Airsail - Dehavilland Chipmunk Kit

[Lew Weaver]

Phil

The whip aerial is just scale detail, seen here on the full-size

[Phil Winks]

I thought it might be but I have heard of whip aerials for 35mhz

[Chinesespaceman]

Hi Richard,

I'm just at the poin tof dry fitting the first wing to the centre section. Did you have to fettle the rear spar from the centre section to get it to fit between the two rear wing spars?

I'm guessing this is ho it is meant to fit together?

Cheers

Gav

P.S. The SC70 will in my opinion be great for this model, the on board glow is a greta idea, i run them on a couple of warbirds that i have, it's so important to have  reliable tickover.

[Richard Duvall]

Gavin, 

I recall that mine was a snug fit that needed no fettling, and Yes it is meant to go between the two spars. The problem I posted on 11/11/08 that the centre spar was short requires W2 padding out (2.5mm I think) to make contact with it - ignore my 2nd post that day that said it would be cut off short of W1A as that is wrong. The centre spar protudes through the 2 wing spars and this is shown as a dotted line on the wing plan. If you are adding the optional flaps this bit will need to be trimmed off. If you look at my test fit photo on 18/11/08 you can just about see a triangular section of the centre spar protruding through.

[Stephen Grigg]

I like your engine test bed,it might fly a bit nose heavy.

[Richard Duvall]

I was looking at another build blog recently  and the builder had commented that he was trying to keep the costs of his build out of sight of his wife. Fortunately I don't have that problem.  However, this came to mind yesterday when I was discussing home decorating costs with my wife and she asked how much my Chipmunk build was costing.  I replied "something around £250" to which she responded "and the rest"!  I didn't actually know how much it had cost so far so I dug out all my bills and totted it up on a spreadsheet. Needless to say I was a little surprised how much the costs had mounted to close to £400. I don't think I've got too much more to spend apart from paint and a pilot.

I did attempt to add a  link to access my spreadsheet which also helps identify parts required to complete the kit but I suspect it will not work.

[Ben Mullins]

Its worked well for me. Its strange to see how the costs add up. If only we knew the prices before we started . . . . . .

[Richard Duvall]

First engine test completed successfully today - ran one tank full through which was enough before I froze . Made a lovely noise - my wife was out walking the dog at the time and said she could hear it from the end of the road!  Seemed to have loads of power - the test rig was clamped to my Black & Decker Workmate and it started to pull it across the garage floor at around half throttle!  Got to make a slight mod to the test rig as the servo was reversed and my next text will hopefully include my "Glo-n-go" system which is set up for normal throttle servo (can be reversed by playing around with jumpers but I can easily physically reverse the servo)

[Richard Duvall]

Two steps forward, one back!

While working on the wing preparing to fit the flaps I managed to put my thumb through the leading edge sheeting. Making a patch as I think I may end up doing more damage if I attempt to replace the entire sheeting. I'll be glad when I can get it glassed over which will strengthen it.

Putting building to one side and going outside to give the engine another run.

[Richard Duvall]

Second engine test run completed OK, this time with the on-board glow system. Worked like a dream; a noticeable improvement at low revs. I would recommend  these gizmos but Timbo is packing up making them. However, there was some talk about publishing the design in the mag.

[Mark Godbeer]

Hi Richard. I have been building the RAF Chipmunk for the past year or so. I chose the Airsail kit as it looked the most true to scale available. Wow it had been a long time since i had built from a kit, so my skills were rusty. I had decided that it was time to build a scale model that i could take time over to get a good result. My original intentions were a little extreme. i,e sliding canopy and huge amounts of scale detail. I have decided that stand off scale is going to have to do as i do not have the time or patience.

It was inevitable that i would build a chipmunk one day, as back in 1975/6 i was a duty cadet at 4 AEF based at Exeter. So i managed quite a few hours of flying.

The Chippy i am building will replicate WB560 the Chippy i flew in the most.

I have a new OS52 surpass to power mine, servos for each aileron and each flap. I could not be bothered with bellcranks and wire links. Good luck with your progress. I will add some pics of mine as i go along. still can't decide on the covering. Current thoughts are White Solartex all over and Car spraypaints.  

