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Obelix Build Log

Mucksmear

Very Strong User
Starting a new project that’s been on my list for at least a couple decades.

Background:

In the late 80’s a friend showed me what I thought was the coolest, compact foam core skinned with brown paper, 36” sport wing and he gave me a copy of the magazine pullout plans for Chas Gardiner’s Obelix.

https://outerzone.co.uk/plan_details.asp?ID=8758

Foam cores were beyond me in those days so I opted for the built up version. I eventually built 2 of them. My 1st one had a poorly matched snake cable diameter to cable housing diameter setup which gave the ailerons a nasty double neutral which resulted in a slow creeping roll to the left or right at all times. Major surgery corrected the control issue and saw the addition of some cool landing lights. She flew great thereafter until a spectacular mid-air. The 2nd flew great and had nav/landing lights and a detailed cockpit - fictional pss style, but was lost over the Muir Beach Overlook. Both could fly inverted with zero elevator trim changes.

IMG_4983.jpeg

IMG_4989.jpeg


If you attended some of the Aloft build nights in the last couple of months you may recognize this black and white one built by oldtimer Arnie Shrick (Joe Strakowski’s neighbor):

IMG_4990.jpeg


I’ve been storing it over the last 30 years (Arnie doesn’t fly anymore) so I gave it to Scott aka the Tape Whisperer who has restored it to flying condition with a new control arrangement and a red/white color scheme.
Incidentally, Mr Gardiner released an updated set of plans more recently and included an electric power option. Oddly the airfoils are noticeably different than the original with no explanation given. Furthermore, there have been reports in the forums of poor flying qualities with the updated design, but with not much detail and unknown build quality.
 
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I’ve always wanted to revisit this design, so finally getting around to it! I’m upscaling the the original 1983 design to 55” and marking a few shape changes to the nose pod, vertical fins and wing tips. Basic build will be white foam cores skinned with 1/32” poplar veneer.

The foam cutting templates were printed out and taped together. I lay the templates out on a sheet of plexiglass with a light shining under it (poor man’s light table). The big “X” marks as well as a long straight edge help align the sections:

IMG_4988.jpeg
 
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Starting a new project that’s been on my list for at least a couple decades.

Background:

In the late 80’s a friend showed me what I thought was the coolest, compact foam core skinned with brown paper, 36” sport wing and he gave me a copy of the magazine pullout plans for Chas Gardiner’s Obelix.

https://outerzone.co.uk/plan_details.asp?ID=8758

Foam cores were beyond me in those days so I opted for the built up version. I eventually built 2 of them. My 1st one had a poorly matched snake cable diameter to cable housing diameter setup which gave the ailerons a nasty double neutral which resulted in a slow creeping roll to the left or right at all times. Major surgery corrected the control issue and saw the addition of some cool landing lights. She flew great thereafter until a spectacular mid-air. The 2nd flew great and had nav/landing lights and a detailed cockpit - fictional pss style, but was lost over the Muir Beach Overlook. Both could fly inverted with zero elevator trim changes.

View attachment 16545
View attachment 16546

If you attended some of the Aloft build nights in the last couple of months you may recognize this black and white one built by oldtimer Arnie Shrick (Joe Strakowski’s neighbor):

View attachment 16547

I’ve been storing it over the last 30 years (Arnie doesn’t fly anymore) so I gave it to Scott the Tape Whisperer who has restored it to flying condition with a new control arrangement and a red/white color scheme.
Incidentally, Mr Gardiner released an updated set of plans more recently and included an electric power option. Oddly the airfoils are noticeably different than the original with no explanation given. Furthermore, there have been reports in the forums of poor flying qualities with the updated design, but with not much detail and unknown build quality.
Did you know Chas Gardiner, Mucky?

Doc.
 
I did not know him, just lucky enough to stumble across his pull-out plan. At the time I did not even know what magazine the plan came from.
 
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I did not know him, just lucky enough to stumble across his pull-out plan. At the time I did not even know what magazine the plan came from.
Years ago Chas was the slope columnist in RCM&E magazine. I knew him very well back in the early 80's. He could be a bit crusty with people he didn't take to, but he was really a great lad.

