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[red181]

I love tinkering and trying to improve performance, probably more than just sailing. Last sunday I got some rear facing camera onboard footage of the huntsman at speed. It was supposed to show the Gautby Road (Birkenhead) lake to put on an existing thread, but the camera was angled too low. What it did show was quite a suprise to me.

On the outside of fast turns, I was suprised to see how much water displacement there was, compared to the inside, which I thought would be doing all the work. You can see how this "V" shaped hull cuts the water. It suffers at speed from torque roll, and I was considering fitting a  trim tab to see if I could eradicate the torque roll, but after seeing this video I wonder if it would work? so any suggestions from the technical boffins amongst you would be interesting please

Compare the water displacement pattern to the much flatter and narrower hull of the Aerokits Fireboat, and the pattern in the water, I think its very interesting how different they are  

http://www.youtube.com/watch?v=FiIXQ_2rbwk

http://www.youtube.com/v/VXwfQ4s533I?fs=1&hl=en_GB

[TomTheKraut]

Hi Red,
I've checked both videos - and if I were you, I'd be proud of the Huntsman. Nothing amiss with the way she throws the water, especially nothing wrong with the displacement.
The Huntsman just creates a much bigger and continuous bow wave than the fire tender in the comparison video.

Attached three pictures (screenshots) that will explain much better than words could do...

[red181]

thanks Tom, great explanation, what do you think about a trim tab to eliminate torque roll, it rolls right, or do the fast boys just compensate with some tx  trim?

Thanks

[TomTheKraut]

Personally I don't like trim-tabs overly much because they create artificial drag in a discipline where everybody wants to avoid drag like the plague...
Is the Huntsman well-balanced laterally when just sitting in the water or going at low speeds, i.e. is the center of gravity exactly along the keel line?

If so and the torque roll is really only due to an "oversized" motor, try to add a small wedge under the transom of the lower side - in other words: make the bottom planking under the transom slightly asymmetric. I would use thin Balsa for a start, which would allow you to sand it down or add a bit of height at the lake, according to the results. Once you have established the required wedge size you can always make it more permanent.

Trim-tabs of the "modern" appearance (sitting behind the transom) are a definitive no-no for a classic like the Huntsman. The "speed wedge" solution has been used on IC-racers since the 1960s. If possible, check with some old-style racing guys, they might have a hint or two on this subject...

[HS93 (RIP)]

see you would not believe me 12 months ago.


Peter

[red181]

yes very well balanced Tom, thanks for reply, as HS93 has hinted ( ) he suggested the same with a wedge, it is an oversize motor, it was only when accidentally recording the wash off the rear that I realised how much water these hulls move, and could it be improved!

I agree, a trim tab probably would look out of place on a 1960's cruiser

Thanks

Paul