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Author Topic: Horsa-ing around  (Read 6525 times)
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ZK-AUD
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« Reply #175 on: May 23, 2019, 04:55:02 AM »

Reminds me of a half eaten packet of biscuits  Grin. Perhaps a spring mounted on the front?
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DavidJP
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« Reply #176 on: May 23, 2019, 04:59:28 AM »

The other thing I meant to add Lurk wS that in a little high start I. Built the tow hook was off set - to the right slightly. Possibly my imagination but it is just possible that the one in the video had an offset hook.  And is the streamer which is quite large inducing a bit of drag which slows it all down and maybe stabilising it like the tail on a kite?  All guesses of course but sometimes the improbable is the key.  The tailplane does indeed look quite substantial.
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Yak 52
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« Reply #177 on: May 23, 2019, 05:33:17 AM »

That's a shame Lurk. Unfortunately a short pull will have that effect, particularly with no wind to help. Providing the trim is correct for a straight climb then height is your friend.

My apologies - I misread your original post as the model having a 22" span. I missed the fact you had scaled it up. Even so 32" at that weight is still pretty small and light. The 1/8 rubber will launch twice that weight happily. Some years ago when we were playing with indoor scale gliders, Andy Sephton was bungee launching his Slingsby Prefect and got down to some very skinny rubber before the balance was found. Can't remember what size I'm afraid but there's some video somewhere. I would seriously be looking at 1/16" and stretching to the 20-40 pace kind of region.

Of course wind speed is a massive factor too, more wind requires less bungee power.

The video of Tom Nallen's Horsa looks to me to have a very forward hook position (low climb angle for the forward speed) and a very soft long pull. The model was on the line for 8 seconds.

There are rules of thumb for bungee pull force but I've only ever applied them to bigger RC gliders. In theory a bungee pull force of 3-5 times the weight of the model when fully stretched should be more than adequate. The 7m of rubber should stretch a good bit, the silicon tube we use for RC will do 3-4x - rubber should do quite a bit more (?)

Jon
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billdennis747
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« Reply #178 on: May 23, 2019, 05:44:10 AM »

Nobody is mentioning that the rubber goes with a 2x or 3x length nylon line. Is that not the case?
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Yak 52
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« Reply #179 on: May 23, 2019, 05:53:40 AM »

Yep. 22.5m static line for the 36" glider rules, ie 3 x

http://peterboroughmfc.org/FlyingRules/PeterboroughRulesFF.htm#Hi-Start

As much as 5 or 6 times will work with a stretchy bungee section though.
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Pete Fardell
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« Reply #180 on: May 23, 2019, 07:51:12 AM »

Very hard luck, but I’m sure you’ll have it back in the air ready for the D Day anniversary.

Will Mr. Fardell please take his welding torch to Lurker Industries. Smiley
Unfortunately all of the Fardell Corp. welding apparatus and all personnel are now needed for a big job on a Consolidated PT-3 which has just moved into the repair shop following the near deadline completion of the Comte job. No rest for the workers here, despite some low mutterings from the union rep.
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TheLurker
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« Reply #181 on: May 23, 2019, 03:38:35 PM »

Thanks for the commiserations chaps, but it really wasn't bad luck.  It was a combination of pilot error and suspect design issues, the hook position and possibly the stab size.  You really can't argue with Physics. It wins every time and just when you think you've cracked it at Newtonian levels it goes all sneaky and quantum on you. Smiley


Quote from: TimWescott
... disassembly on landing is a scale maneuver for a combat glider.
Indeed, but it was usually preceded by something recognisable as a controlled flight.  In my defence (ooh clutching at straws here) it has to be said that TL472 was written off after a bad landing only a few weeks after getting her silver dope finish so I'm claiming scale veracity in that respect at least. Smiley

Quote from: OZPAF
...tail is considerably larger than scale!
It is. The tail on mine is also over scale, but I think you're right; it needs to be bigger.   

