I started this thread because I have some questions about both the 80 sqft sprit and 90 sqft balanced lug. I thought a new thread would be better than adding more posts to the one we already have on Building the PDR.

To start things off:
Michael. In your sail design for both the sprit and balanced lug you don't use darts. You add curves to the luff and foot or head and foot only. Michalak, I think it is, gets quite convoluted in his sail designs and divides the polytarp into many triangles. About how much draft does your spritsail and your lugsail have? In the videos I have seen the sprit and it seems to set very well. Are some sail designers getting more complicated than necessary or does it depend on the material used?

Am I correct in assuming you reef the spritsail by removing the sprit and wrapping the sail around the mast and using it loose footed without any sprit at all?

What is the preffered method for setting up the balanced lug with the minimum number of strings but still keeping lazy-jacks for ease in reefing? I'm asuming 4. Halyard, Downhall, Lazy-jack adjuster and Mainsheet. the parrels should take care of themselves.

Does anyone have more links to PDR videos specially any showing the boat underway using the lugrig?

Finally for general consideration: I use Firefox for my browser and I have downloaded an add-on called "DownloadHelper" that lets you download the .flv videos from YouTube and other sites. I also downloaded "Freez FLV to AVI/MPG Converter" I enjoy looking at the PDR vids and now I can, without logging on and waiting for them to load every time.

The demonstrated performance and stability of such a small, simple boat is impressive.

CN.

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Have you seen my Goat Island Skiff pages? The vids there will show you the lug rig under sail, and that's the same rig we flew on the PDR.

The sails are pretty baggy now (after 15 years) but were very flat to begin with.

Michael will no doubt improve on what I have to say, however:

Sail shape is a constantly moving thing, depending on wind pressure, rig tension, and movement in the spars. Lots of boats have rigs which rely on controlling the amount of tension and spar movement to maintain the sail in a working relationship.

A flat sail will work perfectly well (as you've noted) providing the designer has matched the luff curve of the sail with the expected deflection (bend) of the mast under various wind conditions. The luff curve gives the sail it's shape, and the mast bending as the mainsheet and snotter is tightened, or as a puff hits, will depower it automatically.

Are others making sails overly complicated? YES. That is not to say that racing sails on racing boats should all be flat, but when one is deliberately setting out to build a simple boat, why make things harder than they need to be? Every dart means one more place where a margin for error can creep in, and one more inefficiency.

If you'll pardon me for sounding harsh, lazyjacks in a tiny dinghy are just a nonesense. They are great for controlling a monster sail at sea short handed, but on an 8 ft boat, they are a completely redundant unnecessary waste of string!

Over to Mik for some sensible comment!

cheers,

P

Thanks for the response Midge,

I have seen most of the vids and pics of the GIS. Almost got those plans instead of the PDR. Point taken about the lazy-jacks. I have never used a lug. Had peaked spritsail, lateen, gunter. marconi (cat and sloop) and leg-o-mutton sails. 90 squares and two 10 foot spars in an 8 foot boat just seems a bit much to reef easily without a bit of string helping to hold things up. However I bow to your greater experience with lugs.

I know the balanced lug works great on the GIS. Just want to see it on the PDR up and running so to speak. The sprit sharpie sail seems much simpler and if the difference in performance is minimal I'll probably go with that. I also understand the spars and sail are "married", so to speak, so they work best together in varying wind conditions. Thankfully Mik has designed that in, so I just have to follow directions carefully.

I hear what you say about simplicity. I'm a firm believer in the KISS principle myself. Problem is the more I learn about boats and building them the more I realize how little I know.

CN.

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Howdy Cybernaught,

This is quite a big subject.

Basically if you buy sails from a sailmaker they use two mechanisms to make the sail made out of 2D material acheive a 3D shape.

1/ darts (normally called broadseams) at each of the joins of the different panels that make up the sail and

2/ luff round - where the front edge of the sail is cut to a convex curve and then when it is attached to a straighter mast (or other spar) the excess material is pushed back into the sail and appears as depth.

