Mr. Senoski, you made good rockets! (long)

After working on a clone of the Kopter Pterosaur on and off for a few months, I finally had a chance to fly it at last weekend's Saros launch.

The Pterosaur is a relatively heavy (4.4oz = 126g) D-powered rocket glider. It's about 28 inches long, with a delta wing whose span is 20 inches. The design ducts ejection gases toward the nose then back toward the tail. This pushes a balsa piston that releases an elevon.

I tried a D12-3 in it. Boost was nice and high, very straight, with a dramatic slow spin. Transition to glide was very smooth. The only evidence of transition was the sound of the ejection gases escaping. The glide pattern was a wide spiral, but kinda steep. It landed kinda rough, nose-first.

I remove some balsa from the shims I'd added to the elevon-stop surface on the rudder. And tried it again on a D12-3. Boost was identical to the first flight. This time the glide pattern shallowed out quite a bit. From far away, the glide looked kinda lazy, but close up... whoo, this baby really moves! Glide time doubled, too. The landing was much gentler this time.

The Kopter catalog displaying the Pterosaur (and other cool concept kits) is at Sven Knudson's Ninfinger site at

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The Pterosaur plans are found at Ye Olde Rocket Shoppe at
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This is a project that requires some creative lathe work. There are a few discrepancies in the plans, however. To conform to the plan and catalog pictures and dimensions, the top BT-50 tube should be cut to

16", the long bottom BT-55 tube should be 14" and the short bottom BT-55 tube should be 10". Also, the balsa baffle plug should taper to a diameter of 1", not 0.75". Also, I recommend using 3/16" launch lugs instead of 1/8".

I've found the project to be quite challenging, with interesting parts to fabricate and lots of opportunity for careful fit and finish adjustments. The glider is kinda tricky to trim. I recommend shimming the elevon rather than adding weight to the nose or tail. You need a fair amount of wind when flight trimming.

Overall, I've found the Pterosaur to be a most satisfying build. It shows and performs most impressively, too.

My compliments to Mr. Senoski, for a fantastic design.

Dwayne Surdu-Miller SAROS #1

Reply to
Dwayne Surdu-Miller
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The Kopter Pterosaur's ducting system has me thinking, too, about how the design could be made a bit simpler and lighter. Mounting the motor in the center of an elevon-release piston seems do-able. This would allow the system to work with a single body tube. Any thoughts?

Dwayne Surdu-Miller SAROS #1

Reply to
Dwayne Surdu-Miller

Is this what you meant?

In thrust mode, the piston/MMT would be in the forward position. At ejection, the forward compartment would be pressurized, pushing the piston/MMT assembly back some nominal distance thereby releasing the elevator.

I assume you would put vent holes in the BT, perhaps that would be covered (blocked) by the piston in thrust-mode, but would be cleared as the MMT moved back so as to release excess pressure.

Sounds cool.

Reply to
bit eimer

Yes. That's what I meant. That's how the piston and the venting in the Pterosaur are set up.

If the motor is in the piston, there's an added advantage because during thrust, the piston is guaranteed not to slide back to release the elevons.

Dwayne Surdu-Miller SAROS #1

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bit eimer wrote:

Reply to
Dwayne Surdu-Miller

Ive been doing stuff like this for over 20 yrs, even up to I motor RGs. Heck, on smaller ones, I usually have the motor itself *be* the piston, with a paper clip bent and taped to it to hold the elevator.

An Estes E motor clip, longer than the C or D as we know, is perfect for this, as its front bent part to act as a motor block, while allowing enough travel at ejection to release your elevator (were talking ONE single control surface here, mounted on the top of the wing and centered, dang I like doing them this way) and be retained by the longer clips rear hook.

Im gonna have to use music wire or such to scratch build these, as they are expensive to buy.

Yea, I remember the Pterosaur, seen it in the catalog when I was small, so I sorta cloned one and hacked it myself.

If you want to make other gliders this way, and larger but light without the rigors of cutting and gluing a buttload of balsa parts, please look for the Adams brand of foamboard. This is 1/8" thick, and very light, and strong. Perfect for C and D gliders using deltas or other non convie planforms.

Im fixing to fly one I just made, it is a C RG working the way I described above, and it is a 20x20 delta with a differed elevator scheme, and even with

300 in sq of wing material the whole thing only weighs 3.5z. And it took an hour to make too.

I got mine at a Dollar Tree, if you find it get it and youll be very pleased. Bet I can make a D version work on a 30x30 wing and still stay under 8z, even with RC gear.

You gotta admit, any D powered large glider is a rush!!

AstronMike

Reply to
Mike Lee Kochel

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