Quote from: abl
If it's any consolation, the repairs probably won't take as long as you think.
Hope not, I've got some minor fettling to do on the Swallow before the 2nd, but I'm an hour and a half in already (one weekday session) and the pics. show how little progress has been made.

Quote from: ZK-AUD
Reminds me of a half eaten packet of biscuits  Grin. Perhaps a spring mounted on the front?
Remind me never to eat at your house. Smiley  A spring may be overkill, but a dirty great lump of foam may be the way to go. At least for testing.

Quote from: Yak 52
... I would seriously be looking at 1/16" and stretching to the 20-40 pace kind of region.
... The video of Tom Nallen's Horsa looks to me to have a very forward hook position...
I do have some 1/16" bought with the VMC Osprey in mind I just hadn't got around to making up the line.  That'll teach me to be so dilatory about getting these things dealt with. 

Thanks to you and Bill for the Peterborough link, I had read it but when I made up my bungee line last year but I scaled it down a bit because a properly high launch  from "my" aerodrome would see a model landing in houses and I don't think the BMFA would wear repeated claims against me for damages.


Quote from: Pete Fardell
...you’ll have it back in the air ready for the D Day anniversary.
I had hoped to have it flying for Portmeadow, but I think that's a forlorn hope now.  Never mind still have the Swallow and the Walthew to bring along.

Quote from: Pete Fardell
...Unfortunately all of the Fardell Corp. welding apparatus and all personnel are now needed for a big job on a Consolidated PT-3
That is a shame, Fardell Corporation's reputation for repair work is enviably high and the deadbeats employed at Lurker Industries need to be shown how to buck their ideas up highly trained fitters at Lurker Industries are always eager to learn new skills.

And for entertainment value some pictures of repairs so far.  I have had one sneaky thought which pleased me.  Instead of letting new offset notches into bulkhead No. 2 to take the longerons I can butt either a full or partial former up against with the notches aligned correctly.  See the second pic. 

Lurk.
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TheLurker
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« Reply #182 on: May 25, 2019, 03:15:26 PM »

Fuselage repaired. Somewhere about 12 to 14 hours so far.
Waiting paint and tissue. 
May be ready to resume testing by end of Monday. 
Thank heavens for Bank Holidays.
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OZPAF
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« Reply #183 on: May 25, 2019, 07:32:57 PM »

Neat work Lurk. You deserve a beer - ah that is the Lurker industries workers do Smiley

John
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TheLurker
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« Reply #184 on: May 26, 2019, 03:43:22 AM »

Hah!  The sherry is staying firmly in the cupboard until either

a) It flies acceptably in which case there will be a works do to celebrate or
b) The project is written off and a wake will be held.

Which means, looking on the bright side, the staff get to have some sort of a knees up either way.

Annoyingly the weather here is on the turn and it looks as though we're in for 4 or 5 days of unsettled, breezy and damp rubbish so the chances of getting any test flying in this next week, assuming flight ready by end of tomorrow (Mon.), look poor.
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TheLurker
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« Reply #185 on: May 27, 2019, 07:37:16 AM »

Second coat of dope drying so repairs should be completed some time today.  A couple of extra tow-hooks to be added and canopy to be refitted.

I'm also going to increase the chord of the stab. by about 1/4" with some 1/32" basswood sheet, but before I stick it on I have a question for the house;  tack it on to the top-side or the underside of the stab?  My gut feel is under-side, but I don't know aerodymanics from a hole in the ground*.  Opinions?

In other news.   Finally got around to making up a 1/16" bungee (8m with 9m of line).  In case anyone is wondering why the fishing line is so short see the plan of the test field. The grey area is housing and there's a hedge to the north-western side that varies in height so 15' or so.

