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Author Topic: Little [s]Brown[/s] Natural metal Jug.  (Read 4341 times)
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Prosper
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« Reply #25 on: January 02, 2018, 02:14:59 PM »

Quote from: MKelly
I'm thinking that with your light construction methods there would be a significant risk of breaking stringers and/or formers if one were to try to carve and sand the cowl while attached to the fuselage.
No, I don't think so Mike - at least in terms of stringer or former breakage. The CA coating might be a problem if the cowl and fuselage were one piece; that's because the CA coating is so much harder than uncoated balsa that to sand it fair needs a determined briskness, and any slip with the sanding block might lead to a few fus. stringers being suddenly half as thick as they ought to be! No, the separate cowling is in imitation of the F6F which has a separate cowling as per Bill Hannan's intentions IIRC. I found that very convenient regarding the wing mounting. With no firewall forward, the fuselage is wide open close to where the wings join it, so you can work on the wing joint from the inside, so to speak. That's why I'm not particularly worried that I haven't yet worked out how to join the wings. I know I'll have full access to them until the firewall forward is glued on.

Regarding the planking, yes that's surely easier on a free-standing item - see one of the pix where the planks haven't been trimmed off at front or back. That job is a quick trim with a razor and a quick sand with a block. If the planks had to be individually shaped at the back as well as the sides before fixing, that would add to the work considerably. Anyway it's a damn sight easier than infilling between stringers. I've had my fill of infill for now Smiley.

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strat-o
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« Reply #26 on: January 02, 2018, 02:57:43 PM »

I thought this was a neat picture.  It's from a site that is documenting the rebuilding of a P-47 razorback.  http://www.aircorpsaviation.com/project/p-47d-23-razorback/

It's almost certainly a computer rendering and I think it's an isometric projection judging the way the port wing looks too long.
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OZPAF
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« Reply #27 on: January 02, 2018, 06:13:06 PM »

That's a very neat practical way to do the cowl Stephen. Identifying the main areas of distortion and working around them seems to be a trade  mark of your work. All your efforts with micro delicate structures  obviously helps Smiley

John
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fred
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« Reply #28 on: January 03, 2018, 01:28:24 PM »

Fascinating build sequence full of interesting techniques.  Thank you
 Was initially wondering How? you were going to line up all those barrel hoops into a fuse ..
 But you managed nicely, albeit  (to My mind :-) in a complex, Seriously taxing for precision method.
 I would have thought a removable central spine/strongback could have worked as well . Mebe not?
 Cowl is interesting as well. 
Merely as idle curiosity: did you consider making a Plug and then vacuforming a Plastic cowl ?
 Results in a few spares 'just in case'
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Prosper
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« Reply #29 on: January 04, 2018, 01:46:06 PM »

Hi Fred, if you mean making the whole cowling from plastic, I should think that would be incredibly heavy. Even the plastic nose cowling is 1.5g.

I've waded into some treacle today. Yesterday I had time to make the tail surfaces and refine the nose plug; today it seemed that sanding the tail surfaces took as long as making 'em, and after plunge-mould number. . .I've lost count. . .No. 4? 5? I still haven't got a suitable nose cowl. The one atop the cowling in pic 2 is my emergency reserve but I want a better one. The trouble is that the styrene gets a lot thinner at the trailing edge than I'd shaped the plug for. That wouldn't happen with successful vacuum-forming I imagine, but I don't have that facility.

Edit: since writing the above I've churned out a cowling that fits and is very light (0.65g; pic 3) but flimsy. I aim to reinforce it at strategic points using bits cut from the aforementioned failed efforts.

Stephen.

 
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strat-o
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« Reply #30 on: January 04, 2018, 03:10:53 PM »

Latest cowl looks great!  Is this plastic purchased for the purpose intended or was it some sort of supermarket packaging find?
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« Reply #31 on: January 05, 2018, 04:23:32 PM »

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Latest cowl looks great!

Took the words right out of my mouth. Mighty fine cowl!
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Prosper
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« Reply #32 on: January 06, 2018, 01:49:28 PM »

Quote
Quote
Latest cowl looks great!
Took the words right out of my mouth. Mighty fine cowl!
Ta, gen'lmen. There's a bit of progress here, but in the way that more things are nearing completion though nothing's yet complete.

The tail end is close to a finish and the razorback is more or less puzzled out (you can see it radiating out of the 12 o'clock of the fuselage nose in pic. 1: balsa/aliphatic sheet). I've coated the balsa cowling with CA but it still needs a bit more attention; I've made the nosecone (which in this instance refers to the gearbox of the R-2800 engine) and I've reinforced and nearly finished the plastic nose cowling.

