HobbyKing.com New Products Flash Sale
Reply
Thread Tools
Old Jul 25, 2012, 12:50 PM
Registered User
Ajax, Ontario, Canada
Joined Oct 2004
2,566 Posts
>My Senator wing is as flat as a pancake with mylar under lightweight tissue.

Mine are undercambered ........
Applehoney is online now Find More Posts by Applehoney
Reply With Quote
Sign up now
to remove ads between posts
Old Jul 25, 2012, 12:58 PM
Registered User
United Kingdom, England, Lancs
Joined Sep 2006
310 Posts
Quote:
Originally Posted by Applehoney View Post
>My Senator wing is as flat as a pancake with mylar under lightweight tissue.

Mine are undercambered ........
Oh dear! seems I forgot something!!
Raf_Bob is offline Find More Posts by Raf_Bob
Reply With Quote
Old Jul 25, 2012, 01:22 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,427 Posts
Tissue alone is fine if (a) you don't mind patching and (b) you don't expect your models to last too long or have a very active life. I have mylar/tissue covered models I have been flying for ten years, OK the colours are a bit faded but if it had been tissue alone they would have been like patchwork quilts by now, especially as one of the fields I fly over is stubble for part of the year. Also, tissue alone would probably have been brittle by now.

It is also a fact that a mylar/tissue/dope finish can actually be LIGHTER than a tissue only finish, as the mylar provides air proofing and thus considerably less, and thinner, dope can be used, just enough to shrink the tissue. The total weight of the finish on my 1.8x Sportster was 16 grams, of which just 5 grams was contributed by pre-doping the whole airframe (3 thin coats and rubbed down) and covering the wing and tail in 10 micron mylar using Balsaloc. It is hard to envisage getting the same standard of finish any lighter.

Finally, the Colonel is using water based varnish not dope. I have never done a tissue only finish using this, but would have a suspicion that it might not be very satisfactory from a shrinkage point of view, whereas, if applied wet over mylar and varnished it is fine. And also, I would expect that quite a lot of varnish will be needed for complete air proofing without the mylar, and it is going to be heavy.
Sundancer is offline Find More Posts by Sundancer
RCG Plus Member
Old Jul 25, 2012, 01:23 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,427 Posts
Quote:
Originally Posted by Applehoney View Post
>My Senator wing is as flat as a pancake with mylar under lightweight tissue.

Mine are undercambered ........
Now Jim, stop being obtuse, you know perfectly well what he meant!
Sundancer is offline Find More Posts by Sundancer
RCG Plus Member
Old Jul 25, 2012, 01:44 PM
Since 1952
Harry D's Avatar
Canada, AB, Edmonton
Joined Oct 2004
1,246 Posts
Quote:
...it's not that heavy.
Does anyone have some actual numbers for the weight of the mylar/tissue covering system, in grams per square foot (or some other similarly weird units)?

I've recently started using Litefilm (Microlite, Solite, Ultralite, etc etc) which weighs about 2 grams/sq.ft. I realize it's an apples-and-oranges kind of thing, but I was wondering how the mylar/tissue weight compared to that film.

Thanks!
Harry D is offline Find More Posts by Harry D
Reply With Quote
Old Jul 25, 2012, 02:35 PM
Registered User
Gluehand's Avatar
The windy west coast of Sweden
Joined Sep 2008
2,815 Posts
Hello,

5 Micron mylar (which, acc. to Mike Woodhouse is appropriate for this size of models), weighs 6.8 grams per sq metre.

Esaki Light tissue (also recommended), weighs 12.5 grams per sq metre.

To this should be added a coat of thinned dope (to stick the tissue to the mylar), plus another coat to finish. (with the mylar backing, the tissue is quicker "filled up" with dope)



For comparison:
Esaki Medium (undoped) weighs 14 grams per sq metre....
'Cling Film' (the brand they sell over here) weighs 15 grams per sq metre (!)



I have yet to try this myself. This info is what I've learnt, from what I consider reliable sources....


