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Author Topic: Junkers 87 B-2/R-2  (Read 6429 times)
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OZPAF
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« Reply #175 on: February 05, 2020, 10:02:37 PM »

Perhaps you could have moulded a wet noodle around the cowl for your exhaust pipes Lurk.  Smiley They look ok to me.

John
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TheLurker
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« Reply #176 on: February 08, 2020, 02:06:03 AM »

Quote from: OZPAF
Perhaps you could have moulded a wet noodle around the cowl...
I shall try that next time I want to do something like this.  Seriously.

It occurred to me last night that we (as a group) generally only post when we're happy content with the results so for a change I thought a pic of stuff that needed more than a few goes to get right would be in order.  I wish I'd thought to do this earlier in the build.

Pic.  Attempts to get the fasces sorted.  This is the second set of attempts with a second stencil.  I binned the first set weeks ago.

I think for any future build thread I shall make a point of photographing and sharing the blunders as well as any successes.  I wonder if there enough electrons to spare? Smiley
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OZPAF
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« Reply #177 on: February 08, 2020, 05:44:16 AM »

Ah takes me back to my manual draughting days. A 0.8 pen and possibly 0.35 for the lighter lines with a 0.25 or 0.18 circle.
You didn't do that all freehand Lurk did you?

John
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TheLurker
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« Reply #178 on: February 08, 2020, 04:24:26 PM »

Quote from: OZPAF
Ah takes me back to my manual draughting days....
You didn't do that all freehand Lurk did you?
Aye, right. A right wee Leonardo da Vinci I am.  Nooo.  Stencils* and my ancient drawing kit from when I when did O grade Tech. & Geom. Drawing.  I was just going to use felt pens, but I didn't have one that gave a bounding circle with a card stencil that looked the right thickness so that was done using springbow pen compass and Indian ink.  A picture for (the other) wrinklies of the parish who remember a time before CAD.

In other news; final assembly has started.  Had hoped to have it done today, but I'm pausing before I do something careless.  Really hoping to have it all done and dusted as far as construction is concerned by this time tomorrow.

Lurk.

*Reminds me, must get my hands on some No. 13 (parrot beak) blades.  The 15s are not sufficiently fine to give a good narrow curve.  If you look at the bottom of the fasces you'll see that the rounded ends are a bit ummm, variable.
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flydean1
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« Reply #179 on: February 08, 2020, 10:21:07 PM »

Lurk,

That shot of your drawing instruments awakened old memories of my Engineering Drawing class in High School.  That's about 57 years ago.  I still have it.  Almost identical to yours.  Mine was a Dietzgen, I think.  Probably speled rong.
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TheLurker
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« Reply #180 on: February 09, 2020, 10:05:02 AM »

Quote from: Messrs. Grabbit, Scuttell & Dashe
Dear Sirs,

My client has directed that a protest be submitted as he feels that the board of Lurker Industries has identified a (regrettable) gap in the rules; my client informs me that the member of staff responsible for drafting the rules will of course be subject to the usual sanction.

As you will no doubt be aware, the Ailerons and flaps of the Ju 87 sit below the wing trailing edge and the standard Keil Kraft plan mirrors this arrangement by using small pieces of 1/16" square to fit the flaps to the wings, as shown in the bottom right-hand corner of the plan.

However, the most recent picture of Lurker Industries' Ju-87 build appears to show the ailerons and flaps attached directly to the trailing edge of the wing.

Now, obviously, this departure from the plan should be covered by rule #4 ("If the judge considers that a particular change is detrimental to the overall character of the model, no points will be awarded for that change.") because it clearly changes the overall look and character of the model, but my client considers that this sanction is not sufficient.

The reason for this unusual and forthright view is that my client has submitted the pictures to a number of independant aerodynamic analysts, the unanimous opinion of whom is that moving the ailerons and flaps up to the trailing edge will confer a significant aerodynamic advantage by reducing the drag associated with the original 1/16" wide slot, thus making the achievement of a minimum 12 second flight even more likely than it already is.

My client considers that a fair and reasonable penalty for such a gratuitous change would be:
For each surface that has been moved (6 in all), remove 10 points from the total of penalty points that have already been awarded, and
For each surface that has been moved (6 in all), add 2 seconds to the minimal duration requirement.

I await the judgement of the court with some degree of interest.

sincerely

J Grabbit (acting for the board of Testwood Towers Operational Research)

Mr Barnes-Norway, after much careful and considered thought had the following to say, "Awa bile yer heid..."  and he, most unusually for a Sunday afternoon, not having yet had his accustomed sherry.