The nose cowling is painted because the plastic was covered in a rash of tiny pockmarks - the result of being overheated before plunging. The plastic itself is too thin to have sanded the pockmarks out. I couldn't tolerate the pockmarks but couldn't tolerate the thought of making yet another moulding either. So I slavered the cowl with multiple lashings of paint, and the pits are pretty much filled.

Stephen.

 
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OZPAF
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« Reply #33 on: January 06, 2018, 05:22:14 PM »

It's looking very much like a Jug Stephen . How do you think you will handle the nose plug? You make precise work look easy. It depresses me a bit at times Smiley

John
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Prosper
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« Reply #34 on: January 07, 2018, 07:20:44 AM »

Quote
Is this plastic purchased f. . .
Sorry, forgot to answer this. It's just regular 40 thou (1mm) styrene sheet AKA plastic card.

Quote
You make precise work look easy.
Ah well that's interesting John. Of course you only see the photos and don't hear me growling and cursing. But seriously, this seems to be a build that I'm prepared to go a few extra yards on. I'm highly confident that the model will fly to some acceptable extent, being a tried design (I'd be surprised if the many changes I've made will impair its stability much - just its duration). That's not true of most of the own-design efforts I turn out. I find it really hard to make that extra effort in finish when the project may well not fly in da foist place, so my models are often slapdash and I often fly them before they're cosmetically finished. If they do fly then I immediately want to make another one, only well-finished: but that plan gets lost in the long "to-do"list. . . This model though could fall at the covering stage. I don't have a clue as to how to cover the fuselage.

Quote
You make precise work look easy.
Well here's a fiddly bit of work. The plan recommends "dead soft" 1/8" balsa, to which I suppose tissue would be attached. I used balsa/aliphatic sheet, and getting the two halves joined at the bottom with a smooth transition round to the trailing edge took some patience. And I still have to affix (as instructions used to say when I was a nipper) tissue to the main part of the rudder without an unsightly border between the tissue and the sheet. That'll be a game. . .

The first side wasn't so bad because I had access to the inside, although trimming the bottom seam to a straight edge was ticklish (pic 2). The second half was harder because there's no access to the inside and the sheet has to be trimmed bit by bit until it meets the first side in a butt-joint. In the end there was a slightly raised edge (4) but this was easily sanded fair.

Incidentally the sheet I used was salvage from a failed 16" span Miles Hawk Major I started a few yrs ago. It pleases me to find that the sheet hasn't degraded over time in any way, so far as I can judge.

All the while I was doing the above I was thinking it would have been quicker, lighter and better-looking to've made the whole rudder from sheet material. That's why probably my forays into S&T models of stressed-skin scale subjects will be occasional only. I reckon the simpler models like the F6F give plenty of bang-for-buck, though, and I must admit I was letting the idea of a hoop-formered L1049G run through my mind last evening.

Stephen.
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Prosper
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« Reply #35 on: January 08, 2018, 11:17:30 AM »

Not much done today - workplace 9°C - too flippin' cold - hands don't work properly.

Normally I'd make a pair of wings concurrently but didn't in this project because I was rather vague about how the wings would meet the fuselage. I had expected to make some kind of one-piece wing or at least, two wings with a strong bridge between them. This would have meant cutting bits out of fuselage formers 4 & 5 and today I veered off that idea for sentimental reasons. Pore ickle laminated formers! Couldn't bear to do it. So the stbd wing has a slanted root rib as per the original design, and I'll somehow have to work one into the (already finished)left wing too. The angled rib very close to the root rib is just to act as an anchor for the wing/fuselage fairings.

Normally a wing made this way will hold together without glue but I used a little diamond file to cut the spar and rib slots, and the slots make a sloppy fit with the 1/32" ribs and spars. This has slowed the work too as things can shift about and there's more checking to be done before gluing starts. In the 3rd and 4th photos here, just the rib/T.E. joints, and the bottom rear spar are CA'd in place.

Also with previous wings made this way I've not used a strip leading edge; the thin sheet wrapped around the nose has made a very good L.E. In this case though I was worried about the sharpness of the Republic S-3 nose, so there's a strip leading edge under the balsa sheathing.

Stephen.
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dohrmc
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« Reply #36 on: January 08, 2018, 01:24:13 PM »

Nicely done! This is really excellent. I have always wanted to do a Thunderbolt, I doubt I could do as well.
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« Reply #37 on: January 08, 2018, 01:52:30 PM »

The first model I ever attempted was a WW2 Comet P-47.  This was the one with cardboard formers and pine sticks.  I did manage to get the fuselage built but one of the sets of ribs out toward the tips of the wings was gone, I had traded a cap gun to a neighbor boy for the kit, and I had no idea how to recreate the missing rib.  I did score a WW2 Comet kit about 30 years ago and I guess I need to build it while I still can! I do still remember the dents in my finger from the single edge razor blade that I used to cut out the cardboard parts!!
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I used to like painting with dope but now I can't remember why!    Steve Fauble
Prosper
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« Reply #38 on: January 09, 2018, 02:09:06 PM »

Hi dohrmc and faif2d. Yes, forcing a single-edge razor to cut cardboard would make an impression on a fingertip. Sort of a 'razorback' impression?

