Super Scorpion

[Braddock, VC]

A few months ago I was in the Ashford Model Shop to buy some wood, hanging from the ceiling was a super scorpion (ss) complete with engine, I asked what was the lowest figure he would take and offered a fiver less, walked out of the shop with it.

At first glance it looked well built and was covered with antique solartex, engine was a magnum 30 4 stroke and there were three servos.

I took it straight up the flying field put a freshly charged life battery in, fitted a 4 channel corona faast rx fuelled up and blow me the engine started so out to the strip. Here the first problem raised it's head, the u/c of the ss is not particularly well designed and this one has suffered quite a bit though the plane doesn't seem to have been flown much, a c of g check put the balance point at about 40% chord which is not dissimilar to my other ss(I built one about 8 years ago)

Take off was a squirrely affair and the engine just about had enough power to make the plane climb, I was holding in a fistful of down just to keep the old girl S&L. Nevertheless I enjoyed that and the several subsequent flights until I flew my J60 which reminded me that flying vintage was/is/should be a stress free affair.

So I swapped the 30 fs for my original os 40 fs from 83, when I noticed that the nose weight was loosely held in place, under the engine, by some bubblewrap. So I balanced the plane on the main spar with a selection of copper coins of the realm, weighed those and cut a slab of lead (279 grammes) and bolted it in place.

The switch was held in place by two dressmakers' pins so I epoxied the ply plate to which it was attached to some adjacent vertical fuse members. The u/c was bent back to shape when it was immediately apparent that the soldering of the legs was not good so I dressed them up and will resolder them tomorrow with new copper wire whipping, which I also used to firmly fix the rear leg to the airframe.

The rudder fouled the elevator so I trimmed a segment off the t/e of the rudder and fully intend to fly her tomorrow, after soldering up the u/c.

Watch this space.

Please note I'm not criticising the original builder, his airframe and covering are far superior to mine, it's just the detail differences like the servos were installed upside down before covering and I'll have to strip the covering off if one fails.

Still I love it to bits and it takes off just above walking pace.

Edited By Braddock, VC on 10/02/2016 22:57:47

[Robin Colbourne]

In comparison to the original Keilkraft Scorpion free flight model (there never was a Keilkraft Super Scorpion - that was a Ben Buckle creation), these modern replicas have vastly more power and are generally heavier (all that Solartex...). As a result they generate a lot more lift and drag from the wing, so the nose gets pulled up, hence the need for downtrim. I had an enlarged Black Magic that flew just the way you describe.

As free flight models, these were essentially two speed designs. When trimmed correctly, the pitch up from power would be counteracted by the lifting tail, providing a fast climb. When the engine stopped, the model would slow down and with less lift from the tail, they would settle into a slow glide.

Trying to fly these vintage designs as sports models with powerful modern engines is always going to make them tricky. Some significant downthrust on the engine would reduce the amount of down elevator needed for level flight.

There's a good description of how a lifting tail works here in the post by Myron Beaumont:

**LINK**

[Peter Miller]

Many years ago I built a BB Super Scorpiont, can't remember if it was from the kit or plan.

I used a Webra 4-40, The old belt cam drive engine. It flew perfectly as built.

Eventually I sold t to the club idiot who managed to demolish the model AND engine. I have always regreted selling that model bitterly.

[Jimbo565]

This is my SS,flies a treat on OS20.

[Tim Hooper]

Ten years ago I found myself the owner of three Scorpions - two standard size and one super.

The two little ones have found new homes, but I still have the Super Scorp.

I built it from the BB plan, and made a few mods as I went along; the wing splits in two for storage, the tail surfaces are removable, the trailing edges and outlines of the tail are laminated from thin strips of balsa.

I built the wing halves on a twisted piece sheet of ply to build-in 6mm or so of washout. The covering is cream Litespan, with Solarfilm trim.

It's powered by a brushed Astro 15G motor (which cost £150 at the time!), and was fed by 12 sub-C cells. The pack weighed 1 1/2lb alone. These days I've switched to a 3S li-po, so saving nearly 1lb off the AUW.

It's lovely to fly, although it does have it's quirks; take offs are a mad zig-zag along the strip, the elevator trim needs constant adjustment depending on the throttle setting.

tim

[fly boy3]

Hi all, here is my 1970s S/S/ Flies on a MDS 32, starts firts time and flies like a dream in the right conditions. It must be pointed into wind for T/O, and I use half throttle and let her go. Still covered in the original nylon. Cheers

[Braddock, VC]

Here's my first one that I built about ? years ago.

 

 

Edited By Braddock, VC on 12/02/2016 19:42:06