind no problems at all, he goes up like a train without touching the rudder. To side wind and down wind a bigger rudder is needed.

Well, next spring... Also moving weigth back does balance the boat by moving LCR backwards. Scan my previous post of ping-pong sailing.

 

 

 

Message #7512

Sun Oct 19, 2003 3:32 pm

Questions for Terho

 

--- In proa_file@yahoogroups.com, “RON COOK” <RCOOKDESIGN@T...> wrote:

 

> Dear Terho,

> I have a couple of question. I am asking them on this list because

> I can not get through at the e-mail address on your web site.

 

Sorry, didn’t correct my adresss at pages yet. Anyway, you can post direct to me from this group.

 

> Do you find it easier to do yacht hull design particularly hard chine, in

> Prosurf 3 or in Rhino. I am currently using Prosurf 3, which I find ok but

> not great. Its particularly frustrating trying to work out developed surfaces

> in Prosurf plus it will not do asymmetrical hull shapes. Do think Rhino is better?

 

Rhino doesn’t even know that the surfaces form a hull. It will unroll any decent developable or ruled surface, allmost. Haven’t try asymmetrical hulls in Prosurf.

 

> While looking through past files in the Proa group I read your post,

> cruising proa concepts. The chart with the resistance comparisons

> for elliptical and rectangular cross sections is of particular interest to

> me. I noted that you used Michlet to make the resistance comparisons.

> Rectangular and hard chine hull shapes are of great interest to me.

> In a month or two I will be posting to the Proa group some Proa designs

> where every plane is 90 degrees to the adjoining plane. I am building

> the models now, the numbers seem OK and they do not look to bad.

 

There is one problem though. Rectangular and deep-V hulls act with a different manner compared to round shape hulls when they have some leeway. Their resistance caused by leeway (induced resistance) is bigger, but they also act like low aspect foils decreasing leeway...

 

> I spoke with Steve Holister (Prosurf) today about Michlet’s inter- face

> with Prosurf. He said he has not done any more work with Leo, but

> did say that he should get back to him, he also said talk to you.

 

We had some talk some years ago, but can’t remember if it was about using Michlet with Prosurf. Mainly we discuss from earlier version of Nautilus and it’s VPP.

 

> Steve said that Delt 3 under cals in Prosurf should give reasonable

> results for SLR of 1.34 and less. Have you done any comparison

> with Prosurf and Michlet? Would you recommend Michlet?

 

Delft 3 series is for normal monohulls, for L/B ratios under 5. Using it in Prosurf is easy and straigthforward. Kaper (for light canoes) doesn’t work with SI units. Haven’t done much of comparison. Using Michlet need some try & error method AND READING the manuals. For me it works fine and transfering output to Excel expand the presentation of results greatly.

 

> Terho, in past posts did you share any of the hydrodynamic ratios for

> Ping Pong? If not would you be comfortable doing so?

 

There is nothing top secret in Ping-pong. Cp is over 0.6, L/B near 15, what more? The few differences compared to Wharram hulls is bigger Cp, bigger LWL/LOA ratio, bigger Cw ratio. These all reduce its piching and resistance above hull speed.

 

> Good work with Ping Pong it is a very intriguing project.

 

Thanks. Need some improvement still...

 

 

 

Message #9224

Sat Jul 24, 2004 1:51 pm

Ping-Pong Cruising

 

we (me and my wife) made a two week coastal cruise in Ping-Pong this July. The wole cruise was about four hundred miles along Finnish coast line and archipelago on the Gulf of Bothnia and Gulf of Finland. No big problems appeared during the trip.

 

Ping-Pong proved to be a seaworthy little ship. Certainly wet upwind.

We sailed and motored against 1 – 2 m high steep waves without any problems. Usually my wife get seasick on a monohull, but not once on Ping-Pong.

 

The cruising speed was similar compared to slightly bigger monohulls, the best continuous speed was above 11 knots at side wind.

