Prelude build question

[Flying Dutchman]

I'm building a TopModel Prelude 2.5m glider, and am not clear on the way to install the included double wall rudder push rod. I have never used them, and don't want to mess up this beautiful kit.

The instructions (see below) seem to indicate that the inner music wire rod (0.8mm) and the intermediate plastic tube (2mm) should be cut to equal lengths and then glued together. The threaded coupler is then glued onto the combined rod end, and is also crimped or swaged on, in 2 places. Does that sound right? The description on Aloft's product page for the double wall rod they sell states that the music wire alone is the push rod, and the intermediate tube just "floats". See https://alofthobbies.com/d.html and Q&A.

@Konrad, I hoped to see something on this in your Samsara write up, but you mounted both servo's in the vertical stabilizer... However, you are familiar with TopModel and may have dealt with this kind of thing before.

Thanks,
Steven

 

[Konrad]

Here is my take on the European Bowden tube. That 0.8mm wire is just a stiffener. The real loads are carried by the 2mm plastic inner sheath.
I don't place too much value on the CAing of the wire to the inner sheath, as the detail shows the coupler will be crimped a bit latter in the assembly process.
But if doing this CA step I like to clean the wire free of oils. I then use med. CA on about 50mm of the wire. I then slide the wire in and out of the inner sheath a few times at a good rate of speed to try to get some glue into the inside of the inner sheath. Wipe off any CA that has formed on the out side of the inner sheath. I then come back and clean the end of the inner sheath with acetone to remove all the CA on the outside of the inner sheath.

Now that the inner sheath is prep'd I crimp the threaded coupler with just enough force to grab the inner sheath. You don't want to use so much force as to crush/cut the inner sheath. You want to use enough force to distort the inner sheath to grab the wire. (Here is where I have my issue with CAing the wire in the first place. This crimping with crack the CA joint putting its effectiveness in doubt). After crimping the coupler on I do use some thin CA to fill any gap between the coupler and the inner sheath.

Do try to glue the outer sheath for as much of the run as possible. I like to leave about 30mm loose at each end to allow the Bowden tube to follow the arc of the servo and control surface.

The tubes sold at Aloft are what I think come from different school of thought. They are trying to minimize the drag by having multiple surfaces slide over each other. As I was a metal worker at one time in my life, I like the direct hard wire approach. See my Mefisto thread , black outer sheath is glued to the fuselage. The inner white sheath is free floating and the wire is transmitting the force.

So as with most things in life the answer isn't yes or no.

All the best,

Konrad

 

[Flying Dutchman]

Thanks Konrad, exactly what I needed.

 

[gnichola]

@FlyingDutchman is your Prelude powered? If so, would you mind giving me a measurement to your firewall from, well, anywhere. A buddy of mine bought a powered version and wanted an unpowered one and the picture depicts what he wanted to do. He gave me the airplane, but before doing so, he cut the nose a bit. So...I am just trying to figure out about where the motor originally was mounted.

(yes, that is a Estes rocket nose cone)

 

[Flying Dutchman]

Nice nose... He gave it to you? I want to share your friends!

I get 80mm (3-1/8") from the fuse front edge to the inside edge of the front opening. Or 260mm (10-1/4") to the LE of the wing pocket.

 

[gnichola]

Thanks! Looks like he cut off about 10mm. I am mounting the firewall just behind the nose face with the engine in front. As I understand it the plane is quite tail heavy to start so I want everything as far forward as I can get.

 

[Konrad]

Just about every TopModels instruction sheet places the CG way too far forward.

 

[n1edm]

I'm a newbie here. I just bought a Prelude 2.5M REF and wonder if there are some other threads (along with this one) that I could also follow.

I'm a fairly experienced modeler but this is my first 'serious' sailplane. I'm just wondering what to expect in the complete build.

I'm open to any advice you can give to newbie 'serious sailplane' pilots.

Thanks in advance for any advice that anyone can give, and Konrad, your image on fastening to Bowden tubes are a real eye-opener. I never would have expected that. Thanks for showing.