Chipmonk Surgery

[Brian Massey]

My new Chip flies quite well, but has suffered from a "stutter" when coming out of the bottom corner of inside squares and the triangle. After talking to my older (much older) brother I began to think that the elevator push rod might be flexing with the initial input. Without tearing the entire plane apart I thought the simplest fix would be to sleeve the length of the 4-40 threaded push rod with a carbon fiber tube. If this works I'll be a happy camper.

I'm curious if this is an "OK" way to build a CF push rod from the beginning? Or is there an inherent problem with "sleeveing"? Seems to me that there is no real weight penalty involved.

Thanks for any thoughts.

Brian

[Clint Ormosen]

Brian, If the carbon fiber pushrod goes all the way to the rear of the plane, it's not flexing. You're also not going to get any flex out of the quarter inch of unsleeved threaded rod. At least not a measurable amount. Hard to tell about your ends, They look okay. I personally use quite a bit of JB Weld on them. I'd look for some other reason for your turning problems such as elevator to flap ratio or balance.

.....and you have two weeks to figure it out.

[Brett Buck]

Thanks for any thoughts.

   Did we also have a wire-bending issue?

   Brett

[EddyR]

This was posted http://stunthanger.com/smf/index.php?topic=34850.msg354992#new May be it didn't work

[Dave_Trible]

Brian if its not flexing then I'd suggest its a little stall.  Don't know what she weighs  but it looks like you may be able to dial in a little more flap deflection.  Another way (and could experiment easily) is to add a strip of flap area to the TE of the flaps.  An 1/8" balsa strip taped on for a test run would prove it out.  If you can't dial in more travel,  add more area.  Either way changes the angle of attack for the wing in the turn.


Dave

I should have said add more flap chord, which will add more area but I think it's about the chord in this case.  In other words adding flap span if you could wouldn't help very much.

[Brian Massey]

Brian, If the carbon fiber pushrod goes all the way to the rear of the plane, it's not flexing. You're also not going to get any flex out of the quarter inch of unsleeved threaded rod. At least not a measurable amount. Hard to tell about your ends, They look okay. I personally use quite a bit of JB Weld on them. I'd look for some other reason for your turning problems such as elevator to flap ratio or balance.

.....and you have two weeks to figure it out.

I changed the flap/elevator ratios several times and could never get rid of the hesitation coming off that corner. I'm not sure I'm describing it correctly. When I give it up to come out at the bottom of the triangle or inside square, it starts the corner . . . then doesn't, then does again. Of course by then I've panicked and yanked up which results in a really cool looking bobble at what should be a bottom. (And you understand the panic, what with my bottoms being so close to the ground . . . 20 feet is close isn't it?)

What's in two weeks?? In three weeks my wife and I will be in the motorhome heading for New Hampshire. In two weeks I'll be packing the beast.

Brian

[Brian Massey]

This was posted http://stunthanger.com/smf/index.php?topic=34850.msg354992#new May be it didn't work

Yep, that's my old"er" brother. The fix he performed in the thread worked! His Shark now corners like it should. We had a long telephone conversation and that in part led to my recent surgery on the Chipmonk.

Brian

[Tim Wescott]

You're paying the weight penalty of all the wire buried in the middle of the CF tubing that's not doing anything.

However, at the point that you're doing it, I think it's a really clever save.

[Brian Massey]

You're paying the weight penalty of all the wire buried in the middle of the CF tubing that's not doing anything.

However, at the point that you're doing it, I think it's a really clever save.

I've thought about that very point. On my next build I'm thinking of cutting the ends off a 4-40 rod and epoxying them into the CF tube; maybe an inch or so actually glued in the tube. That gives me the ease of doing ball joints the way I'm use to, with the strength of the CF. I know, there's probable better ways.

Brian

[Balsa Butcher]

Tom Dixon mentioned the CF tube over wire pushrod in one of his designs articles, don't remember which one. Easy to do and will work fine. Your issue may be the pushrod but it just may be the airplane stalling during square maneuvers however insuring there is no bending in the pushrod is a good place to start.

[Clint Ormosen]

What's in two weeks?? In three weeks my wife and I will be in the motorhome heading for New Hampshire. In two weeks I'll be packing the beast.

Brian

FUNDAY is 5/04. Guess you're not making it, huh?

[Brian Massey]

FUNDAY is 5/04. Guess you're not making it, huh?

No, wish I could. My wife has been after me for 13 years to take a motorhome trip to New Hampshire to see her "old family farm". She wants to go in September or October to see the colors . . . but that would mean giving up the MnM or the GSSC. No way! This is a compromise trip; longer, but not the season she wanted. I'm missing the NW Regional this year, but it will be a smaller event due until they get a new location. Hopefully next year.

See Ya!

Brian

[Dick Pacini]

No, wish I could. My wife has been after me for 13 years to take a motorhome trip to New Hampshire to see her "old family farm". She wants to go in September or October to see the colors . . . but that would mean giving up the MnM or the GSSC. No way! This is a compromise trip; longer, but not the season she wanted. I'm missing the NW Regional this year, but it will be a smaller event due until they get a new location. Hopefully next year.

See Ya!

Brian

Brian, where is the old family farm?

[Brian Massey]

   Did we also have a wire-bending issue?

   Brett

Not quite sure what you mean. I only "think" the elevator push rod is flexing under load, but not sure. There are no bends in it otherwise. (Sorry, but I'm sure I'm missing your point. Uhhh, are you referring to Mike's dilemma?)

Brian

[Brian Massey]

Brian, where is the old family farm?

The old farm is now a BnB called Sculptured Rocks, and it's in Groton (http://www.sculpturedrocks.com/). It was her dad's family that owned it, but that was many many years ago. You live near there by chance???

Brian

[Dick Pacini]

I'm in Charlestown, 65 to 71 miles away, depending on the route.  As we say in NH, "Ya can't get thare from heah, but if ya could, I sure wouldn't go this way."

An hour and a half-ish.

[Brett Buck]

Not quite sure what you mean. I only "think" the elevator push rod is flexing under load, but not sure. There are no bends in it otherwise.

    I will PM you.

    Brett

[EddyR]

Brian
   Sorry for the mix up with you and your brother. Sounds like you now have taken care the problem.
Ed

[Brett Buck]

Well, since Brian told me the elevator horn was pre-bent, I guess it's OK to point out that it was *manufactured backwards*! The crooked upright on the horn is crooked so it can clear the stabilizer without requiring a deep slot. This one is the wrong way around. The tails of the horn should have been bent in the opposite direction.

   Brett