A Small Ceuising Proa

Hello fellas

I’ve been threatening since 2006 to publish this design I’ve been working on.

Well truth is, it’s evolved from a 12 meter catamaran to a 7.2 meter pacific proa in the ensuing years. Intensive research, changing circumstances and “certain other things” have lead to this little baby which I’ve already started construction on.

Firstly, absolutely no excuses for the presentation! I’m 58, clueless about CAD and don’t even draw well. What I present is all on a single sheet of A4 typing paper – drawn at a 1: 50 scale mostly utilizing a magnifying glass to get the dimensions right. Even my working plans are very informal although drawn at a larger scale for better accuracy. Instruments of torture were a Tee square, set square, French curves for the non straight bits, an HB pencil, eraser shield and lots of erasers!

This as yet unnamed design has the following basic dimensions…

LOA: 7.2 meters
LWL: 6.6 meters
Draft: 0.3 meters
BOA: 5.7 meters
Dry Weight: 120 kg
Displacement: 600 kg
Sail Area: 16 sq.meters

The aim throughout has been low cost and ease of construction. I’m hoping to keep it within a budget of just £500 – about quarter of the price of a used Laser dinghy!

He (the correct way to refer to proas) is built in three separate 8 foot modules which are bolted together with stainless steel bolts and then sheathed with fibreglass cloth. This eliminates the need to scarf the plywood sheets. The ama is made up of two modules.

The main hull houses two 2ft bunks the ends of which serve as seats for the cabin and there is a porta potty under one of them. To lee is a two plate cooker, workspace and a sink on a 2.4 meter shelf. There are two independent drop leaf tables so one crew can cook while another does chart work. The opposite side will house my books, lap top and cd’s. The lee pod extends somewhat to help prevent a capsize. It’ll heel to 28 degrees before the extra buoyancy kicks in.

There’s ample seated headroom and when in port the whole cabin top pops up supported by a gas strut for standing headroom. Outside is the 2.4 meter by 70cm cockpit with a seat spanning both beams. Mounted on rails on the beam is a “ballast box” which contains heavier items like batteries, tools, anchor and chain and water canisters. As a proa always has the wind on the same side (the ama side), this arrangement allows ballast to be shifted in either direction for stability. Also, as the ballast box is shifted to windward as the wind picks up, the mast support which is attached to it also moves and cants the mast to windward – moving the drive away from the horizontal and further inboard. There are tramps between the beams and from the seat to the bow/stern.

Not been designed specifically as a flying proa, the ama is very fine (about 22 to 1 slenderness ratio) and will support about 130kg at the designed waterline. There will also be an angled Bruce foil which is able to be adjusted fore and aft for balance and leeway prevention. The ama also pivots from its centre and is sprung with bungee chord so it operates independently to the main hull, reducing torque on the beams.

The rig is a Gibbons/Dierking lanteen arrangement. The mast is also bungee sprung fore, aft wind and lee. This proa shunts so when changing ends, the tack is released, the mast springs back to upright and the former head is pulled down and becomes the new tack.

Steering on a boat this small will be by weight shift, sail control and a good old fashioned steering oar. I have a 5 hp outboard for emergency use only.

I’m also starting a blog to document my progress – I’ll post the address when I have some content.

Your comments and suggestions will be most welcome.

 

I think you have done allright with the design. Certainly shows some practical knowledge and flair.
I think the sail solution has a lot of merit, but havent read much about how easy it is to use in practice.
I must admit I am too severely biased in favour of the Harrygami style of proa to want something like this,
having to wrestle the sail around the top of the cabin seems like a downer for me.
It will be interesting to see how it works in practice.
Good luck with it all.

 

Hi and thanks for the comments. Probably never explained the rig properly but here is a link with nice illustrations and some in-depth comment.

Also, because of its orientation to the wind the cabin tops and decks remain sail free (unless you're back winded, of course) then the least of your worries will be wrestling a sail.

A special thanks also to the rig designer designer Gary Dierking who contacted me by private e-mail and offered some good solid advice and pointed out a few errors in my drawings.

Best!

 

Hello Trevlyns,

That sketch is looking pretty good . I went to the Dierkin blog to read up on the Gibbons rig and shunting proas. I also believe there might be a video of this particular rig shunting on youtube. I'll see if I can post a link to that video.

I was thinking how a reefable sail design that can be swapped in place as a stowable alternative to the Gibbons rig would be nice for a more sedate voyage when the occasion arises. The Gibbons rig no doubt can make for a fun E-ticket ride, though.

Will you be trying other shunting rig configurations? Any avenue of ideas to pursue?

Best of luck in this creative endevour. If you have a need for a quick CAD dxf or dwg representation of your sketch, let me know if I can assist.

Best regards,
BobG

 

I had a look at the sail plan and explanation, and it still seems awkward to me.
The problem is you have the mast, lines, sail foot on the same hull as your cabin, and they lay over the top of your cabin roof.

