Hip Pocket Builders' Forum

Indoor Free Flight Forum => No-Cal => Topic started by: Dan Snow on September 16, 2018, 03:37:01 PM



Title: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: Dan Snow on September 16, 2018, 03:37:01 PM
Many, Many decades ago when I was a wee sproutling, My Dad helped me build a Competition Models XB-70 Valkyrie. All sheet balsa, with an .049 pusher it flew fast and glided faster. I think my longest flight with it was less than 2 minutes, but man I loved that ship!!

A few weeks ago I found the plan sheet on line, so I downloaded it as a future Maybe".  Then I started reading some of the threads here and decided what the heck. I'm never going to compete with it so I can just have at it.  So here's what I have so far. Span is 9"


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: Sky9pilot on September 16, 2018, 04:00:55 PM
Interesting so far.  How will you achieve the reflex in the wing?  I look forward to your progress!
Sky9pilot


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: Dan Snow on September 16, 2018, 04:29:10 PM
Yeah, about the reflex! I may have out foxed myself on that one! :P :P :P
Actually, I was planning to make the motor stick the portion of the fuselage under the wing, so my current plan is to cut the airfoil reflex into that, glue the wing to it, then attach the fuselage. If that doesn't work I can slice the elevons off, sand an angle in their leading edge and achieve the reflex that way.

I'm going to get a chance to try making my first propeller because I know this critter is going to come out tail heavy so I'll need to save every gram I can. Yes, this will be a pusher.

Just to let folks know, this is my third rubber powered model. The first is a Guillows Chipmunk which has only had test glides so far, and second is a Dumas Beaver currently under construction and ready to cover.


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: VictorY on September 16, 2018, 05:20:41 PM
Gurney flaps should work for reflex, or at least for experimentation purposes.


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: MKelly on September 16, 2018, 06:12:26 PM
Neat build!  Mike Fedor flew an .049-powered XB-70 at the last couple meets in Gainesville TX.  It flew very well.  Good luck with this one.

Mike


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: NormF on September 16, 2018, 06:18:44 PM
FWIW- there is a laser cut, repro of the Comp Models kit by Bob Holman. http://www.bhplans.com/AMAMISSg1.html

Norm


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: Dan Snow on September 16, 2018, 06:48:35 PM
Well What do you know! Thanks for the  info Norm.

Interesting that it says .020 engine, I flew mine with an .049.


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: Starduster on September 17, 2018, 08:25:30 AM
Well What do you know! Thanks for the  info Norm.

Interesting that it says .020 engine, I flew mine with an .049.

Like many others, it seems that my first airplane was also a B-70 from Competition Models.

I was probably 9 or 10 Years old at the time, and my sister was friends (real friend, not the FB type!) with Ray VanDewalker's daughter, and my mom was a Brownie leader that had both girls in the troupe.

I got the B-70 from 'Van' and my dad and I built the airplane and initially put a Pee-Wee .020 on the back. We flew the heck out that airplane, and when the .020 started to slow down and the airframe started started getting heavier and heavier from fuel soaking and repairs, I put a .049 from an old Cox plastic Control Line on it. Then I flew the heck out of it in that configuration. It was pretty tame with the .020 but the .049 really "hauled the mail"

I'm the one who did the laser cut files for Bob Holman, and the kit is per the original with the exception that I added tabs to the bottom of the Vertical stabs and slots in the wings. The Vertical stabs were always kind of difficult to place correctly.

I even built one a few years ago and did it 3 channel R/C with Electric. It flew pretty well.


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: Dan Snow on September 17, 2018, 03:53:20 PM
It's probably a good thing I don't have any .049's or I might be sorely tempted to order one of those kits! Just like it's a good thing I don't have an .020 and someone hasn't re-cut the Carl Goldberg Ranger 30! I built several around the age of 8-10 or so, and the last one was last seen at around 1500' headed south across Rosamond Dry Lake! i had all my contact info in it but never saw it again. Of course in the late 1950's early 1960 there wasn't much but empty desert in the Antelope Valley!!

Structure is done, need to add motor stick, motor and prop. As it sit in these pics it weighs 12 grams. Span is 9", length is 15.5" and yes, it is massively tail heavy without the motor or prop.
I was able to achieve a small amount of reflex by pinning the trailing edge up 1/8" then shrinking the tissue. Since I'll need nose weight anyway, I will likely add card stock trim tabs to the canard.4

I will consider the thing a success if I can just get it to NOT act like a lawn dart!!


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: strat-o on September 17, 2018, 06:28:34 PM
Wait, reflex?  Why, is the canard too small? 


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: Dan Snow on September 17, 2018, 07:51:24 PM
Some deltas require a bit of reflex, or "up trim" on the elevons for level flight. The flying wing "Combat Gremlins" I flew all required vary amounts of reflex for level flight.


Title: Re: XB-70 Valkyrie No-Cal, sort of, Or maybe a Lawn Dart?
Post by: Dan Snow on September 26, 2018, 10:25:44 PM
It FLEW!!  IT ACTUALLY FLEW!!!  Okay, it flew like a delta, FAST. Test glides had a sharp left roll.  Added some right elevon and put about 100 winds on 2 strands of 3/32 rubber and viola! The torque and right elevon caused a sharp Right turn/roll. Took the right elevon out and added some tabs to the canard. Put another 100 winds in and got a fairly flat 3/4 of a 25' or so circle right.  That is pretty much the limit of my back yard.

I'll make up another motor, install the nose weight so it doesn't keep falling off, and take it out this weekend with the Beaver and the Chipmunk.  I might be able to 20 second flights out of it, but I have a feeling that they will be of the "HEADS UP!!!" variety.  It was a fun little project, and not a model you're likely to see at the fieild!!