Gluehand is online now Find More Posts by Gluehand
Last edited by Gluehand; Jul 25, 2012 at 02:52 PM.
Reply With Quote
Old Jul 25, 2012, 03:01 PM
Registered User
Ajax, Ontario, Canada
Joined Oct 2004
2,566 Posts
> Now Jim, stop being obtuse, you know perfectly well what he meant!

Of course, George .... but I can't help myself .. the Devil makes me do it .... My next design will be called 'Exorciser".

Back to regular programming .....
Applehoney is online now Find More Posts by Applehoney
Reply With Quote
Old Jul 25, 2012, 03:47 PM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,427 Posts
I suspect that in total, mylar and Esaki Liteflite plus two thinned coats of dope might well be a bit heavier than the very lightest heat shrink coverings, BUT what it does do is provide vastly superior torsional rigidity to any of them. The torsional rigidity is the job of the tissue, giving the tissue puncture resistance is what the mylar does.

remember that this technique was originally developed for FAI class contest free-flight models where stiffness is essential.
Sundancer is offline Find More Posts by Sundancer
RCG Plus Member
Old Jul 25, 2012, 04:02 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,480 Posts
All interesting views; and it is quite satisfying when someone with as much experience as Mr S Dancer Esq echoes my own inexperienced suspicions:

Quote:
Originally Posted by Sundancer View Post
.... the Colonel is using water based varnish not dope. I have never done a tissue only finish using this, but would have a suspicion that it might not be very satisfactory from a shrinkage point of view, whereas, if applied wet over mylar and varnished it is fine. And also, I would expect that quite a lot of varnish will be needed for complete air proofing without the mylar, and it is going to be heavy.
The original driver was the desire not to use dope, which would have Lady Blink hefting wine bottles at my head (she would empty them first of course). This initial driver has now been augmented by an element of simply wanting to try it!
Colonel Blink is online now Find More Posts by Colonel Blink
Reply With Quote
Old Jul 25, 2012, 04:11 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,480 Posts
Managed some more playing with hardware positioning this evening...and came to the conclusion that I was reaching the point of paralysis by analysis!! Decided that what I had to do was fix something down so that other things could be shifted to maintain balance. I decided that the best logic would be to start with the lightest and work up to the heaviest, on the grounds that the heaviest is likely always to be able to made to balance the rest.

Held the ESC in the nose with a blob of hot glue; and affixed the Rx to a bulkhead with a blob of the same. Taped the wing and empennage on and realised that (uncovered) it looks like it will be able to be balanced as desired by the lipo in the planned area between the two fuz formers.

I took the opportunity of weighing it; uncovered but with all the electrical units on board, but (as far as I can work out) just the servo linkages, hinges, servo extensions, covering and nose block to add, she is coming in at 113g which I'm hoping isnt too bad......
Colonel Blink is online now Find More Posts by Colonel Blink
Reply With Quote
Old Jul 25, 2012, 11:09 PM
Sic itur ad Astra
sparks59's Avatar
United Arab Emirates, Abu Dhabi, Abu Dhabi
Joined Aug 2009
1,603 Posts
Well done Colonel.
I was having similar deliberations re. balancing on the Coupe and realised the following. The esc is restricted where it can be but needs to be far enough back to maximise the potential for battery movement. The servo('s in most cases) and Rx need to be in an accessible place - under the wing for me. The motor has to be nailed on at the bow.

So that only leaves the heavy bit as you mention to position and ensure you can make a hatch cover and a slot or retainer for the battery. Mine worked out almost on the c of g, more by luck than judgement I think. But this means that if I want to use a smaller / lighter battery the plane should still balance ok.


sparks
sparks59 is offline Find More Posts by sparks59
Reply With Quote
Old Jul 26, 2012, 01:15 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,427 Posts
Quote:
Originally Posted by Colonel Blink View Post
I took the opportunity of weighing it; uncovered but with all the electrical units on board, but (as far as I can work out) just the servo linkages, hinges, servo extensions, covering and nose block to add, she is coming in at 113g which I'm hoping isnt too bad......
That sounds like a very acceptable weight to me Colonel, looks like your wing loading is going to be about the same as the Witch. I reckon this model is going to be a cracker, if it flies anything like the Witch you will be extremely chuffed with it I can assure you.