However a lot of money that you pay for the sail is for the sailmaker to use their extensive knowledge and usually software (though the better ones know exactly where they are going before they touch the software) to find the compromise that maximises performance.

This is the best way to go for performance and durability, but it is not necessarily cheap - though the product is often very good indeed.

The assumption is that a sail is made up of lots of small panels sewn or glued together.

However - what if we remove that assumption - and also remove the skill base? What if we want people to make the best sail that they can at home?

Add to this, that we can make the sail out of polytarp which is already big enough for the whole sail to come out of without having to join anything.

OK ... if you have heard and seen that the remarkable Mr Michelak cuts a sail triangular and then makes either a triangular fold or cuts a triangular dart in the forward bottom corner. This is a quick and simple way of getting some depth in the sail. Very quick and simple

However it is very focussed on the bottom part of the sail. Also there is no attempt to get the mast and sail to work together.

Sails and masts that work together are one of the big advances of the last 100 years (controlling sail twist is the second most important - you can hear my interview on this subject on Furled Sails)

the "luff" is the side of the sail that is supported by the mast.

If you use convex luff round only and put the round up against a straight-ish mast the curve will be pushed straight and the excess cloth go back into the body of the sail where its only option is to create depth in the sail.

Quite a lot of depth - the maximimum possible for that sail.

However if the mast then bends under the load of the wind or the rigging to match the convex curve in the luff exactly then the curve of the mast matches the curve of the sail and the body of the sail is completely flat.

So now in light and moderate winds the mast and other spars are relatively straight making the sail deeper in shape. The deeper a sail is (within reason) then the more power it can develop - so the boat is powered up.

In a gust when the sail would be too full for the ability of the crew to hold the boat upright - the mast will bend, soaking up some of the luff round, so the sail becomes flatter and generates less power - so the boat and crew can handle the extra wind without having to do anything.

The upshot is that the boat set up this way ... if it gets a gust ... it will accelerate cleanly and then when the gust ends the sail becomes fuller and it will maintain more of the speed.

This approach allows sails to be much bigger.

For example most PDRacers were struggling to carry 55 to 65 square feet when we came on the scene. We had a punt and reckoned that we could get away with a lot more than that so went for a crazy 86 sq feet.

Boats handled it well, though our initial masts were too bendy and we even broke one.

You can see the videos of the white boats sailing here. The fifth one down is called "Crash and burn" and has the mast breaking sequence - but note the mast bend when I am sailing upwind directly toward the camera. Those first masts were too bendy.

We did make the two original blue sails slightly differently in terms of luff round distribution as neither of us have made many sails before.

How did we work out the mast bend curve ... here is how.


We measured it taking an estimate of how much they would bend and me standing on the point of maximum bend to get something like the correct curve.

BTW it won't work so easily if rigging is going to prevent the mast from bending naturally - you would have to put the mast in the boat fully rigged and run a line from the top of the mast to the end of the boom and pull on the sheet and the vang about the same as in 12 knots of breeze.

So we re-engineered the masts to become the ones in the PDRacer plan and they are the well behaved ones on the yellow boats. At the same time the sail size was reduced because the luff round had to be reduced for the stiffer masts

Soooooo - here is the point...

While many conventional racing boat sails have little or no broadseaming (you can drop a Laser sail on the floor and there are very few creases - a sign of very little broadseaming) so they are made with luff round making almost all the shape contribution.

However you do need a bit of experience to work out the luff round - either that or have some useful measurements that you can scale up and down using basic engineering.

So ...

1/ If you have mast bend data the simplest possible sail that gives you gust response is one with luff round only. You cut the outline of the sail and do the seaming and patch reinforcing and ... done.


luff round and foot round cut.