This also means you sail outside the shelter of your cabin on the ama platform, so as to have your body acting as ballast.

With the harrigami style, all the sails gear is on the other hull, and you get to steer from the comfort ands protection of your cabin.

But hey - sailing is just a stylish form of suffering anyway!

 

Low budget Proa.

Hi Trev.
I really like your design! It's very close to what I end up with, every time I'm planning for the next step up from our Tiki21. (Mostly going from Bolger AS29 trough a larger Wharram, ending in a minimalistic Proa..)
The only main difference are that the size have grown a bit with our family. Now being me, wife, 2 kids, a dog and a cat.

I belive the Gibbons rig will be to much to handle safely on a boat large enough to have standing headroom in the cabin. So the rig will be either a balancedrig Or 2 Tiki wing-gaff sails.
I'm leaning toward Aluminum for the hull. The main reason are that I spent to many days digging out rotten wood from our Tiki. Maybe plywood or GRP for the deck.

I would also prefer to have the hullsides curved indentical to the bottom rocker, to minimize vortex around the chines.
To prevent leeward in shallow waters, I would extend the bottom to form a chin-runner on the inside of the middle of the main hull. That would also act as the lowest step on a ladder, so a hatch in the deck would be placed above.
A deck pod, with a drop-down floor would be options if the family grows further..

I hope you get your blog going soon.
Keep up the good work!

/Gunnar

 

Yes, nice design. Made a similar size project in 2002 though weight to windward proa.

 

ping-pong

Terho. I cant find the other pictures on your boat i have seen before. Is your web page down?

 

There shoud be some in proa_file group, files and photos (yahoo).

http://groups.yahoo.com/group/proa_file2/photos/album/346186777/pic/list

Too lazy (busy) to build up a new web site.

 

Hi

I have a boat about this length, which for a few years had an 11' beam and a 165 ft^2 laminate Gibbons on a carbon spar. It may be the biggest Gibbons rig yet built and sailed, though I'm not sure of that, there may be things being done in the world that are not on the internet. Shocking thought. Anyway, you can see some pictures and descriptions of my boat here:

http://wikiproa.pbwiki.com/Kevin's-boat

You have to scroll down a bit to find the part about the Gibbons. I started with the smaller white Gibbons, which was about 110 ft^2, then built the clear sail a year or so later.

A few observations and things to think about, if I may:

Listen to Gary. He makes these things work, if he says it will work it likely will, but don't meddle about improving things, even with stuff you think won't have much to do with the rig. For example, if you're going to use a Gibbons I would certainly stay with a sweep to steer, rather than rudders. The sweep gives you positive control over the direction the boat is pointed during a shunt. Rudders don't. Very important thing, you'll discover.

That's a small ama. I bet you end up building a bigger one in a year. We all do. You might skip a step and make one that will hold up 200 or 220 kg, you're going to want it.

A Bruce foil to windward will let go eventually. Take my word for it. And boy isn't that an exciting day.

With the size sail you've drawn that certainly is going to be a flying proa, not counting the Bruce foil you're going to fly the ama, that won't be a sedate cruising boat. You say you're steering with a sweep but you don't say where the sweep is set; if it's to lee of the vaka in the traditional manner you'll have to have someone along to sit on the ama in anything over ten knots, I would think, or you'll want some water ballast out there. Which brings us back to the ama size. It might be funny to go through the proa_file archives and count the number of people who had to go back and build bigger amas; not just amateurs, either. The first Mbuli had a too-small ama, and John Harris knows what he's doing. You need more volume out there than you think.

That's a big sail. You need a good spar. A cheap spar will either break, flex like mad, or be really heavy. A heavy spar is not good during a shunt. I made my spar from two carbon windsurfer masts joined butt to butt, with several layers of tapered carbon cloth at the joint. It was strong enough but only barely stiff enough, I could bend the spar about ten degrees in fifteen knots of wind, the top of the sail would be way flexed off.

You have to control the spar tips swinging to windward/leeward during a shunt. You have to. Or they will try to kill you. This means, I think, that you have to have a line from one yard end to a block on the the bow, along the gunwhale to a block on the other bow and up to the other yard end, intended to more or less keeps the spar parallel to the vaka while shunting. And this means that the spar can't have much, if any, prebend in it. My spar had 18" of prebend. Very bad idea. Very bad idea indeed. I thought it looked cool or something, I don't know what I was thinking, and it seemed to make the spar stiffer. But it also acted as a sort of sheet; if the lower spar tip started to swing to windward during a shunt, and it did, the tips and the masthead were not in line! So the lines to the upper tip acted as a sheet. So instead of swinging a sail around above my head, I was swinging a powered up sail around above my head. Sigh. Very bad idea. Once again, something I came up with, stick to Gary's drawings. Perhaps it's becoming clear to you that if I were really determined to make a Gibbons rig work I'd pay him a few bucks to draw me one and stick to the drawings, or I'd buy his book and build a Wa'apa or a T2.

