Scale Model Testing of Sailing Rigs, ...Outdoors

[brian eiland]

First of all the keywords here is 'outdoors'. Most of us know of wind-tunnel testing on scale models, but wind tunnels themselves are expensive, and time spent in them is expensive. And scaling the results up and down can be a little hit or miss, depending on the scaling 'factors' utilized. So nix the wind tunnels at this point, and lets go to the great outdoors.

I'm looking to perform some far less sophisticated, and far less expensive, side-by-side comparison testing of several different sailing rigs. In this particular case I am just interested in the sailing rigs themselves, not the vessels they are attached to. And since the vessels I have in mind for these rigs are large multihulls, I wish to forgo any heeling considerations. (this should make things even easier)

Many years ago I recall seeing some photos and diagrams in a book by Marchaj and in some publications by the Amateur Yacht Research Society wherein a number of folks where experimenting with different size, small scale rig experiments right out in the great outdoors. Regrettably I no longer have any of those reference dwgs/photos/illustrations.

So I am asking for suggestions and drawings, and whatever,....to make this comparison testing on an inexpensive budget, now that I am retired on a budget. The one advantage that I do have being 'retired' is that I now have a little more free time to do some experimenting.

I have over a good number of years promoted a 'radical' aft-mast sailing rig configuration, and along with that a long ongoing subject thread:
http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623.html
I've had a goodly number of naysayers posting things like it won't point up into the wind very well, and the backstay tensions are too big, etc.

I want to build 2 test models to be demonstrated right next to one another in the same existing conditions. One rig will be my mast aft configuration, and the other will be a fractional rig sloop of the same sail area....like this

http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623-7.html#post198605

Here is one way I am thinking. These will be 'rig only' models that are attached to flat base piece of plywood that might be circular in shape, or maybe just a rectangle approximating the deck of a multihull vessel. These plywood 'bases' will be able to rotate about their centers in order to encounter the prevailing winds at different inclinations. At the moment I have collected a couple of large diameter PVC tubes that might be incorporated to provide the rotating base to the flat plywood bases, and concurrently get these model rigs well off the ground. I might even be able to attach a tiller arm to the rear of these plywood bases and 'helm them' to their optimum sailing angles.

To keep things reasonable I'd like to keep these model rigs down below 6 foot tall from the plywood 'decks' to the top of the mast? I'm also hoping to fabricate the mast tubes with very minimal size and strength tubing in order to demonstrate that my method of rigging this mast will support a 'normal/conventional-size' mast tube.

So pile on guys, give me some ideas how I might build these test rigs, and what size??




PS: I recently unpacked this model of the vessel I took down to the Miami Show in 2005, and it got me hot on the idea again.

 

[messabout]

Brian, explore the AMYRA website to find a list of suppliers. You can get nifty extruded aluminum mast sections that are similar to Proctor or other types of masts. They have slots and all the scale features. You can also find suppliers fro Tri-spi sail material and all sorts of useful hardware to keep your models in proportionate scales.

Warning: you can easily fall victim to the model yacht virus.

 

[rwatson]

What is the proposal for measuring the performance of the rigs ? Are you going to be able to determine the propulsive force from the different setups ?

 

[waikikin]

What is the proposal for measuring the performance of the rigs ? Are you going to be able to determine the propulsive force from the different setups ?

Would be nice............. & fun to use identical floating multihull platforms, & be able to swap rigs & controllers then sail down on a pond/waterway in a race series of various courses & conditions........ even across a pool at different angles.... boat against boat..... rig against rig.... in the end, the winner gets a prize:idea:

You could get sponsors.... beer sponsors would be great,

maybe use an existing model race boat formula like this http://www.radiosailing.org.au/docs/2mrules-word.pdf

or something you can ride on but simple/comparable/cheap.... like old Hobie 14s

Jeff.

 

[brian eiland]

Brian, explore the AMYRA website to find a list of suppliers. You can get nifty extruded aluminum mast sections that are similar to Proctor or other types of masts. They have slots and all the scale features. You can also find suppliers fro Tri-spi sail material and all sorts of useful hardware to keep your models in proportionate scales.

Warning: you can easily fall victim to the model yacht virus.

Thanks for that info, I'll have to look that up. Do they have small scale tensioning devices that might substitute for turnbuckles?

At this stage I have no plans to build any model hulls, etc......no floating models.

 

[brian eiland]

What is the proposal for measuring the performance of the rigs ? Are you going to be able to determine the propulsive force from the different setups ?

Good question. I would like to be able to compare the drag experienced by each model in comparison, but don't yet know how that might be done in this test set-up apparatus.

 

[brian eiland]

Lightning class vessel experiment

Would be nice............. & fun to use identical floating multihull platforms, & be able to swap rigs & controllers then sail down on a pond/waterway in a race series of various courses & conditions........ even across a pool at different angles.... boat against boat..... rig against rig.... in the end, the winner gets a prize:idea:

You could get sponsors.... beer sponsors would be great,

maybe use an existing model race boat formula like this http://www.radiosailing.org.au/docs/2mrules-word.pdf


or something you can ride on but simple/comparable/cheap.... like old Hobie 14s

Jeff.

I'm sure RC boats can be fun, but also quite time and money consuming. I'm just not at that point.

I had given real consideration to performing some experiments with a Lightning class vessel....
http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623-25.html#post420909
http://www.boatdesign.net/forums/sailboats/19-lighting-sailboat-mast-stepping-39028.html

...but again involving a lot more logistics in such a project as a whole.

 

[brian eiland]

Stiletto 23 catamarn experiment

Frame structure for mast support on a Stiletto 23 experiment that was being contemplated...
http://www.boatdesign.net/forums/sailboats/aftmast-rigs-623-31.html#post451215

Never heard back if anything got done?

 

[messabout]

Thanks for that info, I'll have to look that up. Do they have small scale tensioning devices that might substitute for turnbuckles?

.

Yes, there are several varieties of mini turnbuckles, deck fittings, turning blocks, and all that good stuff.

 

[sharpii2]

I think sailing model boats are the way to go.

Two identical boats with the two different rigs, tried in as varied conditions as possible.

This, I think, will get you the most credible results.

Just make sure the balance is correct on both boats, so one is not stuck with an excessive weather or lee helm.

Other than that, you need to measure lift/drag ratios, which I expect to be difficult to do on a fixed structure.

 

[rwatson]

The easiest way would be to support the sails on a rolling platform on marbles or ballbearings in a big table with edges.

Then, attach pulleys at the most useful vectors ( from the stern, from windward etc ) and hang measured weights and see what they platforms pull.

 

[brian eiland]

Brian, explore the AMYRA website to find a list of suppliers. You can get nifty extruded aluminum mast sections that are similar to Proctor or other types of masts. They have slots and all the scale features. You can also find suppliers fro Tri-spi sail material and all sorts of useful hardware to keep your models in proportionate scales.

Warning: you can easily fall victim to the model yacht virus.

What exactly does that abbreviation 'AMYRA' stand for? When I googled it I did not get boat related subject matter.

I did get to this site AYRS, Amateur Yacht Research Society, and I sent them an email.
http://www.ayrs.org/ayrs.htm

(Sorry for some delayed response lately as I have been traveling on the road, and likely not home for several more days)

 

[mij]

Rig comparison

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.

 

[Doug Halsey]

What exactly does that abbreviation 'AMYRA' stand for? American Model Yachting Association http://www.theamya.org/

 

[messabout]

Forgive me Doug. I added an extra letter (R) without intent. Clumsy typing, misleading result, Yes?