I almost finished the stbd wing today but didn't have time to convert the root of the left wing to the same spec as the right. I fixed ≈ 2° of washout into this (stbd) wing. Varying the wash can be achieved best as the leading edge sheathing is CA'd in place.

My F6F model has 2° washout and no wash on the port wing: this seems to me to give a bit too much right-roll, but I figgered that the Thunderbolt will be less affected by that same 2 degrees because of its elliptical(ish) wingtip as against the broad square tip of the other.

Stephen.
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Prosper
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« Reply #39 on: January 12, 2018, 12:20:42 PM »

I made a canopy plug and produced a test moulding. Apart from being strongly reminiscent of an old electric steam iron, the plug is very big - like everything on the P-47, except the wings unfortunately. I keep thinking I've made the fuselage to 1/24 scale but the wings to 1/26 scale by mistake. . .

Although the canopy moulding is thin it weighs 0.8g; more than I'd bargained for. In fact this model is piling on weight at a rate of knots.

Note the slightly bulging canopy sides - this is intentional.

Stephen.
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Prosper
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« Reply #40 on: January 15, 2018, 06:11:34 AM »

The picture shows the airframe lumped together to get a first idea of weight and balance. It's 4.5g heavier (that's ≈1/3 heavier Shocked ) than the F6F in the same state, and doesn't yet have its wing/fuselage fairings which will weigh a good bit. The balance is at mid-chord of the wing at the root. The prop will move that forward and the tissue and paint will move it back. I hope it might get by without added noseweight.

Now the wing fairings. I'm calling them that and not 'fillets' because although minimal, they continue unbroken, right around the wing. For the highly-curved parts at the front I'm moulding paper on a small balsa form as shown. To make the long rear panels I thought I'd just drape wet paper over the airframe structure, since there's little double-curvature. However this has proven to be frustrating work. I found a long spring to keep the drying paper in place which has helped a lot but this won't be the quick job I expected. The fairings are necessary not only for appearance's sake but because I find that if the wings are slotted fully into their saddles they have a lot of sweepback. In other words only the front part of the root rib sits in the saddle, and the rear portion is left dangling in space, if the correct 3° sweepback is to be obtained.

Stephen.
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Prosper
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« Reply #41 on: January 17, 2018, 11:05:44 AM »

Quote from: Prosper
I thought I'd just drape wet paper over the airframe structure, since there's little double-curvature. However this has proven to be frustrating work.
I gave up. The sheets of paper draped along the wing/fuselage join didn't dry in a way faithful to the curves they were supposed to follow - they were just vaguely curved wavy sheets of paper. I'll have to retry later.

However I did have success with the front fairing. I decided to try moulding both top and bottom fairings at the same time. The very visible overlap between the two was sanded smooth before sealing the paper. The result, with one coat of paint to show up blemishes, is shown. There are a few blemishes, but these are from the roughness of the balsa mould and not due to any shortcoming in the procedure, so I can live with them.

I'm giving preshrunk and prepainted tissue another try for the flying surfaces. More later.

I've covered half the fuselage. I thought I'd try with a single piece of tissue but had little expectation, given that the Jug has a fat curvy fuselage that looks like a. . .a. . .well, a jug. I
nearly reviewed Bern's Youtube tutorial to give my morale a boost, but remembering the main points (1.Wet a large sheet of tissue. 2. Apply it to the fuselage), I jumped in.

At first it looked highly unlikely that anything could come of it, the folds and wrinkles were so many - but gradually my hopes rose (always a dangerous sign). The tissue was absolutely drenched so I had to keep manipulating it for some long time before it stuck. I finally had to admit that it's worked Shocked. I took the close-up picture below to ask HPA if tiny puckerings, such as these seen below the top stringer, are a fact of life. After 20 minutes or so I checked the fuselage and even these have gone! Swipe me.

Now, I trust tissue covering about as far as I could throw one or two models I've made in the past, so I'm fully expecting to wake up tomorrow to find the fuselage either C-shaped or exploded, or the tissue split wide open or somesuch, but for now I'm pretty bucked.