Unfortunately he needs stronger wind to sail at all than monohulls and shunting angles are only 110-120 degrees. The next project needs a centre board. Junk rig works, but is very strict of the right sheeting angle. Also the control sheet get entangled at times.

 

Shunting upwind was very easy after I changed the sheeting points to the ends of the mast hull. Shunting downwind was more difficult when the turn down needed a fair speed and easying of the sheet at the same time. This was the only manoeuver where the wrong balance of CE and CLR (negative lead) really bothered.

 

The rudders seemed to be too smal, the boat was difficult to steer in a marina. Also the beams and the bridge are too low for sea cruising.

Just when the speed growes up the waves hits the beams and the boat slowes down. Ping-Pong was designed for sheltered waters but can operate at sea despite of low bridge.

 

Living in a little proa is a study of syncronizing. The cover made of polytarp was essential to get over. The proa had three different states: sailing, having a meal and sleeping. Every state needed some kind of tranport of things and having a good division of labor. After the cruise we are still married and live in a same household...

 

It was a very good experience for the nex (proa) project. Few new photos are added to EQL7 file.

 

 

 

 

 

Message #9268

Sun Aug 8, 2004 9:11 am

Ping-Pong Cruising

 

--- In proa_file@yahoogroups.com, “jameshanahan” <jameshanahan@y...> wrote:

 

> With a dagger board, do you expect the tacking/shunting angle to be

> smaller than 110/120 degrees or just limit leeway? It might be a dumb

> question but I’m not sure whether you are talking about pointing into

> the wind or the effective angle actually sailed.

 

 

I was talking about the real angle read from the plot of GPS.

Pointing angle is about 90-100 degrees. For me, after I was familiar with the junk sail, it wasn’t so bad at all. Dagger board could be the solution, but I will try to use bigger rudders to minimize moving parts. I’ll also move the rudders onto the inner side of the mast hull. The main improvement will be however to rise the beams and the bridge about 250 mm (10”).

 

 

> Will the Eql 12 you mention be similar to the eql12 that was in the

> photo section some time back?

 

 

I think more round design and more space inside.

 

 

 

Message #9712

Sun Oct 17, 2004 3:53 pm

Re: Car-topper

 

Hello Sakari and others,

I put a proposal car-topper or “a personal multihull” to proa _file2, photos, EQL 5. Made from okume plywood, he will weight well under our limit. The hulls don’t even need to be dissembled for transporting. The mast and battens are carbon tube from store, alloy tubes will work too.

 

LOA 5 m, BOA 2.4 m, SA 8.7 m2

 

Easy reefing and shunting by aerodynamic junk rig (tested in EQL 7, ping-pong), tilting centerboard for setting balance, oar for steering when needed, etc.

 

 

 

 

 

 

 

 

 

 

 

Message #9717

Mon Oct 18, 2004 12:10 pm

Re: Car-topper

 

--- In proa_file@yahoogroups.com, “Todd” <ktsrfer@m...> wrote:

 

> Hello Terho,

>

> Nice design looks clean simple and fun. How well does the junk sail

> shunt? Any snaggs or hang ups with the sheelets or sheets

> encountered on ping -pong. If so what was your fix?

 

 

Junk sail shunts very well. The sheetlets did stick time to time to battens ends. This can avoid to knot the sheetlets at the battens in one fifth from the ends. Didn’t test that in this summer, but it looks obvious. Main sheet worked without problems.

 

 

> Also on ping-pong and eql’s alike, Does the leeward hull the

> one with the sail in it being smaller in size compared to the windward hull

> and being “to the lee” compared to a pacific proa “small hull to

> windward” Do eql types have to counter lee helm as apposed to weather

> helm on outriggers with small hull to weather?

>

> Todd

 

 

The size of the mast hull is only a matter of bouyancy and immersion.

Why to build volume you don’t need (and pay for it)?

 

 

 

Message #9718

Mon Oct 18, 2004 12:40 pm

Re: Car-topper

 

--- In proa_file@yahoogroups.com, “Todd” <ktsrfer@m...> wrote:

>

>

> Do eql types have to counter lee helm as apposed to weather

> helm on outriggers with small hull to weather?