Sail making for the polytarp sails here

2/ If you have no idea how the mast is going to bend and don't have enough knowledge of the boat to guess how the spars are going to bend ... then the Michelak "dart" method might not be the most efficient in terms of getting gust response, but it is "sure fire" and if you use the adhesive tape assembly method he suggests ... it might not be all that durable (even he suggests additional stitching if you want the sail to last) but geez they are fast to make.

However a very large part of the OZ PDR performance is because we have worked it all out and providing the mast is made with timber of around the same stiffness as ours then your sail will work as nicely as ours do too.

And still cost only $50 out of polytarp rather than paying $450 to $550 for a full professionally made sail.

A number of sailmakers have come out and said the sails cut this way won't work. But they clearly do - and quite well because we have gone to considerably effort to get the mast/sail unit working together to get "gust response".

Have a look at the videos and see how all the boats accelerate the moment the sails are trimmed correctly - after the tacks in the "Crash and Burn" video the boat just GOES, after doing the manouvers in the "donuts" video it accelerates cleanly as well. This is why the boats are such fun out of all proportion to their cost.

I am sure you can add more speed by having a professionally made sail out of proper sailcloth - but that is banned for racing under the OZ PDRacer rules.

We want everyone in the class to use $50 sails or get these simple sails put together by tarp makers or friendly sailmakers for a couple of hundred dollars. If we allowed the option of more expensive cloth then it would be impossible for people to build sails at home to compete with the knowledge and computer power of sailmakers - not to mention the skilled labour.

So the basic cost of a PDRacer would increase by $450. Considering that with good scrounging skills you can build the whole thing for around $350 ... it just doesn't make any kind of sense.

Michael Storer

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The triangular sprit sail is not designed to reef. It is really a racing sail - though I had no problem at all in the 20 to 25knots and more at Goolwa. The reason I took the boom off and wrapped the mainsail around the mast to reduce the sail (probably only works reaching and running) was simply because I didn't want to come back into the tiny "corral" where I had launched at high speed. If there had been an unobstructed beach to land on I would not have reduced sail at all. In fact I had gone into just such a beach a bit further up so I COULD reduce sail.

http://www.pdracer.com/records/speed/mik/index.htm

though the three boats in West Africa used it for their maiden sail too



The lug is designed to reef. The boom is rectangular in cross section which gives plenty of space to attach a couple of cheap blocks to allow the sail reef/s to be pulled down to the boom.

Usually small boats only go out for a few hours and people choose their weather and (also) they are often not too far from shore. All of these factors conspire to mean that most reefing will be done ashore at any rate.

Michael.

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G'Day Michael,
When you answer a question you're very thorough about it.

Thank you for the response. I understand your points and on previous sails I have used both darts and curved edges to get draft. The sails worked ok. How well is questionable. I made them smallish to avoid overpowering, specially on the sailing canoe because reboarding after a capsize was a real chore and was impossible without a paddle float. This makes sailing in light breezes boring but safer in the stronger winds. I see the lug as a way around this. Which you pointed out also. Sail reefed in moderate to strong conditions and use the full sail in light airs.

Part of my situation is this. I have access to Maylasian lumber that is of poor to lousy quality. I can probably get fiberglass cloth and polyester resin in Cebu, somewhere, but not sure and I doubt it will be easy to find epoxy resin. I'll check into ordering it from Manila??? Repeating your methods and getting the same results is questionable. More so when you look at my skill level and lack of patience. The widest polytarp, locally, is 8 foot here so I'll be making joints. Not a problem. I've done it before. Getting the mast right is my biggest concern.

In the docs for the PDR lugsail you put curvature in the head and foot of the balanced lugsail, the only sides with spars. From what I have read, I was under the impression, before, that with a balanced lug the amount of twist was a product of downhaul tension (luff tension) and that the mast should be relatively stiff. For best performance most of the time and specially going to wind? I thought with a 3 to 1 mechanical advantage on the downhaul and jam or cam cleat to make adjustments quickly that sail shape could be dealt with adeqauately. Though not automatically as with bendy spars. Am I correct in assuming that mast bend is a bigger factor with the PDR sprit than with the PDR balanced lug?
I'm not trying to question what you say I'm just trying to understand my options. You said in the interview that you saw "perfomance" as one of the biggest safety factors in sailing and I agree 100%. I want decent performance, however, with available materials it will be at the cost of some compromize. In the end I'll do my best and I'll live with the results.

