Anybody remember Carl Spurlock flying around the Byrofan powered A-7 in the mid nineties? He brought it here to Lubbock for our turn for the SW Fan Fly in 95. Sounded really great and he campaigned it well. Then, Byron went out of business and haven't heard a thing since. Wonder how Carl is doing or even flying RC any more? That was 20 years ago. The biggie then was Garland Hamilton flying a BVM F-80 with JPX propane turbine. The A-7 back then turned just as many heads as the turbine.

Not big by todays standards but large for a DF. I wonder if Iron Bay has the molds for that one?

I like the various color schemes the "Greeks" threw on their airframes. Chic

Carl did the 2-seater. I don't think Byron ever got the molds, I think Carl still has them.

ERH,

Yes, I'm using the JetFan90 on 12s. It's running a Neu 1415/1.5y motor with 12s 30c 5800s. AUW is about 14.5 lbs which is about what it weighed fully fueled with the turbine in it. I think my folks still have the vac formed plastic pylons set still available, but none of the glass ones unfortunately. I'm not a big gyro guy and so can't really say about the benefits. One thing to note about them is that since they are damping out the accelerations in all axes, they can actually mask the onset of stall at slow speeds. With all the stick time I have on the A-7, I've not felt a need for a gyro.

I believe Carl's A7 was his own project and not in anyway connected to Byron.

Ive seen a few kits that have sold fast over the last few years. Which are the ones to keep an eye out for, good ones that is. Id really like to have one before they are unavailable.

Here's a link to a build thread for the Century Jet A-7; http://www.rcuniverse.com/forum/rc-j...s-7-build.html

The model was built by John Pryor. John worked for CJM at the time. I saw the model at Kentucky Jets a number of years ago and John did a GREAT job building it! I watched him fly it late one afternoon and, while it flew, it was significantly underpowered. I believe he had a RAM 750 in it at the time, only 17 pounds of thrust. John would have to verify it. I walked away with the impression that a 28 pound turbine would make that model come alive.

CJM kits are builder's kits. If you're not a craftsman, they're not for you. You get a solid foundation for building a nice model, but you will have to put effort, time and some modeling into the build. I'm a fan of the CJM A-7 and will have one some time in the future. It's a good size and looks to have an accurate outline.

For the sake of knowledge and accuracy, the leading edge devices on the A-7 are leading edge flaps, not slats. They are hinged and simply droop, they do not extend to create a gap between them and the wing. The A-4 is an example of an airplane with leading edge slats.

Great thread!

Tom

I thought there was a video of John's CJM A-7.....and found it! Definitely underpowered but still well behaved.

https://www.youtube.com/watch?v=-OR1sQeMlD0

Ive seen that thread, unfortunately not a lof of building to show. I think by definition kits are for builders. Wish I knew exactly what is so hard about this particular kit. Does't seem too band. I have been told before that a 30 pounder is the magic number. Sluffs are just draggy airframes. I have friends who flew it for the ANG, and it was in fact temperamental. Engine was marginal at best, and lacked sufficient cooling.

This is the one I want to model it after.

im cutting all the parts for a 1/4 scale a7. my friend did the plans in cad. i should start the assembly in january. its going to be a slow moving project. but move it shall.

Barry I don't think there's an engine powerful enough for that size. Are you planning on using a tuned down Allison TF41?

B-300F will be a good match. If not, the 500 should do it .

Oliver on the 300's and higher you really need to start developing an accessory drive to plug in all sorts of goodies. Power/pneumatic pump/smoke pump........imagine the possibilities of a low pressure pneumatic system that does not lose pressure. If the starter core is large enough, you could turn it into a generator after startup.

just mad ideas! ;-)

It's not that simple. A single shaft turbine is designed for a specific amount of drag on its shaft. Anything that adds drag, means lower RPM and lower compression ratio, thus different ( degraded ) operating parameters for the combustion cycle. This means that the combustion cycle will be offset and will need a different compressor, NGV and turbine stage operating characteristics as well. In other words, this would only work with variable blade geometry. It would mean complex 3D printed aluminum diffuser and Inconel NGV, bumping up the price of the turbine by about 50 k USD...

An online genrator is possible since it keeps a fairly constant load on the shaft. Any random accessory addition would render a normal single shaft engine inoperative.

Yeap, thats exactly what I meant. Keep the design the same, and take a small pressure loss (or speed). That's why I think the larger diameter engines would be ideal. A valve with a large gear ratio should only have minimal load. I think the very early turbines had a pressure tap on the compressor for oil motive flow, didn't they?

The early ram 750 had a pressure tap. There was no rpm sensor it monitored it's rpm with bar pressure.
Vin...

QUOTE=FalconWings;12139935]Yeap, thats exactly what I meant. Keep the design the same, and take a small pressure loss (or speed). That's why I think the larger diameter engines would be ideal. A valve with a large gear ratio should only have minimal load. I think the very early turbines had a pressure tap on the compressor for oil motive flow, didn't they?[/QUOTE]

i think a 220 behotec would fly a 1/4 a7. its not much bigger then my tomahawk hawk, not a draggy airframe at all.