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Sep 21, 2018, 04:59 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
Discussion

good one day bad the next


recently handed off a model called the "baby moffet to a member that had a problem with screwing in to the right thinking they might be able to solve the problem but haven't heard yet, so now we have the same problem with a korda victory that flew perfect big circles 200 winds for a couple of flights but now wants to screw it self in to the right about 10 ft from a gentle hand launch

after it started this behavior I added some tail weight and gave it more wing incidents but still screws it self in on a power off glide test or after around 50 winds, very frustrating when something was doing so good.
Last edited by lectroglide; Sep 21, 2018 at 05:26 PM.
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Sep 21, 2018, 06:00 PM
Registered User
gossie's Avatar
Tail weight?
Where's the CG with and without?
Sep 21, 2018, 06:27 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
being the stab is big the cg was 75% time of the nose dive, but believe it was 50% prior
Sep 21, 2018, 08:19 PM
B for Bruce
BMatthews's Avatar
Dan, we may as well 'fess up. We may get more help and some options we didn't think of from the gang.

Folks, I'm the guy that stopped by and tried to sneak in some quality trimming time with Dan before we got shut down by a monsoon like rain storm.

The Victory showed all the signs of being too nose heavy and needing too much decalage. In the short time available it was very much a case of "slash and burn" tactics to try to at least start towards the right direction. It didn't help that the nose had some slight pre-existing damage so the nose block didn't seat solidly and that we "bruised" it even more during the testing. I wish we'd had better weather and more time so we could have done some field repairs to the damage as it occurred instead of trying to shim the soft damaged spots to get by. Doing it the way we were forced to by the incoming weather didn't do us any favors. But between the oncoming storm and the covering becoming progressively more soft with the humidity and light drizzle during the session it was tough to do more.

We pulled out the lead in the nose which shifted the CG back a lot. To roughly 75% in fact. A couple of test glides and some rapid wing and tail shimming started to make things look promising. We got in one or two low powered flights that did a circle or so at head height and looked fine. Had proper response to stalling and everything.

But due to the rain starting up that's where we had to leave off. All in all it was a rather manic hour and a half at the little baseball diamond size field. I was hoping that the start we made would have been the beginning of some good results. But it sounds like you've had some reversals. I'm sorry to read that.



Dan, your Moffet is sitting here on the chair by my computer. It has spent most of the time since arriving staring at me and making me feel guilty. But there's really only been a couple of days where I could have taken it out to try flying. And those had other commitments already. The rest of the time when it wasn't raining it was too windy to learn anything.

What I am seeing is that the covering isn't properly stiff on the wing. What did you use for a finish on the tissue? I'm thinking that the covering is slack enough, which got even more slack in the drizzle that day, that the wing may be flexing when flown and the wings are not holding their flatness or proper warps.

I'm going to try a small patch of nitrate dope on the tissue to see if it's compatible with the finish you used. The goal being to give the tissue more shrink and tighten up. Then I should be able to steam in the warps I want and then I can try to get the model flying. But first I'm waiting on some dry weather to try it as is to see if it's any different and if I can make it respond correctly when it's dry outside.
Sep 21, 2018, 09:08 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
think I shrunk it 1st with water then butyrate on the esaki which is obviously is not holding its taughtness ...and plez dont worry about the moffet only reason I ask is cuzz you might have found out what was wrong which could have given me a hint about the victory problem and yes the moffet wing is extremely sloppy prolly due to the kit wood I used and moisture in this area, but re the victory think I might try a ROG thing "after test glide" and see what happens
Last edited by lectroglide; Sep 23, 2018 at 12:48 AM.
Sep 24, 2018, 01:55 AM
Registered User
Suggestions:

Make sure that the wing, nose block, and anything else that might get loose are snug and won't move. If not, you can trim all you want and not get very far.

Do you have a bit of wash-in on the inside wing? That might help. Or wash out on the outside wing, I suppose.

Do you have the full dihedral shown on the plans? In my experience, bigger vertical stabs and smaller amounts of dihedral make a model more prone to spiral dives. There's sort of a balance between the two.

Posting a video might help.
Sep 24, 2018, 11:51 AM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
will get back to ya on that but nothing had changed prior to the spiral problem, I also have no way to take a moving picture
Last edited by lectroglide; Sep 25, 2018 at 02:07 PM.
Sep 24, 2018, 06:13 PM
Registered User
SOMETHING changed or it would still behave the same way.

