Scale Model Testing of Sailing Rigs, ...Outdoors

[Doug Lord]

Testing

Brian, if you haven't already get a hold of the latest issue of Professional Boatbuilder-page 66. There is a story on model testing with a neat towing set- up with some wireless data transmission....

 

[Jamie Kennedy]

You can tie off the a mooring and measure the total thrust for different apparent wind angles and wind speeds.

 

[brian eiland]

There's a ton of information on the Web pertaining to model sailmaking. I recommend the "Claudio Gadget." Google on the words
claudio gadget sailmaking for a start.

Since you're not worried about them getting wet, I'd use ripstop nylon from Goodwinds:
www.goodwinds.com
Earl

I'll look up that info when i get a bit more time, and get closer to trying this out.

Realize that I am thinking of utilized 'hard sails' rather then soft sail materials, in an attempt to eliminate another variable that might influence the test results,...the cut & settings of soft sails.

 

[brian eiland]

Are you sure you want to test outdoors where the only useful results you produce will be relative ones between two rigs? Have you considered using a long hall and an electric-motor-driven trolley to replicate the main functions of a wind tunnel. It won't produce wind shear, but the air flow should be constant and smooth. You'd only need to run the rig far enough for the air flow over the sails to settle down and then get a measurment of the force it's applying to electronic scales, the readout of which could be recorded throughout by a video camera. The rig itself would be attached to a second trolley sitting in a hole in the of the main trolley (to prevent it from adding its own drag), and it would have rubber wheels to ensure it can only move in one direction without rotation or sideways slip. You should then be able to measure the forces developed by the rig in any direction: you'd measure how much useful lift it produces by aligning the upper trolley in the direction the hull would be pointing (or at a variety of other angles to find the maximum lift), or else measure the drag by aligning it in the same direction as the main trolley underneath.

This would make my test much more complicated. I'll just repeat a posting I made earlier:

I'm liking your idea the more I think about it,.... now some thoughts.

I do realize that my rig is going to be the higher drag rig of the 2, if nothing more than its a 'ketch' with 3 sails rather than the sloop. So if I were to place the two experiments at an equal distance from the center of rotation of that big disc you suggested, its no doubt which one would win....not mine.

But what if I could make it so that the distance from the rotation center of the big plate could be varied,....then I might find a balance point that should be a good indicator as percentage of difference in the 2 by way of determining the difference in the radial arm of each rigs location on the plate :idea:

And that 'round plate' need not really be a big circular one, but rather could just be a 'rotating/swinging beam' connecting the 2 experiments.

In the end I might be able to show visually that my rig will point as high, at least, as the sloop (if it is commanded to do so). And I will have some good idea of the relative drag/propulsion forces between the two without having to physical measure those individually and then scale them up, all of which can suffer in mathematical scaling problems.

 

[brian eiland]

Brian, if you haven't already get a hold of the latest issue of Professional Boatbuilder-page 66. There is a story on model testing with a neat towing set- up with some wireless data transmission....

I recall seeing that article, but I don't care to enter the hull characteristics of the vessel into the equation.

I'm simply trying to dispel two notions that naysayers have voiced in opposition to my rig design,
...that it will not point good to weather
...that it will have excessive drag

 

[brian eiland]

Just a little note to myself about some model sail materials.

The jib and mainsail on the tri closest to the camera are made from 75 micron mylar
Rgds

 

[Doug Lord]

Brian, I added some more RC sail info on the second to last page, last post(scroll down) :
http://www.boatdesign.net/forums/mu...f-righting-trimaran-test-model-36058-154.html

 

[brian eiland]

Got it Doug, and thanks.
I'll repost it here in case I should forget.