The Obelix was a bit of a thing on the late 70's and '80's UK slopes when there really was not too much to choose from - mainly because it was so small, cheap, and easy to build, easy to transport, plus it was quirky, tough, and flew well. That list pretty much ticked all the boxes for many of us at the time, and probably still does today. At that time you didn't see too many moulded models!

As I remember, the wing section was something akin to an E375?? Anyway it's funny how things go around - quite nostalgic.

I wonder what a foam version would be like? Hopefully, covered in balsa and not EPP foam and packing tape.

Cheers and keep the progress reports coming!

Doc.
 
Years ago Chas was the slope columnist in RCM&E magazine. I knew him very well back in the early 80's. He could be a bit crusty with people he didn't take to, but he was really a great lad.

The Obelix was a bit of a thing on the late 70's and '80's UK slopes when there really was not too much to choose from - mainly because it was so small, cheap, and easy to build, easy to transport, plus it was quirky, tough, and flew well. That list pretty much ticked all the boxes for many of us at the time, and probably still does today. At that time you didn't see too many moulded models!

As I remember, the wing section was something akin to an E375?? Anyway it's funny how things go around - quite nostalgic.

I wonder what a foam version would be like? Hopefully, covered in balsa and not EPP foam and packing tape.

Cheers and keep the progress reports coming!

Doc.
Doc, great that you knew Mr. Gardiner! In the mid 80’s I was just transitioning from RES to ailerons and here in the US, my impression was (based on the magazines) that the slope scene in the UK was a comparatively more active and connected community than over here. The Obelix was always one of my favorites (hence this build). Another is Les Rudd’s Mid-Jet, yet another full size pull-out plan feature from the 80’s and incidentally my introduction to RCM&E and its Silent Flight supplement.
 
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Doc, great that you knew Mr. Gardiner! In the mid 80’s I was just transitioning from RES to ailerons and here in the US, my impression was (based on the magazines) that the slope scene in the UK was a comparatively more active and connected community than over here. The Obelix was always one of my favorites (hence this build). Another is Les Rudd’s Mid-Jet, yet another full size pull-out plan feature from the 80’s and incidentally my introduction to RCM&E and its Silent Flight supplement.
Haha...I made a Mid-Jet from the same plan - they fly really well and look very different in the air.

We once got a battered-up old one and connected a bottle rocket to the empty arse-end of the fuse with a crude ignition system (Broken light bulb and a battery!) I went really fast for about 3 seconds until it burned through the stab! We'd intended to put some kitchen foil around it first, but needless to say we forgot.

It would have been pretty nice to see windmilling down, trailing fire and smoke from Ivinghoe beacon...but video was an expensive rarity in those days.

Lucky we didn't catch the bloody wheat field below on fire...

Good times!

Doc.
 
Here's the general idea. Right now I'm mulling over whether to build it as a 3-piece or a 1-piece wing. The design has a top surface discontinuity which is simply addressed if I make it 3-pieces. Added bonus is ease of storage. My shop is getting cramped.
Obelix_55_sm.jpg
 
Here's the general idea. Right now I'm mulling over whether to build it as a 3-piece or a 1-piece wing. The design has a top surface discontinuity which is simply addressed if I make it 3-pieces. Added bonus is ease of storage. My shop is getting cramped.
View attachment 16587
Great work Mucky! Beautful plan!

You remind me of me.

Just a quicky though: Those root aerofoils look a little thick, and maybe a little bit odd. Are they the orginals from Chas? If so they could have been drawn around one of his size 14's. Anyway with a semi symmetrical at the root and symetrical at the tip the washout (Aerodynamic) is taken care of.

Just a thought.

Doc.
 
Great work Mucky! Beautful plan!

You remind me of me.

Just a quicky though: Those root aerofoils look a little thick, and maybe a little bit odd. Are they the orginals from Chas? If so they could have been drawn around one of his size 14's. Anyway with a semi symmetrical at the root and symetrical at the tip the washout (Aerodynamic) is taken care of.

Just a thought.

