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Jun 23, 2019, 07:30 AM
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One of my all time favorite planes. I built and flew the 40 size twice back in the 90's and both were flown 100's of times. I literally carried it my pickup truck passenger seat area and flew it daily.
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Jun 24, 2019, 02:09 PM
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Gameengineer's Avatar
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Thinking ahead a little, the kit comes with nylon pushrods for the elev and rudder. I'm thinking of replacing the rudder with a pull-pull system. A guy at the club said one issue with the nylon pushrods is temperature and humidity can vary the length so he tends to have to adjust trim each day he flies it.

I have a lot of time before I get to that point but now is a good time to address this so I have a plan. Have any of you 4* 60 owners had many issues with varying lengths? Should I replace the elev with a metal pushrod?
Jun 24, 2019, 03:31 PM
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kimchiyuk's Avatar
I will be watching with great interest! I love the Four Star planes. I have built two 40's, a 20 and actually just am finishing up another 20 as my last one was crushed by a box.

The O.S. 91 will be a great match. I fly four strokes almost exclusively and wouldn't put anything else on a Four Star.
As you said you noticed on the wing, it's almost meant to use CA. What I usually do is use thin CA as I'm building and then go over most joints with medium CA as it does soak in a bit but also stays put and creates a fillet. You'll also notice the fuselage seems intended for CA as well.
Good luck with the build!
Jun 24, 2019, 03:34 PM
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kimchiyuk's Avatar
Quote:
Originally Posted by Gameengineer
Thinking ahead a little, the kit comes with nylon pushrods for the elev and rudder. I'm thinking of replacing the rudder with a pull-pull system. A guy at the club said one issue with the nylon pushrods is temperature and humidity can vary the length so he tends to have to adjust trim each day he flies it.

I have a lot of time before I get to that point but now is a good time to address this so I have a plan. Have any of you 4* 60 owners had many issues with varying lengths? Should I replace the elev with a metal pushrod?
I've used nylon pushrod on many planes and have never experienced the problem you mentioned. I have heard other's say they've had the issue, but since I have not; I go with my positive experience.
Jun 24, 2019, 03:42 PM
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The nylon pushrods are known to cause issues in high end pattern planes where the difference in expansion rates can cause subtle changes in trim. I don't fly at that level and have never really noticed any issues in any of my sport planes where I've used them in the past. In fact, I'm getting ready to install them in my Sarpolus Sportster 20.

Tom K
Jun 25, 2019, 12:34 AM
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The only place I’ve seen nylon pushrods give trouble is with sailplanes. They’re long enough that they shrink and grow noticeably from the heat of the sun. It may have something to do with the limited volume of air in a sailplane fuselage that heats up easily as well. In planes where it could be a problem I use solid pushrods with ball type rod ends from DuBro. Prob solved.
Jun 25, 2019, 09:01 AM
Sagitta Fanboy
The Sig nyrods are insanely temperature sensitive in my experience, much more so than Gold’n’rods. I’d definitely replace them with something else
Jun 25, 2019, 09:28 AM
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Gameengineer's Avatar
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Quote:
Originally Posted by kimchiyuk
I will be watching with great interest! I love the Four Star planes. I have built two 40's, a 20 and actually just am finishing up another 20 as my last one was crushed by a box.

The O.S. 91 will be a great match. I fly four strokes almost exclusively and wouldn't put anything else on a Four Star.
As you said you noticed on the wing, it's almost meant to use CA. What I usually do is use thin CA as I'm building and then go over most joints with medium CA as it does soak in a bit but also stays put and creates a fillet. You'll also notice the fuselage seems intended for CA as well.
Good luck with the build!
That seems to be the consensus on the engine size. I got it off ebay used from someone who moved to gas only. The compression is really good. I can barely turn it using the drive washer alone. I did end up using CA thin and med when building the wing and use wood glue on all the joints once set up.
Ok so you certainly have build experience with this plane! I was thinking of picking up the 20 just to have a smaller version and to have it gain more build experience.

Quote:
I've used nylon pushrod on many planes and have never experienced the problem you mentioned. I have heard other's say they've had the issue, but since I have not; I go with my positive experience.
That's a good data point. I think to eliminate all the variability as I can since I am new to flying too and this is my 3rd plane so I am leaning toward replacing the nylon with a typical metal pushrod through nylon sleeve.


