Airsail - Dehavilland Chipmunk Kit

[Richard Duvall]

I'm just starting out building my first RC Aircraft (apart from my ARTF trainer). I've read with great interest some very good build diaries on here and I know I've got a lot to learn! I thought it might be useful to chart my progress on here and hopefully pick up some tips from the experts when I go wrong.

I chose the Chipmunk as it seems a reasonably simple kit and also represents a modest step forward in flying from my current high wing trainer with which I hope to acheive my A Certificate before winter gets in the way of flying.

Before I get too far into the build I will need to select what engine I am going to use; I am currently thinking of the OS 46AX.  

The kit instructions and main plan do not include flaps but they do provide a supplementary sheet which describes the variations need to include them. I'm a way off from getting to that point, but I am leaning towards including them.

Further down the line I will have to tackle the black art of covering and painting and I've already read a lot of the advice about that but have not made my mind up on what to use.

I will add photos later to show what I have completed so far.

[Bruce Richards]

Richard, I look forward to reading you build blog. You know there are plenty of helpful people here to answer any questions you may have.

Good luck

[Ernie]

Hi Richard,

This all sounds just fine....OS engines are of course excellent, but expensive..Have a look at Just Engines website for cheaper alternatives.  http://www.justengines.unseen.org/ 

I can well see the attraction of flaps, but if it's only your second model then, I'd go for the KISS thing (keep it simple stupid) Maybe you could build them in, but fixed, and activate them when the rest is sorted out.

Now about covering, maybe we could have a whole new thread

Love to see the pix.......................................................................ernie

[Richard Duvall]

Tailplane framework completed so far. Didn't find that too difficult. Got to skin it next and carve a couple blocks to finish the outer ends of the elevators, only snag here is that the kit only included one block! Already started preparing the fin and rudder.

[birdy]

Looks nice!

[Richard Duvall]

Progress has been a little slow as I've been busy helping my son with a house renovation. Also had a near disaster with the kit - readers will no doubt be familiar with the tongue twister "The cat crept into the crypt and cr............" replace crypt with box of kit parts! Luckily she selected the box of plastic parts which were easily cleaned up.

I've now skinned the tailplane and made the fin and rudder; forgot to take any more intermediate photos. Next step it to fix the elevator and rudder hinges. Not absolutely sure how to do this; instructions simply say "cut slots for the hinges on the centre line of the spar". I've knocked up a mock-up using some scrap balsa and seem to have achieved a slot without being too distructive; next step to do the same on the model.

[Lew Weaver]

Looking good

The Airsail kit Chipmunk elevators seem to be non-scale?

[birdy]

Looks Good!

[Richard Duvall]

Lew;  I think you are probably correct about the elevators. I don't know much about Chipmunks so after your comment I had a browse around for the real thing and found a range photos and plans which show a variety of tailplane/ elevator designs. The Airsail kit seems to have some similar characteristics to some versions but not exactly like anything. I think the same could be said about the rudder! But never mind; my objective remains to develop my building skills and at the end of the day it should be recognisably a Chipmunk.

[Ernie]

Yes, go for it

ernie

[Terry Whiting]

Richard,

Try and keep it's rear end light as possible, my pals Airsail Chippy came out tail heavy. The wood selection in his kit was quite  hard, and that usually means heavy.

 His  power was an OS 52 Surpass 4st, which I think weightwise would be the same as your  OS 46.  He  required 9oz lead in the cowl even with the flight pack accommodated in the cowl. Even so it was a fantastic flyer, but weight made the landing speed was a tad higher than he would have liked.      

[Lew Weaver]

I found the wood fairly good in my kit.

A.U.W. was 6.25 lbs and no nose weight needed

Are you fitting the optional flaps (recommended)? 

[Richard Duvall]

In my limited experience the balsa in my kit seems quite soft, so if that means it's not so heavy all well and good; in view of Terry's comments I just hope I've not been too heavy handed with the glue!

On the question of scale - if you've built the kit, were your elevators the same Lew?

I am intending to include the flaps but haven't looked too close at that yet.