I am very glad that we all managed to press gang you into starting this build, it has been a most enjoyable thread to follow and it is obvious that you have enjoyed the experience. All we need now is a successful flying conclusion!
Sundancer is offline Find More Posts by Sundancer
RCG Plus Member
Old Jul 26, 2012, 04:45 PM
So I'M meant to be in control?
Colonel Blink's Avatar
Ilkley, West Yorkshire, UK
Joined Nov 2008
3,480 Posts
Talk about three steps forward, two back......!!

Having fixed the positions of the Rx and ESC, I found that (even though I'd taken all this into consideration) the wire which was supposed to join them together wouldn't quite reach. Also the wire to the Lipo wouldn't quite reach to where the Lipo hatch would be, meaning that I would be needing to try and get my sausage fingers within the fuz to connect/disconnect the battery. Damn.

So I decide to try moving the ESC out of the compartment I had thoughtfully made for it and affix it to the back of the bulkhead. Lets just say that the hot glue holds things well and there was much a-cursing in the marsh! This move didn't gain me enough wire - whichever way up I put it. Double damn.

Whilst trying to reconnect ESC to motor in one of the many places I tried, my gorilla hands managed to break one of the fuz uprights - and it did have to be one with gussets at the bottom - Triple damn (which I believe is almost equivalent to an 'awwww ')

Plan B for the ESC meant removing the bulkhead that had boxed in the back of the nose compartment, and adding a 'floor' in the next bay back, and hot gluing the ESC to that. Now the nose hatch isn't required, I have glued the hatch shut - though that may be summat I regret in the future!!

Next job was to repair the upright. Using a square rat tail file, I made a V in the 'stump' and sanded a comparable V in the end of a hard piece of 3/32" sq, cut and sanded to length and glued it in. Seems to have worked well - almost invisibubble, though I may add a 'splint' behind the join.

My [current design of] Lipo hatch incorporates a long tab which means I will be able to position the Lipo anywhere within two fuselage bays, so hopefully that will be enough range to get it balanced. Velcro & magnets still to be added.

I really need to have a bench tidying session - I looked for my razor saw in order to begin rough hacking the nose block - but I can't find it!!!
Colonel Blink is online now Find More Posts by Colonel Blink
Reply With Quote
Old Jul 27, 2012, 12:53 AM
I like real wooden aeroplanes!
Sundancer's Avatar
South-west France
Joined Sep 2007
4,427 Posts
Phew Blinkie, bit of an epic! And illustrates why it is best to get these things sorted before covering! Re the hot glue; it is nice to have things permanently fixed, but I must say I prefer double sided tape for things like this - a bit easier to undo if things aren't quite right.

Ah, the wandering razor saw - it is a well known fact that all tools grow little legs and after you put them down, the minute you look away, they are off! I have probably spent as many hours scrabbling about the bench looking for tools as I have actually building!
Sundancer is offline Find More Posts by Sundancer
RCG Plus Member
Old Jul 27, 2012, 01:02 AM
Sic itur ad Astra
sparks59's Avatar
United Arab Emirates, Abu Dhabi, Abu Dhabi
Joined Aug 2009
1,603 Posts
Good that your reverse steps didn't go too far back Colonel. Seems that you are now back on the forward track. Keep plugging away.
sparks
sparks59 is offline Find More Posts by sparks59
Reply With Quote
Reply


Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log Britkit Build Off May 2012-31/12/2012 - Keil Kraft Sportster x1.8 Sundancer Vintage & Old-Timer Designs 66 Aug 17, 2013 10:45 AM
Build Log KK Gipsy for Britkit build off kkphantom Vintage & Old-Timer Designs 150 Mar 30, 2013 08:37 AM
Discussion "Britkit" Build Off April 2012 - 31/12/2012 Sundancer Vintage & Old-Timer Designs 303 Jan 01, 2013 03:47 PM
Build Log Britkit build off (Senator) Raf_Bob Vintage & Old-Timer Designs 128 Dec 11, 2012 02:35 PM
Build Log "BritKit" Build Off 2012 - Veron Phoenix RFJ Vintage & Old-Timer Designs 37 Jun 08, 2012 05:28 AM