Stephen.
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DHnut
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« Reply #42 on: January 17, 2018, 01:37:37 PM »

Stephen,
              You are providing the usual enlightenment during the build. I have used this technique that was in the Model Builder book on WWII aircraft as used and documented by Doug McHard. I have used it on the Hurricane and the Me 109 in that book. I agree it is a delicate process but works well using dope and thinners as the adhesive. The tension on the tissue does not seem excessive and stress is distributed better over the panel. It is certainly less fiddley than individual panels.
The fairings are always a challenge, for the Hurricane I used a mold as you have done and used layers of tissue and it worked well. The rear fairing was paper rolled around a dowel and was a bit of a pain. I found an art paper for the Magister fairings that when dampened molded nicely and was nuch nicer to handel. It is heavy though.
 Photos to follow.
Ricky
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« Reply #43 on: January 17, 2018, 05:57:32 PM »

Interesting result Stephen. It looks pretty impressive. I would say you have just about mastered tissue covering.
Did you use the dope and thinners approach? I just checked his video and noted Bern actually used glue stick and a hot air dryer!

Would you consider moulding the rear section of the wing fillet similar to what you have done with the front section?

John
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Prosper
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« Reply #44 on: January 18, 2018, 12:57:00 PM »

Hullo Ricky and John. I must admit I'd missed that Doug McHard tutorial in the book so thanks for pointing it out. The Bern covering video is good for dimwits like me, but is anyway worth a look for entertainment value alone. Although I see the value of dope-and-thinners in some cases (I'm thinking of complex and delicate structures; I was encouraged to try it by George K and Marco and it makes the impossible seem possible. . .), in this case I used my SOP which is a wallpaper-paste type glue applied to the perimeter only. And no hair dryer Smiley. I just kept tweaking and tugging and stroking until things looked tolerably OK. Unlike Ricky's description I found I was using quite a lot of force, or so it seemed to me. Covering the other side will be more difficult I suspect but I have a good excuse for leaving it a while - I want the glue of the initial fixing to be absolutely dry and hard before wetting it again with more glue.

I'm reluctant to make moulds for the rear portions of the fairings because they're so big. I'm just going to see what happens when the wings and fuselage are joined. The advantage of this paper+CA is that it's tough, stable and virtually waterproof. It is heavy though - I got a rough measurement once of 80GSM. In my all-sheet models I use it structurally but in this case it'll just be dead weight.

I managed to cover a wing today with preshrunk and prepainted tissue.

Stephen.

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« Reply #45 on: January 18, 2018, 01:37:29 PM »

Quote
I'm reluctant to make moulds for the rear portions of the fairings because they're so big.

What about carving moulds out of foam?  Foam being cheap and easy to carve.  Then you would have some possibilities along the direction you were going or even try some tissue machet.
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« Reply #46 on: January 18, 2018, 01:42:41 PM »

Any method Stephen chooses seems to be the right one! but just to add to the discussion this could be an application for Hearty Clay either as an easy method of forming a suitable form,  or even as the part itself, suitably hollowed out once dry
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« Reply #47 on: January 18, 2018, 03:42:51 PM »

Stephen,
             There always other options and you have demonstrated another method. It seems that provided the adeshive sets before the shrinking takes place the method will work. It is the ability to capitalise on the stretch in the tissue that matters. I must admit the first time I tried it it was some trepidation that did the Hurricane but it worked a charm.
The rear fairings were not molded but dampened and formed free hand while damp, so hardening with cyano to lock the form would work well.
The wings look good and a testament to you covering ability as I think the silver tissue is a real challenge to get right.   
Ricky
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« Reply #48 on: January 18, 2018, 11:19:09 PM »

Another good covering job there on the wing Stephen. The printed tissue looks neat. Did you print on white tissue or silver?

John
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Prosper
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« Reply #49 on: January 19, 2018, 04:16:25 AM »

Hi fellers. In principle making these rear fairings with their minimal compound curvature should be easy, and I'll be unhappy if I have to revert to fancy solutions especially as this build is 'over time and over budget' already. I recall that you've mentioned Hearty Clay before Mike, it interests me and I've just seen that it's available in Blighty.

Quote from: Ricky
It is the ability to capitalise on the stretch in the tissue that matters.
Spot on Ricky. When I'm cursing Esaki for its fierce, distorting shrinkage, I should remember that it's the same property that allows it to conform so well to curvy shapes.

Having said that, I can't really curse the tissue on the wing for overshrinking and bending several ribs Sad. Seriously, that's what greets me thismorning. They're only very slightly wavy but the air's very humid - might worsen over time. My fault for cutting too much out of the 1/32" ribs.

Just to clarify on the tissue - it's white lightweight Esaki which I've painted. The insignia and stripe were done with brush and stencil and the lines drawn on with pencil with the control gaps emphasised with black pen. The pencil drawing is just a test. The other top wing surface was done first, using a 5B pencil - mistake, it's far too dark and obtrusive! The pictured wing was done with an HB. Consequently, assuming I can cover the other wing successfully the lines will be a lot darker. Oh well, it's an experiment. I think it could be used to good effect with some practice.

I hope to get more done this weekend.

Stephen.
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