Logarithmic device on flaps

The model is actually finished, if you are curiouse follow this link:

http://www.netax.sk/hexoft/stunt/the_max_ii.htm

Hi Igor,

This looks like a very innovative model in general! Your photos show some very nice workmanship.

I will be interested in your evaluation of the device. It does just the opposite of an Expocrank, which is slower around neutral and gets progressively faster with larger control deflections.

Keep us posted on your experiences with this device.

Best regards,

L.

Yes, Larry, I will, but I have only 6 flights until now (including engine break in ). But I plan to go to Sebnitz this weekend - it is a "warm up" WC 2002 contest so I will probably post monday.

Thanks Igor for all of the data you collect and share with all of us. Would also like to hear more about this device and if you feel it works, will it be available. Thanks again, BAD ANDY

Hi All,

I am back from contest in Sebnitz. It is rather turbulent place between trees. I did not have too much luck. The wind direction changed too often and after all I did all 3 flights against the wind, but it looks all others had similar problems, so I placed on second place anyway (19 contestants).

The model has some 20 flights now, and it is almost trimmed, so I do not expect any significant improvements anymore. In comparison to the similar model without the device I would say following:

1/ As I already wrote, the straight segments are very stable; round figures are nice smooth and round.

2/ I am used on sensitive models and I like to fly very sharp corners. My first impression was that the model with the device does not make so sharp corners. I already adapted myself after those 20 flights, but I still feel that I would like to fly it sharper. I asked several peoples for impression from outside the circle and they told me that it looks good – probably because of clean difference between the round segment of corner and very stable straight segment, plus its big advantage in suppressing waves after corners.

3/ I also explored that even in wind to the face the model is still able to make corners. Round figures was little more problematic thanx to changing line tension, but I do not plan to do it too often

4/ The model has no reserve in danger situation. I mean a moment when the nose is close the ground and still pointed down. It is because the device limits maximal deflection, so you cannot count that strong input will save you. But it is not a problem for those who do not sleep those 7 minutes

So now the only not answered question is lifetime of the device compared to the regular bellcrank, but this will take a time. Until now no signs of wear and device is still without a slop.

Igor,

Thanks for the report. I'm now better aware of what this device actually does, which I didn't quite grasp before. While the elevator operates pretty much as a normal setup, the amount of flap deflection decreases as control input increases.

Essentially you are decreasing the flap/elevator ratio as control input increases.

This differs from what an Expocrank does, which retains the flap/elevator ratio, and increases the deflection of both as control input increases. This makes an Expocrank less sensitive at neutral and more sensitive at maximum deflection.

I don't think you will have any wear problems, it looks like a well made mechanism.

Best regards,

L.

Hi Igor,

Very interesting idea!

Why don't you give us a demonstration of the setup at Herentals, Belgium, June 29th and 30th? International F2B contest, counting for the Worldcup. 5 judges, Lots of grass circles.

Great opportunity for that last practice before the World Championship! AND a great barbecue!

No reason not to come!

Paul

Hi Paul,

I can not come just because I am actually home. It is 1300km to you and it is too much. But it can happen that I will go to Oberhausen and in this case the models go with me everytime ... so we will see but it is for maximally 10%.

Larry,

You wrote:

>>>While the elevator operates pretty much as a normal setup, the amount of flap deflection decreases as control input increases.<<<
Yes, exactly said. The trick is in feedback, which is also decreasing with the ratio, and it gives the feeling of easier cornering.

>>>This differs from what an Expocrank does, which retains the flap/elevator ratio, and increases the deflection of both as control input increases. This makes an Expocrank less sensitive at neutral and more sensitive at maximum deflection. <<<
I do not think that the functionality is too different. If you will think of controlling the large model by force (better said by the moment on handle), it has very similar function. I tested my device also on small model with Saito .30. Unlike problems with engine run, the model performed well, but I did not feel advantage of the device so much as on large model. It can be because the small model with 4” bellcrank does not make such strong feedback. It could be that expo crank will be good way for small models, while Logarithmic device for large models. Could be worth of testing.