Re: Question about motor lenght on indoor high performance models

From: Chris <pseshooter3d_at_yahoo.com>
Date: Tue, 22 Aug 2017 08:04:58 -0400

Manuel,

Motor length is very dependent on the event being flown. For events like F1D and F1M, motor weight is limited. You always want to be flying with as much rubber (weight) as you are allowed. So with that in mind, as the length of the motor changes, so will it's thickness and density (mass per unit length). What you need to do is find a motor capable of providing the torque needed to fly the model, while still being long enough to accept a large number of turns. In this case, you want to use all of the turns on the motor. So if you land with turns, make the motor thicker or shorter. If you run out of turns before landing make the motor thinner or longer. The weight allowed and how the model is flying will determine which approach to take. But the idea is to use all of the turns in the motor, so as to not waste available energy and fly as long as possible.

So that is for rubber restricted events. But for unrestricted events, almost everything other than F1D and F1M, there is more freedom in choosing a motor. Also, there are no set rules per say, but the same principles apply. Personally, I like to fly with as little rubber as possible. That keeps the overall model weight down and allows the model to fly as slow as possible. I have seen my times go up as a a result. I also generally land with very few turns left on the motor. Other fliers use large amounts of rubber, wind the snit out of it, back off like crazy, land with tons of turns, but fly winning times.

So no real set rule. The best advice I can give you, after writing all that, is build something, test fly it, and listen to what the model and stopwatch tell you.

For a new model I like to start with a motor similar to the one the original designer had success with, wind it so it climbs to about 15-20 feet, and get it trimmed as good as I can. Once it's trimmed, I then play with motor length and/or thickness to get the flight times I want. It takes some experimenting and test flying to get it right.

Hope that at least gives you some direction to get you started.

Chris

Sent from my iPhone

> On Aug 22, 2017, at 3:22 AM, Manuel Cisneros macs8953_at_yahoo.com [Indoor_Construction] <Indoor_Construction_at_yahoogroups.com> wrote:
>
> Forgive my ignorance on the subject, but is there a general rule about how long a motor should typically be used on high performance indoor models (F1D, F1L, F1M) in relation to the prop hook to rear hook distance?
>
> I know these classes are different WRT to motor weight specification - F1D and F1M specify maximum motor weight, F1L doesn't - so I would expect the selection of a relative motor length would be different for different classes, but I am trying to understand the adage that seems to implore flyers to adjust motor dimensions based on how many turns are left in a motor at touchdown to optimize flight time based on available motor energy for different cross-section/length combinations.
>
> One reason I ask is that in perusing some (admittedly older) designs, I've found motor lengths to be specified anywhere from 80-90% of the hook-to-hook distance to as long as 120%-130%.
>
> TIA.
>
> Manuel.
>
>
Received on Tue Aug 22 2017 - 12:05:00 CEST