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Old May 25, 2012, 08:13 AM
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Nice looking plane, Mike. Good luck with it this weekend!

Hey, how did you "waterproof the servo's with vaseline"? Just glom some on the outside?

Thanks!
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Old May 25, 2012, 08:23 AM
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I have designed several deltas with large rudders, both indoor and outdoor, and haven't seen the problem you mention. With expo and the correct CG, this shouldn't happen. I'm more concerned about the CG being right, since I have added a strake. Regarding waterproofing, I appled gobs of vaseline to the outside of the servos and dare the water to enter.
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Old May 25, 2012, 08:34 AM
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Thanks for the headsup on the roll info. We'll watch out for it. I have an ace test pilot who will maiden the plane.
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Old May 27, 2012, 03:40 PM
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FLYING REPORT of the Advanced Sea Dart: Today, we tested the Sea Dart off grass, and it flew very well, very stable, flew beautifully. The test pilot has a Polaris and he said it flies a little better than the Polaris. We did not experience a quick turn over with the rudder as Otto
predicted. I adjusted the rudder with modest throw and good expo, so the rudder acted about normal, about the same as any other plane. To get the plane to turn over with the rudder, it had to be very aggressive on the rudder, and the turnover was not quick. As long as the rudder was used for normal turning, there was no problem. We did find a minor problem when turning down the throttle for landing; the nose see to come up a little. Might have to mix elevator with throttle a little to prevent this, but everyone was happy how well and stable the plane flew. This is a very promising floatplane design. Next tests will be on water. It also demonstrated good thrust to weight ratio.The plane was capable of very tight loops. With this design, there is no slot/prop noise, totally eliminated. Pleasure to fly without slot noise.MIke
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Last edited by Mike St; May 27, 2012 at 07:48 PM.
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Old May 27, 2012, 04:48 PM
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Quote:
Originally Posted by Mike St View Post
FLYING REPORT of the Advanced Sea Dart: Today, we tested the Sea Dart off grass, and it flew very well, very stable, flew beautifully. The test pilot has a Polaris and he said it flies a little better than the Polaris. We did not experience a quick turn over with the rudder as Otto
predicted. I adjusted the rudder with modest throw and good expo, so the rudder acted about normal, about the same as any other plane. To get the plane to turn over with the rudder, it had to be very aggressive on the rudder, and the turnover was not quick. As long as the rudder was used for normal turning, there was no problem. We did find a minor problem when turning down the throttle for landing; the nose see to come up a little. Might have to mix elevator with throttle a little to prevent this, but everyone was happy how well and stable the plane flew. This is a very promising floatplane design. Next tests will be on water. It also demonstrated good thrust to weight ratio.The plane was capable of very tight loops. MIke
Great to hear of your success. You'll love it on water. Sounds like you need a little more down thrust vector to eliminate the pitch up on power reduction. The issue I have with the Polaris besides being very wet is the poor inverted characteristics. The SeaDart is much better.
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Old May 30, 2012, 11:26 AM
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Glad the Sea Dart is doing so well! I was surprised at the "extreme" downthrust on the motor. Most of my foamies have the prop shaft in line with the wing. Now with a sea plane, you have to elevate the motor ABOVE the wing (can't do prop-in-slot) so that moves the thrust line up. Is the down thrust to compensate for this elevated motor?
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Old May 30, 2012, 11:33 AM
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Mike, I'm looking again at your pix of the Advanced Sea Dart. Can you please point out the STRAKES?

"After designing many planes, my research has shown that a delta wing flies better slow with a strake or canard."

Not sure what I'm looking at...
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Old May 30, 2012, 12:16 PM
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OK, Steve the normal Sea Dart wing is a triangle, but if you note in picture 2, there is a slight strake, which breaks the triangle and intersects at the forward wing. Compare it to the normal Sea Dart, and you should see the difference.
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Old May 30, 2012, 01:35 PM
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AH! You're talking about the "innie" in the leading edge of the wing. I was thinking of a strake as something akin to a wing fence or the "fins" they put on jet nacelles.

Thanks!
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Old May 30, 2012, 04:20 PM
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No fins, just a change of angle to the center line. Improves slow flight performance. The Polaris has a strake; take a look.
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Old May 30, 2012, 07:13 PM
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Originally Posted by Flyboy Steve View Post
Glad the Sea Dart is doing so well! I was surprised at the "extreme" downthrust on the motor. Most of my foamies have the prop shaft in line with the wing. Now with a sea plane, you have to elevate the motor ABOVE the wing (can't do prop-in-slot) so that moves the thrust line up. Is the down thrust to compensate for this elevated motor?
It is all about forces and moments created about the CG. Every plane has a CG and most think of it in the front/back sense but it is really a 3 dimensional point in space. All aircraft forces act around the CG to create pitch, roll or yaw. In level stable flight everything is in balance. If your setup is for aerobatics you really want no pitch or yaw change from high to low throttle. Most passenger aircraft are designed to nose up slightly on power application as well as RC trainers. Wherever you place the motor during design you usually orient the thrust vector close or through the CG to minimize pitch effects due to thrust. If the motor is to the front or the rear this can be done. If the motor is midship, high or low, you create pitch problems that can only be resolved with flight controls. On the SeaDart, tilting the motor down at the correct angle, will result in little pitch change during throttle transients. I have never had an airplane perfect and generally shim the motor to get the response I desire. I usually trim the aircraft at high speed in roll, pitch and yaw so it is tracking true. I then make a pass and cut power and see where the nose goes. If it goes up power off what you learned is that there is up elevator compensating for pitch down thrust. On the SeaDart you would add more down thrust vector and remove a little of the up elevator trim. You do this a bite at a time until the plane tracks true. It usually takes 5 visits to the field before I get mine squared away. Approach yaw the same way and you'll be amazed the improvement this makes on any platform.
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Old May 30, 2012, 09:33 PM
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I shimmed the motor 2 more degrees down thrust to help eliminate the nose up on low throttle, and the rest I'll try to accomplish with battery placement and elevon trim. Should be ok. Somewhere's there's a sweet spot to handle all throttle settings, high and low
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Old May 31, 2012, 09:00 AM
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Thanks for the explanations on thrust line and CG. Had not thought of it in that manner before.

For a 4-screw motor mount, I've generally put the screws at 10, 2, 4, and 8. To be able to better shift the thrust lines for a pylon mount motor, should you rotate the mount and put the screws at 12, 3,6, and 9?

Also, thanks for the explanation on the wing strake. Any idea WHY it helps at low speeds?
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Old May 31, 2012, 09:27 AM
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Strakes and canards provide lift at the front end. I have a eurofighter which I believe is about the best pure flyer I know, and I've tested many designs with canards. When set up right, a canard is very sweet. Read up on canards and strakes.
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Old May 31, 2012, 09:40 AM
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I just googled canard, and found out it means "duck"! Then I thought about Otto's flying duck and his noise tests. Then I thought about your new Sea Dart. Then I got confused and my head hurts!

Actually, I found a lot of good info on canard wings. Interesting way to alter the aerodymanics of a plane.

Thanks!
Thanks!
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