Lurk

*As can be seen from TL472's repeated attempts to create a hole in the ground. Smiley
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flydean1
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« Reply #186 on: May 27, 2019, 09:34:06 AM »

Span increase is more effective.  Some balsa sheet the thickness of the stab CA'd to each tip.  Add to this a trailing edge extension to keep the same profile.  Avoid basswood--heavier than balsa--especially at the tail.
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TheLurker
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« Reply #187 on: May 27, 2019, 10:41:44 AM »

Span increase is more effective.  Some balsa sheet the thickness of the stab CA'd to each tip.  Add to this a trailing edge extension to keep the same profile.  Avoid basswood--heavier than balsa--especially at the tail.
Thanks for that.  Fact duly noted and filed.  The span is already 125% scale so bumping the chord up on its own will bring the proportions back in line.  FWIW I was trying 125% span with a slightly overscale chord to see if I could get a better cosmetic result. I can't; physics.

Given the vaguely aerofoil shape of the stab and stab tips tacking extra span on is a bit of a non-starter without cutting the stab to the outermost rib and remaking it.

Agreed basswood is heavier, but 1/32" basswood versus 1/8" balsa I think I can live with as a short term measure to establish good flying characteristics even if it means bumping the AUW with more ballast up front and losing out on flying time.  If I can get the launch off a bungee sorted then I can redo the stab. from scratch in slow time.

The other simple alternative is to slap new 1/16" balsa sheet outlines over the existing stab.
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Yak 52
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« Reply #188 on: May 27, 2019, 11:47:28 AM »

To be honest Lurk, I wouldn't be altering the tail plane at all until I'd tried improving the bungee set up. Only change one thing at a time  Smiley
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TheLurker
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« Reply #189 on: May 27, 2019, 02:23:41 PM »

To be honest Lurk, I wouldn't be altering the tail plane at all until I'd tried improving the bungee set up. Only change one thing at a time  Smiley
I do so like it when someone gives me an excuse to be lazy.  Smiley

Whatever happens the weather forecast indicates there'll be no chance of testing anything before the weekend so am tempted to take it along to Portmeadow and give it a go (untested) on a full spec. line just for the hell of it. 

More or less back to square one, but you can see from the poorer fit of the ballast chamber door that alignment has suffered a bit forward of bulkhead 1.  The canopy isn't quite such a good fit now either, but we do now have two (count em!) new tow hooks, well three if you include the VMC Osprey which got caught up in the enthusiasm.  The Osprey was not at all happy on a 1/8" line with the original tow hook and the plan was (is) to try it on the 1/16" line, but it'll be interesting to see how it behaves on a 1/8" with the forward hook.

And I have finally worked out a way of keeping a glue stick steady.  Jam jar, cardboard collar and some weight in the jar. This has been bugging me for a couple of years now. Was finally prompted to action by the glue stick falling onto a newly covered wing panel and denting it.
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OZPAF
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« Reply #190 on: May 28, 2019, 04:13:06 AM »

I agree with Jon - there are now 2 reasons to be lazy Smiley Theory and analysis only indicates the most likely solutions to the problems - testing confirms it. thus launching on a softer longer pull will give a better indication. Also height will give the model a better chance to save itself - unless it wanders into the neighbouring housing estate. Smiley

John
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TheLurker
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« Reply #191 on: June 02, 2019, 02:38:41 PM »

Ladies, Gentlemen, Girls and Boys I am declaring the build complete.

TL472 flew successfully and well of a 1/16" bungee on the foremost hook in some really choppy wind - wind conditions were horrid for light gliders - at Port Meadow today.  Unfortunately the pilot cocked up the next launch (misjudged wind direction and speed) and she ploughed in nose first and ripped the nose right off.  The worst bit about this is that the ballast was scattered to the four winds so I can't give an indicative value in the build guide, best guess is about 6-8 grammes but might be a bit more.

Need a minor tweak to part NF1 and some notes on the tow hook positon and also need to check that I won't be infringing anyone's copyright by posting plan and guide the gallery.  If I'm not then it'll appear there in a few days, mebbe a week. See how I am for time.

I think I'm going to scrap the current fuselage  and re-use the wings and other bits on a new fuselage because although the current fuselage is repairable it'll look pretty scruffy and I'm not at all happy about the covering job I did on it.  But that's a job for later in the year as I have other aeromodelling fish to fry and I want to spend some time flying rather than building for a wee while.