After a little further thought (and a fortifying glass or two of sherry) he went on to say, "If there is a gap in the rules then no rule can have been infringed so no sanction is applicable. " he also went on to point out that the flaps are attached in a similar manner to that indicated in Mr. Hatfull's plan; split cocktail stick replacing 1/16" balsa strip and that TTOR's ambulance chasing shysters should be,  to use a delightful American phrase, "Run out of town on a rail."  Nor does this trivial difference represent a change to the overall look or character of the model.  The enclosed photographic reproduction is presented as evidence of adherence to the spirit as well as to the letter of the rules as originally drafted.


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TheLurker
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« Reply #181 on: February 09, 2020, 10:54:14 AM »

The Lurker Industries Aviation Co. Ltd. is pleased to announce the roll-out of its latest machine, a licence built Junkers R2.  The Board of Directors has expressed every confidence that this will be a market-leading addition to the already highly regarded range of aeroplanes constructed and sold by Lurker Industries Aviation and many export as well as domestic orders are expected to be placed desite some doubts expressed by other, less well regarded, aeronautical concerns.

Or...
Ladies, Gentlemen, Girls & Boys, Tobitd has been reached.  Despite Abl's late protest I'm calling construction done, barring the shouting. I've still got to fit the stabilizer braces and elevator mass balances but I need to do that slowly and carefully so am downing tools for the day to rest my patience and powers of concentration.

That was the good news.  Now the less good.

Unballasted (with a few cocktails sticks thrown is as make-weights for the stab braces) it tips the scales at 33g cf 30g for K5083.  More worryingly it's balancing between the LE & main spar and given that wing plan I'd expect it to further back than that so tail weight (*shudders*) may be required on an already weighty machine.  I am now cursing my attempt at the open rad inlet which has left some 1/32" ply reinforcing up front.  Am also seriously considering drilling holes in the back of the nose-block to ease the nose-heaviness a little.  I had harboured the, wildly optimistic, hope that it might be light enough to fly indoors, but I'm not that surprised that it's not.

ETA - That 12s qualifying flight time is looking pretty ambitious now.

Pics. Various views of the beastie as it is now.  Heir to the usual Lurker tissue wrinkles and build asymmetries* but it looks not unlike a Ju87.  

I'll post a bit more when I've had a natter with the CD who is, despite the weather, out gallivanting somewhere at the moment and not answering his telephone.

*A polite way of saying, "cock-ups".  Smiley


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TheLurker
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« Reply #182 on: February 09, 2020, 01:11:12 PM »

Quote from: flydean1
...Engineering Drawing class in High School.  That's about 57 years ago.  I still have it.  Almost identical to yours.  Mine was a Dietzgen, I think.  Probably speled rong.
You have the advantage of age experience over me. Smiley 
My drawing kit, Berrick, is slightly younger than yours; it only dates from 1977.
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Squirrelnet
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« Reply #183 on: February 09, 2020, 01:19:37 PM »

My congratulations to Lurker Industries for a very good looking Ju87 a credit to all the team involved.

Personally I think the threat of avocado toast has passed, if it looks that good it can't fail to fly
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Pete Fardell
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« Reply #184 on: February 09, 2020, 01:30:15 PM »

That's one really good looking Stuka, Lurks. I'm sure it'll fly, indoors as well as out.
(And it is a dive bomber after all, so you'll only need tail weight if you want to replicate the pull-out section of the flight as well as the screaming-swoop-of-doom part.)
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Russ Lister
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« Reply #185 on: February 09, 2020, 01:52:01 PM »

Very nice Lurker .... it has to fly  Smiley
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USch
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« Reply #186 on: February 09, 2020, 02:02:05 PM »

Compliments to the Lurker Industries Aviation staff, great bunch of technician's. Couldn't have be done by a single worker  Wink

One thing though, does Lurker Ind. have a specialist for acoustic matters? The Stuka did indeed have a alarm siren to scare the population during the attacks.

Urs
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TheLurker
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« Reply #187 on: February 09, 2020, 02:06:00 PM »

Thanks Gents; the kind words are appreciated, but if TTOR's last challenge carries any weight with His Honour I'm doomed, doomed I tell ye.

Sirens?  Blast! I knew there was something I'd forgotten!

To business.  

Earlier I said I'd post more if the CD telephoned. He has.  I am now honour bound to tell you that what you see is not the Keil Kraft Ju87, but I think most of you had already worked that out.  It started out as the KK kit, but the points of similarity between the original* plan and a B2/R2 were few and far between so we have ended up with a brand new plan.  In my defence I will say that the LE of the fin/rudder and the KK kit are the same and in keeping with Keil Kraft's idiosynchratic wood selection policies I made no attempt to select especially** light wood from my stock so that (in spirit at least) it is a Keil Kraft production.

Pleasingly (well, sort of, in a "oh you juggins" sort of a way) I managed to get one thing notably wrong and that is the cross-section of the fuselage near the tail;  it should be more oval than rectangular so Albert gets his revenge for my presumption.  I didn't pick up on this until I had the built fuselage in my hands, seems there's something to be said for modern 3-D tools after all eh? Unfortunately my build schedule didn't have enough slack in it for a brand new fuselage to be built.  It isn't an irretrievable foul-up though as it only requires a change to one frame and a slight rejigging of stringer alignment to correct.

