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Old Jul 29, 2012, 05:25 PM
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Ajax, Ontario, Canada
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Nice work, Colonel - very tidy.

I have to admit I'm so happy with the simplicity of a rubber motor, though .... All this electricky and steerage stuff is way beyond me.
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Old Jul 29, 2012, 11:10 PM
Sic itur ad Astra
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United Arab Emirates, Abu Dhabi, Abu Dhabi
Joined Aug 2009
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Great progress Colonel, now that you have re-arranged all of the internal organs
Looking at your piccies, with the tractor unit and weight of the equipment concentrated at the nose end, I might be tempted to add a bit of 'gussetry' around the joints forward of the cabin, up to the infill sheeting, just to spread the load across the connection nodes.

Just a thought from a person well experienced in less than perfect 'arrivals'
sparks
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Old Jul 30, 2012, 01:32 AM
So I'M meant to be in control?
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Ilkley, West Yorkshire, UK
Joined Nov 2008
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Well, the wiring hasn't come out anywhere as tidy as I'd hoped, but it's...er....'functional'!

And I must admit that I keep reading people saying 'build in lightness' and 'build to fly, not to crash', but still I have thoughts the same as you, sparks!
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Old Jul 30, 2012, 03:32 AM
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I think it's a fine balance between achieving the lightest construction to aid flight, and the heaviest to withstand a good bludgeoning, the latter of which is somewhat self inflicted with increased mass.

But, experience reminds us that the lightest planes are often ruddy hard work to fly in anything other than calm conditions, and they don't hold up well to the rigours of transportation, tight storage space on the wall or the all too often occuring heavy landing where the kinetic energy available from the mass of the battery is imparted on the airframe.

I do prefer to build light, but my best planes, in terms of flying and durability tend to err on the heavier side of my builds.

As for the wiring, welcome to my world
sparks
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Old Aug 01, 2012, 03:53 PM
So I'M meant to be in control?
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Ilkley, West Yorkshire, UK
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Well, on Sunday I managed to score a small (250ml) pot of the Ronseal Diamond Hard Wooden Floor Varnish (7.99, B&Q Keighley) so that takes an elephant of doubt out of the equation....

I have now got to the stage of running out of things to do before starting the covering. I have even prepared a couple of 3" square test frames to practice on. In general, I enjoy covering; it's when you can first feel the wing you've built actually producing lift! However, it has been a few years since I covered a model, and even then it was with iron on film. So, just to be sure I've got this right (the more I read, the more contradictory the advice seems to get!), am I correct in thinking....

a) The airframe areas which will be taking the Balsaloc should be sealed with 2 coats of the varnish (thinned? 60V/40W??), lightly sanded between coats.

b) The periphery of each panel to be covered is given a 1/8" line of Balsaloc (thinned? 50B/50W???), as are the ribs and spar on the undercamber.

c) Each panel covered with mylar (not overlapped), even but not tight, sealed around edge with iron.

d) Mylar then shrunk with iron.

e) Mylar covered with tissue laid on 'wet' (ie floated on surface of water - shiny or dull side down on water? Shiny or dull side down on mylar?)

f) Varnish brushed through tissue to adhere to mylar (Thinned? 50V/50W???). Overlap.

g) Stand back and admire or cry dependent upon result.
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Old Aug 02, 2012, 01:26 AM
I like real wooden aeroplanes!
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South-west France
Joined Sep 2007
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That is more or less the way I do it Colonel, except I don't thin the balsa loc or the varnish normally. Also, when using varnish as opposed to dope, since you are brushing varnish through the wet tissue over the whole area, rather than leaving a bare wood overlap at the edges I cover the whole airframe with the mylar. The "bare overlap" technique is what I use when using dope/thinners, as the tissue is then stuck down round the edges with thinners reactivating the pre-doped bare overlap and the rest is not doped until after the water has dried out and the tissue has shrunk.

Also, be prepared for it to look 'orrible after you have varnished the wet tissue down, but fear not, it all turns out OK as the water and varnish dry out.

I recommend covering the whole of the model with mylar first, but then tissue one surface at a time - e.g. top of wing, one fuselage side - waiting for it to dry before doing the next, otherwise it is easy to spoil the wet panel.

But DO practice first!!!!

Anything to add RAF_Bob, you clearly have the technique cracked?
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Old Aug 02, 2012, 03:32 AM
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Quote:
Originally Posted by Sundancer View Post
That is more or less the way I do it Colonel, except I don't thin the balsa loc or the varnish normally. Also, when using varnish as opposed to dope, since you are brushing varnish through the wet tissue over the whole area, rather than leaving a bare wood overlap at the edges I cover the whole airframe with the mylar. The "bare overlap" technique is what I use when using dope/thinners, as the tissue is then stuck down round the edges with thinners reactivating the pre-doped bare overlap and the rest is not doped until after the water has dried out and the tissue has shrunk.