>

> Todd

 

 

Sorry, your question above is too complicated for me to understand, but... Eql can have a weather helm or lee helm like any sailboat.

Ping-pong has some weather helm just after shunting. Normally this doesn’t cause any harm while shunting. If he stops in the irons, just move the crew somewhat backwards, until the bow turns down and sheet carefully in again. Shunting downwind need more space to collect some speed to enable the turn downwind.

 

 

 

Message #9743

Wed Oct 20, 2004 7:31 am

Junk Sail

 

--- In proa_file@yahoogroups.com, “jameshanahan” <jameshanahan@y...> wrote:

 

>Terho

> could you tell me if you experienced any trouble from your junk sail

> once wind and speed increased?

> What do you estimate the top speed you have achieved with it is?

> “Common wisdom” says junks are unsuitable for multihulls because you

> can’t get decent speed from them. You seem to have disproved this. Is

> this so?

 

 

The best top speed when reaching with Ping-Pong was over 13 knots and best continuous over 11 knots. Measured with GPS. How much more du you need in a small cruising boat? With performance rig and sail his speed would be higher but costly.

 

Junk has more drag, is more strict of the sheeting angle and is more complex to se up, but using it is easy (especially reefing), the cost is very low ($200 with canvas, blocks and ropes), forces are low etc.

 

Next I’m going to make a new Junk sail and rigging by using carbon mast and battens to decrease drag and weigth and designing each panel to have more camber.

 

Do you know anyone tested a junk sail unsuitable in multihull? (James Wharram mayby?) What type and design of junk?

 

 

 

Message #10124

Thu Nov 25, 2004 6:12 am

Daysailer EqlFast 5

 

 

--- In proa_file@yahoogroups.com, Kevin O’Neill <K_S_ONeill@y...> wrote:

 

> With 93 sq ft of sail, I can see wanting a downwind

> sail, some sort of spinnaker say. How hard do you

> think it would be to arrange?

 

 

Junk sail works well downwind. For simplicity, no spinnaker or gennaker.

 

 

> I’m mostly worried

> about how to run the lines so the sail can be set and

> struck from the weather hull, and so the lines don’t

> get in the way of the mainsheet.

 

 

No big worry at Ping-pong, why here.

The mainsheet blocks (the lowest ones) are at the ends of the lee hull. The upper blocks are knotted to maisheet. At Ping-pong the sheetlets sometimes sticked at the ends of the battens, but this can be fixed be knotting the the sheetlets at the 4/5 of the batten length and removing the top loop of sheet control.

 

 

> What are your thoughts on rudders, with your

> experiences in Pingpong in mind? I think you wanted

> bigger rudders for the Eql-7 than the original design,

> right?

 

 

EqlFast5 has a tilting center board to create side force (deep-V hulls at Ping-pong). The balance is adjustable by changing the fore- aft angle of the center board. Also the seating place at the cockpit helps to control balance. Steering works by oars in such a small boat.

 

At Ping-pong the deep-V hulls and small rudders made turning radius too large while motoring. Shunting downwind (to turn downwind after shunting) also need bigger rudders at Ping-pong.

 

 

 

Message #11377

Sun May 15, 2005 8:01 am

Getting most from the ama

 

--- In proa_file@yahoogroups.com, "southernoutrigger"<southernoutriggers@x> wrote:

 

...

 

> But think that sideways pressure is lost when the sheets are free.

> maybe by using the tiller control line to pull the blade to the new

> stern, some steering correction can be effected to stop the bow

> turning into the wind.

> If the leading edge of the blade is kicked outwards while it is

> being pulled to the new stern, it will pull the nose off-wind, then

> once past mid-ships will be set “ weather helm” which is what is

> needed with the sloop rig when sheeted.

 

 

I have observed, that proa always drifts a bit sideways during the shunt, even the sheet out, so there will be a small side force. Does this prevent moving the rudder, perhaps not. We’ll see (hear) when you test it...

