Big YF-12 RC Rocket glider for G-12 motors

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tab28682

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After If I finish up the little Japanese rocket fighter, which is now painted and needs just a few details, I might have to skip a couple of planned projects and do something for G40 and similar.

Current front-runner is a large XB-70 with a built up Depron fuse. Physics and motor performance would dictate a model about the size of Frank's YF-12A. I am out of 9mm depron so it might need to be a layer of 6mm bonded (in a low weight manner with spray contact glue) with 3mm for the wings and tails.

If the new Athena flies as nice as I hope it will, a 3" diameter upscale with 9mm surfaces might work well.
 

AtomicStorm

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I remember building the sr71 kit when i was about 12 years old. Spent soooo much time making it look perfect and boy did she look amazing and flew even better. On the other hand the wind picked up after the maiden launch and it took the rocket into the trees a.k.a. into orbit. Your project has influenced me to build one of a similar caliber. Have you thought of putting retractable landing gear on it and maybe a lightweight landing parachute for scale? Looks amazing!!!
 

burkefj

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It's funny people always ask these questions about adding edfs in the pods and landing gear and tail chutes but it's a complete waste of time. These models are designed to fly perfectly at extremely light weight with the motors they're designed for. If you add weight for landing gear or edf's it'll be too heavy to boost and you wind up with a crappy flying model. Retractable landing gear on a model like this is useless especially if you're flying out of a grass field or on rough ground.

I remember building the sr71 kit when i was about 12 years old. Spent soooo much time making it look perfect and boy did she look amazing and flew even better. On the other hand the wind picked up after the maiden launch and it took the rocket into the trees a.k.a. into orbit. Your project has influenced me to build one of a similar caliber. Have you thought of putting retractable landing gear on it and maybe a lightweight landing parachute for scale? Looks amazing!!!
 
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burkefj

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I did just pull the YF-12 back out, used a 29mm motor tube, hardened at the end and sharpened with a belt sander, and reamed the slot in the wing so I can mount the 29mm longburn H-13 motor further forward. It sticks out the end now about a half an inch, the same as the G-40 which is shorter. It worked great, and although I had to add 40 grams more nose weight, it came out at 32.7 oz ready to fly which I think will be right at the edge for that motor for liftoff the pad, we'll wee this weekend hopefully. I just painted and weighted a new nose cone for the H-13 motor so I don't have to have removable nose weight depending on what motor I use, just swap nose cones. With G-40 it weighs 28.4 oz and it turns out the CG was about half an ounce further back that I orginally marked it when I scaled it down from the YF-12 kit I make. For reference, my Avro arrow weighs 31.8 ounces, the Aurora Clipper weighs 32.3 ounces, and the Orbital Transport glider weighs 30.9 ounces all with the H-13 motors..
 

Brian V

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Can’t wait to see that one Fly!!!😃👍
 

AtomicStorm

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It's funny people always ask these questions about adding edfs in the pods and landing gear and tail chutes but it's a complete waste of time. These models are designed to fly perfectly at extremely light weight with the motors they're designed for. If you add weight for landing gear or edf's it'll be too heavy to boost and you wind up with a crappy flying model. Retractable landing gear on a model like this is useless especially if you're flying out of a grass field or on rough ground.
I could see how adding edfs would be too much weight because you would then have to add another battery. Retracts are a different story, they make really cheap and good looking sets of retracts that have built in micro servos that can run off of your current battery. I was looking at some on banggood that are very lightweight, even have little doors that cover the bay that the retracts sit in if you decide to take them off and fly without them to keep the scale look. You know, just incase you didnt have a runway to land on. ;)
 

burkefj

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I'm right at the limit of the motor liftoff weight, 32.7 oz, any weight is too much. I'm only running a 1s battery for the two servos, adding three retracts even small ones would require bec and 2s battery at least, I'd need to reinforce the wing for the servos, it's just a bad tradeoff, if I was under the max liftoff weight for the motor I'd have margin.

I could see how adding edfs would be too much weight because you would then have to add another battery. Retracts are a different story, they make really cheap and good looking sets of retracts that have built in micro servos that can run off of your current battery. I was looking at some on banggood that are very lightweight, even have little doors that cover the bay that the retracts sit in if you decide to take them off and fly without them to keep the scale look. You know, just incase you didnt have a runway to land on. ;)
 

AtomicStorm

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I'm right at the limit of the motor liftoff weight, 32.7 oz, any weight is too much. I'm only running a 1s battery for the two servos, adding three retracts even small ones would require bec and 2s battery at least, I'd need to reinforce the wing for the servos, it's just a bad tradeoff, if I was under the max liftoff weight for the motor I'd have margin.
Yeh, i think retracts may be a better idea on another glider or if you plan for the extra weight before the build. I just switched from nitro and gas 1/3 and 1/4 scale rc warbirds to rockets so im all about scale and functionality. Looks amazing and im sure she's a beaut to fly!
 

