High Ceiling Strategy

[jajefan]

Since you are still at experimenting stage, add some clay to the nose.

Once this is tested, and if it works, then you can worry about getting back down to weight.

Think of the motor stick as a beam in bending (and buckling). It has the highest loads in the middle. So you can sand both height and width at the two ends to reduce weight (or just at the tail end to move CG forward). You could sand both ends a bit, then add clay to get back up to 8g.

This year's plane should be build-able in the 6g range, giving 2g of ballast to move around. Not sure which kit you have. It it is FFM, it has carbon wings, so the big weight issue is in the motor stick. Judicious selection of MS wood, and careful reinforcement can get you a lot.

But focus on the moved CG and increased decalage first, see if it solves your problem. Then go to weight reduction to make up for clay.

Coach Chuck

Hey Coach Chuck,

On a partially related note, we are having trouble with our motor stick flexing (inducing negative climb at the beginning of our flight, oftentimes causing a dive which hits the floor). We have only been using one strip of carbon fiber on top as per the FFM kit plans, but we find that it is not enough. We are wondering how your team was able to stop the motor stick from bowing (whether it was extra carbon fiber strips, a kevlar truss--like in Helicopters 2017--or some other method)?

[Rossyspsce]

Since you are still at experimenting stage, add some clay to the nose.

Once this is tested, and if it works, then you can worry about getting back down to weight.

Think of the motor stick as a beam in bending (and buckling). It has the highest loads in the middle. So you can sand both height and width at the two ends to reduce weight (or just at the tail end to move CG forward). You could sand both ends a bit, then add clay to get back up to 8g.

This year's plane should be build-able in the 6g range, giving 2g of ballast to move around. Not sure which kit you have. It it is FFM, it has carbon wings, so the big weight issue is in the motor stick. Judicious selection of MS wood, and careful reinforcement can get you a lot.

But focus on the moved CG and increased decalage first, see if it solves your problem. Then go to weight reduction to make up for clay.

Coach Chuck

Hey Coach Chuck,

On a partially related note, we are having trouble with our motor stick flexing (inducing negative climb at the beginning of our flight, oftentimes causing a dive which hits the floor). We have only been using one strip of carbon fiber on top as per the FFM kit plans, but we find that it is not enough. We are wondering how your team was able to stop the motor stick from bowing (whether it was extra carbon fiber strips, a kevlar truss--like in Helicopters 2017--or some other method)?

Carbon fiber on the sides of the motor stick should work(part of FF plans).

[jajefan]

Carbon fiber on the sides of the motor stick should work(part of FF plans).

We also have the side reinforcements, but they do not help with motor stick bowing upwards.

[CrayolaCrayon]

A simple kevlar truss would probably work the best, and its weight would be negligible.

[coachchuckaahs]

Sorry, I have been offline. My entire flying team went to Round Valley to compete in AMA competition this weekend. One team member came home with a National Record (pending AMA approval).

Think of the motor stick as a beam. Adding in compressible material to the top and bottom makes it like an I-beam, harder to flex. Often only one surface (usually the bottom) is reinforced, to prevent compression of the balsa. As you get longer, reinforcing top and bottom helps.

As in real world engineering solutions, there are many ways to keep a beam form flexing. Trussing is certainly one way that may prove effective, depending on your design. Trussing does add a complication in that rubber that breaks or comes off the hook before entirely unwinding could get tangled. Care must be used, but like was done on heli, it can be managed and effective.

Coach Chuck

[klastyioer]

itd be a bold move to start considering tube motor sticks like the ones mentioned earlier in one of these forums
theyre strong enough to prevent any flexing in the stick and are lighter or around the same weight as the sticks youre probably using right now, depending on the wood you choose to use
theyre kinda hard to make not gonna lie on that but there are videos online that can instruct you on how to make the tube itself and with a little bit of research, you can find some jigs for gluing the seam, inserting tissue tubes, and implementing the rear hook, tb, and bearing.

[Airco2020]

Well I just wanted to give an update and thank everyone for their help. We had our state competition Saturday. The good news, we had a personal best time with this plane of 2:37. The bad news is we could not get the climb needed for the big building and finished 9th in state. I don't know the top time, but I did time one of the winners practice runs at 3:42. The venue is an armory with a 90ft ceiling in the middle. The winning plane was able to corkscrew almost straight up for the first 30 - 40 ft and then the plane flattened out and kept climbing to right under the rafters.

[Airco2020]

Sorry, I have been offline. My entire flying team went to Round Valley to compete in AMA competition this weekend. One team member came home with a National Record (pending AMA approval).

Coach Chuck

Congratulations!!! You've really got a powerhouse team going!

[coachchuckaahs]

It was a blast to fly in a 100' ceiling! My kids all got times right around 10 minutes with their penny planes. Like described by airco, the flights in the high venue were very powerful climbs initially, then leveling off under the rafters. Imagine hitting rafters, repeatedly, at 100'! Only 2 got stuck, and we freed them with helium balloons.

I am happy to report that our testing at home scaled well to the 100' room. We tested with 1/5 rubber, generally 0.5g of rubber and a 2g stick, flying to 20' at home. This gave us an excellent starting point for the 100' ceiling.

Interestingly, the kids found different solutions to get to 10 minutes. The top flyer had very high pitch, with slow prop RPM and thick rubber. That is also the route I took. However, another kid had fairly low pitch, with higher RPM, and she was beating up the rafters. We kept cutting the rubber thinner and thinner, and she reached within a few seconds of the high pitch kid!

All of the kids used the SO log sheets that we have, and analyzed the data, changing one variable at a time. They progressed from 6-7 minutes to over 10 minutes throughout the weekend.

All of this translates directly to SO. The planes were lighter (3.1g), but the processes to improve are the same. It is amazing to see these planes go up like a rocket, then level out and float on the air.

Coach Chuck

[klastyioer]

It was a blast to fly in a 100' ceiling! My kids all got times right around 10 minutes with their penny planes. Like described by airco, the flights in the high venue were very powerful climbs initially, then leveling off under the rafters. Imagine hitting rafters, repeatedly, at 100'! Only 2 got stuck, and we freed them with helium balloons.

I am happy to report that our testing at home scaled well to the 100' room. We tested with 1/5 rubber, generally 0.5g of rubber and a 2g stick, flying to 20' at home. This gave us an excellent starting point for the 100' ceiling.

Interestingly, the kids found different solutions to get to 10 minutes. The top flyer had very high pitch, with slow prop RPM and thick rubber. That is also the route I took. However, another kid had fairly low pitch, with higher RPM, and she was beating up the rafters. We kept cutting the rubber thinner and thinner, and she reached within a few seconds of the high pitch kid!

All of the kids used the SO log sheets that we have, and analyzed the data, changing one variable at a time. They progressed from 6-7 minutes to over 10 minutes throughout the weekend.

All of this translates directly to SO. The planes were lighter (3.1g), but the processes to improve are the same. It is amazing to see these planes go up like a rocket, then level out and float on the air.

Coach Chuck

congrats to them! sounded like a lot of fun im glad yall had a good time