Author Topic: Trimming Question on my Electric Powered Legacy 40 (Read 7595 times)

Brett Buck · « **Reply #50 on:** September 08, 2015, 01:40:35 PM »

Quote from: Doug Moon on September 08, 2015, 01:05:08 PM

Yep. With the flap slightly deflected down, with the elevator slightly up or close to neutral as possible, a line drawn from the LE of the wing to the TE of the flap gives the wing a positive AoA and the plane gets off the ground while the fuse is maintaining a level flight attitude.

That is all true, however, it works without the flaps, too. In that case the camber remains zero. Either I am misreading your previous comment, or it doesn't seem correct. You do not need camber to create lift.

Brett

Howard Rush · « **Reply #51 on:** September 08, 2015, 02:08:53 PM »

Quote from: Doug Moon on September 08, 2015, 01:05:08 PM

Yep. With the flap slightly deflected down, with the elevator slightly up or close to neutral as possible, a line drawn from the LE of the wing to the TE of the flap gives the wing a positive AoA and the plane gets off the ground while the fuse is maintaining a level flight attitude.

That is not a very useful way of looking at it. In level flight an airplane needs enough lift to balance its weight. It's more useful to look at lift vs. fuselage angle of attack (coinciding with flaps-zero wing angle of attack for stunters). A line drawn from the wing LE to the flap TE has no particular aerodynamic significance. The relationship between lift and a line drawn from the wing LE to the flap TE (at some place on the wing) is something you could possibly use along with airfoil shape and dynamic pressure to figure the relationship between fuselage angle and the direction the airplane is going, but nobody who does any calculation uses that convention.

Doug Moon · « **Reply #52 on:** September 08, 2015, 02:53:56 PM »

I going to gracefully bow out.

Igor Burger · « **Reply #53 on:** September 08, 2015, 02:56:35 PM »

Quote from: Howard Rush on September 08, 2015, 02:08:53 PM

The relationship between lift and a line drawn from the wing LE to the flap TE (at some place on the wing) is something you could possibly use along with airfoil shape

0.11 * (alpha + c * 0.11) ?

Tim Wescott · « **Reply #54 on:** September 08, 2015, 03:06:24 PM »

Quote from: Doug Moon on September 08, 2015, 02:53:56 PM

never mind

I knew Howard was going to get all picky.

Crist, did you get your question answered sensibly before we spun off on this (admittedly quite fun for me) tangent?

Crist Rigotti · « **Reply #55 on:** September 08, 2015, 05:51:24 PM »

Quote from: Tim Wescott on September 08, 2015, 03:06:24 PM

I knew Howard was going to get all picky.

Crist, did you get your question answered sensibly before we spun off on this (admittedly quite fun for me) tangent?

Well Tim, I can't remember what the question was!

Crist Rigotti · « **Reply #56 on:** September 11, 2015, 01:01:42 PM »

I took it out today and no joy. Same as before. Time to get the #11 Xacto out.

Crist Rigotti · « **Reply #57 on:** September 11, 2015, 02:36:59 PM »

The epoxy is drying. Then more epoxy, etc. Then on to refinishing.

Paul Walker · « **Reply #58 on:** September 11, 2015, 04:09:57 PM »

Does this mean that you cut the HT out and put it back in a 0 degrees incidence?

With electric, you don't have to make it pretty before flight testing it. Once glued in enough, I would be back out to test before spending any time refinishing.

Target · « **Reply #59 on:** September 11, 2015, 04:22:33 PM »

Me too, and good luck Crist.

Crist Rigotti · « **Reply #60 on:** September 11, 2015, 05:05:29 PM »

Quote from: Paul Walker on September 11, 2015, 04:09:57 PM

Does this mean that you cut the HT out and put it back in a 0 degrees incidence?

With electric, you don't have to make it pretty before flight testing it. Once glued in enough, I would be back out to test before spending any time refinishing.

Yeah Paul, the HT back down to zero degrees. After a few more repairs, it'll be ready to fly again. Hopefully the weather will cooperate this weekend for further test flying. If it won't then I'll just have more time to refinish!

Crist Rigotti · « **Reply #61 on:** September 11, 2015, 06:10:00 PM »

I just checked the weather. Looks like Sunday afternoon for the next set of test flights.

The wing, motor, and stabilizer are all back to zero-zero-zero. We'll go from there. I'll bench trim it with neutral elevator too. Stay tuned. I'll post some pictures of what I did to lower the HT to zero a little later on.