Not much progress for the last few days as I've been installing some shelves in my work room to improve storage of parts and work in progress.  

[Lew Weaver]

Yes - I just followed the plan for the elevators.

A clubmate had the BARF version (Black Horse I think?) which deviates from scale quite a bit especially around the nose area, but had different elevators which I though were wrong, but turned out to be true to scale.

[Chinesespaceman]

Hi Guys,

I just started by Airsail DH Chipmunk build, the RAF version. The instructions are really very poor and leave a lot to the builders interpretation. I've found several shortages of wood already. Anyhow, I am going to take a close look at the elevator / horizontal stab design, the real size type I have seen do indeed have the elevator tips extended forward of the hinge line.

I am going to go up to Breighton Airfield at the weekend and if I can get access, take a load of pictures of their full size. I'm especially interested in the detail such as the trim tabs before i go much further.

 There is a really helpful site I found of a previous build:

http://pages.infinit.net/catses/stephane/

My first challenge is going to be working out how to work out the right shape for the ribs and how to shape them to achieve this.

 You seem to be making good progress - I look forward to following your build

Cheers

Gav 

[Lee Burke]

I'd be realy pleased to have a look at any DH Chipmunk photos you take, Gavin.  I too have an Airsail Chippy building - at the moment held up for lack of space - and would like some detail photos. 

Good luck on your getting access to the full size job and lots of luck with the build. 

 Lee

[Richard Duvall]

Gavin,  Thanks for the link to Stephane's website; what a lot of detailed photos! The kit seems to have been updated a bit since 2004. The tailplane and fin ribs are now supplied pre-cut (ableit 2.5mm too deep on the fin!). The shape of the tailplane endblocks also seems different.

I was interested to see his choice of a glass finish. I haven't made up my mind on what covering to use and had thought that glassing might be on the heavy side. Seemed to work for Stephane, even with his sheeted elevators and rudder.  Anyone got any advice on covering the elevators and rudder  -  would it be easier to cover them before attaching them?

[Lew Weaver]

It is much easier to cover the rudder and elevator before hinging and attaching

[Richard Duvall]

While I decide upon what covering to use I am putting the elevator and rudder to one side and skipping on the the cntre wing section. The first snag I've come across here is that one of the pre-cut main spars seems to vary from the plan by as much as 3mm at each end (see photo). At this stage I'm not sure how this part mates with the wing sections but I would guess that good fit is crucial to strength.

Anyone got any thoughts on this?

[Richard Duvall]

Problem solved!  I've looked further at the plans and the shortage would result in it not reaching wing rib W2. I could solve this by simply packing out that rib, however, the modifications for flaps seem to require this spar to be trimmed back by about 25mm to end at rib W1C, although the instructions don't go to that detail. The trimming back is required because otherwise the spar would extend into the flap.

[Chinesespaceman]

Hi Richard,

I find the destructions to be next to useless, very much a case of interpretation.

My kit doesn't have preformed ribs for the tail feathers, just a shed load of 1.6mm x 10mm balsa strip (actually not enough wood included)

My dad is over at the weekend, so a trip to Breighton might fit in well - I'll get the "when I was flying Tiger Moth's" tale a few dozen times, but it'll keep him happy 

Will post a link to any photos I manage to get

Cheers for now

Gav

[Former Member]

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[Lee Burke]

My kit didn't have preformed ribs in the tail either and was also short of a few bits here and there, although I have not advanced very far so maybe much more is missing.  As for the instructions they are clearly written for someone who does not need them.

It is true that there are masses of photos around - there are some good ones here Photos- but not many give detail shots which would be useful later on in the build.

[Richard Duvall]

Completed the framework for the centre wing section, including variation to accommodate flap servo. (btw, please excuse my ingorance, but do you just use an ordinary servo for flaps or is it something special?)

Needs skinning and holes drilling for control rods.

Next step - the wings, unless I return to complete the tail parts if I can make my mind up on covering. I'm leaning towards glass and assume that I will need to skin the open sections. I'm not attracted to stick on plastic.

[Former Member]

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