Finally, that's a big sail. If you're determined to make a Gibbon's rig work on the boat, you might think about building a smaller one to teach yourself to handle it first. I promise, even a 70 ft^2 Gibbons will be fun and lively to sail, and will be much easier to shunt than your big rig as drawn, and you may find out it's all you need or want. That's a really big sail you've drawn.

Finally, really finally this time, I've said a couple of times "If I were determined..." and "If you're determined...", implying perhaps that I don't think it's a good idea. I don't, really. A Gibbon's rig in this size is a hot rod, it may be a great rig for a hot beachcat style boat if you're smart enough to rig it right and determined enough to get through the iterations to make it work, but on your boat I'm not sure it fits. If I were you I'd put a crab claw on that boat, or a schooner. I love my schooner. A crab claw may suit you better, for one thing you can then steer with a sweep and avoid rudders. At that size I think a crab claw is easier to shunt than a Gibbons, has a lower CE, the CE is still well forward which is good, and it can be brailed up in a second if you get in a tangle and shunting can be done in a leisurely and relaxed way. Have you seen this video:

http://www.youtube.com/watch?v=YQ-YF7AXW98

? Man that's a nice boat.

Good luck, hope this helps,

Kevin

 

Ping-Pong proa

Sent all my pictures of Ping-Pong proa here:

http://picasaweb.google.com/terhohalme/PingPongProaConstruction2002#

http://picasaweb.google.com/terhohalme/PingPongModification2005#

Trevlyns, you can find there some hints of building stitch & glue boats.

 

Thanks Terho. Very inspiring pictures.
Have she ever surfed in big waves?
Have you tryed any, more efficient rigs then the djonk rig?
Will we get to se a larger version?

 

I have a few questions also Terho.

You modified the height of the crossbeams. Was that because they were occasionally hitting the water?

Have you ever sailed it with the windward hull coming out of the water or just grazing the water?

Am i correct thinking you have two passive (as in they do not have stays going the other way to counter the tension) stays to windward?

It seems you had breakage. Why and how did it happen?

How does the double sheet system work? As in you seem to have one coarse pitch loop and then another loop for finer trim...is that correct?

I saw you made three foils but could not see where or how the smaller foil goes/works.

I very much like the build - very simple and straightforward but well done and sturdy. Congratuleren. Hope you get a lot of use out of it.

 

Ping-Pong was originally designed for a lake boat. After we moved on the south coast of Finland and sailed him along Baltic Sea we notised the bridge box stucked in the water (what did not happen on the lake). Also the rudders were too small and ventilated easily (as they act like daggerboards too) so I made the bigger ones. They worked perfectly.

The windward hull (bigger one) never lifted out of water. Windward hull is quite heavy (with sailors) and junk sail is very easy and fast to reef. We occasionally sailed well over 30 knot winds. Maximum speed was 14 knots, (just me) and 12 knots when cruising.

First we had stays only to windward hull ends. Once I was returning to our marina from test sailing just a day before our sommer holiday course. A recue boat of the fire brigade came towards and made big waves. They pased me and saluted. Their big waves rolled me so violent that the rotten mast falled down. The sceen was like from a pirate movie. Nothing else get broken and I survived unhurt. The rescue boat didn't even noticed what was happening. I made a new mast from aluminium tube and off we went to our cource as planned. After he mast failure I increased stays to all four bows. The mast failure was a result of many experiments of rigging equipment. Water got in the epoxy coated wooden mast through many drilled holes and the mast rottened in few years.

Double sheet was an exellent solution, coarse rope for fast shunting and fine rope for trimming. Coarse loop needed two decent cleats. Later the sheetlets was about half a meter from the end of the battens and worked better there.

The Admiral judged: no more proa, so I am building a catamaran now (Catharsis 27).

 

Ditch the leeward pod or be prepared to fill the cabin in order to right.

Where is your downfoil attached. If it is to the ama consider what pitch input it gives.

It is not a catamaran, you don't need to unstress the beams. If you have good pitch control on the ama then maybe pivoting it is useful.

You could possibly have sheet going to laterally tilting foil, releasing when no pressure.

Have pitch authority of vaka or have tall beams. 35cm is wet in no weather at all (even if motor drive lifts the bows) but 45 may be fine if you have similar bows to mine. My beam is almost 3m behind stems. Bows are narrow at waterline but grows a useful bit upwards.
6m by 40cm cat, some rocker, 3m BOA, 100kg+, empty. 11kt on 6hp.

Finally ditch the rig (or make it for very light wind), buy a kite and reinforce your board(s). (And you may want to put vaka to windward)

1/2m long Kun Fett, towed: