Test model building

[ErikG]

If I were to make a scaled down model of a design for exterior evaluation and preliminary testing (ie. towing in real life instead of a tank).
Towing tank time is expensive. To be able to do some preliminary testing without having to build a fullscale prototype seems like a good idea to me.

What are the pitfalls or problems connected to this.

Are there any books that take up model building and testing as such?

Most grateful for any information

ErikG

[DavidG]

Suggest you look at Bethwaite "High Performance Sailing" who did comparative full scale testing of NS14 dinghies by towing two boats on a balance arm behind a power boat.

Without a tank, obviously a lot of precision is lost, you also need to consider that the laminar region is proportionally greater in model scale.

Be interested if you develop this, as cheap testing is a bit of a holy grail.

[ErikG]

Well as a beginner in yacht design. I can see myself spending a lot of time making up models with different afterbodies and such. To be able to measure the different drag and look at the wave components aft in the water I belive there is a lot to gain.
My idea would be to make 3-4 models and just do one tank test.
I really don't see a way to get a perfect result without the tank test.

Wouldn't it be great if we didn't have to spend all that money on tank tests?

I also believe that modelmaking can make up some of the knowledge that a newcomer lacks out of experience by watching models. As long as the size isn't to small. I'm thinking at least 5:1 (maybe I'll try a 10:1 also) based on loa of more than 10 m.

Sure the laminar resistance will not be comparable to the larger boat, but maybe there's a way around that to?


If anyoneelse has any opinions or ideas they are most welcome.

ErikG

Model testing helps you to undestand how does the hidrostatic(and also the trimed situations) of the hull works, in true scale!. They need to be done with the same tecnic and materials like in the reality, and if the speed and performance are not required, like in an cruizer sailboat, the aproach of the dinamics of the situation may be avaliate as well.

[duluthboats]

Erik,
I know Tom did some test with models out on the water before he built Liz. Maybe he can give some pointers.
Gary