stan simpson iv
Well-Known Member
- Joined
- Sep 5, 2011
- Messages
- 1,039
I will Protest the first boat I see at the next race that does this... HAS TO BE ILLEGAL!!!
![default_smile.png](https://www.intlwaters.com/uploads/emoticons/default_smile.png)
Lmao some will try to duplicate by adding who knows what on to there boatsI will Protest the first boat I see at the next race that does this... HAS TO BE ILLEGAL!!!![]()
Niklas, the slide can be minimised but not eliminated! Minimising should always be the aim of course!The easiest way to get rid of the fin flutter, of course, is to have a boat that doesnt slide in the corners...![]()
every time the prop hits the water it loads the fin . when it leaves the water it unloads the fin. I am thinking a good performing prop in the corners will load the fin more making a more pronounced pattern? Also the performance of the fin will make it more dramatic?
This is what I was thinking too. A great experiment would be to photograph a rigger the same day. One with a 2 blade and then a 3 blade prop. That has to be where the pulse are coming from. Even at 30,000 it is a series of very fast pulses which to our naked eyes seems seamless. But isn't. Same way a acoustic rpm meter works. To our ear it's a constant noise. But it isn't. But a test with a 2 blade and a 3 blade prop should show differrant patterns.every time the prop hits the water it loads the fin . when it leaves the water it unloads the fin. I am thinking a good performing prop in the corners will load the fin more making a more pronounced pattern? Also the performance of the fin will make it more dramatic?
I agree Mark but a 3 blade is taboo enough. Lol. A four blade would be even smoother.Danny,
A four bladed propeller would be even smoother to test with?
Does someone have a 67-Hydro to try and see if the fin pulsing can
be reduced with a different propeller set up?
I have some propellers for the test? Anyone want to try this?
Let Me Know?
Mark Sholund
231-590-3023
Email is: [email protected]
Guys, I think you would be on the money in summing it up
For the loading/unloading cycle of the prop to manifest in the wake of a turn fin, that oscillation would have to be translated through the tub, and I would think the booms would absorb a frequency like that. I've seen this sort of thing in machining where a milling cutter is running too fast on a thin part not supported between clamping points. Usually, all you have to do is lay a finger on the part, acting as a dampener, and it will go away (except in more severe cases).
This looks like harmonics to me. The old lead crystal wine glass trick, anyone?
Anybody remember any of the discussions from days past on rudder cross sections? If you have a double taper (leading and trailing), a vibration will set in so severe, they've been known to destroy servos. This can also be seen in rudder cross sections where the wedge terminates short of the trailing edge, leaving a parallel condition, meaning no load from the termination of the wedge on back. This cavitation will actually cause a rapid pressure/vacuum oscillation. Since our turn fins have this condition of the wedge terminating before the trailing edge, is it possible that this is just the nature of the beast and we're just noticing it? When the turn fin is fully positively loaded in a turn, it may not happen. When the fin is at least partially loaded negatively in the straights (I think most of us toe them in some, countering prop walk), it probably wouldn't present itself, either. But in those brief instances where the overall cross-section is at a truly neutral state, this high frequency harmonics may onset for a short time. This may just be the first time anybody has caught the boat right at that magic moment with a fast enough aperture time for it to show up. Different materials, thickness, length, depth, shape, anchor location, wedge profile, including wedge termination condition (angle, rounded, feathered) etc... even rigidity of the booms would all factor in and make every boat unique.
Thoughts?
Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine And Precision LLC
Some good points Brad.Guys,
For the loading/unloading cycle of the prop to manifest in the wake of a turn fin, that oscillation would have to be translated through the tub, and I would think the booms would absorb a frequency like that. I've seen this sort of thing in machining where a milling cutter is running too fast on a thin part not supported between clamping points. Usually, all you have to do is lay a finger on the part, acting as a dampener, and it will go away (except in more severe cases).
This looks like harmonics to me. The old lead crystal wine glass trick, anyone?
Anybody remember any of the discussions from days past on rudder cross sections? If you have a double taper (leading and trailing), a vibration will set in so severe, they've been known to destroy servos. This can also be seen in rudder cross sections where the wedge terminates short of the trailing edge, leaving a parallel condition, meaning no load from the termination of the wedge on back. This cavitation will actually cause a rapid pressure/vacuum oscillation. Since our turn fins have this condition of the wedge terminating before the trailing edge, is it possible that this is just the nature of the beast and we're just noticing it? When the turn fin is fully positively loaded in a turn, it may not happen. When the fin is at least partially loaded negatively in the straights (I think most of us toe them in some, countering prop walk), it probably wouldn't present itself, either. But in those brief instances where the overall cross-section is at a truly neutral state, this high frequency harmonics may onset for a short time. This may just be the first time anybody has caught the boat right at that magic moment with a fast enough aperture time for it to show up. Different materials, thickness, length, depth, shape, anchor location, wedge profile, including wedge termination condition (angle, rounded, feathered) etc... even rigidity of the booms would all factor in and make every boat unique.
Thoughts?
Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine And Precision LLC
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