Brian , here is more on RC sail material:

http://bbjsails.com/bulk-materials/

http://www.ec12.info/Sail Material.htm

https://www.siriussails.com/materials.html

Scott Morgan, Sails by Morgan(in Cocoa) has made all my sails for around 20 years. He made production RC sails for me in the late 90's including spinnakers. You might check with him to see if he has any triSpy mylar left or any suggestions. My next set of sails will be experimental cuben fiber(haven't talked to Scott about this yet) but it has drawbacks including wrinkling easy and cost but it is very light weight.
His phone is: 321-633-4275

 

[brian eiland]

Easy Foamboard Wing Airfoil: the Basic Version

Don't know that I will use this, but pretty neat idea :idea:

https://www.youtube.com/watch?v=qJZoqGHAIDE

Part 0 (a basic intro to the Armin Wing concept). A really quick and simple way to build an actual airfoil for an RC airplane wing. For a rectangular wing it's at least as easy to make and as strong as a KF airfoil and has the proven high-lift design approximating the "Clark-Y" airfoil used on many real and RC airplanes. Videos to follow will include improvements that take a little extra time but will make the wing more aerodynamic, water resistant, and have an integral control surface for flaps and ailerons. This is just the wing construction - overall airplane design is up to the builder!

https://www.youtube.com/watch?annotation_id=annotation_51333&feature=iv&src_vid=qJZoqGHAIDE&v=karr67ZYho4

https://www.youtube.com/watch?v=RgBSbnZh_KM

 

[brian eiland]

Some of my latest thoughts....

I like this idea that Mij suggested, but I have a few modifications to it.

If you are interested in comparing two rigs under identical conditions you could test them against each other by putting them on the same platform. For example, take a floating circular disk, put rig A on one side and rig B on the other and set them so that they are working against one another. The rotation and movement of the disk should give you some insight into how the rigs behave relative to one another.

I have acquired a long rectangular beam that will preform the same function as the circular disc suggested by mij. The sizable flat surfaces of that rectangular beam will allow for a bearing at its center that allows the beam to swing around.

At either end of that beam there will be mounted the two different model rigs,...one the std sloop model, the other the aft-mast model,...both of equal sail area.



These model rigs will be representing just the sailrigs themselves, from deck level up. The 'deck level' will be flat rectangular pieces of thick plywood onto which the mast and rigging attach. These flat pieces of 'deck' plywood will be mounted onto either end of that long rectangular beam, and they will be mounted by a single pin/bolt to that beam such that they are free to rotate (with some resistance) if commanded.
I want to make these two plywood 'decks' steerable with a tiller arm similar to that utilized in this video
https://www.youtube.com/watch?v=z91al4uBm9g

With this 'tiller steering option' I will be able to orient the rigs in two different manners,...
a) as Mij suggested, "put rig A on one side and rig B on the other and set them so that they are working against one another"
b) rig A on one side, and rig B on the other but both acting on the same tack. This will allow us to see a difference in tacking angle capabilities of the 2, and some differences in the drag presented by the 2 sailplans.
(I will provide for a few different optional pivot holes at the center of that long connecting beam that should provide for 2 different lever arms for the forces created by the 2 different sailing rigs.

 

[brian eiland]

The mast tubes themselves will be some small dia (.5 inch) alum or copper round tubing flattened into an elliptical/oval shape. Both rigs will have the same mast tube. The rigging will be primarily fishing 'leader wire'

The sails remain in question. There are a number of materials from which they might be made. But I have a few questions to ask of the naysayers as to the shape and sophistication of these sails to satisfy their 'demands' for accuracy.
1) Being that these are such a relatively short rigs (~6 foot), I do not see any necessity for modeling any twist in the sail shapes?

2) How much effort should there be to panel these sails to produce what optimum draft in the sails?

3) Perhaps it might be easier, and as accurate, to produce these model sails over a 'form' much as they do with the big boys in 3Di?
http://www.northonedesign.com/Technology/3DiExplained/tabid/20214/language/en-US/Default.aspx
.....ideas, suggestions....??

 

[brian eiland]

Sail Shape, via broadseaming or what?

...
The sails remain in question. There are a number of materials from which they might be made. But I have a few questions to ask of the naysayers as to the shape and sophistication of these sails to satisfy their 'demands' for accuracy.
1) Being that these are such a relatively short rigs (~6 foot), I do not see any necessity for modeling any twist in the sail shapes?

2) How much effort should there be to panel these sails to produce what optimum draft in the sails?

3) Perhaps it might be easier, and as accurate, to produce these model sails over a 'form' much as they do with the big boys in 3Di?
http://www.northonedesign.com/Technology/3DiExplained/tabid/20214/language/en-US/Default.aspx
.....ideas, suggestions....??