Also, be prepared for it to look 'orrible after you have varnished the wet tissue down, but fear not, it all turns out OK as the water and varnish dry out.

I recommend covering the whole of the model with mylar first, but then tissue one surface at a time - e.g. top of wing, one fuselage side - waiting for it to dry before doing the next, otherwise it is easy to spoil the wet panel.

But DO practice first!!!!

Anything to add RAF_Bob, you clearly have the technique cracked?
Thanks for your vote of confidence George!

I must stress that I don't consider there to be only one right way here. I'll describe what I do and have found to work ok but you may well develop your own "wrinkles".
1) Sand the framework smooth making sure there are no raised areas or dips in sheeted areas and that all joints meet cleanly.
2) It's optional, of course, but I recommend coating the entire airframe with thinned varnish. Thinning reduces weight and still provides a sound surface on which to work. Since the varnish is water based it will tend to raise the grain a bit, so re-sand with a fine grit (600, or so) being careful not to overdo it.
3) Brush on Balsaloc to ALL surfaces where the mylar will touch. Thin the stuff with water as this makes for a smooth application. I find that Balsaloc can be a bit thick and gungy at times but that may be only because mine's an oldish bottle and probably has thickened up a bit. You want it to brush on smoothly without leaving ridges or any build-up. There's no need to do the whole model in one go, just the panel your working on. Allow to dry.
4) Cut the mylar a little oversize as you would tissue. I find an "all surface" marking pen handy for laying out the stuff. Set the iron to mid heat and tack the mylar to the framework at one end. Then tack at the other end and, starting about mid way along the length, ease it out to the edges and tack into place at points opposite each other. Work along the entire framework like this and you will have a "spot welded" covering. Now start evening up the mylar and seal all around the edges. If necessary, untack the covering and manipulate into place until it is as EVEN as you can get it without putting yourself into a psychiatric ward. Raise the iron heat to full (assuming a normal covering iron) and start shrinking (the mylar, not you). Working slowly across the narrow width of the component seems to work best. Now, you will almost certainly find that wrinkles appear in places. If so you can remove them by dragging them to the edges with a little more pressure applied to the iron. This is why it's so important to get the mylar on evenly in the first place. Don't rely on shrinking alone to produce a smooth result. Be aware that imperfections in the mylar will show through the tissue! Have a soft cloth at hand and as the mylar shrinks use it to rub it down onto all parts of the structure. When it's as good as you can get it trim it with a VERY sharp scalpel or razor blade. At wing leading edges I wrap it a little way round and trim into the wood. I apply a little more adhesive along here so I can overlap the covering later.
5) Right, onto the tissue at last! Oops, look at the time!! I have to go now but will be back asap. I hope what's here will be of some help.
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Old Aug 02, 2012, 08:08 AM
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Right I'm back. First I'd endorse George's advice to mylar the whole model, or at least the component your working on. As a simple way to start I'd suggest the fuselage underside.
If using lightweight Esaki then it's probably best to attach the glossy side to the mylar. It's not particularly critical but seems to give better adhesion. Also, there have been suggestions that the slightly rough outer surface improves airflow at low speeds (on wings, that is). Whatever the case do it all the same way or the finish will be patchy. Cut the tissue as usual a bit oversize. Here's a tip learned from using sheet film cameras in the days of "proper" photography. Place the tissue glossy side up and cut a small corner off the top right end. this will enable you to tell which side is which when it's wet. To wet or not to wet? Some like to use the tissue in it's dry state and it is easier to handle like that but I find it better to immerse it in water. If it's sopping wet it's easier to remove creases etc. but is more tricky to handle.

6) Now coat the mylar with varnish being careful to avoid loose hairs or other clag as this will show through the finished covering. If the varnish is thinned a little it works well but it's not essential as the water in the tissue will accomplish a similar result.
Soak the tissue by completely dunking it in clean water and pull it up to drain a bit. It will stick to itself and resist hanging straight but just work carefully to remove all the folds etc. It helps to attach the top edge to a cupboard edge or something so the tissue hangs free. You could enlist the help of wife or daughter to hold it! Now the notch you clipped into it will help you orientate it such that the glossy side is in contact with the mylar. Place on the model and very, very carefully pull it into place until it covers the component. Starting in the centre work it slowly and gently to remove bubbles, wrinkle and creases. Take pad of kitchen roll or similar and wipe over the surface and you'll see the tissue assume an even tone as it adheres to the mylar. I usually then brush more varnish over the component and wipe this off with a pad of tissue. The idea being that a small amount will penetrate and strengthen the bond. You now have a beautiful covering that is totally finished except for neatening off!

