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Old Aug 05, 2012, 04:14 PM
Sic itur ad Astra
sparks59's Avatar
United Arab Emirates, Abu Dhabi, Abu Dhabi
Joined Aug 2009
1,603 Posts
You'll be setting fire t'summat with an 8x3.8 SF on that likkel motor Colonel! 6x3 is the most I use on that combo, but I guess you might get away with a 6 x4 if you did need a bit more whump.

Sounds like you're having lots of laughs with the covering

Keep at it!

sparks
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Old Aug 06, 2012, 12:44 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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Originally Posted by sparks59 View Post
You'll be setting fire t'summat with an 8x3.8 SF on that likkel motor Colonel! 6x3 is the most I use on that combo, but I guess you might get away with a 6 x4 if you did need a bit more whump.

Sounds like you're having lots of laughs with the covering

Keep at it!

sparks
Once I felt how hot it got, I soon concluded that the 8 x 3.8 wouldn't be my best idea.... It was only a current test, and was the prop that I had handy. However, I've noticed that the motor is only rated for 4.5A constant and 6A burst, so the ESC is likely to fry at the same time as the motor if I overprop it. But if the Ajax comes in at my upper target of 180g, 25W input power @ 70% efficency gives 44W/lb which probably sounds about right.

Re the covering - I'll crack it - it may not be as pretty as i would have liked, but I will get there. I just need to research various warp-removing techniques post mylar and also post mylar & tissue!!!
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Old Aug 06, 2012, 12:59 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
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Stick at it Colonel; you are starting mylar/tissue on a difficult subject, the lighter and smaller the airframe the harder it is. But don't worry too much about the warps, when the covering is finished a diligent session with the steam kettle will straighten things out. You actually started with the hardest components in the thin fin and very lightly built tailplane, sorry, I should have made that point. Personally I would have recommended starting with the fuselage, then the wing and leaving the tricky little bits until you had some practice. But you WILL get it done in the end.

And yes, re the motor, definitely no bigger than 6 x 3. It'll be plenty to fly this model.
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Old Aug 06, 2012, 01:06 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
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Originally Posted by Sundancer View Post
...don't worry too much about the warps, when the covering is finished a diligent session with the steam kettle will straighten things out. You actually started with the hardest components in the thin fin and very lightly built tailplane....
Just what I wanted to hear! Fuselage next then.........
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Old Aug 06, 2012, 05:10 AM
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where's the piccies?
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Old Aug 06, 2012, 05:35 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
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Originally Posted by kkphantom View Post
where's the piccies?
Honestly, you are a wicked man..........

Here you are. I'm not quite so worried as I was - the fin will be having a fair amount of decoration on it. I think the main problem was a lack of cleanliness - and with that mylar being so statically charged that armchairs get dragged towards it, even dust from downstairs makes its' way to the model! I have dug out some sprayers' tack cloths which from now on I will wipe the part with just before laying the tissue over the mylar.

The tailplane warp that remains I will try removing with steam once the covering has been completed. Believe me, that twist is nowt next to how it was just after the mylarring, when it resembled a Möbius strip....
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Old Aug 06, 2012, 06:41 AM
*jj
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Originally Posted by Colonel Blink View Post
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 doesn't 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???
I did tell, you, remember? I'm not sure, also, that it is a good idea to use Esaki tissue. I have taken to use non-shiny tissue for mylar/tissue coverings, as the dope soaks through and sticks it to the mylar. Dope doesn't seem to penetrate Esaki (another reason why I use pritt stick for attaching it to the frames)
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Old Aug 06, 2012, 09:06 AM
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>Dope doesn't seem to penetrate Esaki

Then why does it have to be sanded off any part of the airframe that it touches when one wants to re-cover a model? Why does Esaki get so much stronger when dope filled?

