Chris Freeman 3

David Boddington wrote this in AMI August 1996

It is very easy to over complicate this discussion. My son and I normally test fly our models in Primer and once happy with the flight performance we paint the aircraft. It can be surprising to see how just the weight of the paint can affect the flight performance. Another example is if you fly at sea level and then fly the same aircraft at a higher altitude airfield. Many of the scale competitors at the world champs in held in South Africa were surprised at the difference in performance or lack of it, Thinner air is effectively the equivalent of a heavier aircraft.

A big difference between a scale aircraft with a higher wing loading than non scale lightly loaded aircraft. Scale or semi - scale aircraft normally have smaller tail surfaces and tapered wings which also has a bearing on the stability.

Take 2 airframes, 1 heavy and 1 light and you will see the difference in stability. I once did a kit review for David Boddington and when I had issues with the flight performance of the aircraft which was heavy and then compounded by our thinner air in Johannesburg, David said I should move the CG forward of the recommended position and it did help the flight characteristics. I have done this ever since and had good results. CG is also a personal preference as some pilots do like a twitchy airframe and others do not. Stability at low speed quickly shows if the CG is correct.

The heavier the airframe the less stable the aircraft will be so a more forward CG will be required. Always hard to put more weight in a heavy airframe. Elevator movement is critical as too much can result in a snap roll. EXPO can work against you on a test flight if the trims are out and you need to say up before trimming. I have always found it best to fly the aircraft to see how it handles as some aircraft can handle excesses better than others. Tomorrow we will be flying a 1/4 scale S6 that the builder never flew as he thought it was too heavy and would not fly. It flew very well when Byron test flew it and the original builder will be with us to see how well it actually flies.

I have normally a few projects that I am building at the same time. I often get sidetracked by articles and forums like this that manage to get me going in another direction. A son and friends also manage to add to the confusion by bringing new projects into my workshop. A 70% framed up Ziroli P38 is a recent addition to the build program! How can you say no to that!

A drop in revs could be mixture too rich, it can also be the fuel might not be good, more nitro needed or the plug not good or incorrect heat range.

More work done.

I recently decided that I needed to test some Motors that I had replaced bearings and also recently acquired. These are motors in the 30cc to 50 cc range so not easy to test. I also found that static conditions are not always a true reflection of what happens in the air and also the recommended propellers for most motors are not very accurate or even helpful. I decided to drag the old stick out that had been built for this task for glow and petrol motors. The firewall is designed to accept the power pod as we call it with just 4 bolts so I made up some new power pods for the motors that needed testing. The Stick has a very wide CG range and handled the motors easily even though I was testing 8 and 12 cell setups.

Sorry for the late reply, I have a Surpass C 6354 200 KV with a Castle Creations 75 amp ESC on 8 cells with a Zinger 18 x 8- 12 propellor. Plenty of power and duration. I tend to use glow props as I have quite a large selection of them so I can test what is needed. I find the information and recommended propellers very poor on many of the motors and ind the amp meter vital when it comes to set up.

Took the Blackhorse Stuka which has an electric set up in it and a Phoenix P47 which has a ST3000 and had some great flying. The ST sure knows how to spread the 12% oil in the fuel over the airframe!

Byron is doing some work on the airframe and has done the exhausts on the 3d printer and also working on the canopy. We plan to fly it again and then strip for painting.

Being a cheap modeller I often get things that I might use one day, one of these was a local Mustang fuselage based on the old Byron kit. I managed to borrow a foam wing and stab from a Byron kit and then made my own wings and stab that was sheeted in balsa and then glassed and filled. The wings were made for Robart retracts to be used, the Top Flight kit is about the same size so these retracts were the ones used. For some reason I then stopped work on the mustang after all the building was done and packed away. Byron was at a loose end after the MB 5 was returned to me when I needed to get it ready for flight and said he really enjoyed working on it so I suggested he take the Mustang and do some work on that. He has done a great job so far and I think this airframe will be great to take to the flying field with the MB 5 so people can see the difference. The wings on real Mustangs were filled and painted to improve airflow on the wings and fuselages left in bare metal so our model will be the same.

I see that Robart is stopping making retracts after 50 years!.

Very sorry to hear about the closure and very glad that you managed to get other work Jon. It might be nice getting your hobby back and not having it as a business! It also just shows how the hobby industry is changing and it is a concern.