7) To tidy up you can do one of two things. a) Whilst the tissue is still wet trim it with a VERY, VERY sharp blade. I prise the blades from chuck away razors for this. A NEW scalpel blade might be ok but I've never tried one. b) Allow the tissue to dry making sure it does not attach to edges where it's not wanted. Unlike dope, varnish cannot be softened once it is dry so if it sticks in the wrong places you've got a problem! This is also why it's best to make it only a little oversize in the first place (say 3/8" all round or so). When dry it can be trimmed to a 1/16" or so and a lick of thin balsaloc will permit ironing down.
That's about it really. I strongly agree with George that here is no substitute for practice. I'd recommend you make a test panel about 3" wide, 12" long and 3/8" deep with several "ribs" along it's length. It doesn't have to be balsa. You then have a double sided component to cover on both sides. This should give you a real feel for the technique and boost your confidence no end.
I hope all this helps you and anyone else who's thinking of trying it. I notice a number on the Groups who express interest in tissue over mylar so perhaps it will encourage others too.
Please, please get some experience before attempting it on the Ajax. That beautiful framework has cost you a lot of effort and some money and it would be a shame to use it as a test bed! Sorry if that sounds patronising
One last thing for now. Once the tissue has dried it is not necessary to apply any more varnish. This is why the combination can be lighter than doped tissue alone and also why thin varnish is better than thick. Of course, a gloss finish can be brought up with further coats but at the expense of weight.
The result is a tough, beautiful and very vintage look.

just as a ps. Coloured varnish works well too. I used some antique pine to finish the Senator and it has added a richness and warmth to the tissue and is not at all obvious. Would be fine on white tissue for an antique finish for early scale types I think.
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Old Aug 02, 2012, 09:26 AM
I like real wooden aeroplanes!
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Good stuff Bob. Just a few things I do differently, but I'm sure either way works just as well:

I cover with the tissue shiny side out.
To wet the tissue, rather than dunking it I drag it across a shallow tray of water, shiny side up, the surface tension "sticks" it down to the water and you finish up with a wet side and a dry side, hang the sheet off the end of the bench as it comes off and you don't get any sticking together. In my system I "flop" it onto the surface wet side down. Alternatively I spread it dry over the component and use an atomiser to wet it. Either way seems to work equally well.
I don't varnish the mylar first, but apply the coat through the wet tissue.

All details really, the secret is practice and patience.

I like the idea of the tinted varnish. Wish I had thought of that when I built my Eastbourne Monoplane, although that used the dope/thinners method. I dyed the tissue with cold tea to get the right "antique linen" effect, the varnish would have been easier!

As far as I am aware, the only possible disadvantage of using the varnish versus the dope/thinners is that I discovered that the tissue does tend to slacken off a little in very damp evening air, which is doesn't do with dope. It is fairly minor, and has to be pretty damp, it tightens back up as soon as you have it back indoors. However, since I have managed to source decent dope and thinners, and I don't have any problems with the fumes (Ali used to say that if there wasn't a faint whiff of cellulose drifting from the workshop at all times she was worried I might be ill!!) the last three models, Mamba, Witch and Sportster have used that. But the previous three, Zephyr, Tom Tit and Bantam which used the varnish are equally satisfactory and I would have no qualms about using it again if I should run out of dope.

So there you are Colonel; lots of advice, just get on with it
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Old Aug 02, 2012, 09:36 AM
I like real wooden aeroplanes!
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Originally Posted by Applehoney View Post
Nice work, Colonel - very tidy.

I have to admit I'm so happy with the simplicity of a rubber motor, though .... All this electricky and steerage stuff is way beyond me.
Only just picked that one up Jim! Simple??? You must be joking. The complexities of rubber, the variable power output, the ever changing torque, pre-tensioning, clutches, free-wheels, folders, featherers, the fact that the stuff just gives up the ghost and breaks sometimes at half turns etc. etc. make getting a good performance out of a power, electric model or glider, free-flight or radio, a doddle by comparison! I am full of admiration for people who get rubber models to fly well, in many years of trying I never really mastered the things.
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Old Aug 02, 2012, 02:02 PM
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George, you mean that non-rubber flyers take the easy route? I must admit I've never considered the flying of rubber models in the context that you set out, all just comes natural .. and that to me as a dedicated power flyer who has neglected such in recent years but has a number ready to take out next week in the hope of getting them checked out again whilst making some healthy noise.