Esaki over mylar seems to be generally accepted.
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Old Aug 06, 2012, 03:59 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
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Originally Posted by Applehoney View Post
>Dope doesn't seem to penetrate Esaki

Then why does it have to be sanded off any part of the airframe that it touches when one wants to re-cover a model? Why does Esaki get so much stronger when dope filled?

Esaki over mylar seems to be generally accepted.
Absolutely true Jim but I think you have to distinguish between covering dry and wet. Properly thinned dope certainly DOES penetrate WET Esaki Liteflite perfectly well, and sticks it both to the airframe and to the mylar. The bond with the mylar is such that if you ever cut a panel out due to damage, you will find that the tissue and mylar are totally inseperable. I know this because I "arranged" a test by dropping my field box on the wing of the first model I ever covered this way, an "Aquila Grande" thermal soarer, hence the need for a repair! And as you say, the bond with the rest of the airframe - e.g on sheeted areas - is such that it is the very devil to get off. With dry tissue it doesn't penetrate so well. But of course when covering I don't use dope, but thinners, again through wet tissue, to re-activate a pre-doped airframe.

Mind you, the Colonel, due to issues with dope fumes, is using varnish, but that also penetrates wet Esaki perfectly well.
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Old Aug 06, 2012, 05:40 PM
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Ajax, Ontario, Canada
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I do take your points George but with a differing basic technique I have always covered dry.. but the way Esaki sticks to the rest of the structure when doping ... I don't see dope having any problem penetrating through it. However. over mylar ... I bow to experience

Sometime I'll play around with trying tissue over mylar. Maybe ... I'm very much stuck in familiar ways and slow to move away from them..
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Old Aug 07, 2012, 05:04 AM
*jj
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United Kingdom, Birmingham
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Originally Posted by Sundancer View Post
Absolutely true Jim but I think you have to distinguish between covering dry and wet. Properly thinned dope certainly DOES penetrate WET Esaki Liteflite perfectly well, and sticks it both to the airframe and to the mylar.
Obviously where I was going wrong; although the one time when I tried to use wet tissue, it wrinkled like Norah Batty's stockings ...
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Old Aug 07, 2012, 06:20 AM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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Last night I covered the other side of the fin, though this time I dunked the Esaki completely rather than floating it on the water. I also spent less time removing water from the tissue before laying it on. This seemed to get better contact between tissue and mylar, and whilst brushing through would thin the varnish more - which would hopefully assist in its permeating the tissue fibres. Looked better than the first side whilst wet - I haven't had the chance to check it today so no idea whether it has worked or not. But the issue does seem to be getting the varnish into the fibres homogeneously. Wondered about adding a drop of detergent to the water.....
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Old Aug 07, 2012, 07:35 AM
Sic itur ad Astra
sparks59's Avatar
United Arab Emirates, Abu Dhabi, Abu Dhabi
Joined Aug 2009
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Originally Posted by Colonel Blink View Post
Wondered about adding a drop of detergent to the water.....
Or wetting agent as photographers like to call it...

I hear the bubble effect is about to be yesterdays antique look....

sparks
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Old Aug 07, 2012, 03:58 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
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The second side of the fin has indeed come out far better than the first; so it looks like (for the white Esaki at least), a complete dunking is the order of the day. Phew.

Regular readers will be relieved to hear that there will be no progress for the next two and a bit weeks, as it is time for the yearly sojourn to foreign climes. Lady Blink has been pushing pins into a map of southern Spain for weeks, marking vineyards and distilleries for her cultural edification. She is currently marking with string the shortest route that joins them all, whilst hypothesising that with the correct organisation she could manage two laps. It appears that we will be taking an aero service to that Southern European land; I wanted to take the flying boat from Southampton, but Her Ladyship is insisting on the Imperial Heracles out of Croydon - something to do with the Moët served in First Class....
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Old Aug 07, 2012, 04:49 PM
I like real wooden aeroplanes!
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Looks OK to me Colonel.

Have a good holiday; pity it isn't France, you could have dropped in, we have lots of vineyards here too and we aren't so far from the distilleries at Cognac!
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