It only remains to say that if it flies (and you can see now why I'm a mite worried it might not) the, corrected, plan will be published somewhere. Although it might involve signs saying, "Beware of the leopard."

Lurk.

*The more I look at the KK plan, the more I think it's meant to represent a Dora rather than a Berthe.
**Given the weight I now wish I had.  Hey ho. Smiley
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Andy Blackburn
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« Reply #188 on: February 09, 2020, 02:24:53 PM »

I have to say Lurk that notwithstanding the outstanding protest, it looks quite Ju87-ish. Very nice indeed. It's not until you look at the top view that the length of the nose becomes apparant. If it's still a problem after the rubber is installed, then maybe you could move the rear peg back one bay? It's not a big job because there's no paint to touch-up.

> ... but if TTOR's last challenge carries any weight with His Honour I'm doomed, doomed I tell ye.

Nonsense, my good man. Pull yourself together - you don't find me complaining, do you? Well, then...  Smiley

I am very confident that your Ju-87 will attain the minimal duration expected of aeroplanes produced/designed by TTOR*

A.

* 25 seconds.

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TheLurker
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« Reply #189 on: February 09, 2020, 02:32:46 PM »

Quote from: abl
...maybe you could move the rear peg back one bay? It's not a big job because there's no paint to touch-up.
It's certainly worth considering.  It would mean re-numbering and re-applying the tail band, but that's all tissue work so it wouldn't mess up the appearance too much.  See how it goes with flight trials.  If it flies acceptably as is I'll leave this particular airframe well alone and mark up the plan with the alternative peg location.   

Five and twenty seconds!?  Oh dear, please excuse this fit if hysterical laughter I thought you said 25 seconds.... oh, wait, you did.  Tell me, is there a remedy for incurable optimism?

Quote from: abl
> ... but if TTOR's last challenge carries any weight with His Honour I'm doomed, doomed I tell ye.
Nonsense, my good man. Pull yourself together - you don't find me complaining, do you? Well, then...  Smiley
Aye, but you like avocado.  Smiley

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Andy Blackburn
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« Reply #190 on: February 09, 2020, 04:22:17 PM »

But I'm going to have to fork out the brass to pay for your 300 tons of black pudding...
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OZPAF
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« Reply #191 on: February 09, 2020, 07:57:36 PM »

Black pudding? The staff of Lurker Industries deserve a reward surely. Smiley

I think Lurker Industries could be trusted with an order for more licence built Stuka's after this fine effort. Pat the man on the back but don't give him black pudding.

That's a fine drawing instruments set Lurk - I was a manual draughtsman from around 1970 to 93 and my set is nowhere near as good!

John
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TheLurker
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« Reply #192 on: February 10, 2020, 01:22:01 AM »

Quote from: abl
But I'm going to have to fork out the brass to pay for your 300 tons of black pudding...
It'll still be cheaper than 3oz of Hand Picked Sun Ripened Avocado mashed with a Blackthorn Shillelagh on Artisanal Sourdough Toast with a Sprinkling of Freshly Milled Hedgehog Spines served on a Mess Kid Hand Carved by Traditional Forest of Dean Bodgers from the Keel of A Genuine Sixth Rate Battleship in some teeth-grindingly up-to-the-minute pop-up bistro.  Which, as I understand it, is the forfeit.  Smiley

Quote from: OZPAF
Black pudding? The staff of Lurker Industries deserve a reward surely. Smiley
The staff at Lurker Industries have been known to cut up very, very rough when the canteen has been unable to provide Black Pudding.  In one now notorious incident the the company lost 3 days production because the staff walked out over this very issue. You can be sure that Mrs Gordon, Canteen Head Cook, is now extremely careful to ensure there are adequate stocks.

Quote from: OZPAF
That's a fine drawing instruments set ... and my set is nowhere near as good!
I expect my drawing instruments have seen rather less active use than yours so perhaps not surprising? Smiley
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DavidJP
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« Reply #193 on: February 10, 2020, 01:15:52 PM »

I always coveted those sets of drawing instruments as a lad but never did any of that kind of thing so my desire went unsatisfied.

I think it was Victoria Street in London that contained many shops that sold them and their window displays meant I spent hours admiring seemingly huge cases with dozens of those wonderful instruments in them - quite why any draughtsman would need about 100 different instruments I never did understand.  They were mainly German I am sure and this was, looking back, a bit surprising, because the War had not long been over so how they arrived here is somewhat of a mystery.  They were absolutely beautiful.  Now all the skill and artistry is gone - just touch a few buttons on a computer and stand back for ten minutes of so.  I used to watch them in the engineers office at a place I worked once. Shame, but I suppose anything goes in the name of progress.