Lurk.

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« Reply #192 on: June 02, 2019, 05:02:04 PM »

off not of - idiot
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Crabby
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« Reply #193 on: June 02, 2019, 05:57:00 PM »

Damn shame Lurk. Those Horsas did have that reputation though. Great looking glider though. I'd love to see a payload event someday, to see if that design could haul some scale weight.
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TheLurker
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« Reply #194 on: June 03, 2019, 12:13:50 AM »

Thanks Crabby, but no need for sympathy, I'm feeling quite chuffed about the whole thing.  I, courtesy of great deal of invaluable help from the members of this parish, have a plan for a buildable, flyable small-ish, scale-ish Airspeed Horsa.  I call that a damn good result.  If I'm daft enough to try flying the model in patently unfriendly conditions and get the launch wrong into the bargain then it's my own stupid fault.

Edit to add.  Large glasses of the very best Amontillado in the board room at Lurker Industries last night.  Smiley
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« Reply #195 on: June 03, 2019, 05:37:28 AM »

Well done for getting the launch sorted, Lurk; it's a fine-looking machine.

A.

P.S.
Er... Large glasses of Amontillado?...
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TheLurker
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« Reply #196 on: June 03, 2019, 02:31:39 PM »

abl> ...Large glasses...

Of course.  It saves washing up and Mrs Arbuthnot and the rest of the ladies* who look after catering in the Directors' Dining Room are deserving of some consideration for all their hard work.  Smiley

Lurk.


*Lurker Industries has yet to catch up with the late C19 never mind late C20 in some things. Now, if you'll excuse me,  I've just been told I've got to go and do some washing up and I'm not going to argue with my superior.
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« Reply #197 on: June 05, 2019, 02:04:14 PM »

Ladies, Gentlemen, Girls and Boys

Some closing business.

Those of you paying close attention will have twigged that all the really good ideas that have gone into this project and that have made the difference between a decent plan and a bundle of artfully arranged sticks came from abl, this build's Éminence grise, and I'm not letting him get away without pointing this out. So three cheers for abl!    Hip! Hip!

Thanks also to everyone else who chipped in for the help, comments and general chaffing, it improved both the quality of the thread and that of the model no end.

The plan, build guide and other bits and bobs have been submitted to the plan gallery and should appear in the, "Outdoor Gliders" section in due course.  After Sunday's fun and games I think the model is best reserved for fair weather flying in light winds.

If anyone else builds a model from this plan and finds any problems or works out a better way of doing things please let me know and I'll update the guide and plan as required. Any feedback on both bungee launching / hand towing and alternative hook positions will be of particular interest.  There are already some suggestions for improvement at the end of the guide, but the list is not exhaustive

As for my plans for the evaluation model; the fin, stabilizer and other bits have already been stripped from the wrecked fuselage and I will be building a new one some time later this year or early next with a view to having something to fly in the scale glider comp. at next years Oxford FF rally. I may also revisit the design for the stabilizer. We'll see.

Finally a word about AeroModeller plan copyright. I contacted Andrew Boddington for permission to publish the re-draughted plan and he's willingly and generously granted it but if you find yourself seeking permission to publish an updated AeroModeller plan bear in mind that the publishers of AeroModeller don't hold the rights to the plans that were issued through the plans service, those are held by Sarik.  AeroModeller does hold the rights to the free plans published in the magazine.

Time for a sherry I think.
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« Reply #198 on: June 05, 2019, 07:16:18 PM »

Well, that's just great. What am I going to do for entertainment now? I know! I'll download the plans and may even build one. Thanks for a fun thread, Lurk.
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« Reply #199 on: June 06, 2019, 12:48:03 AM »

Well, looks like they all broke!

http://iloveww2warbirds.com/wp/wp-content/uploads/2015/05/Landing_zone_N_7_June_1944.jpg


Here's a practical application

https://youtu.be/tCkzxOcwg_Q
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