mirwin

My Feedback: (1)

Maybe it hates him like my Husky did.

tomfiorentino

There could be something to this and it is worthwhile verifying. There could be a structural problem with the dowels that is causing movement and the erradict trim condition you are experiencing. A coule pictures would be nice.

Tom

AA5BY

Tom, I've a '70s era P-51 that the back of the wing tucks into and locks into the radiator scoop with the wing bolts on the front. Depending on how much torque is used on the bolts, the plane will require a lot of elevator to lift off or it will lift off without any elevator and of course trim differently... hence my reason for following up on the OP's question of whether wing bolt tightness could be at play.

As an aside, unfortunately the plane has been decommissioned. It was a scale orientated build with hidden control linkages with both flaps and ailerons using a single servo each and bell cranks were used. If your guessing flutter with bell crank looseness then you hit the nail on the head. It needs to have servo bays cut in, which probably wouldn't be too hard but it has a .61 glow engine and that equates to oil cleanup, which doesn't excite me any more. And... it is fast, which also doesn't excite me any more.

jester_s1

That's a sweet looking P51. I don't think I could let that sit in the garage without fixing the problems and flying it.

On every plane I have, I take an hour or so to fit the wing saddle to the wing which includes fitting the wing bolt blocks to snug up tightly to the wing. I'm looking for a very positive spot where the bolts are tight instead of a springy feel. If your wing saddle is not fitted right or your wing bolt area isn't right, you'll get to the point of snugging your bolts down and then be able to keep turning probably 2 turns as everything flexes and then notice that the effort to keep tightening goes up as the bolt stretches. If it's fitted right, 1/2 to 1 full turn is about all you can do without feeling like you're about to twist off the head of those nylon wing bolts.

tomfiorentino

Nice Mustang indeed!

And good comment on the nylon bolts. I have found that if they feel "spongee" somethin' ain't right! Once it bottoms out, 1/2 a turn...I agree.

Related to that, the saddle on my Phoenix doesn't fit as well as I would like so I am going to do the silicon deal; wrapping the wing in syran wrap etc.

I remember years ago (lots of years so dont ask how many) I read reports of the fumes from the drying silicon, being trapped inside the fuse, somehow created some issues with the servo wiring and electronics. So perhaps being not as informed as I should have, I always made a habit of silicon on the wing before the radio gear went in...but it is already in on the Phoenix and I really don't want to shoehorn everything back out of there.

Fact or fiction on the fumes?

And where is the update from the OP on the nose up question? Engine mount, wing, elevator pushrod, bad servo??

Tom

rcbadger

My Feedback: (14)

M,

Metal clevises are made of a flat metal piece, cut to shape, then "folded" and threaded (not drilled and tapped) to make the hole that the rod goes into. On one occasion, I came close to wrecking a model due to the rod nearly slipping completely out of the hole in the clevis. The rod (not the control stick) was used in a pushing-up/pulling-down configuration on the elevator, and during flight I suffered the same condition you had: gradually increased upward pitch throughout flight. I aborted the flight as soon as I realized the condition was getting worse, not just a one-time trim adjustment. After landing and checking everything out, we found that the rod was loose in the clevis, and had nearly pulled out entirely. When I had used down-stick (pulling on the clevis) the rod had slipped outward in the clevis resulting in greater up-trim on the elevator.

As best we could figure:

My solution was never to use metal clevises, with or without a locking nut. (The locking nut prevents the rod from slipping inward, but not outward.)

I never used a metal clevis again, and on anything .40 sized or larger, used carbon clevises made by Haynes. There are other manufacturers, but Haynes is what was available to me in Denver.

Also, as I recall, you said you were using standard Futaba servos, and I've used a ton of them over many moons. They're economical and for the most part, dependable. However, a few questions come to mind. a) was this servo used in a previous aircraft? b) one that crashed?

If not, I've had "wandering" trim settings due to the lack of centering on even new, non-digital servos, it was always random though, not continually working in one direction as you describe.

I never use a previously used servo on a new model. While this may seem economically irresponsible, if the original plane survived my use and was sold, I included the servos. If not, and the plane was wrecked, I'd never use them again anyway.

Lastly, I use steel bolts on wing mounts. They don't add THAT much weight, and they don't strip out or have the tops pop off in cold weather as I've seen nylons do.

Best of Luck.
Joe

Flyin Beagle

My Feedback: (1)

I am no expert at this, but as far as I know, you are correct about the vapors from the curing of regular silicone causing problems in electronics. I believe that it releases acetic acid vapor which causes corrosion on the circuit boards of electronics that can lead to failures. My understanding is the RTV silicone does not release these vapors and is safe to use in our airplanes. I have used RTV silicon in several of my planes and have never had a problem, but It also does not have that acidic smell like a bathroom tub and tile caulk does.

tomfiorentino

Ah....very good. With the acedic acid reference I was able to do some very intense and thorough research on the matter; I Googled it! Here is the link for anyone that is interested:

http://www.logwell.com/tech/servtips/RTV.html

Thanks...

Tom

PS Plus I learned that RTV stands for Room Temperature Vulcanizing...admit it...NONE of you guys knew that.

markhamregular

This weekend I plan to buy a new servo and try again.

A few things I remember well: I did tight the wing saddle screws more than usual. I’ve had 6 planes so far and I have never had problem because of tightening the screw.

As for the servo, it’s at the tail of the fuse as I said. It’s only 2 inches from the horn. Everything seems that same it has been since I have the plane (about 6 flights so far). I did notice that the elevators can be flexed with my finger, but when I tried to push the pushrod by hand, it’s a little hard. I cleaned residues of CA between the horizontal stab and the elevator. Maybe I did not realize that before, but the servo does the binding noise even when pushed slightly.

