Flights of Fancy

[TheLurker]

Here we go, a short flight.  This is a rarity, most flights, if there's any sort of a breeze, are a nice LH circuit.

https:// vimeo.com/ 443164836  <-- Stitch the URL together*.

Eleven or twelve paces on the line.  Still needs a bit of fettling, but it's good enough (by my lights) to share.  Ignore the ugly great lump of blu-tack, that'll be converted to a sliver of lead glued to the back of the NB when I've got trim properly sorted.

AUW is about 33.5g

As I expected the only way you'll get any endurance from this is if you catch a thermal, but as it flies I'm chalking this one up as a win it being only my second blank sheet project.

Best flight this evening was about 12s, nice LH circuit.


*Can anyone shed on any light on why the forum sw chokes on vimeo URLs?  I'd be interested to know, cos it's irritating.

[philip]

If I put the URL

Code: [Select]

https://vimeo.com/443164836 in a post then the preview automatically converts it to an iframe containing the URL

Code: [Select]

https://player.vimeo.com/video/443164836 The SMF sofware is automatically embedding the video.

I'll put the first URL here:

[philip]

The posted version looks much like the preview. Is it broken for you?

[ElyDave]

RIGHT, more newbie questions.

Instructions (1970's vintage I think) refer to use of tissue paste, dope, thinners etc.

Quick review of t'interwebz suggests that
1- Glue - UHU, watered down PVA ... basically anything that will stick the tissue
b - water or diluted ipa for initial shrinking (not the beer kind!)
iii) Ambivalent on additional shrinking dopes and laquers

I have some tissue past in the kit box, which is now >20 years old, what's the voice of experience here?

[TheLurker]

At work ATM.  Will reply properly later outlining what I do.   Bear in mind nearly everyone has a, "Works for me." approach and no two modellers use identical techniques.

[andytheflyer]

RIGHT, more newbie questions.

Instructions (1970's vintage I think) refer to use of tissue paste, dope, thinners etc.

Quick review of t'interwebz suggests that
1- Glue - UHU, watered down PVA ... basically anything that will stick the tissue
b - water or diluted ipa for initial shrinking (not the beer kind!)
iii) Ambivalent on additional shrinking dopes and laquers

I have some tissue past in the kit box, which is now >20 years old, what's the voice of experience here?

1) watery IPA, applied with a brush
b) water, misted from a spray bottle
iii) DeLuxe Materials Eze Dope - it's water based.

20 years ago it was tissue paste and dope.  We've gone all touchy-feely since then.

[ElyDave]

I assume you mean
1 - watered down PVA, not IPA

[pcolbeck]

I assume you mean
1 - watered down PVA, not IPA

If you water down IPA make sure you don't sell it or you'll have weights and measures after you. Also it will taste rubbish.

[TheLurker]

Speaking of IPA, I have some Whitstable Bay which I shall be drinking later, but first this, while I can still type...

Choice of tissue.
a) Domestic.  Relatively heavy, no wet strength.
b) "Esaki".   Dearer than domestic.  Good wet strength.  Rumour is that it's not being made any more.  There *are* comparable tissues so ask around.

Choice of Doping compounds.
a) Solvent based.  Shrinking and non-shrinking.  Various compositions available.
b) Non solvent based.  Only know of one ATM.  EzeDope by Deluxe Materials.  Of which more later.

Tissue Fixative
a) Tissue paste. Various mfrs.  As far as the tube that came with the kit goes, ask yourself if you'd trust the glue that came with a 20 YO tube repair kit.
b) Dope
c) PVA.  Thinned
d) Glue stick and PVA.

What follows is *not* prescriptive.  Others will have their preferred way of working and will swear blind that it is the one true way.  Bollocks.  Whatever works best for you is the way to go.

I haven't used dope to fix tissue to an airframe since 1973.  It was straight-forward and some of the (even) older builders still use it. Especially for under-cambered ribs.

My preferred technique is to use glue stick, UHU for pref. - consistency is good, to put a thin bead around the edge of the piece being covered and then fix the tissue in place, teasing out the worst of the wrinkles and bags.  When the glue has cured properly (min. of a couple of hours) I then go over this with water thinned PVA (50% by volume) using a fine, 00, paint brush gently rubbing the glue in with the dampened end of the brush.

