Large X-15 Delta RC RG

[burkefj]

Dave Schaefer shared this on rcgroups, he was asking me about my cg that I used on my X-15 delta styled kits. I don't think he has flown it yet, looks great, the weight is up around 11 pounds and I think will fly on I motors, given the wing area, glide will be steep and fast I believe. Not floaty like mine Anxious to see his flight report.
For those that don't know him, he flew the large X-30 years ago, and more recently the K powered X-2 rocketplane and his lovely I powered fiberglass conversion ME-163 Komet.

Frank

 

[Zebedee]

https://www.rocketryforum.com/showthread.php?131258-BALLS-25/page3&highlight=Balls looks like it crashed - maybe why he's asking.

 

[rstaff3]

Too bad. High power Delta X-15 gliders seem to be a challenge.

 

[burkefj]

I did not see the other posting, that's too bad, interested to see what the issue was, I know wing loading was going to be high..

 

[tab28682]

I spoke to Dave a few days ago about the Delta X-15 flight at BALLS. He indicated that he had set the CG too far forward. Boost was fine, but he did not have enough elevator authority to bring the nose up for landing, due to the excessively nose heavy condition. No doubt the overall weight played a part as well. It more or less plowed into the desert in a shallow dive, short of the intended landing spot.

He said the damage was not too bad and that the model would be repaired and fly again. He texted me the above picture of the "up".

 

[tab28682]

A PS to the above: per the BALLS postings, the Delta X-15 model was completed in an intense effort during the last six weeks before the event. Dave would have normally built a smaller RC model or a chuck glider to establish a good CG range.

I believe the story was that he and a friend used a CG calculator or something similar that did not work well at all with the very low aspect ratio delta wing of this model.

Frank offered him some advice over in the RC Groups rocket glider thread based on his proven flight experience with Delta X-15 models. With that ever so clear 20-20 hindsight, that would have likely been the way to go to get a good CG.

I have a 38mm powered 4" diameter Mig-21 RC RG with wings and tails of balsa, ply and carbon in work. My plan is to use water ballast that is dumped during the boost to optimize the CG for both boost and glide. George Gassaway proved that this approach works well on his well known X-1 model and I think this is very likely the best way to go to optimize both boost and glide CG on F and G and higher power rocket gliders that otherwise would have large CG movements between boost and glide modes.