But Lurk that is an exceedingly nice Stuka. Don't worry about the siren - they made an awful racket.  I don't think you will have any problem with duration... is there anything in the rules about launching from 6 or 7 storeys up?   You could get a very realistic flight.   
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TheLurker
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« Reply #194 on: February 10, 2020, 01:53:01 PM »

Quote from: DavidJP
.... is there anything in the rules about launching from 6 or 7 storeys up?   You could get a very realistic flight.  
A charabanc from the Lechlade, Fairford and District Motor Traction Co. has been engaged to transport the flying staff to Sutton Bank when suitable weather for flight trials presents itself, but that's between you, me and the gatepost; the CD would have an absolute fit if he found out.  Wink

Quote from: DavidJP
Now all the skill and artistry is gone - just touch a few buttons on a computer and stand back for ten minutes of so...
Indeed, but then again you don't get numbskull mistakes such as rectangular instead of oval frames, see above, nor bad cases of "wobbly stringer" as seen in the Keil Kraft Minimoa and you can run off multiple, accurate, copies of a plan without the distortions and blurring that creep in over multiple of generations of photocopying so it's not all bad. Having said that it is still quite satisfying to draw up bits of plan "properly".

Thanks for the compliment, does the ego a power of good.  Now, I really must sort out an appointment with my hatter, this hat has become unaccountably tight, and see about getting those Boardroom doors widened. Smiley

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TheLurker
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« Reply #195 on: February 14, 2020, 04:09:47 PM »

The air here turned a very, very, very deep shade of blue here tonight.  Now if this had been the result of a flying incident I wouldn't have been angry at all, disappointed?, sad? yes, but because it was my damn stupid clumsiness in letting something slip from my hands....

Stab braces now fitted.

I was joking with Abl about hammering the elevator mass balances out of lead, but that's looking less and less like a joke.  I've managed to take somewhere between 0.4g & 0.5g out of the nose by removing the piece of sheet inside the front that was intended to take any nose ballast that might have been required, hah!, and drilling a 3.5mm hole into the back of the nose block.  No dice.  Even with stab braces in place it still balances just on/in front of main spar and test glides onto the bed have no glide about them - noses straight in.  Take the noseblock off and the glides aren't bad.  Green goo on toast here we come.  *sigh*

For info.
Fuselage et al.           25.95g
Noseblock assembly     7.25g

The prop has already been balanced, but I'm wondering if there's any point in shaving it down a bit more.
ETA. Probably not.  An unbalanced prop of the same sort tips the scales at 2.5g.

To end on a positive note I borrowed the 4 strand 3/32" motor from No. 5 and it's a surprisingly easy job to fit the motor.  I was a little concerned given the lack of room in the fuselage that it might be a bit of a fight.

ETA.
Also thinking about making up a new spinner & prop assembly to seeing if I can make a lighter one as well as stripping the paint off the nose-block and repainting with the new yellow as the dud pot lead to many more coats going on that ought to have been necessary.
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Andy Blackburn
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« Reply #196 on: February 14, 2020, 05:18:43 PM »

I think you're going to have to move the rear peg back a bay or two. Failing that, there are three options:
  • Add tail weight, or
  • Add some more negative tailplane incidence, or
  • Man up and order some Avocado on Toast...

A.

P.S.
And don't think I didn't notice the Sutton Bank Subterfuge. You want to watch it on those hilly roads, very dangerous, they are. Particularly the ones that are mined...
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TheLurker
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« Reply #197 on: February 14, 2020, 05:30:24 PM »

It's tail weight or nothing.  The stab. is well and truly fixed and moving the peg back is a non-starter for two reasons.  First and insuperable is the fact that the frame 9 is solid.  Even if it were open there'd be no room to get a stuffing stick in which is, partly, why 9 was made solid.  The other reason was I didn't think open frames 9 & 10 would be sufficiently robust.

I don't much care about having to eat the green goo, but I am deeply, deeply narked that it's not going to fly well and I am sorely, sorely tempted to bin it as a bad job.
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« Reply #198 on: February 14, 2020, 10:48:07 PM »

Don't do that Lurk - you have put too much good work into this model. If the tail plane is glued on with PVA I would suggest considering removing it by painting the glue line with water using a small paintbrush. When the glue turns a milky white it can be removed by gently twisting fore and aft and levering up and down. This should remove it with minimal damage if any at all.

I would then incorporate a adjustable elevator - which will help move the CG back. The new Cg withe tail resting in place(not glued) can be checked and if necessary weight added to the fuselage inside under the tail.

The elevator will give you the option of adding a bit more decalage if necessary.

John


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flydean1
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« Reply #199 on: February 14, 2020, 10:48:57 PM »

Don't move the rear peg, whatever you do.
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