Wing bow! Argh! I didn't show the leading edge but its nearly as straight as an arrow. The TE however, well pictures show it. The bow starts near the center of the TE and bows up on each end about 1/8". I'm pretty sure I know how I did it. The shaped TE piece bevel angle does not match the rib angle so the top TE sheet needs to get pulled down. I wasn't sure how to handle that drop other than CA and clamp the rear edge down with a few hand clamps. The edge glued down beautifully however I had to lift it from the building board and was not holding the wing flat to allow the TE sheet to set. I think that was my downfall! Live, try and learn I guess. The right wing will not have this problem! I think what I need to do is hold down the wing with weights when gluing anything.
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So right now I'm trying to reverse the bow by placing the TE on my straight alum bar, added a 1/32 metal plate under the center of the TE, wetted the wing at the center and am holding down both ends of the wing against the bar. I'm letting it sit for >24 hrs. If it doesn't help I might see if adding the LE sheeting helps (don't think it will though) and/or covering and stretching the bow out. The plans don't call for LE sheeting but I'm adding it up to the spars.

It does not appear to be a wash out or twist in the wing, just a bow along the spar axis.
Last edited by Gameengineer; Jun 25, 2019 at 10:15 AM.
Jun 25, 2019, 09:31 AM
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Gameengineer's Avatar
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Quote:
Originally Posted by David2011
The only place Iíve seen nylon pushrods give trouble is with sailplanes. Theyíre long enough that they shrink and grow noticeably from the heat of the sun. It may have something to do with the limited volume of air in a sailplane fuselage that heats up easily as well. In planes where it could be a problem I use solid pushrods with ball type rod ends from DuBro. Prob solved.
I am leaning toward solid metal pushrods in nylon sleeve. I am changing out the metal clevis' on the ailerons with ball type and I might consider doing the same for the elev.
Jun 25, 2019, 09:38 AM
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Quote:
Originally Posted by slow_flier
The nylon pushrods are known to cause issues in high end pattern planes where the difference in expansion rates can cause subtle changes in trim. I don't fly at that level and have never really noticed any issues in any of my sport planes where I've used them in the past. In fact, I'm getting ready to install them in my Sarpolus Sportster 20.

Tom K
Thanks for the next data point on them. With the given feedback already and the way I'm going to fly it sounds like its a toss up to which way I should go. My instructor brought his 4* 60 a couple weekends ago and had to trim it a little but not too much. He was also doing a lot of maneuvers.
Jun 25, 2019, 09:45 AM
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Quote:
Originally Posted by mawz
The Sig nyrods are insanely temperature sensitive in my experience, much more so than Goldínírods. Iíd definitely replace them with something else
"nyrod" ok now I know their name. Thank you for the data point! I value the feedback.
Jun 25, 2019, 05:56 PM
Registered User
I always use Sullivan pushrods and have never had any issues with them. I remove the stock pushrods from the kit and use them for something else.
Jun 26, 2019, 02:45 AM
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Quote:
Originally Posted by Gameengineer
I am leaning toward solid metal pushrods in nylon sleeve. I am changing out the metal clevis' on the ailerons with ball type and I might consider doing the same for the elev.
That would be a rock solid control system. After reading subsequent posts it occurred to me that the troublesome pushrods in a glider were in an otherwise excellent Airtronics kit. Iíve used lots of aftermarket Sullivan and DuBro pushrods and donít recall them changing length significantly with temperature changes.
Jun 26, 2019, 09:17 AM
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Quote:
Originally Posted by David2011
That would be a rock solid control system. After reading subsequent posts it occurred to me that the troublesome pushrods in a glider were in an otherwise excellent Airtronics kit. I’ve used lots of aftermarket Sullivan and DuBro pushrods and don’t recall them changing length significantly with temperature changes.
I see a lot of the connection and hardware types in modern rc planes and much of it bothers me. Yes I'm certain those wood screws that have been holding the servos and other things have lasted 30 years but it just doesn't feel right. So those plastic pushrods just don't feel right to me. Given the feedback from you all it appears they are fine although some, like my field instructor, have to mess with their lengths changing but he's been flying over 30 years so he probably "feels" the difference. I probably wouldn't notice. But the metal rods just feel better.

Ok so the setting of the bowed wing on a straight edge helped a little bit. the bow isn't as bad. I wet down the wing again and left it weighted. I'll just leave it pressed until I can get back to building. Its been a little busy the past few evenings. My plan is to plane the rear of the TE, add LE sheeting and add the mounting to the servo bay and fit the door. I am using (4) 4-40 blind nuts to secure the door.

The kit doesn't call for it but I am going to make D-box wings.
Jun 26, 2019, 01:44 PM
Registered User
Full disclosure: I am somewhat of a pattern snob, but I also have built quite a few sport planes for fun. I would stay away from Golden rods or their Sig equivalent; they do expand and shrink with temperature and humidity and they also have a fair amount of built in friction, especially if curved. I used to have a LT-25 which used them and the plane needed to be trimmed and re-trimmed as it came in and out of the basement onto the flying field.

For the elevator I would put the servo in the tail and use a short pushrod rod to drive it. Using pull-pull for the rudder works well. For the wings, I would ditch the single servo and use dual servos.

Good luck,

Teo


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