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Airsail - Dehavilland Chipmunk Kit


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Hi Richard, you're on fire man - at this rate you'll have your chippie in the air next year

I see the spars don't meetthe plan, but it is the distance between the slots in the spars and the length of the ribs that I found to be a problem - I guess there isn't a lot of repeatable accuracy from one kit to the next.

I can get the plans scanned and converted to a cad file, then with some cleaning could produce some accurate laser cut parts. Maybe a possibility for th next one

The Poly C seems like a good option for covering - I will leave this until the airframe is fully built 

Cheers

Gav 

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Although I have put some effort into devising cunning central servo mounts for the aileron and flap servos, I am now seriously considering using wing mounted servos. I recall that someone suggested this earlierbut I had discounted the option on the basis of Stefane Sevard's photo showing a partially externally mounted servo.  I think there is just about enough room in the wings.   I will need to make up some mounts/ cover plates which should not be too difficult. My only concern is whether the extra weight might be a problem (2 extra servos and the mounts/ covers).  However, some weight will be saved by eliminating the long control rods. If the weight is on the high side I can compensate by going for a more powerful engine on which I am keeping my options open.
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Having decided to go for wing mounted servos, I'm trying to work out how best to position them. I'm assuming they should be aligned at right angles to the trailing edge so that it's a straight push/ pull to the horn.  I'm making covers which will act as mounts so there won't be much difference in the weight. I think I can work it so that the connecting rod comes out though a hole/ slot in the cover rather than as in Stefane Sevard's solution where he had the horn coming out of a slot with the control rod all external.
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Another step forward - one wing attached to centre section.

http://forums.modelflying.co.uk/sites/3/images/member_albums/31908/DSCF2921.JPG

Next step to add the other wing and start skinning.

I've been thinking ahead to the engine and am now thinking of an OS 70-FL four stroke, 2nd choice might me the SC 70 that Gavin is thinking of using. Anyone got any thoughts/ knowledge of these engines?

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A little more progress to report. Now joined on the other wing and sheeted leading edges.

http://forums.modelflying.co.uk/sites/3/images/member_albums/31908/DSCF2922.JPG


Had minor accident while adding the top sheet; managed to damage the sheet already fixed to the underside. Debated whether to replace the whole sheet but decided to cut out the damaged sections and fill in. Can't see the join!

Next step is to cut off the ailerons and flap and complete them. After that I will look further at my servo mounts in the wings prior to sheeting the rest of the wing which is not specified in the instructions.

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TIP FOR OTHER BUILDERS OF THIS KIT: 

Having followed the instructions and left cutting off the ailerons and flaps until now, it has occurred to me that it would make more sense to cut them off much earlier in the process such as straight after applying their top sheets. There appears to be no reason to leave them on while the wing assembly is completed and the leading edge sheeting done. Getting them out of the way earlier would make the wings easier to handle and protect the ailerons and flaps from damage.

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Thanks for your comment Simon. I'm surprised you want to buy one of these after all we've said about the inadequacy of the instructions and incorrect sizing of some pre-cut parts!  However, I am pretty happy overall with the kit and I am finding it a great learning experience.

I'll post some updates soon but it has been a bit slow going completing the flaps and ailerons.

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  • 2 weeks later...

I can now report a little progress after sorting out the aileron and flap controls with individual servos mounted in the wings. Below shows an aileron temporarily fitted with the servo in position.

http://forums.modelflying.co.uk/sites/3/images/member_albums/31908/DSCF2957.JPG

I decided to use Robart hinge points rather that the flat plastic ones supplied with the kit. Used epoxy to glue them to the aileron (lesson learnt - keep the epoxy out of the hinge joint).

Planning ahead, I've taken delivery of my SC 70 FS. I need it early as I have ordered one of the last ever Timbo special on board glow systems and will need the engine to test it out. It looks as though I will need something like a 90 deg manifold to position the exhaust in the cowl.

http://forums.modelflying.co.uk/sites/3/images/member_albums/31908/DSCF2930.JPG

Other progress is the addition of the leading edge - will post a picture when I have finished shaping it. Finishing the flaps and ailerons was delayed while I sorted out the controls which determined the position of the horns. I am also glassing them with Poly-C before final attachment.