BTW, my first reaction is that tail weight won't fix it. I think it's just possible that moving the cg forward might help, but I don't consider that very likely. Easy to try, though. If it was diving straight ahead, that ,might be a sign that it's either tail heavy or has too much decalage or downthrust, but if it's turning hard, then it's doing to dive even if otherwise properly trimmed. I suppose it's possible that it was right on the edge before, and a change you couldn't even see sent it over the edge. If it was my plane, and the vertical stab could be easily removed, I'd put on a temporary one made from a foam plate that was slightly smaller than the original tail. Then I'd keep snipping away until it was stable. That worked for me with a scale Seversky. The stable vertical stab was about the size of a couple of postage stamps! In that case I separated the rudder from the fin and hinged it with tissue so it could flop around. If this is what's going on, and you want it to look exactly per plan, you may have to increase the dihedral a bit.

Hypothetically, you might be able to achieve a similar effect with a slightly larger prop, but I think that's probably going to be complicated.
Sep 24, 2018, 07:34 PM
Registered User
gossie's Avatar
My thoughts are the wing and tail are NOT locked down in EXACTLY the same place between flights.
Tabs are always built onto wings and tails of all my models regardless of size and type, and they fly the same flight to flight often over many years.

Generally I use 1/8th to 3/16th dowel split in 1/2, then glued to wings/tail against the mounts so things just can't move. Even a 1/16th of movement on a wing or particularly a tail with a fin on it = CRASH.
Sep 24, 2018, 10:40 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
Quote:
Originally Posted by gossie
My thoughts are the wing and tail are NOT locked down in EXACTLY the same place between flights.
Tabs are always built onto wings and tails of all my models regardless of size and type, and they fly the same flight to flight often over many years.

Generally I use 1/8th to 3/16th dowel split in 1/2, then glued to wings/tail against the mounts so things just can't move. Even a 1/16th of movement on a wing or particularly a tail with a fin on it = CRASH.
interesting suggestion and will keep that in mind
Last edited by lectroglide; Sep 25, 2018 at 12:27 AM.
Sep 25, 2018, 11:05 AM
B for Bruce
BMatthews's Avatar
One of the suggestions that were being thrown around when we met was some way of keying or at least checking that the wings are on straight.

If you don't take up the idea of adding keys to ensure things go into position the same each time at least set things up and put fine marker pen marks on the wings, tails and fuselages so you can check that things are correctly lined up before each flight. The guys are right about how even a small change we can easily miss is enough to cause major differences from flight to flight.
Sep 25, 2018, 02:19 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
Quote:
Originally Posted by lincoln
SOMETHING changed or it would still behave the same way.

BTW, my first reaction is that tail weight won't fix it. I think it's just possible that moving the cg forward might help, but I don't consider that very likely. Easy to try, though. If it was diving straight ahead, that ,might be a sign that it's either tail heavy or has too much decalage or downthrust, but if it's turning hard, then it's doing to dive even if otherwise properly trimmed. I suppose it's possible that it was right on the edge before, and a change you couldn't even see sent it over the edge. If it was my plane, and the vertical stab could be easily removed, I'd put on a temporary one made from a foam plate that was slightly smaller than the original tail. Then I'd keep snipping away until it was stable. That worked for me with a scale Seversky. The stable vertical stab was about the size of a couple of postage stamps! In that case I separated the rudder from the fin and hinged it with tissue so it could flop around. If this is what's going on, and you want it to look exactly per plan, you may have to increase the dihedral a bit.

Hypothetically, you might be able to achieve a similar effect with a slightly larger prop, but I think that's probably going to be complicated.
Hypothetical can also produce an answer and keep thinking about that bigger prop solution and do have bigger ones to experiment with...…...also seem to notice the model takes off and flys differently with different props ,but am aware winds strand count and length come into play
Last edited by lectroglide; Sep 25, 2018 at 04:00 PM.
Sep 25, 2018, 05:35 PM
Registered User
If the wing and stab are not keyed you are just wasting yours and anyone trying helps time.
Sep 25, 2018, 06:38 PM
BOYCOTT SCAMAZON
lectroglide's Avatar
Thread OP
Quote:
Originally Posted by BMatthews
One of the suggestions that were being thrown around when we met was some way of keying or at least checking that the wings are on straight.

If you don't take up the idea of adding keys to ensure things go into position the same each time at least set things up and put fine marker pen marks on the wings, tails and fuselages so you can check that things are correctly lined up before each flight. The guys are right about how even a small change we can easily miss is enough to cause major differences from flight to flight.
have made alignment practices for many years on all kinda models and more so on these things, so doubt thats where the problem lys but will always listen to "constructive inputs sir, all others will be DISREGUARDED
Last edited by lectroglide; Sep 25, 2018 at 06:54 PM.
Sep 25, 2018, 06:48 PM
Registered User
gossie's Avatar
Quote:
Originally Posted by dan berry
If the wing and stab are not keyed you are just wasting yours and anyone trying helps time.
Good one Dan. But is this guy understanding yet what we have been telling him for months now?


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