Doc.
Yes I’m sticking with the original airfoils from Cha’s 1983 design. For a sorts flying type design, they worked very well on the stock builds I did way back and I’m not looking to squeeze more performance out of it beyond adding ballast (incidentally another reason to go with a 3-piece wing).They are indeed thickish - both my 36” builds had standard servos hurried completely inside the wings.

In his build article (see Outerzone link above) Chas mentions “Much midnight oil was burnt on the vexing problem of reflex sections and pitch control, solved eventually by a semi-symmetrical centre section set at an effective negative incidence …” I would be surprised if the airfoils were actually not born of a French curve or the side of a shoe!
 
Yes I’m sticking with the original airfoils from Cha’s 1983 design. For a sorts flying type design, they worked very well on the stock builds I did way back and I’m not looking to squeeze more performance out of it beyond adding ballast (incidentally another reason to go with a 3-piece wing).They are indeed thickish - both my 36” builds had standard servos hurried completely inside the wings.

In his build article (see Outerzone link above) Chas mentions “Much midnight oil was burnt on the vexing problem of reflex sections and pitch control, solved eventually by a semi-symmetrical centre section set at an effective negative incidence …” I would be surprised if the airfoils were actually not born of a French curve or the side of a shoe!
I think you got it right.

In any case on this small model maybe the aerodynamic washout is a better solution than the reflex sections - Chas probeby had it right there, too.

Incidentally I have been doing a bit of "Bump" reseach recently - brought on by some delving inot BWB type structures for work. It turns out that at model scale, the BWB. or even a plain wing (Curved or not) with no frontal projection does not really work very well - until you get over 4M or so that is. It's something to do with that darned scale effect where unfortunately our air is the same thickness/viscosity as the full sized planes.

At our size flying wings, the isobars tend to do strange and wonderful things if not diverted side to side by some kind of frontal projection (like a fuselage for instance) in front.

But anyway, as to the Obeix - If the machine works...

Doc.
 
Interesting - I would not have guessed that scale effects would have a threshold as high as ~4m to start complaining for BWB arrangements.

The Obelix is a strange beast with its twin oversized vertical stabs that may even be acting a little like fences right where the upper surface of the wing is doing strange things as it steps down to the outer panels.
 
Interesting - I would not have guessed that scale effects would have a threshold as high as ~4m to start complaining for BWB arrangements.

The Obelix is a strange beast with its twin oversized vertical stabs that may even be acting a little like fences right where the upper surface of the wing is doing strange things as it steps down to the outer panels.
For sure they are acting as fences. Without them I think the flying would be 'interesting'

Doc.
 
Haha...I made a Mid-Jet from the same plan - they fly really well and look very different in the air.

We once got a battered-up old one and connected a bottle rocket to the empty arse-end of the fuse with a crude ignition system (Broken light bulb and a battery!) I went really fast for about 3 seconds until it burned through the stab! We'd intended to put some kitchen foil around it first, but needless to say we forgot.

It would have been pretty nice to see windmilling down, trailing fire and smoke from Ivinghoe beacon...but video was an expensive rarity in those days.

Lucky we didn't catch the bloody wheat field below on fire...

Good times!

Doc.
Hey Mucky, I just looked at the Midjet plan you referred to on Outerzone - well its not the one I remember fitting the rocket to, which was a twin boom thingy.

The Midjet 2 plan is also a model which a bunch of us made, but we called it the "Shoebox Jet" because all of the parts would fit nicely into a common shoe box. And it would also take a bottle rocket - I remember Dave Woods making one.

Obviously my menory has suffered...but now I'm wondering what the twimboomy thing was! I'll have to find out or it will bug me.

(later edit) Found it! Boomerang! https://outerzone.co.uk/plan_details.asp?ID=10619

Dooohhh...

Doc.
 
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Odd, Outerzone lists it as “Mid-Jet 2”, and the write up references a wing section that is not flat bottomed, but they are clearly showing the plans for the original flat bottom winged “Mid-Jet” that I built from a set of Silent Flight pull-out plans. The crude flat bottom wing actually worked very well except of course inverted. We eventually put different sections on it and got good inverted performance and higher speeds in exchange for more abrupt stall behavior. I think I've built at least 5 of them over the years!
 
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