Scale Model Testing of Sailing Rigs, ...Outdoors

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....

 

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

 

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.

 

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

 

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

 

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

 

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

 

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

 

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

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

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

 

Some of my latest thoughts....

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

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.

 

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....??

 

Sail Shape, via broadseaming or what?

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

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??

 

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

 

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

 

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?