Colin Leighfield's Chipmunk build.

[Colin Leighfield]

Good one Jeff. Looks like that's it!

[Mark Kettle 1]

Looking forward to this build.

[Colin Leighfield]

I ordered the OS from JE on line last night, I'll consider the best silencer option when I've got it. If Jeff can give me his address I'll blame him when SWMBO finds out and send her round there.

Mark, don't get too excited, I ain't no Danny Fenton and it will be alternating on the building board with a Supermarine 317. I'm a very cluttered worker, so don't be surprised if I get mixed up and you see the first ever Chipmunk with 4 Bristol Hercules engines or twin fins and very short of rivets.

[Terry Walters]

Oooooh! Nice! Xmas come early this year then Colin! !

Terry

[Colin Leighfield]

It's called buying your own presents and not telling anybody else. I suppose I could have it concealed it inside a cracker but when it was pulled someone else might have got it instead of me.

[Colin Leighfield]

I've decided to join the band of those who make more than one of everything and without touching the wooden parts set, just decided see what a fin looks built on a Depron core. Nothing much to show yet, but there will be more by this evening. I'm pretty sure that I'll use Robart hinge points for the rudder at least, I've got no Paxolin and hinge points are pretty good for embedded hinge designs. I'm a bit shaken by Danny's comments about lack of accuracy compared to the Airsail kit and difficulty of build, but in for a penny - - - -. I'm never going to get this up to a Class 1 standard anyway, I just want it to look close so I'm not too worried about it.

[Danny Fenton]

Interesting idea Colin, will be good to see how the weight compares to the balsa cored and non cored.

Cheers

Danny

[Tony Bennett]

looks interesting colin.

mine should be all depron with only balsa leading and trailing edges.

[Colin Leighfield]

Thanks Danny, I don't think there'll be any worthwhile difference at this stage, but it does give a dead straight structure. Also the 3mm wood I've got handy is a bit on the heavy side.

Tony, I was going to do that but the Depron ribs were such flimsy fiddly things when slimmed down to two halves for gluing to a pair of 2mm Depron profiles that it wasn't worth the hassle. It's definitely a goer for some of the bigger bits though.

[Andrew Price 2]

Signing in Colin. Good luck.

[Colin Leighfield]

Here's some more:- I built the fin in two halves, each on a 2mm Depron core. I did the fin differently, putting ribs down both sides of a single 2 mm depron core.I've skinned the fin also with the same 2mm material and it looks ok. Next job is to sand everything to profile and fit the Robart hinge points. I have to think about the covering over the Depron open rib structure on the rudder, but I think I can get around that.When it's done I'll weigh it all. I don't expect much of a saving, if any at all, on the fin, but there should be some on the on the rudder. Not that it matters that much, particularly when I stick a meaty four stroke on the front. Some tail ballast might be needed! I'm not committed to this and might build an all wood alternative as on the plan, but this is probably perfectly serviceable.

[Mark Kettle 1]

Looks the way to go.

[Tony Bennett]

agreed.

looks good to me and right up my street.

[Colin Leighfield]

Thanks Andrew, Mark and Tony. Here we are then. Fin weighs 18 gms and rudder 10 gms, 28 together. I need to do some fiddling to get the inset hinges sorted out. Can't do anything now until tomorrow evening, I'll do it then. Afterwards I'll get on with the tailplane and see what sensible Depron substitution can be done there, but I want to do a bit more on the 317 first.

[Colin Leighfield]

I apologise that this doesn't look great, but I wasn't happy with the strength of the mechanical connection of the top hinge mount to the fin post, so beefed it up and it looks "untidy" However, it's tough enough now and won't show when it's covered up. Upon consideration I've continued with the composite balsa/Depron approach and used a bit of 1/32 and 1/16 balsa for the bits I want to show through the covering on the rudder. On balance, I think this is good enough to stick with. This afternoon I'll have a go at the tailplane.

[Danny Fenton]

Looks pretty good to me Colin

[Colin Leighfield]

Thanks Danny. I think it's ok. The Robart hinge-points are perfect for this as well, the rudder rotates perfectly in the shroud, which is simply the 2mm Depron covering extended 3mm beyond the rudder spine instead of being added separately afterwards.

I will give the fin a coat of Ezekote and then cover it with 17gm glass-cloth. The open structure of the rudder needs a different approach, not sure whether I will use Solartex, or a fabric such as nylon or silk, I've got both. If I do that I have to keep dope away from the foam. What I would probably do is attach it with Ezekote and depend on that to prevent direct contact between dope and foam. The balsa capping strips help to maintain that separation as well. Before doing it I will give the Depron rudder top a couple of coats of Ezekote anyway.

Edited By Colin Leighfield on 15/10/2014 15:05:28

[Tony Bennett]

use easy dope diluted with water it wont melt the foam, or polyc that works as well.

[Colin Leighfield]

Thanks Tony. I was thinking of using the Ezekote to stick the nylon/silk down if I go that way, I think it's pretty much the same as PolyC. Beyond that I was thinking that if I do use the nitrate dope that I've got to shrink it afterwards I might need to be careful, but it would only be on the open areas and there is balsa at the contact points. The top of the fin will be covered with Ezekote and glass cloth anyway. Here is the tailplane, it's a very economic structure and as I've got the wood pack, I've used it. The only alteration is to glue in some balsa blocks to take the Robart hinge-points. No Depron so far, however I'm going to cover it with 2mm Depron, Ezekote and17gm glass-cloth instead of 1/16 or 2mm balsa. I found with the Depron Barnstormer that it's probably tougher than balsa, so I've got no qualms. I might do the whole plane that way, we'll see. If anyone is watching the pennies, it would be a much cheaper way of covering the airframe than balsa planking, I can't see a downside to it at this stage.Back in the shed later, so I'll finish this off and see how it looks, then start on the elevators.

[Tony Bennett]

skinning the whole model in depron would work well, then just tissue and easy dope over the top, job sorted.

save weight and look smooth.

[Colin Leighfield]

I'm increasingly thinking that way Tony, it's starting to look like a no-brainer (very appropriate for me, as SWMBO would definitely suggest).

[Colin Leighfield]

Here it is then. Dead easy to do this with one piece of 2mm Depron each on top and bottom. Looks strong and rigid, weight at this stage 31 gms. Sadly I've got to work tomorrow and Friday and have things I've got to attend both evenings, so I'm snookered now until Saturday. Hopefully I can get on with the elevators then. JE have despatched my OS FS62V today, so the other focus will be looking at the fuselage to work out any issues with mounting the motor and working out silencer options.

[Colin Leighfield]

Forgot to mention that after remembering to allow a 3mm overlap of the Depron on the fin to create the shroud, which worked perfectly, I forgot to do the same thing with the tailplane! That's created an unnecessary job. Ah well.

[Danny Fenton]

And there was me about to ask did the "shroud maker" worn on depron, I guess it must?

Looks great Colin, but this is not going to get you out of rivetting

Cheers

Danny

[Colin Leighfield]

It works perfectly Danny, one coat of Ezekote and it really stiffened up perfectly. With the glass cloth on top, it will be robust enough to need no further attention .Can't believe I forgot to do it with the tailplane, I'd got enough surplus on the cut pieces to do it, all I had to do was to position them correctly.

Can't mine be flush riveted for extra speed please mister?(Groan)!