Crist Rigotti · « **Reply #62 on:** September 11, 2015, 10:12:45 PM »

OK, some details of how I lowered the stabilizer LE 1/32". With my #11 blade I cut above and below the fillet. This way the cut will include the stab platform inside the fuselage sides and will only cut through the sides and the 1/4 TRI stock. Then I cut along the LE. This was the tough part. I also used a hacksaw blade to cut the bulkhead in half and to have enough saw kerf of 1/32 that I needed to lower the LE. I then took my #11 blade and cut into the vertical fin because it was glued onto the top of the stab. I used an Exacto saw blade removed from it's holder to do this. I think Zona Saw has one like this but I don't own one. Once the vertical fin was cut in half, the LE could then be lowered the 1/32 that I needed. I used 15 minute epoxy forced into the bottom slots on each side then jigged till it was cured. I then added some thin CA to where the vertical fin was cut and filled the gaps with balsa and Gluit glue. When dry, I cut the excess balsa away and sanded the areas with 80 grit then 320 grit.

I then used some AeroPoxy Lite filler and applied it around the repaired areas smoothing with alcohol the best I could. In the morning, I'll sand the area smooth and reapply the filler as needed. When done, I'll go on to the doping refinish.

The pics should show how it all worked out.

Crist Rigotti · « **Reply #63 on:** September 11, 2015, 10:17:52 PM »

The rest of the story......

Crist Rigotti · « **Reply #64 on:** September 14, 2015, 05:12:08 PM »

All done with the paint touch-up and clear. Tomorrow I'll test fly it.

Target · « **Reply #65 on:** September 14, 2015, 06:59:59 PM »

Good luck! Hope it's damn near prefect!

Crist Rigotti · « **Reply #66 on:** September 14, 2015, 07:28:14 PM »

Thanks Chris. Full report after test flights.

Paul Walker · « **Reply #67 on:** September 21, 2015, 02:58:16 PM »

Quote from: Crist Rigotti on September 14, 2015, 07:28:14 PM

Thanks Chris. Full report after test flights.

It's been awful quiet since your last post....

Did things not go well?

Crist Rigotti · « **Reply #68 on:** September 21, 2015, 05:49:54 PM »

Quote from: Paul Walker on September 21, 2015, 02:58:16 PM

It's been awful quiet since your last post....

Did things not go well?

Paul and others,

Last Tuesday I had a chance to try it out. The air was very bumpy but I was able to fly a few 1 minute flights. It looked promising, but I had to leave for Cleveland on Wednesday morning. On Friday, I was able to do several more 1 minute flights getting things better but again the air was very bumpy. Then that evening, the air was great and I flew more full flights. I flew it in competition on Sunday. First flight was in nice conditions, and the 2nd flight the wind had come up but I scored a lot higher! Bottom line is that the airplane is flying real good and in the correct attitude with equal turn rates in both directions. Lowering the stab did the trick. Of course, there is more trimming that needs to be done.

john e. holliday · « **Reply #69 on:** September 21, 2015, 06:49:05 PM »

So did you win?

M. Scott · « **Reply #70 on:** September 21, 2015, 06:59:30 PM »

Hi Crist,
I will be out this Wed. & Thursday about sun up till noon if I can help.

Crist Rigotti · « **Reply #71 on:** September 21, 2015, 09:17:38 PM »

Quote from: john e. holliday on September 21, 2015, 06:49:05 PM

So did you win?

Nope, last place as a matter of fact. The last 3 places were separated by 1.5 points.

Crist Rigotti · « **Reply #72 on:** September 21, 2015, 09:19:38 PM »

Quote from: M. Scott on September 21, 2015, 06:59:30 PM

Hi Crist,
I will be out this Wed. & Thursday about sun up till noon if I can help.

Mike,

Thanks for letting me know, but I'm out of town this week. Next week for sure we'll meet at the circle.

Paul Walker · « **Reply #73 on:** September 21, 2015, 09:37:52 PM »

Glad to hear that the issues have been resolved.

I have never had a plane that liked incidence in the HT.

Good luck on your final trim settings.

Crist Rigotti · « **Reply #74 on:** September 21, 2015, 11:02:18 PM »

Quote from: Paul Walker on September 21, 2015, 09:37:52 PM

Glad to hear that the issues have been resolved.

I have never had a plane that liked incidence in the HT.

Good luck on your final trim settings.

Thanks Paul. I've been reviewing your articles in SN. BTW, good article on flying in the wind!

Paul Walker · « **Reply #75 on:** September 21, 2015, 11:35:27 PM »

Quote from: Crist Rigotti on September 21, 2015, 11:02:18 PM

Thanks Paul. I've been reviewing your articles in SN. BTW, good article on flying in the wind!

That was only part one. A mere 6000 words await Bob to publish in SN for part two.

Crist Rigotti · « **Reply #76 on:** September 22, 2015, 06:27:39 PM »

Quote from: Paul Walker on September 21, 2015, 11:35:27 PM

That was only part one. A mere 6000 words await Bob to publish in SN for part two.

I would like to personally thank you for the trimming articles and appreciate you taking the time to share your thoughts with the rest of us. I know it's a lot of work. Thank you.