I'm up in the UNESCO port town of Lunenburg Nova Scotia on holiday from the FL heat, and I got to rethinking about the making of the sails for my model test. I ran across this discussion topic on another forum...
Broadseaming Theory

We realize that before this modern day of 3D lamination and load path making, etc that most real boatsails developed their shape in 2 manners,...shape built into the sails themselves,... and constraining the edges/corners of these sails. I'm concerned
primarily here with how the shape is built into the sails,...known for years as broadseaming. I've searched around quite a bit and I do NOT detect the utilization of 'broadseaming' in model boat sailmaking. What I do find is a lot of cutting along the edges of singular pieces of flat panel material to affect the shape of the sails when rigged to straight edge restraints. looks nice, but of questionable accuracy to get good drafts and twist etc in model sails.

Why be so concerned? If I really want to convince some of the naysayers about my aft-mast rig, I think I need to make the most convincing model of real sails for the two 6' tall side-by-side model rigs as I can,...And that means the most accurate draft-twist model sails I can build (hopefully without excessive expense).

I had been thinking I might be able to bend a large rectangular sheet metal piece int a nice smooth arch with something like a 50% draft shape, then lay out a piece of my model sail material (unknown exactly which material at this time), over this 'sheet metal mold' ,...and on a skew cut out my triangular model sails with varying drafts and twist from top to bottom.

But I had run across this website reference that sort of put a wrinkle in that plan...
Sail making http://www.onemetre.net/Build/Sailmake/Sailmake.htm

From my understanding of sail making, there are two ideas I want to contradict.

The first idea is that you can make sails by accurately cutting a curve on a panel, and then attaching it (stitching, gluing) to another panel. Well, while you might be able to cut a good curve some of the time, your fingers just don't have laser accuracy in them to stick A to B and you'll hardly ever obtain reproducible or reliable results. (It might be possible to butt-join the curved edge to another curved edge with a little more reliability, but this doesn't yield what the Equipment Rules of Sailing define to be a seam. Such a sail couldn't be used in sanctioned IOM competition, though it would be OK in a development class.)

The second idea is that you can drape your panels over a "camber board" and get a nice shape that way. Well, let me be clear about what I'm knocking here. I take a "camber board" to be a length of curved surface, where the curve is like the surface of a cylinder. In this case, your panelled sail will have exactly the same shape as a single un-panelled sail and, if you wanted a three-dimensional shape, you've wasted your time (though the result certainly looks the part).

Larry's booklet is the only source I know which carefully explains the use and construction of a sail block. I am sure that this is really the only way (in your garage, please, not in some specialist workshop!) to make professional sails, to obtain reliable and reproducible three-dimensional shaping, and to be able to tweak and change your shaping as you learn about the whole business.

Sail Blocks Analysis www.onemetre.net/Build/Sailblok/Sailblok.htm

Any other ideas as to a relatively simple way to build accurate sails for these 6 foot tall models??

 

[brian eiland]

BTW these sails I made for the display model were made by stretching plastic sheet material over a metal sheet mold, then heating it to set to a curved shape,....looks good, but not accurate.

Aftmast rigs??? https://www.boatdesign.net/threads/aftmast-rigs.623/page-46#post733497

 

[Earl Boebert]

Er, broadseaming is quite common in model sailmaking.

If you want an alternate method, Google on "Claudio gadget."

Or you can check the AMYA calendar for a major development class event in your area and drop by for a look-see. Marblehead (M) class boats have about 6 foot high sails and are very high tech.

Or you can order a set of sails from somebody like Rod Carr and analyze how they were made.

Cheers,

Earl

 

[brian eiland]

Er, broadseaming is quite common in model sailmaking.
If you want an alternate method, Google on "Claudio gadget."
Earl

That video was about as clear as mudd,...didn't show the special gadets. nor where he inserted them in the ends of the Claudio gadget after he removed the business cards.?

The EC 12's seem to be a fairly large class here in northern FL, but thus far I do not detect them utilizing broadseamed sails. Perhaps the old Model Yachting mag I was given recently is to old to discuss this?