 

 

[Richard Duvall]

Mark, You seem a fair bit ahead of me as I haven't started on the fuselage yet. You will have seen from my earlier postings that I am using glass cloth/ Poly-C to cover. I haven't decided what paint to use but like you was thinking car sprays wuold provide a readily available choice of colours. No fancy replications for me - I'm just going for the standard colour scheme with the decals from the kit.

 

It's been recommended to me to make the tailwheel steerable - have you looked at that option? I can't see that it would be too difficult to put a control arm on top of the rod and then hook it up to the rudder control rod, but until I start putting the fuselage together I'm not bothering to dwell too much on it.

 

I've not made much progess lately as I've been doing some decorating. I think I'm still on course for a maiden flight in the spring and that assumes that I can finish learning to fly in the meantime. Hope to post a update soon to show the completed wing.

[Richard Duvall]

After what seems a very long time, I 'm ready to post an update on my progress.

I've repaired the damage I made by putting my thumb through the leading edge sheeting and now completed the set up of the aileron and flap controls. At this stage the ailerons and flaps are only temporarily fitted as I intend to paint them before final fitting.

 

Each servo is mounted on a removeable ply plate. I haven't done the final wiring for the flap servo leads but have installed conduits (plastic drinking straws) for them to be routed after the wings are covered.

 

This picture shows the underside of the wing with the servo access plates.

 

Next job is to finish covering the wings before starting on the fuselage.  

 

 

 

[Mark Godbeer]

I see you went for a servo for each surface as well. beats the hassle of all those links etc. Are the extra leads for wingtip Nav lights?

I noticed on my wing that i have washout on the left wing which is correct. but the right wing is flat so i have to find a way of warping it to get it right. Something went wrong with my build there dohhh!

Good luck with the Fuselage. You will find that pretty straightforward. certainly easier that what you have acheived so far.

Heres a pic of the Crew for mine 70,s AEF style. I don't remember any of the pilots having the Iron Cross though?

[Richard Duvall]

Mark, Well spotted - the extra leads are for navigation lights. I thought the moulded plastic wingtips cried out for lights to be fitted so I've got a couple of LEDs and I took the view that the couple of strands of telephone wire would not have a significant weight impact. My son, who is a dental technician, is going to make some clear acrylic covers for them.  As to washout, I'm not sure if I would recognise it! However, I am fairly confident that my wings have the same profile as each other.

 

One thing I meant to mention the other day was that, for any future builders of this kit, if you follow the additional instructions for the flaps you end up with different interfaces for the flaps and ailerons.  It would be worth looking at the aileron interface to improve it on the lines of the flap version, however, it would have to be different as they need to go both up and down.

[Martin Harris - Moderator]

Just come across this thread.  I built the RAF version 5 or 6 years ago as the first model buld since I had last flown radio models in the late 70s and don't remember any great problems with the instructions or parts fits.

 

I did not build particularly lightly  - covered flying surfaces with Humbrol painted Solartex and tissue/doped the fuselage.  Also fitted an onboard glow, sliding canopy and the flaps mod.  Top half of an Action Man and one of Barbie's girly friends (not the lightest of pilots) go along for the ride except when Action Man took a small movie camera up a few times...see http://uk.youtube.com/watch?v=sjJLOqqbVxI or an earlier attempt http://uk.youtube.com/watch?v=F-BzNTwjgko

 

All this is on an OS52 FS but I usually use considerably less than 1/2 throttle to achieve a scalish take-off.  Scale aerobatics are easily achieved with this engine so the 70 will leave you with a decent reserve of power.

 

I replaced the wire legs with sprung "oleos" which improves the look of it while taxying (lots of bouncing and shimmying with it as standard).  The importer offered an exhaust adapter which locates the exhaust outlet at around the scale position and encloses the silencer completely within the cowling which I've never regretted investing in. I don't know whether one is still available but if you can get one for the 70 it would be a nice touch.

 

I use @ 15 degrees of flap (which steadies things a little, possibly by effectively introducing a little washout effect) for take-off and 30 degrees for landing (as per full size) and handling is excellent and predictable in all configurations. One of the earlier postings mentioned scale transit speed for the flaps but as the full size used a direct "handbrake" lever controlled linkage I wouldn't worry about your standard servo.

 

Good luck with the rest of the build and as long as you've built it without any glaring errors I'm sure yours will fly superbly.

 

Martin

[Richard Duvall]

Martin,   Thanks for your post. I think my standard exhuast is going to fit in the cowl OK with the aid of a 90deg manifold.   One thing I don't quite understand is how you acheive different flap settings for take off and landing. My radio seems only to have a simple on/off switch for the flaps - is dual rate the solution?

