Courier #2

[Bark65]

I finished the second Courier today. Total weight including rubber was 19 grams. I had it balanced out perfect. Nice glide, nice low power flight. Everything looked great. I took it to the field tonight and put about 100 turns on the motor, let it loose. Nice climb, nice glide, nice landing. Put some serious turns in it with the drill for the second flight. Let the plane loose. 2 seconds later the balsa motor stick snapped in half and the plane fluttered to the ground in a ball of rubber, balsa and tissue. Wing survived the ordeal as well as the tail grouping. Lesson learned. Will rebuild using a basswood motor stick instead of balsa. I did take some digital photos of the plane today at work using a cooworkers digital camera. As soon as she e-mails the photos I'll post a few.
Good flying,
Bark

[Dave Robelen]

Hello Bark,
I am sorry to hear of the experience. Someone once remarked that you can find the lightest weight for a part by making it lighter until it breaks, then make it a little stronger. It is possible that the balsa was a poor grade for the fuselage. Tough, stringy balsa is at least as strong as basswood, and a bit easier to work with. Of course, making the stick a bit deeper would help matters. It is also possible that the rubber motor is a bit short. Somewhere between 1.2 -1.5X the distance between the hooks is a good general length for the motor. This will have the torque, but less tension between the hooks. Good luck getting it back together.
Regards, Dave

[Bark65]

Dave,
You could be right about the balsa being a poor grade. I've thought about that. I have been buying my balsa from an Arts and Craft store. I don't know what grade of balsa I am buying. I probably need to pay more attention to this next time. I've been using a 14 inch motor for these planes as specified on the plan from the book. At that length, the motor is slightly longer than the front hook to rear hook distance. Not 1.2 to 1.5 the distance. I probably need to go to a better hobby shop and find a higher quality of balsa.

[Dave Robelen]

Hi Bark,
The main reason the kit and plans designers suggest such short motors is that they expect you to wind by hand, and not be terribly patient with a long motor. Also, the shorter motors are less likely to bunch up, or fall off of the hooks when they unwind. The downside is the large amount of tension they put on the attachments as they are wound, and shorter flights. A longer motor with more turns wound in=longer flights, and puts less strain on the attachments.
We have not mentioned lubricating the motors, but I am fond of silicone grease. This may be found as refrigeration material for gaskets & such, or trombone slide grease. Lubricating the motor wil extend the life a whole bunch. The advantage to the silicone is that it does not make the model messy. Just be sure and tie any knots before rubbing lubricant into the rubber material.
Regards, Dave

[Bark65]

Here's a photo of the 2 Couriers. The white one on the left was the one that cracked in half. The red one is a decent flyer but is very overweight.

[Bark65]

Dave,
I've been lubricating the rubber using Armorall spray. I've been washing the rubber in cool water and a little soap to remove the talc. I break the motor in by stretching it and applying the armorall. Before flying I lubricate the motor in a baggie. I've been getting 6 to 8 flights out of a motor before it starts to develop nicks in it. I need to try the silicone grease. Ive heard that works really well and the rubber holds up better. I need to figure a way to wind a long motor in this plane. The nose bearing is not removable as it was in the first model I built. I'd have to unhook the rubber from the front prop shaft, stretch, wind and place back on the prop shaft. I'll need to figure a way to hold the plane to do this. There's a lot to learn about these little planes. I really appreciate your help.
Good flying,
Bark

[Bark65]

Here's a shot of the prop hanger. The hanger is made out of a paperclip.

[Dave Robelen]

Hi Bark,
My method of holding a plane while I wind by myself is to make the rear motor anchor from aluminum tubing. I can then slip a steel wire through this and a "U" shape braket that fits around the rear fuselage. Sometimes I hang this on a car window, other times on a short pole that has a couple of bracing ropes to pull against.
Armorall does a pretty good job, the silicone stays with the rubber a bit better, and does not get slung on the model parts like the more liquid lubricants. There will always be more to learn, I am certainly still picking up neat information from columns in the magazines, and going to the meets I can find to see how the other guys are getting things done.
Cheers, Dave

[Dave Robelen]

Hi Bark,
We apparantly both posted at about the same time, so I did not see the bearing until later. That is a neat solution to have an adjustable hangar from very available materials. Do you stretch the rubber while you wind? I stretch mine about 3X when I start winding, and start slowly moving in as I reach 1/2 winds. The goal is to arrive at the model as you reach maximum winds. This usually removes some of the tension in the motor, and allows more turns without harm.
Regards, Dave

[Bark65]

Dave,
I just noticed your response last night. I have not been stretch winding with this plane. Next time I fly it I'm going to install a longer motor in it. I need to drill a hole through the motor stick so I can attach it to my homemade winding stooge. Also need to make an S hook out of the wire I ordered so I can stretch wind the rubber. Then I can slip the S hook off of the hook on the cordless drill and slide it on the prop shaft hook. This should improve flight times and reduce torque on the plane. I also ordered 32 feet of 1/8 inch rubber so I can experiment with different size rubber as well.
Good flying,
Bark