My biggest question is: the plane flew straight and level for 6 flights, why now nosing up?

This weekend I will replace the servo and see how it goes.

KitBuilder

its not the servo.. since you metioned you get different results based on flught speed and landing speed. Be sure both elevator halvaes are secured togehter properly.

Cna you have a friend take video and show the issue?

markhamregular

I replaced the servo and the new is binding too. Will postpicturestonight. So, the servo was not the problem. I can flex the elevator easily with my fingers, but when I disconnect the servo arm and try to push the pushrod like my finger was the servo, it’s hard. So I have to work on that elevator to make it flex smoother.

However, this does not tell me why the plane flew level on a few flights and start to nose up all of a sudden having changed nothing. I will fly it this weekend and asked friends at the field. Maybe I’ll find the problem. Thanks all for your help.

markhamregular

captinjohn

I know a guy like that...he builds the same planes over and over and over some more....and sure as _ell will not touch a ARF. Stuck in a rut forever!!!

rcbadger

My Feedback: (14)

Captinjohn,

I'm not sure what your point is. Perhaps it's to ease your concsience over some perceived deficiency in the hobby by not being a builder.

I have built only one kit in my adult life, and it took me years to complete because I ASSEMBLED a number of ARF's in the interim to keep flying during the process. Constructing an ARF IS NOT building. It IS assembly. Assembly is the acquisition of previously constructed components, and combining them with other previously constructed components. Building would constitute the construction of at least one of the assemblies.

I love ARF's. Nearly every plane I've ever owned was an ARF, or, as mentioned, except for one, was built from a kit by others. I don't feel any shame in buying/assembling/flying ARF's or even RTF's. But I don't take credit for building it because I simply overcame the aerodynamic issues of balance and adjustment due to the component selections I made while assembling one either.

I know several people who build from sctratch, build from plans, or buy and build from kits, some of them don't even fly, and I am oft held in awe of the talents they posses, but have come to know that I am a flyer, not a designer. Nor am I a builder. Given the choice, I wouldn't even be an assembler. I'm a damned good driver, and that's good enough for me, because that's all I aspire to be, it's what I love. Some of the builders I know are also held in awe of my abilities to fly.

I'm thrilled that there are those that derive pleasure from the aforementioned "construction" activities, because, after having dipped my pinky into the bracing waters of actual building, I have come to know that what I enjoy is flying, and the efforts of others who derive their pleasure (or income) from building frees me to pilot planes with relative ease, and THAT'S what I love, and why I fly. Nothing more, and nothing less.

jester_s1

Without seeing the plane all we can do is guess about it, but assuming your servos are good the only three things it could be is a break in the stab mount that lets it change incidence, a change in the wing incidence, or a loose motor mount that lets the thrustline change. I had a stick that developed a crack where the stab was mounted. It still looked solid but the elevator trim did change noticeably until I found it and fixed it.

markhamregular

We will never know. I had an expert look at it, and he found that the elevator horn was not correctly attached.
He "fixed" it. I went to test it, the nose went even more up and the engine quit.
No need to tell you the end of the story: trying to land a nose up plane with no power.

Adieu Nitroplane.  

rcbadger

My Feedback: (14)

Bummer! From this side of the screen, it defied conventional wisdom and experience. I kept coming back to CG, but that would have created up AND down pitch oscillations, not just up... Again, sorry to hear.

jester_s1

What was wrong with the elevator horn?

markhamregular

Apparently the horn was not screwed properly. My friend told me it may have caused the nose up.

It was my third crash in 1 year and a half. This time, I did not feel bad. I never had 2 consecutive flights with this plane.

If it was not the tank, it was the retracts (which I changed twice).

Needless to say, it was my first and last Nitroplane.

jester_s1

A loose horn would definitely cause the problem you had. I'll bet you had adjusted the trim with the horn loose, then when it was retightened you were way out. That's too bad you lost it though. I haven't ever heard much good about nitroplanes stuff.

AA5BY

A friend crashed a Cub... repaired it... crashed again and totaled it. Problem was discovered to be wrong horn on servo.

Sorry about the loss.

rcbadger

My Feedback: (14)

In my earlier days of R/C flight, I had a GP Easy Sport, and had used a number of components from another plane I'd wrecked. After assembly, I'd checked all the controls at varying throttle settings, etc. and everything worked well. About 1/2 way through the maiden flight, the plane suddenly seemed to go full left rudder and ailerons, and full down elevator for just a second, then returned to normal control, at the time inverted and heading toward terra firma. I rolled it back upright and climbed to altitude. I assumed (NEVER a good idea) it must've been just a "radio hit," and decided to keep flying.

A few seconds later, the condition was repeated, but for several seconds this time, and retuning to control almost too late to save the plane. I landed as quickly as I could and literally disassembled the whole plane trying to figure out what was wrong. Finally, with the radio system connected on the bench, and everything working fine, I took the case off the rx and pushed on the circuit board with a pencil eraser and all the servos went to extreme limits in one direction or the other. After removing and examining the circuit board, there was a small crack that went through the printed circuit which could break/make contact intermittently. I checked the pc's on the servos and found them to be fine, but decided then and there never to use anything with a printed circuit that had been in a wreck again.

Since I had no way of knowing which rx's and/or servos had been in wrecks, (though it was probably all at that time) I scrubbed my whole inventory of rx's and servos and started over. That Easy Sport eventually lasted longer than any plane I owned for years to come with over 200 flights on it (I used to keep a log) before a gusty landing claimed it.

From then on, if a plane lasted long enough to be sold, it got sold with all the electronics, and the new planes got new gear.