[Martin Harris - Moderator]

Well, originally I used an old style Futaba FF7 and worked out a way to use a helicopter mix and the 3 position switch for no, half and full flaps.  When I upgraded to a FF9 it has nicely placed levers which give a short bleep at mid position so I now use one of those. In theory, the flaps can now be set anywhere from 0 to 30 degrees

 

I don't know which radio you have but a lot have a rotary knob (which I must say I find horrible to use and the reason for using the first method) for flaps and a simple switch intended for undercarriage.

[Richard Duvall]

I'm using a Futaba 6EX and I've check the manual and there seems no way to have multiple flap settings. Dual rate is not the answer as it is only available on Aileron, Elevator and Rudder.  Maybe I'll have to settle on a compromise of 20 degrees or only use flaps for landing. As flaps are only an optional extra on this kit it will no doubt take off OK without flaps.

[Martin Harris - Moderator]

I believe you're right - as far as I can see you don't have a proportional control available for flaps.  I'd go with 30 degrees - the model will be fine for a flapless take-off  (mine just feels happier with a little flap but another club member's has often flown clean on take-off).  Don't drag it off - let it get flying speed balanced on its wheels and let it take to the air when its ready and you'll have no problems.

 

By the way, I've just weighed mine after seeing references to a 6 lb model being marginally powered with a 70FS and if it puts your mind at rest, mine is 8 lbs dry and more than adequately powered by the 52FS.

[Martin Harris - Moderator]

Just a thought - looking at one of the earlier postings, either make the tailwheel steerable or fixed but DON'T follow the instructions and make it freely castering.  Mine was a pig to taxi in any crosswind until I locked it, allowing a small amount of movement by screwing a bar over the angled part of the rod with silicon tobe over the screws - worked out neater than it sounds. The locked tailwheel allows good steering on the ground but a steerable tailwheel would be even better.  The free castering version is scale but we don't have the advantage of differential braking as per full size.

 

Also, I'm a bit bemused by earlier comments that the tail components aren't scale. - mine look pretty much correct and I'd hav e thought that the model was intended to be as scale as possible bearing in mind the detail around the wing/fuselage joint.  I wonder if there's confusion between the British and Canadian versions which have different wing and stabiliser tip profiles?

[Richard Duvall]

Now started on the fuselage.  First side part made up, second side waiting for glue to dry.   When but haves are ready they will be glued together before completing the sheeting.

 

While I'm waiting I've started making up the tank box/ engine mount - I hadn't realised that the engine has to be angled to such an extent. I guess it's all to do with compensating for the torque effect.

[Richard Duvall]

Martin, Thanks for your message agout the tail wheel. I had already decided to make it steerable. I haven't worked out how to do it yet but I'm fast approaching the time I will need to sort it out before I go too far with the fuselage. I'm assuming that it will be easy enough to fix control arm on the top of the rod rather than just fixing it with a spring washer as specified in the instructions. Next problem is how to connect it to the rudder rod which may be difficult as it is designed to exit the fuselage just by the rudder.

[Richard Duvall]

While I was laying in bed this morning, drinking a cup of tea, a solution to my tail wheel steering suddenly came to me!  It was simply to make up a "splitter" towards the end of the control rod and have seperate rods to the rudder and tail wheel. (for the benefit of future builders of this kit, the split is between F7 and F8)

 

The splitter is made of a small piece of metal in which I drilled 3 x 2mm holes. A 2mm bolt is screwed into the end of the plastic inner going back to the servo and similar onward to the rudder and tail wheel.  Just need to find a suitable control arm for the tail wheel rod - there's not much room at that end of the fuselage.

[Gaz Elliott]

I have a tail wheel on some of my aircraft and to be honest some are a pain in the rear end. However on reading ( probably on here) I have found a good solution is to attach an arm to the rudder and secure springs either side to the wheel on the fus. That whay the pressure on the rough terrian is not laiden onto the servo with the risk of stripping gears. Kind of shock absorbing.

smc have one here there are the type which fix straight in to the rudder which i also have and are a little cheaper ( search SMC for tail wheel) Neither style require a splitter. Which is really only another linkage to worry about/fail and how would you tighten/adjust easily once the model is covered?

Hope this helps

Gaz