Working this way means you can use domestic tissue without too much stress.  Thinned PVA and domestic tissue under tension is not a good combination.

Doping.
I use two approaches.

For a single colour domestic tissue finish with very small areas of tissue decoration Deluxe Materials EzeDope.  The first coat, 5% by volume with water,  is misted on.  You can buy small pump sprays in the travel section of Boots and the like.  The second and subsequent coats, 30% by vol, can be brushed or sprayed on.  You have to be v. careful with EzeDope & domestic tissue, see the earlier point about wet strength.  Deluxe recommend using "Esaki" or similar for obvious reasons. It can be used in the house without choking everyone else and it can be sent through the post.   I've used it for models up to 36" span.


If I'm doing a two or three colour tissue finish, the Ju87's splinter camouflage is a good example, I'll use thinned non shrinking dope (30% by volume with cellulose thinners or more dilute depending on size of model) after steam shrinking the tissue.  You can buy dope by electronic mail order, but it has to be shipped by courier so can work out very expensive if that's all you're buying.

Companies.
Vintage Model Company
SLEC
Balsa Cabin
Free Flight Supplies - A one man band, but good.

And I strongly suggest that you sign up at the Hip Pocket Aeronautics forum where you will get some *real* expert help rather than my idiotic ramblings.

[andytheflyer]

I assume you mean
1 - watered down PVA, not IPA

er, yes...........

[ElyDave]

Oh dear!

EzeDope - Check
New model kit - Check

[TheLurker]

...New model kit - Check

My work here is done. *evil cackle*.

Sounds like someone visited the VMC site.  C'mon Dave, don't tease.  Which one is it?

[ElyDave]

In my defence, I only went there 'cos I couldn't find the EzeDope elsewhere.

I was torn between the Cessna 140 and Bird Dog, went with the Bird Dog in the end.   If they had a Cessna 150 I would have had that as that's wjhat I did my Air Cadet Flying Scholarship in

[TheLurker]

Well, cor, blimey strike a light!  Guess what I've just started on?  Yup.  The Bird Dog.  It had been sitting in my kit hoard for a couple of years and was looking all forlorn.  Only got the wing centre section so far.  Mine'll be a USAF grey tissue finish O1-E and if I'm feeling adventurous it'll be a shark-mouth scheme, tail No. 5-62534. If.

You've chosen a good one.  Andrew Darby's designs fly pretty much off the board and I know that models built from that kit have a reputation for flying like they're on rails. 

The only thing I'd suggest at the moment is that you make two dihedral guides for the centre section (3 deg. off vertical).  The kit parts are cut to give that angle, but it's a bit of a three-handed job to get the centre section put together and having a couple of guides to prop. up the ribs makes it a tad easier.

Fin Mods

[ElyDave]

OH appears scrolling through credit card entries on the phone
"Is this yours? The Vintage Model Company?"

[quick thinks]

"yes, it's the bits to finish this" says I pointing at said model [not mentioning new kit at all, nothing to see here]

[ElyDave]

Slowly, slowly starting the covering, tail plane and fin done so far with no dramas.  Manged to snap the single, very thin piece connecting the two wings whilst trying to shape and do the initial gluing of the tissue.  I've pared the remains out of them, luckily there is a spare in the kit so my plan is to cover the wings as much as possible then rejoin them and cover the final gap before shrinking.

Any tips of stopping a gull-wing from warping? I was thinking of doing one side at a time and building some props to go underneath to maintain the line whilst I weight it or pin it down from above.

I think it might be very tight on tissue to cover the fuselage.

[TheLurker]

I was thinking of doing one side at a time and building some props to go underneath to maintain the line whilst I weight it or pin it down from above.

Warping.  Yup, you've more or less got it sussed.  With kinked wings (Ju87, Minimoa, Walthew MKII) I wrap cling film or some other covering around the part that isn't being shrunk, apply the shrinking agent (steam / 5% EzeDope / water) to the uncovered part and pin it to the board.  Pin it to the building board using spacers at intervals under the LE & TE.  If you're using EzeDope use 1/8" min thickness spacers, 1/4" is better, use the scrap sheet from the kit, because the tissue can bag quite a lot and stick to the board when it's wet.  With an anhedral wing like your kit you'll need a block that raises the wing section being treated far enough off the board that the "tip" of the untreated section is clear of the board.  I generally use a stack of Model Board glued together (see HobbyCraft) because it will take pins and is easy to cut to the appropriate size  / shape and it's cheap enough that I don't feel dreadful about the single use.

