So, does this mean that, alongside being an X-Men fan, you are also a closet-TMNT fan as well??? :p

Craig said,



What's an TMNT??? :confused:


James Pierson
NAR# 77907

Teenage Mutant Ninja Turtles.

1st day Before Christmas.
 

1st day Before Christmas.

Aaah, I get it. Shredder. Just a little slow in the head lately. :o

Kowabunga DUDE!

Here is the last of the 12 days before Christmas designs. We, in the past twelve days, here in WA have had 60-90 mph winds, 6" of snow twice, record rainfall as usual, and now more wind, snow, and rain on the way :eek: . Power is still up and here is the last design called the Time Runner, and just in time :rolleyes: . Its an 13 mm motor mount and falls in the VR class.

Enjoy and to ALL a Merry Christmas.

James Pierson
NAR# 77907

I know the feeling...

I've been clogged in the sinuses for several weeks now, so being a bit on the "slow side of life" seems appropriate.



It's raining here in Mobile, Alabama right now. Cold rain. Steady rain. Miserable rain. Not the blowing downpour sort of rain, but the hard drizzle that makes driving hazardous because folks believe it isn't hard enough to sensibly remain indoors. I'm being sensible tonight, myself: I'm about to start fixing up a pizza and go absolutely nowhere. Rain is in the forcast for a few days here, too.



Actually, if it's 13mm, it falls into the Schoolyard Sounder class more than the VR...

Thanks for the series, James! I really don't know how many designs this makes for 2006; Scott's going to be posting a basket-load of plans soon, probably after the holidays are over, and even then there will be about that many more to send him in the second round. I think we've doubled the number that have already been posted on BARCLONE. If this rate continues, by the end of 2007 I think we'll have as many designs on BARCLONE as Estes and Centuri had together after their first two decades of operation!

Andromeda Update
 

I worked up a RockSim version of the Andromeda using the ringtail function as opposed to the inside tube method [used in the first version]. There is a drastic degraded difference in the performance using the ringtail, at least as shown in the simulations. My conclusion is that RockSim places a much higher drag value on ringtails as a class than it does on the tube itself.

Attached are both RockSim files...

Stability margins are different, even though no changes in the components are made: 5.04 [empty] for the IT version, and 4.56 [empty] for the RT version.

Center of Gravity (CG) locations: 13.3226" IT, 13.3224" RT
Center of Pressure (CP) locations: 18.0688" IT, 18.5643" RT

As you can see, there is a 1/2" difference in the CP location just for changing between an inside tube (IT) and a ringtail (RT).

Note the differences in performance:

B4-4: 351' for the IT version, 193' for the RT version
B6-4: 362' for the IT version, 192' for the RT version
C6-5: 881' for the IT version, 381' for the RT version

I can vaguely remember something from my early RC days in the late '70s, when some of the local fliers had a model with simulated engine nacelles along the body. Someone commented that they had to "block off the passage" near the front opening in order to get the model to fly correctly. I think they were experiencing the same effect I'm seeing with RockSim on these tubes. It may be necessary to "block the passage" with some kind of bulkhead near the front openings of each tube to prevent them from acting as ringtails. The bulkheads would actually produce less drag on the model than the airflow through the tubes.

More on this as I get the first prototype ready for flight...

Additional notes: I made some corrections involving the slots for the ST-16 tubes, adding some "spacers" at the openings to hold their shape during construction. These should be removed before final assembly. A beefing-up of the base around the rear shroud was done to reduce the chances of breakage during assembly. This problem was identified in the construction of the prototype. Also, a change was made with the inner and outer armature cores. I changed the material to a 3/16" diameter spiral tube instead of hardwood dowels. Essentially, this is a length of launch lug material. It lightened up the fins a little. Both attached files reflect these alterations.

New Plan -- Tau Cestius
 

A Schoolyard Sounder.

Length: 14.90"
Diameter: 1.040"
Fin Span: 3.794"
Weight: 0.664 oz

1/2A3-4T......220'......Dv 22 FPS
A3-4T.........545'......Dv 19 FPS

Recovery is with a 10" parachute.

The four bulkheads used as supports for the launch lugs are each made from a 0.05" thick CR-710 ring with an equal-thickness piece of ST-10 glued around the OD to act as a gap filler.

Enjoy!

Thanks for all the great info on the Inside Tubes VS. the Ring Fins Craig. I totally agree with you the Rocksim is allowing too much drag on those ring fins. I hope you get some flying weather soon for a test flight.

Very nice design with the Tau Cestius as well. ;)

James Pierson
NAR# 77907

New Andromeda Fin Pattern
 

Here's an updated fin cutting pattern, based on my recent message. This image shows the construction alignment tabs inside the shroud slots, and has wider openings for the 3/16" launch lug armature tubes.

I'll probably build a second prototype using this pattern.

Craig,

That is a stunningly beautiful design.

But with the small tolerances between parts keeping the blade vertical while cutting will be important. Better yet would be to laser cut the parts.

Think you might be able to interest Carl?


Again, truly a wonderful and original design.