Modifying a kits flight surfaces
 

I've just started building one of Balsa USA's Eindecker 40 kits and I'm planning on making a number of scale improvements to this decidedly "sport scale" kit. I plan to leave the main wing as is (a thick, flat-bottomed, trainer-like airfoil) but I'd like to replace the kit's current rudder and elevator setup with scale full-flying rudder and stab. The scale rudder and elevator are much smaller than the kit versions and I would consider enlarging them a bit (perhaps 10-20%) if this will improve the flyability.

But here's my question:

If the surface of a full-flying rudder is comparible in size to the movable part of a much larger vertical stab + rudder will these surfaces do the same job? Ditto on the elevator (on the EIII the leading edge would dip down on up elevator).

RE: Modifying a kits flight surfaces
 

I did exactly that change on the larger BUSA Eindecker.. made the horizontal closer to the scale size, and also the vertical, both converted to full-flying.
The image is another one in my club done up in the early "stealth" cellophane covering tried in 1915..
Flying tails and wing warping. Based on the BUSA kit.
Wing warping didn't work all that well, it requires a very loose wing structure..

RE: Modifying a kits flight surfaces
 

Tall Paul, Man! That is just georgious! I'll be thrilled if I get mine looking even half this nice - love the scale gas tank behind the pilot! Luckily I'm going to cover mine with the antique solartex so I can hide a non-scale interior (although I am going to do a built-up fusalage). Thanks for the encouragement. I think I will just go ahead and either use the scale size surfaces or bump both up to 110%.

RE: Modifying a kits flight surfaces
 

Paul, any chance you could post some pictures of how you set up the tail?

RE: Modifying a kits flight surfaces
 

Certainly...
Reshot this morning..
The long tail moment on the Eindecker creates a big tail-heavy problem.
On most of ours, we throw out the sheet sides and substitute spruce longerons, also gives the scale look under fabrid.
My Eindecker has 14 oz of lead in front of the firewall.
Saito 91 motor.

RE: Modifying a kits flight surfaces
 

One note... lookig at the detail pic of the rudder linkages.... I note the use of crimped wire pull-pull cables.

Not sure how much pull is on those cables.. but for the crimped ends on C/L lines I always took the free end (a bit longer than the loose ends seen..) and ran them around the tube sleeve and back through again before crimping. the effect is the wire almost has to break befre it can pull free of the crimped sleeve.

Sullivan pre-made control lines have the crimp just as seen... and every one I tested FAILED at less than 1/8 the rated strength of the lines after one drop of fuel was put on the crimp.

Something to think about. Watch the crimped ends. Exhaust oil might allow some slippage (which could be disastrous.)

*********

He's also lost a screw on one of the elevtor horns...

RE: Modifying a kits flight surfaces
 

If you modify this approach a bit, you can actually have failsafe pull - pull cables. Take the free end, route it through the control horn again, and then through the crimp tube leaving a loose loop there. It's a redundant loop. This way, you have the "first" loop tight and doing all the work. Should that one get worn-thru on an edge, you still have some control with the second loop, albeit with a noticable change in trim. I started doing this after a pull-pull on elevator was cut through. A friend gave me this idear though.

RE: Modifying a kits flight surfaces
 

while "picking on";) the setup. ( its a good one generally... He's probably not having problems with it)

The steel cable being threaded through a nylon control horn... probably not the best idea. The wire will eventually wear through the nylon. (another thing to inspect regularly)

When I do pull-pull... I use a 2-56 0r 4-40 clevice with a eye-bolt on the end of the cable. This puts a clevice pin in the control horn, and they tend to not wear out either the pin or the control horn. That allows some fine adjustment of the cable length too. [8D] It is a bit of added expense... and added weight... and might not look as pretty for scale effects...


He was probably after a more scale appearance in this case... and thus I bet he's aware of the added inspection requirements for his setup.

RE: Modifying a kits flight surfaces
 

If the crimping procedure in the photos wasn't up to the task, it wouldn't be used.
Oh, and note the "missing screw" .. It goes from the top of the surface and threads into the nylon plate. That one is shorter than the others, but is there.