It will take longer to dry out completely than you might expect.  I often leave even small wings pinned down for 12+ hours.

I think it might be very tight on tissue to cover the fuselage.

*Cough*

There'll probably be only just enough tissue in the kit.  Buy some more, it's dirt cheap,....

What colour tissue is it?  If it's white I have some spare domestic and it'll be far cheaper for me to stick a couple of sheets in the post than it will be for you to ring up VMC/{some other company} just for that and get stung for postage.  It also give you a bit of spare for patching.  If you'd like some let me know where to send it.  It'll be sent flat so you'll have to iron it to get the worst of the creases out.

[ElyDave]

I'll let you know, thanks - looking at it I might have enough by flipping the fuselage sections 180-deg alternating fat end to thin end.  I'm keeping scraps for repairs and small sections as necessary.

I've worked out that three cassette tapes is the height of the wing tip angle, and three erasers is the point of the gull wing angle change. 

Tailplane and fin now fully dry, and I'm happy enough with the results. Could probably be better, but first attempt and all that

[TheLurker]

...I'm happy enough with the results. Could probably be better, but first attempt and all that

Don't worry about it.  I think there's only one or two stick and tissue models in thousands that have wrinkle free covering.  Other people looking at it don't see the flaws or if they do they discount them.  As long as the flying surfaces aren't warped and are true WRT each other it'll fly and that is the primary objective.

I put my VMC Osprey through some post refit, ballasting changes, test flights last night. The pilot requires a bit more tutelage, but for something that many would dismiss as a "toy" it's pretty good indeed and suggests that with a longer tow (40-50m rather than the 20m line I use) some fairly long flights ought to be achievable.

Endurance is a gnat's north of 15s, 16s if one is really optimistic, on a 20m line in very, very light winds.   

https://vimeo.com/ 445680677  <-- stitch it together.

It's not the best flight, see the stall when the tow drops, which is the result of a hurried reballasting after total loss of ballast on a previous flight*. This leads me to today's top tip, "When you've established the base trim, glue the ballast in place. Clot."


*When you hear an odd rattling noise** in the steepest part of the climb and the flight is very, very, very, stally do investigate immediately.  Don't assume it was a rubbish launch, carry on and then stand there looking like a lemon on the subsequent equally stally flight wondering what's gone wrong.

**The fishing weights bouncing off the canopy I expect.

[ElyDave]

What colour tissue is it?  If it's white I have some spare domestic and it'll be far cheaper for me to stick a couple of sheets in the post than it will be for you to ring up VMC/{some other company} just for that and get stung for postage.  It also give you a bit of spare for patching.  If you'd like some let me know where to send it.  It'll be sent flat so you'll have to iron it to get the worst of the creases out.

LBS has a model section, popped in today and picked up a couple of sheets, Means I can re-cover the bits of wing I don't like becasue of compromises

[TheLurker]

LBS has a model section...

You have an LMS*!?  You lucky, lucky ... you.


*Or Dept. at least.

[ElyDave]

Here she is, just need to add the runners underneath and a launching hook for towlines.

Will need ballasting as well as currently tail heavy.  AUW unballasted is 57g.
I can see several imperfections, and the covering on the fuselage is a bit patchy. As a first stick-and-tissue build I think it was quite a complicated one and with hindsight of experience there's a lot I'd do differently if I did it again. Lots of learning points for the next one.  Hopefully it won't take me 2-3 years next time, though the build did accelerate towards the end.

[TheLurker]

I think you've made a very nice job of that.

Will need ballasting as well as currently tail heavy.  AUW unballasted is 57g.

It's a rare model that's not and better that than nose-heavy. However, looking at the relatively long nose on that I don't think you're going to need a huge amount of ballast.   Go on, give the PMFC a call.  Unlike a lot of other clubs these days they've got a lot of bods who are into tow-line gliders and they'll be very pleased to help you get it flying.

[andytheflyer]

What TL said.  Well done Dave.

[ElyDave]

thanks both.

Looks like needing somewhere north of 20g ballast from quick experiments. I'm thinking of removing a section of fuselage covering at the bottom and gluing a flat fishing sinker to the back of the nosecone.