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Author Topic: Horsa-ing around  (Read 2976 times)
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OZPAF
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« Reply #75 on: March 07, 2019, 06:32:22 PM »

Well that is looking a lot better - definitely worth the redo.

Perhaps the Lurker Industries Management will now let the Chief designer out of solitary confinement where he was sent - complete with drawing board to redo the fuselage dwgs. Smiley

John
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TheLurker
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« Reply #76 on: March 11, 2019, 04:57:01 PM »

There's a John Mayall song, "Crawling up a hill."  Sort of sums it up.  Noseblock finally shaped and it only cost two broken longerons and all weekend. 

On the plus side fuselage No. 2 is shaping up to be no heavier than fuselage No. 1 and there's the ghost of a suspicion of a rumour of a chance it may even be slightly lighter despite all the splints on the broken bits.  With the lower UC mounting tubes and wing platform to fit the fuselage sans skid is 20.5g and 21.1g with.  Thirty grammes or under for the larger fuselage will be reckoned an encouraging result.

Quote from: OZPAF
...let the Chief designer out of solitary confinement...
He'll be lucky.  He'll be in purdah a good while yet.  Apart from anything else our head stores wallah has had to chase around suppliers to replace the wasted materiel and you have no absolutely no idea the hoops the Ministries make you jump through these days.  The poor fellow has been buried under an absolute mountain of bumf and you really wouldn't want to hear his opinion of the Chief Designer. The language would make a matelot blush.
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dohrmc
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« Reply #77 on: March 12, 2019, 10:09:57 AM »

Put him on a diet of bully beef and biscuit for a week.  That will mend his ways for good.
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abl
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« Reply #78 on: March 13, 2019, 05:11:49 PM »


I think we might get better results by taking away his keys1 to the Sherry cabinet.  Smiley

Andy

1Temporarily, of course; I'm not a complete monster...
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TheLurker
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« Reply #79 on: March 14, 2019, 05:08:55 PM »

Sherries all round.  Even the Chief Designer; although he only got a very small glass of Bristol Cream left over from the staff Christmas party and he can count himself jolly lucky he got that.

Right.  Where are we?  Ah yes.  Fuselage No. 2 is now slightly ahead of where I'd got to with No. 1. So heading in the right direction again.

No. 1.  Weight including skid and pegs for rubber bands.  28.8g
No. 2.  Ditto  26.1g

Over 2.5 grammes lighter and a larger fuselage? Aye, I'll take that thank you very much.

No. 2 fuselage is currently balancing about 1.5" back from L.E. which is encouraging.


Pictures show revised wing platform, lower undercarriage leg mounting points and a closer to scale nose profile.  I was never very happy with the wing platform on No. 1.  The dirty great slab of sheet seemed like overkill.
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TimWescott
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« Reply #80 on: March 14, 2019, 08:46:30 PM »

So, did you leave room to stick a 1/32 scale Jeep in there for balance?
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TheLurker
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« Reply #81 on: March 17, 2019, 08:23:15 AM »

So, did you leave room to stick a 1/32 scale Jeep in there for balance?
Damn and blast. I knew there was something else I'd forgotten. Smiley

A morning of coffee and arithmetic working out wire lengths and angles for the UC wires and making minor mods to the plan to accommodate same.  Also learning yet another useful lesson viz:  If you have a copy of the Pilot's Notes read them all the way to the end and not just the leading particulars.  You might find things that save you some grief. See attachments.

Never mind. It made correcting the UC strut angles and positioning a fairly straight-forward task.
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OZPAF
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« Reply #82 on: March 17, 2019, 08:02:00 PM »

Amazing amount of info on those rigging sheets that you have appropriated from the offices of Airspeed.
I hope the arithmetic suitably improved the flavour of your coffee!

John
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TheLurker
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« Reply #83 on: Today at 04:00:23 PM »

Quote from: OZPAF
I hope the arithmetic suitably improved the flavour of your coffee..
Umm. No.  I'm not very good at arith. Smiley

Right. I think I've finally got a solution for the vertical UC strut that I'm happy with.

This is a bungee launched glider so no ROG and a very short landing run which means all that's necessary is enough resistance to hold the fuselage off the ground for any posing felt to be necessary before launching and enough give to collapse gracefully and reusably on landing.

So what have we?

+ Spar mounted eye as noted upthread.

+ Tissue covered drinking straw.  

+ Two short sections of tissue covered dowel made to push fit very, snugly into each end of the straw.

+ A hook mounted in each piece of dowel.  

+An eye for the lower hook fitted to the lower UC wires.

+ Part way down the straw, possibly disguised / hidden within a damper shroud a series of lamp style vertical slits.

The dowels take up the initial landing shock by travelling within the straw and if/when the limit of the dowel travel is reached the slits allow the straw to deform and absorb the rest of the impact.  For this incarnation the dowel travel should be enough to allow the skid to absorb really hard landings, but I think this solution allows a skid free (GCU) model to be built with some confidence that the important bits will survive a hard landing.

Being push fit the dowels should also allow the vertical strut to come away if the undercarriage is dragged on landing.

I did try using the flexible section of the straw as the fallback shock absorbing element of the strut, but some very rough and ready testing with the kitchen scales indicates that the slit straw starts to deform somewhere between 50 and 75g whereas the flexible section didn't start collapsing the load was well in excess of 100g.   Mucking about with the prototype also suggests that a prudent modeller will force the slit version through at least one collapse to condition it before fitting it to the model.

And as drinking straws are cheap and easy to prepare replacement in the event of destruction or loss on landing is no great effort and spares can be carried in the field kit.

Pictures show the prototype strut and some deformation tests using 1/8" and 1/16" strip as substitute spars.  These are plastic straws but paper straws should do just as well.  

Edit to add.  The straw is slightly over scale diameter, but I'm not going to worry about it.
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