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A .70FS? The poor thing was designed around a .40 two stroke. You better hope that between the glassing of everything and the final covering (that fabric Solarfilm stuff?) and the extra servos you don't end up with an overweight, overpowered bomb. The originals were Solarfilm on the open areas and dope and tissue on the sheeted bits. They also had admirable flying qualities, I think there was a writeup in one of the English mags where the builder mentioned that the engine he used was way too much power and he had some trouble getting a low enough idle to land the thing. I think he was using a .54 FS. He was, however, most appreciative of the flying. I would advise caution about anything that adds to the weight, and isn't actually needed.

Evan.

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There are some differences in all ailsail kits I think, as I found out. I probably found it easier than some, as have built some free flight scale before from scratch. But It is annoying that in some of their kits parts don't seem to quite match up. The preformed plastic parts to are sometimes not formed as well as they might be. But on the whole the plane I built (the DH Beaver) was quite easy with the exception of the nose cowl fixing and fixing radio gear You are doing a great job! I hope you have many flying hours on it.
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Or so they claim. We just did some 'poly C and .75 oz glass cloth' on a wing for a scale aerobat, and there is as much weight gain as h/weight tissue and lots of dope coats. In its defense the finish (before paint) is quite good, and much less work than epoxy and glass. On a big model it makes sense, on something as small as the Chippie one needs to be very careful. Lightweight tissue and  dope is the way to go. You must realise too, that the kit manufacturer has little control over the wood supplied in the kit, whilst every effort is made to match the wood with the intended task, he is always limited to what is available at the time of kitting. If the modeller is not satisfied the the wood should be replaced with what you consider suitable. These little scale models were never intended as a 'first scale build', being small and quite close to scale they require quite a bit of experience before you attempt a build, hence the instructions are aimed at an experienced scale modeller and are quite sufficient for anyone who has built from, and designed his own, plans and models.

Evan.

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Evan, Thanks for your comments. You've got me a little worried that it might be coming out a bit on the heavy side but the build documented by Stepane Savard made the same choice of wing mounted servos and glass cloth covering. Mine should come out lighter as I am using Ploy-C instead of epoxy.  I'm not sure where "little scale models" comes from as this plane has a 69 inch wingspan. With regard to the choice of  this kit as a first build, I am finding it a bit of a challenge but it has been an excellent learning experience for me so far and with help and advice from forum members problems get resolved. Let's hope it will fly OK!
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Say you guys who have flown this plane(and the ones building). Some time in the future I hope to build this Chippie (or the DH Beaver, depending on the answer to my following question!). Would this fly on a Electric setup which has the same power as a .40 2st? I Know the Beaver deffinatly will. If it wont then I would bother with the Chippie and go for the Beaver. For me the Airsail kits offer great value, all wood (CNC and stock/sheet), All hardware, Plastic parts and Decals and a nice end result plane. All that for just £80-£90 quid!

Dont worry for haste with the answer, It wont be along time off yet! At least 6 months!

Thanks For a great thread and a your answers!

Ben.

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I have heard of the Airsail Volksplan, Beaver and Auster being electrified, but not a Chippie, yet. Come to that I haven't heard of a Tomahawk being sparked either, but I don't get to hear everything. And yes, the Chippie is a small scale model, the wing area is not great, and it was designed for a .40. Given that most scale models tend to be quite a bit bigger, 2 metre span and more, then you can see that, despite the quoted span, the actual thing is really only a wee thing and will respond magnificently to the addition of lightness.

Evan.

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Although I am a long way off needing the engine I have already obtained it so I want to give it a run so I decided to but together a test rig.

http://forums.modelflying.co.uk/sites/3/images/member_albums/31908/DSCF2959.JPG

Set up ready to run. Probably won't be able to run it tomorrow as it's the one day a week that I do voluntary work. I've set it up with a servo for the throttle as I will be using an on-board glow which I will also be testing.

http://forums.modelflying.co.uk/sites/3/images/member_albums/31908/DSCF2960.JPG


Shown here with the Glo-n-go system in place. Engine is an SC70.

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