 

 

> Clearance under the bridge? You could surely help here!.

> What do you regard as minimal clearance, given that the hulls are

> 1.4 M apart ander the brige deck.

> Theoretically the ama lifts as speed increases, and so does the deck.

> Jerry

 

 

Unfortunately, the closeness of hulls doesn’t matter so much on clearance. It is the question of waterline length, the direction of going. The clearance sould be more than some 6-7% of waterline length. Put your cockpit floor also above this clearance number.

 

 

 

Message #11913

Tue Jul 12, 2005 4:04 pm

Ping-Pong relaunched

 

Finally got Ping-Pong relaunched after a five week rebuilding. We, my wife Anne and me worked total some 300 (wo)man-hours. The main chances was:

1. Bigger rudders (about 100% more area)

2. Higher clearance (from 30 cm to 50 cm)

3. More camber at the new junk sail

 

Added some photos to proa_file2, ping-pong.

 

Test sailing tomorrow.

 

Janusz, late but warm congratulations.

Wade, proa is not a project it is a prosess.

 

 

 

 

 

 

 

 

 

 

 

 

 

Message #11920

Wed Jul 13, 2005 2:35 pm

Ping-Pong dismasted

 

I was test sailing Ping-Pong today, SW wind 10-15 knots, no clouds, perfect weather for testing. Course straight to windward, new junksail work well, new rudders too. Shunting angle was between 90-100 degrees, satisfied. New rudders could have more balansing area in front of axis line, now they are heavier to steer than the old ones while there is some weather helm.

 

I shunted upwind about three hours and was pleased of his performance.

Then I shunted downwind approx. one hour with few nice surfs and was near my home marina when a big rescue boat of fire department came agaist on the same route. Her wake was quite high and when the wind was from behind (so pressure forward) and high rolling wake at side, the mast broke at the deck level and fell in slow motion on the deck.

No other harm. I collected the sail and mast on the deck and motored to marina. The rescue boat didn’t notice the accident and didn’t respond at any way.

 

The mast was rotten at the deck level. Too many drilled holes during the evolution and water could go in the mast. I didn’t notice that when I repainted the mast (yes there were some blue stain...). I will change to an aluminium tube.

 

 

 

 

 

Message #11924

Thu Jul 14, 2005 1:55 am

Ping-Pong dismasted

 

--- In proa_file@yahoogroups.com, Kevin O’Neill <K_S_ONeill@y...> wrote:

 

> Hi Terho

>

> The boat looks good. I like all the improvements, the

> bigger rudders look good and will help windward

> performance, I bet, and the higher tramp will be nice

> in cold weather. Congratulations on being back on the

> water.

>

> As far as the broken mast, any boat wreck where no one

> is hurt and the boat floats back to the dock is still

> a good day. I look forward to more reports from Ping

> Pong soon.

>

> I remember that you were thinking of adding foam to

> the lee hull to increase volume. Did you do this as

> part of the refit, or is it not needed?

 

 

When I rebuild the bridge and beams, I also assembled the mast hull about 50 mm lower. So now he floats at level. The mast hull has volume just enough.

 

 

 

 

Message #16344

Fri Dec 29, 2006 1:09 pm

Proa Toroa video

 

--- In proa_file@yahoogroups.com, “Gary Dierking” <garyd@...> wrote:

 

> I’ve uploaded a 3 minute video of Harmen Hielkema’s “Toroa”. It’s a

> bit fuzzy being taken from a re-copied vhs tape, but you’ll see how

> long a shunt takes and how fast he’ll go.

> http://www.youtube.com/watch?v=a4FADWXmuHk

>

> Gary

 

 

Yes, nice stuff, thank you!

 

It also shows that center of gravity is too in front when pushing. In a small proa moving weigth (crew) backwards should be easier.

 

As I remember shunting “Ping-Pong” takes approximately the same time.

But the acceleration is much smaler than at “Toroa”.

 

(Below are a few more videos of Ping-Pong sailing.  Ed)

 

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