Rubber motor

I am mainly used to building indoor peanut/KK flying scale models. Just finished Guillows S5A, also for indoor use, a bit heavy at 93 gms but wood was not the lightest. Need help on establishing how much rubber to use, I was working on 20% of model weight, i.e. 19-20 gms which would equate to 8 strands x 3.32" x 2.3 times prop to hook length. Does that sound about right or is it overkill? Also help with attaching pre wound 8 strands of rubber to S hook, 'O' ring doesn't seem up to the job.
Any advise appreciated.

The amount of rubber will depend on the size of the prop and the span of model as well as the weight. However, I would start with 6 strands of 1/8" the same length as the distance between the rear peg and prop hook. This will be enough to see whether you have the amount right. It's also easier to hand wind if the rubber is the same length as the hooks; for initial test flights, you don't need much rubber. All you are doing is seeing if the model will fly. Once you have discovered how much rubber to use, you can increase the length to get the duration you require. Further, using 1/8" will allow you to add a loop to increase the power available if it's required.

The motor can be looped directly over the prop hook, or, if you're using a winding tube/torque meter, a small figure of 8 loop of wire should suffice.

Thanks Andy. The 95 GM's came as a bit of a shock for a 24" biplane, especially after building peanuts to 10-14 GM's!

You're welcome DMK. I would also suggest that you do the first few flights outside over long grass. I see you come from Oxfordshire; the Oxford Club has a number of successful Free Flight Scale modellers who could give help if you really need it.

As far as this forum goes, welcome aboard! If you have time, we'd appreciate a brief introduction post in our intro thread here:

www.aeromodellers.co.uk/forum/thecafe/10...elf?start=1620#88409

We then know who we're talking too and what level to pitch any responses.