Challenger RCME September 1984

[Andy Stephenson]

On 11/10/2022 at 07:00, Nigel R said:

The wing has progressed a little.

 

First off, some careful bending and gouging has seen these installed:

 

 

Yes, I know, everyone does two servos, because it's obviously better and easier. But is it ? I actually find torque rods take less time than doing two outboard servos. Plus you get an easier time when it comes to covering, and it looks neater. Differential is not a big deal. Bend the torque rod appropriately or use an offset on the servo horn. A non issue for aerobatic models like this though.

 

 

Nigel,

You could always achieve aileron differential more easily by having two servos at the centre of the wing each one driving an aileron separately. This way you get both advantages, the torque rod installation and programmable differential from the Tx.

[Nigel R]

Andy

 

You're quite right. If I find I want differential and can't get it with an offset horn and two new pushrods, I can open up the servo well a bit and stick in a pair of 225s or similar.

 

Must update this log with some actual progress..!

[Nigel R]

How time flies!

 

I've been adding a small forest's worth of wood to the fuselage. Lots of soft block for razor plane and sanding...

 

 

Canopy:

 

And on the raw, unshaped fuselage:

 

 

Different angle:

 

 

Side on:

 

 

It was actually quite tricky to get the bottom to fit nicely to the deck. Challenger has a few sneaky curves on that lower box (i.e. a slight "hump") that made fitting the canopy structure a little taxing. Plus, I thought I knew better than the plan, for some reason, and bought the wrong wood (thicker than needed) which made it difficult to form nicely.

 

After some shaping, it looked like this:

 

 

What you don't see there is where I messed up the height of the rear deck, removed the rear deck entirely, cut a sliver out at the rear to reduce the rear height but keep the front end the same, then reattached it, then reshaped it. Whoops.

 

On to the cowling...

 

 

Foamboard to the rescue. I built the cowl up around the motor.

 

A different angle:

 

 

And eventually, after much more shaping and sanding, and some fuelproofing, and a little neatening up of the wing saddle, I have reached this point:

 

 

Starting to look like a proper smooth sleek airplane shape. Fair few mistakes made on this one but I've managed to disguise them so far. I'm going to end up with a few gobs of filler around the join between the canopy and the rear decking. It is still not permanently attached - I avoided doing that, to make it easier to shape the front decking. The shape around the transition between canopy and deck was another really tricksy little bit of construction. This fuselage actually hides quite a few bits that look deceptively simple but took a bit of thinking / working out / re-doing-after-I-did-it-wrong. I think I still have some fine-tuning of the curves to do yet and if I'm honest I got the shape at the rear just a touch wrong - I didn't stick to the plan when it came to the fuselage width, and that then affected the shape the top deck took right at the back. Still, if I don't tell anyone, nobody will notice.*

 

Next I need to attend to the underwing fairing. I shall probably close up the bottom of the fuselage first though. That will nearly be the end of the woodwork!

 

* except everyone reading this thread of course, but, shhh.

Edited January 9, 2023 by Nigel R

[john stones 1 - Moderator]

Nice lump up front Nigel. 👍

[Nigel R]

One of OS' best, that.

[Ace]

Wow what a lot of shaping but lovely sleek results, plus IC too 👍

[Nigel R]

Thanks Ace

 

I quite like block and sand type designs. Find it quite therapeutic to knock it all back and gradually sculpt the final form.

[Nigel R]

Slow progress this month. Lots of family birthdays in January = not much building time...

 

 

Wing is fixed in place. The usual 5mm nylon bolts:

 

 

And from the tip:

 

 

Then I started thinking about the belly pan. I decided I'd cut some side parts and top it with a bit of 3/4" wide block. The pipe will need a big hole down the middle and unless I wanted to make a fancy curved or planked cutout it would have to be some simple thick blocks:

 

 

And after sticking some lumps together:

 

 

These have been planed and sanded to some sort of shape. Might tinker with the shape a little but they're close enough for now.

 

I've also final fixed the snake and close loop guides, sheeted the underside and put the tailplane and fin in place.

 

 

 

Turns out I made a slight fist of the rear end - the sides were vertically misaligned (although the fuselage was free of twists) so anyone looking too closely will see a few slight oddities about the rear deck. And the underside is wonky. Never mind. At least the sides are vertical, the wing is aligned correctly and the tail feathers align properly to the wing.

 

I think I need to make a rudder and a tailskid next. Then I must tidy up the canopy/deck join.

Edited February 8, 2023 by Nigel R

[Nigel R]

Got the rudder made up. Time for photo op!

 

100mph while standing still:

 

 

 

 

 

 

Edited February 15, 2023 by Nigel R

[john stones 1 - Moderator]

Lovely build Nigel, she's a looker. 🙂

[Stuart Z]

Looking very good

[Nigel R]

Rumours of my demise have been greatly exaggerated. Although life has got in the way of this project...

 

 

 

I have yet to complete the trim colours, but the covering film is close to being finished. 

 

Some last details are left to do on the throttle cable and gear legs.

[Stuart Z]

Nigel

Looking great!

S

[Nigel R]

Trim just about done

 

 

[David Foley]

Looks great, Well done

[Nigel R]

On her own feet now... Only the plumbing remains to tidy up, otherwise she's ready for ground runs / pipe setup. 

 

AUW is (drum roll) 6lb 13oz or 3.1kg.

 

Wing loading is 22oz/sqft (the cubic wing loading is fraction under 10).

 

 

Front view showing off the period correct Graupner Super Nylon 11x10, and very special lightweight spinner*

 

 

* SLEC 68mm / 2-3/4", £1.90

 

The very purple header (ebay, I think, for £5) looks a bit odd - I'm considering getting Weston or JE to knock up a custom job that matches the fuse lines a bit better.

Edited September 7, 2023 by Nigel R

[Ace]

Just engines use to sell headers and tuned pipes called - Purple Pipes (I have a couple of different 2* sizes)

[Nigel R]

Challenger has finally flown!

 

Very smooth maiden with no problems. Really pleased. OS performed flawlessly and provides endless vertical. The pipe length is set about right, although i need a longer header than the current one. 

 

Rolls are axial, loops smooth, snaps are sharp and precise. I still need to trim the cg, it is a little forward. I also have some adjustment to do in the throttle to get a slower idle,  but, all things considered, I am a happy chappie. It also looks pretty darn good in knife edge. 

 

Photos were taken after returning to terror firmer. 

[GrumpyGnome]

"Terror firmer" ... love it!

[Nigel R]

Flew her for a second time yesterday. Aside from a blown OS#8 plug (argh! £££!) and the loss of an M4 exhaust header bolt during flight, it was all good. She definitely needs a little CG adjustment but a promising airframe for sure. Quite docile near stall with current CG, yet the spin is lovely and flat on rudder/elevator alone.

 

The only fly in the ointment, so to speak, is down to how sleek she is - she is fast, the glide slope is quite flat, and slowing her down on finals takes up a fair amount of sky - she could really use something (flaps or breaks or whatever) to dirty up the airframe a bit. Maybe I've just forgotten what "proper" classic pattern airframes are like! It's no particular big deal at the field I'm flying these days at but it would be very tight on a short strip.