burkefj

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Rocket gliders in general and especially with ones with motors in the tail are a bit of a challenge. You have to design them large enough for the CG shift that happens between liftoff and burnout, you have to be able to launch in a stable configuration and then be able to trim out the nose heaviness after burnout. Or you have to design a complex ballast shifting or water ballast type solution that drains as the motor burns, or you have to do some kind of ejecting mechanism to eject the motor and nose weight after burnout. You also have to design the model for the speeds and stresses that you'll have, All of these can impact the weight. Often times if you design things to be very lightweight they can't stand up to ultra high speeds. Low thrust longburn motors are much preferred because they give you much more time to react to wind or out of trim conditions, but the long burn motors don't have a large thrust Spike or sustained thrust so you have to be very careful to design within an envelope that will allow you to boost safely with a reasonable altitude. Many times you're right at the edge of the envelope and any extra weight will kill the design. It's not like a normal RC model or rocket where you can just stick a bigger motor in and that will solve your problem, that often times just makes things worse.
Yeh, i think retracts may be a better idea on another glider or if you plan for the extra weight before the build. I just switched from nitro and gas 1/3 and 1/4 scale rc warbirds to rockets so im all about scale and functionality. Looks amazing and im sure she's a beaut to fly!
 

AtomicStorm

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Rocket gliders in general and especially with ones with motors in the tail are a bit of a challenge. You have to design them large enough for the CG shift that happens between liftoff and burnout, you have to be able to launch in a stable configuration and then be able to trim out the nose heaviness after burnout. Or you have to design a complex ballast shifting or water ballast type solution that drains as the motor burns, or you have to do some kind of ejecting mechanism to eject the motor and nose weight after burnout. You also have to design the model for the speeds and stresses that you'll have, All of these can impact the weight. Often times if you design things to be very lightweight they can't stand up to ultra high speeds. Low thrust longburn motors are much preferred because they give you much more time to react to wind or out of trim conditions, but the long burn motors don't have a large thrust Spike or sustained thrust so you have to be very careful to design within an envelope that will allow you to boost safely with a reasonable altitude. Many times you're right at the edge of the envelope and any extra weight will kill the design. It's not like a normal RC model or rocket where you can just stick a bigger motor in and that will solve your problem, that often times just makes things worse.
I would think that ejecting the motor would be best, kind of like space shuttle endeavor. I do know from flying planes that you want it a little nose heavy. And i would much rather be nose heavy then tail heavy "took a 81" gas piper cub to figure that out :( ."
 

burkefj

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Well it depends on where you fly, ejecting a motor POD at 1200 ft in a field where there's tall wheat is problematic at best. That would not work at many RC fields. The kind of CG shift I'm talking about is one and a half to 2" in something this size, it's pretty dramatic.

I would think that ejecting the motor would be best, kind of like space shuttle endeavor. I do know from flying planes that you want it a little nose heavy. And i would much rather be nose heavy then tail heavy "took a 81" gas piper cub to figure that out :( ."
 

tab28682

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I am ready to see the video of the YF-12A on the H13!

Frank, I note that your launcher is set to vertical in the recent videos. Have you considered a slight tilt of 10-15 degrees for the less robust motors?

I typically set the Hobbylab F-14 to about 75-80 degrees for launch, similar to the Aerotech Phoenix setup, which is actually tilted a bit more than that. I often tilt my current RC RGs a few degrees. Gets them on the wing a bit sooner and keeps me from having to look straight up.
 

burkefj

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Tom, my pad is a very simple fixed unit with no angle adjust, typically I just pitch a slight bit right off the rail to get an angle away from me like you are talking about and haven't found the need yet. Some of my rail guides are on the top right of the model, or on the bottom, so angling without using wing supports would cause binding and I was more worried about that.

Frank

I am ready to see the video of the YF-12A on the H13!

Frank, I note that your launcher is set to vertical in the recent videos. Have you considered a slight tilt of 10-15 degrees for the less robust motors?

I typically set the Hobbylab F-14 to about 75-80 degrees for launch, similar to the Aerotech Phoenix setup, which is actually tilted a bit more than that. I often tilt my current RC RGs a few degrees. Gets them on the wing a bit sooner and keeps me from having to look straight up.
 

burkefj

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It worked! I was able to re-fit and re-balast my 1/20 YF-12 for an H-13 and got a boost this morning to 1170 feet.
 

Brian V

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I loved that flight!!! Just got my YF-12 kit and the F-14 kit THANKS FRANK👍😃
 

Brian V

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I see why you like that motor for the big birds that was another AWESOME FLIGHT!!!!!!! 👍😃 Nice Frank!!!
 

burkefj

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HI all, I had put a video of my larger YF-12 I built as a one-off to fly in the new 29mm H-13 longburn motors and I was contacted on facebook by Ray Scalise. He worked for Hughes and was the FCO on initial YF-12 test flights and missile ejections of the AIM 47, he gave me permission to distribute this. His was in a book form with a reader, I cut and pasted the stories into a word/pdf doc to make it easier to share, hope you enjoy it. PDF attached.
 

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Brian V

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Hey Frank thanks for that report that was some great reading. I like researching the history of each model that I fly. I do that on every airplane I restore also.😃👍
 
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