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Colin Leighfield's Chipmunk build.


Colin Leighfield
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If I was choosing from scratch at this stage of the game Terry, I'd say that for this application Depron is a better choice than balsa. It is dead easy to cut accurately. With your fingers you can carefully manipulate it into shape before fitting, even to a degree of dual curvature which would normally need wetting or ammonia with balsa.

In a composite structure with balsa like this one, it is strong, rigid and very light. With Ezekote and lightweight glass cloth on top, I'd say it's tougher than balsa and certainly less brittle. On top of all that, it's cheap by comparison. I'm not at a level to emulate Electriflyer or Simon Chaddock by any stretch, but I'm getting very confident with this composite approach, it might offer the best of both worlds.

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image.jpgimage.jpgimage.jpgimage.jpgBob, it's built exactly to the plan, with balsa leading edge, but covered with 2mm Depron instead of 1/16" balsa, lapped over the top of the l/e and simply sanded down, exactly as the balsa would be. Pleased to say that the OS FS62V has arrived. Packed beautifully in the box and a typically OS work of art. I think it's bang on for this build and will fit very snugly in the space designed for a Merco 61.image.jpg

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image.jpgElevators almost complete. When I've sanded them to profile I will put 1/32" balsa cap strips over the ribs exactly as on the rudder. They add far more strength than you'd expect and stiffen up the mechanical connection between leading and trailing edge. The all Depron tips might seem flimsy, but from experience with the Barnstormer, when the Ezekote and glass-cloth are applied, they are more than tough enough. Afterwards I will cover with silk and dope, exactly as the rudder, which I'm quite happy with. I've been following progress on the wing and particularly discussion on the undercarriage. I think that if the wire is good quality, the excellent torsion bar characteristics featured in the design are probably perfectly adequate, as long as the clips are well made and securely fixed. I'm inclining towards doing the fuselage next and the wing last. Disappointed to see the wood pack doesn't include the hardwood engine bearers though.image.jpg

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I've had a busy work load over the last few days and sadly very little shed time. Managed to do a few minutes sanding last night, but I'm off early tomorrow to join my wife in Spain for two weeks, so much as though I'm looking forward to the break, building on all projects stops. When I get back, it looks as if half of you will have finished. I'll do my best to catch up later. image.jpg

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Colin

I appreciate you are probably away by now but the build looks very interesting

I do have a slight concern that 2mm Depron is not structurally equivalent to 1/16 balsa. Certainly a lot lighter but I fear a lot more flexible with the danger of a 'starved horse' effect particularly when any sort of fuel proof layer is added.

I will follow with interest.

Edited By Simon Chaddock on 21/10/2014 23:46:54

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Thanks Danny. The co-incidence in dates isn't deliberate, honest guv! It just happens, like a business event I've had to attend for 30 years or so always seems to clash with the TT races. Grrrr!

Simon, thank you for that advice, which I appreciate. The Depron I'm using here is the aero quality that I ordered from Steve Webb as 3mm. Because they advise that it will no longer be available, I ordered 12 sheets of it for stock. When I received it, I found it is closer to 2mm rather than 3, so I've described it as 2mm. It really is excellent stuff though, and it's a great pity if it is going to be unavailable. I used it on the upper panels of the Barnstormer wing over widely spaced ribs and it's proved to be very rigid, with no sag, although no doubt the camber probably helps that. Covered with Ezekote and 17gm glass cloth, I reckon it's tougher than balsa.

As you might have seen on the thread, I've made the top and bottom sheets for the Chipmunk Tailplane from it, each one piece. It's really tough and again rigid. Therefore I'm optimistic that it will work equally well on the wing and also the fuselage sheeting. However, I will keep an eye on it bearing in mind your advice.

( From Birmingham Airport At 05-45, waiting for the 06-30 to Alicante)!

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Posted by Colin Leighfield on 17/10/2014 19:30:16:

Thanks chaps, I like electric but I think that for this project, this motor is ideal. It's about time I built something sensible, appropriate to my doddery piloting abilities these days. Hopefully as it's going to be WP848, I will suddenly become 53 years younger!

Dear Colin this're very well defined ..... I feel a nostalgia for classic buildings .. but ,this time, let it be yours.face 1

Cheers

Jo

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Thank you Joseph. What I'm trying to do here is stick to the plan but see where there is an opportunity for simple substitution which will (a) reduce the cost of construction (b) reduce airframe weight without making it less robust and (c) perhaps make it easier to build because I'm finding the Depron dead easy to cut and, to some degree, form. Therefore it's an attempt to introduce an element of advantage from a modern material into a classic build. Although the Depron Barnstormer had a few unexpected problems, it gave me a lot of confidence and the Chipmunk is an opportunity to apply what I learned from it. As you can see, I arrived in our apartment in Calpe a few minutes ago and what's the first thing my mind has turned to, my Chipmunk! Someone is glowering at me from the balcony, can't think why.image.jpg

Edited By Colin Leighfield on 22/10/2014 11:22:00

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