Wright Stuff C

[calgoddard]

As Coach Chuck indicated in the previous post “perfectly wound” is a relative term. Extensive practice will first be necessary in order to determine the optimum rubber motor size and optimum launch torque that will cause the model to climb to a max height just below the beams and/or light fixtures and produce the longest flight duration for that particular model, indicating that the rubber motor has been “perfectly wound.” The maximum number of turns (“max turns”) that can be put into this specific rubber motor should be determined by winding several identical lubed rubber motors (in terms of length, weight, and batch of rubber) on a stooge to the point that they break. All of the data that is collected during test fights and test winding must be recorded in flight logs that can be referenced at the competition. This point cannot be over-emphasized.

Here is how to wind a rubber motor for an indoor duration stick model airplane, such as a WS airplane. As previously stated, the rubber motor should have an optimum size in terms of length and weight, determined via extensive test flights.

Make sure that the rubber motor has a pair of O-rings and that it is sufficiently lubed, e.g. with a silicone lubricant such as DOW CORNING 33. It is sold in small tubes as a lubricant for paint ball guns. Another excellent lubricant for rubber motors is NAPA Sil-Glyde. An 8-ounce tube of the later silicone lubricant can be purchased from Amazon for $14.72.

Connect the lubed rubber motor between a winder and a torque meter that is firmly anchored to a table. Step out with the winder until the rubber motor is fully stretched, i.e. until it extends approximately 6-8 times its relaxed length, before you commence winding.

Half the max turns should be wound into the fully stretched rubber motor without moving the winder inwards toward the torque meter. The remaining half of the max turns should then be wound into the rubber motor. Do this while gradually stepping in with the winder until the wound rubber motor has a length roughly equal to the distance between the prop hook and the rear hook of the model.

As you approach the max turns, observe the torque meter to confirm when the torque jumps dramatically higher with the last few very slow turns of the crank arm of the winder. This sudden rapid rise in the torque indicates that the rubber motor is near its max turns, and is about to break. It may be beneficial to pause winding several times to manually massage the rubber motor with one hand as you approach the max turns in order to spread out the knots and to get a more accurate torque measurement. Then back off turns in the rubber motor until the torque meter shows the lower predetermined optimum launch torque (i.e., previously determined via extensive test flights) that will produce a max altitude “no-touch” flight. Unhook the forward end of the wound rubber motor from the winder and transfer it to the prop shaft hook of the model. Unhook the rear end of the wound rubber motor from the torque meter and transfer it to the rear hook of the model. Walk slowly with the model to the launch location. Get the attention of the timer(s) before launching your model on an official flight.

There is nothing new, unique or secret in the rubber motor winding routine that I just described. The foregoing routine is standard practice by serious indoor fliers. Sometimes minor variations are executed, e.g. winding 60% of the estimated max turns into the rubber motor before stepping in. Here is a link to a video which demonstrates the standard practice for winding the rubber motor of an indoor duration stick model airplane:

https://www.youtube.com/watch?v=xyXeTJno0sI

Brian, Coach Chuck, retired1, and jander (Jeff Anderson), please chime in.

[klastyioer]

holy crap that was a long response

[coachchuckaahs]

Cal presents a good summary of the winding process. Optimal winding cannot be done without data and a torque meter. Many simple torque meters are online.

For lube some use armor all, which is silicon suspended in water. We now use r/c car shock oil, from local Hobby shop. We put some in a snack size baggie, and massage the rubber until coated. This keeps hands less oiled.

One piece of data we use is lap by lap altitude. First lap has a lot to do with launch torque, and prop flex. Mid laps have to do with prop flex and rubber thickness. Letdown is strongly dependent on rubber thickness. Other variables play as well.

One final note is to monitor the number of flights on the rubber, and to inspect the rubber carefully for large nicks that can result in failure.

Coach Chuck

[Rossyspsce]

For torque burner discussion, see replies 95 through 99 here:

http://www.hippocketaeronautics.com/hpa ... c=17412.75

This strategy requires a lot of gym time to perfect. As in A LOT. Your time would be better served by improving propellers and propeller and rubber matching and getting lots of turns into the motor.

Brian T

I attempted the method in which is described in the posts, putting a straw in between and winding as normal without backoff. However, I ran into an issue with the rubber not winding past where I had the straw. Anyone know what is wrong/happening and how to fix?

[bjt4888]

Rossy,

The straw should be a little short segment like 1/4” - 3/8” and probably a thinnish straw like a coffee stirrer (maybe 3mm OD).

Brian T

[bjt4888]

Calgoddard,

I agree with your description of winding, torque meter use and overall objective. Another thing we do (Cal and Chuck and others I’m sure too) is graph or chart unwinding torque to compare motors of same density and length to help identify and select future possible best motors (for a particular propeller and pitch and trim settings).

Brian T

[Rossyspsce]

does anyone know of/have an alternative to the ikara prop hooks, as mine keep breaking?

Thank you,

Ros

[klastyioer]

does anyone know of/have an alternative to the ikara prop hooks, as mine keep breaking?

Thank you,

Ros

breaking?
do you mean the bearing of the prop or the hook?
cause the hook shouldnt be breaking per say

[bjt4888]

Rossy,

See third post here for a different hook. Similar to Freedom Flight kit hook. Wire pokes deep into the stick at an angle to resist tension of rubber motor.

viewtopic.php?f=191&t=6085&start=75

Brian T

[Rossyspsce]

sorry to ask another question, but does anyone have a solution for broken spars on the sym ikara props or ways to repurpose the props once broken?

Thank you,

Ros