As for the complexities of rubber flying that you note... you put as much, and maybe more, into power models in the past so elastic powered models should not be a deterrent. Have just been browsing through all the Northern Area News's published through the 60's (from Gordon Roberts effects - remember him?) and your lengthy voluminous writings on power model development, aerodynamics, fuel systems, trimming and flying make good reading.

Before you were seduced to the dark side, of course ...........
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Old Aug 04, 2012, 03:16 AM
So I'M meant to be in control?
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Ilkley, West Yorkshire, UK
Joined Nov 2008
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In all honesty, the main thing that has put me off rubber in general is all the pre and post faffing that needs to be done; lubrication, removal of lunrication, hanging motors in darkened places under a full moon to reduce (but not remove) the chances of an exploding motor wiping out the whole shebang. I actually found a box of FAI Tan in the loft unused (and never likely to be!). But I digress.....

Well, last night I had a spare half hour whilst young Pippa Blinkette was at Pony Club and Lady Blink had taken car & trailer to Oddbins to stock up, so I had a bash at this here covering malarkey. I covered one of my test frames. I used a single sealing coat of unthinned varnish on the wood, unthinned Balsaloc, mylar, damp tissue floated across water a la Sundancer, and a single coat of unthinned varnish brushed through to attach the tissue. I covered both sides of the test frame, and although possibly not perfect, I am reasonably pleased with the results - especially when dry. I know that this is about the simplest thing in the world to cover, but at least a decent proportion of the Ajax is square!

The weight gain of the test piece due to covering was 0.5 - 0.6g. Allowing for a fair amount of error in weights as low as this on a set of cheap scales, this still gives a projected weight of covering in the low 20s; so lets say c25g. If this proves to be true, this will still enable to total weight to still be close to my upper target of 180g.

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Old Aug 04, 2012, 04:58 AM
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Looking good Colonel. Yes, I use gloss varnish, but your satin should give a pleasant enough finish, especially if you put the tissue on shiny side out.

I think your weight estimate is probably about right; when I did the KK Bantam wing it added 20 grams, but that included extra tissue trim panels on the tips and two logos and trim lines cut from Solartrim (which is heavy), so I reckon the mylar/tissue and varnish probably added 10 grams which equates to about 6 grams per square foot of area.
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Old Aug 04, 2012, 01:37 PM
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Actually, I quite like the matte finish Colonel. The test looks good.
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Old Aug 05, 2012, 03:57 PM
So I'M meant to be in control?
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Ilkley, West Yorkshire, UK
Joined Nov 2008
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I finally charged the lickle 360mAh 2S Lipo today and connected it up to my Wattmeter. I have been a little concerned in that I selected a 6A Turnigy ESC to save a few grammes over the 10A. Turned out not to be a problem - with the 6x3 TGE type prop, it was knocking out 25W (well, input power) @ 3.5A. Just because I had one, I plonked an 8 x 3.8 slowfly prop on and carefully monitored the current as I opened the throttle. Got to full chat OK - 33W @ 4.5A. But after only about 10s of running, I nearly burnt myself on the motor! Probably wouldn't last long if I used that prop......

This morning, I covered the second test frame with the shiny side out. There was very little difference in finish, but the 'shiny side out' test seemed to look marginally better, so I decided to use the Esaki that way. Time to start covering in anger! I picked the fin & tailplane to start on, on the grounds they would be easier and quicker to make if it all got terminal.

Well it may have got terminal....

What seemed to go very well on the test frames doesnt seem to be going as well on proper parts. Shrinking the mylar induced various bends and twists - I'm trying to work out whether this is due to the iron being too hot, my wood selection, or the mylar not being even enough before shrinking and 'pulling' more in one direction than another. I worked with the iron to counteract the worst of the induced inaccuracies. I got the tailplane pretty much back to how it was before, but I'm wondering whether it would be worth pinning the tailplane down raised say 1/4" off the board, and playing a hairdryer over and under it......????

The fin was OK, so I began applying the tissue. However, the white tissue feels more 'crackly' and seems to be far less pervious to the varnish and didn't want to adhere nearly so well to the mylar as the red & blue used on the test frames. Finally got one side of the fin covered, but it has come out very patchy - possibly due to dust holding the tissue off the mylar? Oh, and a slight twist has worked its way in again which I will have to attack with iron again before applying the Esaki to the other side.

Eeeeh, it's all a challenge, innit???
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