I have looked at many videos of the PDR and GIS, inlcuding the manouverablily videos, Crash and burn, Capsize drill, Twilight sail, and may others. I have downloaded the good ones and converted them to .MPG format so I can watch them off-line and not have to wait for them to load. I also downloaded your interview #129 but I haven't found the second interview yet. I'd like to download that also. I really enjoyed the first one and put it on my Zen Stone. (I-Pod like device) There are two .MPGs, the Yellow boat on the river and Capsize that I want to convert to 3gp and put on my Nokia 5300 Cell phone. Thank God for technology!

CN

PS. Off Topic: Should I forget about the PDR and just build a Goat?

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Howdy Cybernaught,

First interview was at
http://www.furledsails.com/article.php3?article=760

The second interview is at
http://www.furledsails.com/article.php3?article=761

MIK

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Howdy Cybernaught,

The edge round of any sail needs to be pushed straight(er) by a spar (or luff wire in the case of a jib) to push fullness in the sail.

With a sprit rig the mast is the most important influence on any of the edges - so that's where the edge round has to go - on the edge that contacts the mast.

With the lug - the curve needs to be along the yard in particular but some along the boom is useful too otherwise the sail can be too flat. The other option is to have a loose foot.

Downhaul on a lugsail or lateen sail cannot put fullness into a sail if it is not already there. However it can remove excess fullness if the spars are correctly dimensioned and the downhaul is strong enough. 3:1 and the cleat as you suggest is plenty. I use a truckies' hitch knot to give the 3:1.

With the sprit rig there are two adjustments that can help flatten an overdeep sail. Snotter or boomvang tension which bends the mast directly or downhaul tension that pulls the depth into a fold close to the mast.

All of these adjustments and sail shapings are just as important for both rigs.

The choice between the Goat and the GIS ... They are both great sailing boats (self promotion!!!) but smaller boats do get used more. When staying at Biting Midge's house we had 2 PDRacers and the Goat all part rigged on the lawn by the river.



It often seemed easier to get the PDRs into the water. However the sailing area at Midges is a little restricted - so the Goat can cover all the available ground in a short time. The other thing is the PDRs are so stable and forgiving and non-precious that almost anyone can jump in and take one for a sail.

Now to the Philippines

There was one fellow building a GIS in the Phils last year. I'll give him an email and see if he wants to respond about the materials.

However going through his emails

Here are some Phil's materials people
Boat builders that may have materials http://www.ecochest.com/customboats/materials.html

West System Epoxy - BD Marine Technology - Delbros Cargo Centre, - South Atlanta Street,
Manila, Philippines. 1018 - Tel: + 632 527 8141

If using a cheaper epoxy make sure
1/ it doesn't smell of thinners (a slight ammonia smell is fine)
2/ it is not 1:1 resin and hardener mix
3/ that you have to add a powder to make it thick enough to use. Prethickened ones can be a lot weaker.

Also there is a wooden boat builder's group in the Philippines with a forum. There are some great things and great advice but also some strange things and strange advice on their discussion groups - so run any changes/suggestions past me first. But looks like a best first stop for epoxy suppliers and timber species
http://www.pinoyboats.org

Good quality non epoxy marine glues and polyester for the glass taping and glassing of the foils are an option. However the performance of epoxy is so much better that it has truly superseded the older approach for light plywood boats.

You would need to discuss some of the details of construction with me if you didn't want to use epoxy to work out alternative strategies that would minimise problems.

Michael

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Considering the variety of bamboo there, what are the pros and cons of using that for masts and spars?

Richard

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Pros are availability and price.

Cons are getting the right stiffness for the yard in particular.

