FF kit being stubborn...

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Maxout
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Re: FF kit being stubborn...

Post by Maxout »

KingDelphinus wrote: December 2nd, 2022, 7:00 am Hello. I am having trouble understanding 6b in the rules. It states: ". A bonus of 10% of the Flight Time will be added to the Flight Score of an aircraft that has the entire surface of the wing between at least 2 ribs or at least one of the wingtip fences or a vertical stabilizer completely marked with black marker or black tissue. If no ribs are present, the whole surface must be black. Aircraft with no wings or vertical stabilizer must have at least one black-colored lifting surface". May someone further explain to me what this means and the purpose of this bonus?
It's a dumb rule and needs to be binned, but the purpose originally was to make the planes more visible at altitude. In reality it has proven uphelpful, but someone thought it would help in the higher sites (yes there are SO contests in 80-100' ceilings). Just do it, doesn't add more than maybe 50mg and it's a free bonus (or more to the point, consider it 10% subtracted from your times if you don't do it, because everyone else does do it).
bjt4888 wrote: November 28th, 2022, 8:28 am Moving the CG forward 1/8" can sometimes increase the circle size 25-50%. You'll notice that I have never commented on circle shift. This is pretty much always due to airflow in your flying site. Airflow is often in different directions depending upon the flying height or the flying location within the site and it's only a concern if you're getting shifted towards obstructions or being pushed down or up.

Keep using numbers in your reporting. I can help you with data analysis best if you give specifics. Instead of relating that you had no performance change regardless of how much you changed a trim, tell me that "I moved added 1 g of clay to the nose, with the wing st 6.5 cm back from the nose and all trim settings per the kit which shifter the CG from 2.125" in front of the TE to 2.1875" in front of the TE and this is what I observed during my glide test.

Be sure to do the glide tests per the method I mentioned earlier and add clay till the stall is almost completely gone.
I've actually flown a FF Div C plane now, and so I have some thoughts on the various phenomena. The marked CG is not the aft limit. The plane does in fact fly well at that CG location in mild turbulence. What I have noticed is that anytime it gets the nose down, it pulls hard to the right. This is a function of a design that relies heavily on enormous wing wash to provide a steady circle. My guess is the tiny horizontal tail is at least in part to blame for the need for so much wing wash. I was also unable to get the plane to fly without adding 1/20" incidence under the stab TE. Above a certain amount of wing incidence, the angel between wing and thrustline becomes so great that the plane will no longer respond to that adjustment in the power phase. I did find that with a correct CG and stab incidence, a good glide configured using wing incidence for fine tuning results in a good power pattern. I did need a goo bit of rudder trim to get the circle correct in cruise and descent, as thrustline alone was not enough to maintain a turn at low power.

Very important to anyone reading this, all of your ballast needs to go on the nose. Mark the CG target on the wing, load on a rubber motor, and then slide the wing around until the plane balances correctly.

Mine seems to want 3/32" rubber to fly efficiently in low ceiling environments. Were it possible to trim with less wing twist and less angular difference between wing and stab, I think it would be able to fly on less power, but that's going to require more research than I have energy to devote to the project.

Overall it's a good design that's not hard to fly. There are some nifty features in it and the build and flight process are fun. My video review will be out in a couple weeks.

-Josh
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Re: FF kit being stubborn...

Post by jander14indoor »

Well, to THESE old eyes, it does help see the plane in the tall sites. Especially when its the wing, tip fins or rudder isn't as helpful, but rule doesn't distinguish.

And like Maxout said, not doing it is a silly 10% to give away!

Jeff Anderson
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with 64 year old eyes!
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Re: FF kit being stubborn...

Post by pumptato-cat »

An update on my "stubborn" plane in case anyone else is having similar issues(taken from DMs-I am not going to share video links publicly, but if you DM, I can send them):

Hey bjt4888,
THE PLANE'S WORKING!!!!! THANK YOU SO MUCH!!!!
I figured out what went wrong... I was glide testing wrong and I thought the plane was diving.. it was actually gliding a little, and then diving after a very slight stall, but I couldn't tell. I can't believe it was this simple. I added ballast to the nose in increments of .05g until the "dive" went away and it's now flying much better, with pretty much all my problems fixed. I will send a video and update the forums for others to see how it was fixed(and avoid the dumb mistakes I made). AGAIN, THANK YOU SO MUCH!!!!!
Cat,

Looks good!

The instability you're seeing near the end of the flight is due to air currents and is not a trimming issue. You can tell this as the instability is not continuous and only occurs occasionally and at certain parts of the flight path.

tldr: I apparently have no idea how to tell the difference between stalling and diving :D So yeah, the FF plane isn't being stubborn or anything-I am. Oops! Hopefully this helps somebody else who has similar issues.
anything'll fly if you throw it hard enough
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