Scale Soaring UK

I love my 1/3 scale World Models Super Cub.
I love everything about it.
I love that it's so easy to fly, so convenient, so realistic in the air. You just want to cuddle it sometimes.

The only fly in the ointment has been the undercarriage. They'd obviously spent their budget when they got round to it, because it's pretty horrible. Skinny piano wire soldered together and dipped in red paint. It is heavy, way-off scale, and doesn't have much give in it - a valued feature given the rough pasture I fly off.

So what to do? Well Robart make a lovely articulated landing gear, much nearer to scale and with suspension....

Nice, eh?
Only problem is that
(a) it's rather pricey(£300+)
(b) heavier than the WM gear - and as my Cub's electric I'm not looking for extra weight
(c) I didn't make it.

So I decided to make my own.

The design was easy - a quick Google turned up the full-scale drawings. Can't get much more scale than that. I also took loads of photos of the Cub at the Yorkshire Gliding Club.

The problem was that I haven't got welding gear. Also, it would probably end up heavier than the Robart gear if made from steel. But as aeromodellers we're good at using whatever tools/materials/skills we have to hand. I've worked a fair bit with composites so decided I'd form the main frames of the landing gear from carbon fibre.

Quick calcs suggested carbon should be lighter and stronger than steel providing strength could be maintained around the corner joins of the main triangular frames.

To keep structural integrity and maintain a good surface finish, I made the frames from cheap HK thin-walled carbon tube, accurately pieced together in a jig to get all the angles correct. Although fairly strong, these were just cosmetic "shells" though which I pulled a bundle of epoxy-soaked carbon tows, down through the side-legs and then drawn together through the axle-stub.

The first attempt was a disaster. I'd calculated how many tows could be pulled through and tested it dry no probs. But when soaked with epoxy they swelled up and the whole lot got jammed halfway through...the pull wire snapped and I had to abandon the whole soggy mess.

With advice from Simon WS I tried again, and although difficult (the aim is to fill the tube with carbon not epoxy) the second attempt was great.

When trimmed up, I was delighted to see that the frame was absolutely crammed with carbon and the join felt rock solid.

In all, the main frames used 120m of 12k carbon tows (this includes some binding around the outside of the joins for reinforcement).

With both triangular frames made, my confidence in the whole carbon-based approach was boosted.

What I hadn't banked on was how many hours would be taken up with the rest of the landing gear! Using a mixture of carbon, aluminium and brass for the remainder, I was amazed at how much time it took to drill all the holes, cut, trim, make assembly jigs etc.

Anyway, I am now 99% done.

Here's the before and after photos...

The new DIY gear

(a) is very close to scale
(b) is 70% the weight of the stock gear, and 55% of the Robart gear
(c) has lovely working suspension (tested here with rubber bands but I have some thicker rubber on order)
(d) cost around £50, including resin etc
(e) has given me heaps of fun, absorbing challenges and a rewarding sense of achievement.

I hope to test fly it before the end of the Summer.

Rog

Rog, will it stand up to the sort of landing that I saw you perform at Leek and Moorland?
Brian.

Wait and see. I'll crash test it in due course...

Jolly Roger wrote: ↑29 Aug 2019, 10:53 Here's the before and after photos...

The new DIY gear

(a) is very close to scale
(b) is 70% the weight of the stock gear, and 55% of the Robart gear
(c) has lovely working suspension (tested here with rubber bands but I have some thicker rubber on order)
(d) cost around £50, including resin etc
(e) has given me heaps of fun, absorbing challenges and a rewarding sense of achievement.

I hope to test fly it before the end of the Summer.

Rog

Maaate that looks spec-tac-u-lar ! ! ! UC envy . . .

I have been looking at the cub for a while and doing electric as well.
So, if I get one will you make me a U/C for 50 pounds?

Nice job,
Phillip C
New Zealand.

Don't listen to BC . . he's jealous too.

No worries Phil. £50... that should be about $40.


Oh, and now $30.....


Uh, $20.....

etc.

Looking good, and if BC`s Cub is anything to go by, the landings will outnumber the take offs by about 3 to 1
T.

Jolly Roger wrote: ↑30 Aug 2019, 09:38 No worries Phil. £50... that should be about $40.


Oh, and now $30.....


Uh, $20.....

etc.

Ha ha, I'm not sure if you're commenting on the decreasing pound or the increasing NZ$ . .
But I think you're selling yourself short. £50 = $96NZ (0.5182) today.
Lets see it action please - the landing gear I mean - while showing how you only need one landing per take-off.

Happy Landings
Phillip C
New Zealand
(NO, we don't land upside down here . . . I could hear your thinking from here . . )

(NO, we don't land upside down here . . . I could hear your thinking from here . .)

B****r, that's ruined my day......



BC

The nice farmer cut the field and baled it so I finally got to test the new landing gear. It coped well with the rough pasture so I ran touch and goes until the sun melted into the horizon.