(Duplicate post from the US1meter yahoo forum)
Its been about 5 years now since I have last posted to the forum. Life got busy with 2 children and buying a house. With that out of the way and a proper basement shop setup, hopefully I can get back into building.
As my first post back, I wanted to share my latest shop acquisition and potentially make its resource available for others to use.
I was fortunate enough to come into possession of (the late, great and infamous US 1 meter character) Hal Robinson’s flow tank designed to study flow around scale size foils (keels and rudders). Beyond the sentimental value it really is neat to be able to examine the stall conditions of different potential keels and rudders.
I have uploaded to the “photos section” 2 pictures of this setup as well as a couple example photos of a test specimen. They are in a folder called “Hal’s Flow Tank”
Photo11 is of the front of the setup with the two larger controller boxes on the middle shelf. The first controller is for the speed of the tank; the second is for the intensity of the linear light source.
Photo12 is an overhead view of the tank to show the layout.
-When filled, the outer section contains water and the center section remains dry. In the upper right hand corner you can see the top of the trolling motor that provides the flow.
-Flow goes counterclockwise.
-The trolling motor is mounted in a special cowl designed to deliver non-spinning flow by the first corner.
-Each corner has flow diverters to soften the corner effects on the water. In the bottom left hand corner there is a wire screen to which another diffuse/flow straightener is normally mounted (currently removed).
-The test section sits in the front section slightly right of center.
-The test section is intentionally made narrower in the front to increase the flow rate through the test section.
-Above the test section is a narrowly focused linear light source that illuminates a very thin plane of light along the sample’s chord for study.
-Flow is visualized through very fine silver powder mixed into the water.
This particular test sample is a cut off of a windsurfing skeg that Hal was evaluating as a potential keel. Results on this sample were quite disappointing. As can be seen in the photo titled test10.jpg, due to a flat spot on the trailing edge, this foil develops a circulating back flow at very low angles of attack.
Currently the tank is only set up to measure angles of stall and flow reattachment after stall at low speeds. Hal was studying foils on the edge of stall condition as he was exploring the fact that when we are sailing fast and pointing, we are always on the hairy edge of stalling.
As Hal regularly opened up his house for others to come over and work on boats and use all of his tools, I thought I would open up my virtual door to others as well. If anyone has test samples they would like to study for stall effects, please feel free to contact me. If anyone is in the metro Boston area that would like to see and use this first hand, please feel free to set up an appointment.
If there is interest, I can try to shoot a video tour of this setup running the next time I have water in it.
Minuteman Model Yacht Club.