Completely unsuitable for the mast - won't be strong enough.

Also impossible to fit blocks to the side of for the boom to be reefable on the water (still recommend dropping the sail, reefing and rehoisting).

MIK

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Pros are availability and price.

Cons are getting the right stiffness for the yard in particular.

Completely unsuitable for the mast - won't be strong enough.

Also impossible to fit blocks to the side of for the boom to be reefable on the water (still recommend dropping the sail, reefing and rehoisting). The blocks and lines are so you can sit in the middle of the boat and gather the reef in by pulling on ropes attached to the sail and boom.

MIK

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Edna and I have been busy the last few days. We now have Vinyl on the floors in our bedroom, kitchen and the main living area. See! Contrary to what you thought not all the money goes on boats and boating.....

In our travels we hit several hardware stores and checked out the availability of marine ply. Everything up to 1/4" is the thick cored 3 ply stuff with veneers top and bottom. One place, and only one place, had 5 ply in 3/8" which was two thick cores with 3 veneers. Nothing to write home about I'm afraid. Here Marine doesn't necessarily mean "Marine". Hell! I''m not sure it even means waterproof. "Water resistant" maybe???

The spar stock was even a worse selection in my opinion. I wanted to get 2 pieces of 10 foot 1 1/2" for the the boom and yard of the planned lugsail. I'll do the ones for Aquila my punt as an experiment prior to The PDR spars. I figured I'd see if I can copy Michaels instructions about planing to a 16 sided shape, rounding and tapering the ends. I got the least crooked pieces I could find. It's green and heavy, not aged but without knots. Most of the stuff was just terrible. All the folks at the hardware store know is it's "Malaysian Lumber". What I got was the result of a 3 day search involving hardware stores in three towns, including the provincial capital. the store with the 5 ply 3/8" plywood and the one with the semi-decent spar material are about 50km apart.

Here is the boat I'm finishing up before I start the PDR. It was originally a 16 foot decked sailing canoe and now it's a 9 foot punt.



Yes. That's bamboo!

Michael, I'll be sending you an email soon with some questions and thoughts about my Oz-PDR.

tkr all,

CN

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i'm a newbie here. just got GIS plans from good people at duckworks. intended to start new thread but there is info here that's related to my query.

i'm here in the philippines and see not much problem in the build, thanks to detailed instructions of designer. but i see a hurdle down the line when sourcing balanced lug sail. is there any update on GIS builder also in the philippines who asked for quote from Hyde Sail (i guess the philippine operation based in cebu)? freight if sourced from duckworks in texas would be a killer.

the alternative is making my own. will polytarp do as quick as dirty sail? is the sail drawn in the plans laid flat? do i work in some camber and how much?

will holler for help when stumped after starting to cut wood.

thanks

agtawagon

Hi agtawagon,

Welcome aboard.

It's surprizing how well a polytarp sail can work if it's made right. Follow the links at the botom of any of Michaels (Boatmik) posts. He's probably written more about the balanced lug than anyone else on the net.

Here's an article on Duckworks that talks about tradtional rigs and performance.
http://www.duckworksmagazine.com/08/...rer/index1.htm

Here's one guy's way to build a lugsail from polytarp using duct tape.
http://www.pdracer.com/sail/page7.htm

If you get on Google you you should find plenty of info. I'm sure others will jump in with suggestions too.

Good luck,
CN

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Hi Agtawagon,

You could do a polytarp sail, but it might not last as long as it does with a PDRacer - purely because of the extra stability of the Goat Island Skiff.

Also because the Goat is so fast, using good cloth and a well cut sail will make a lot of difference - just because a bit more power makes so much difference.

I would think that the Hyde sails are in the Phils - so if there is a factory in CEBU then it is the one. (I just checked the net and it seems to be the right one) they should have the other guy's sail on their database, so should be able to give you a quote easily - just ask about a "Goat Island Skiff" sail. If you need a separate PDF of the sailplan to email to them, I can send you one.

Michael

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