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Author Topic: Polikarpov Po-2  (Read 7891 times)
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Phugoid
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« Reply #25 on: September 06, 2012, 02:31:58 AM »

Ha ha! Grin

Ah yes the disc of doom!

Yes I still intend to do the Puss Moth, I've still got to get my head around this three view business though.  Mind you I've been too busy and tired of late to do much building at all, so it might never happen.

You'd best get cutting those ribs!

Cheers

Andrew
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danmellor
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« Reply #26 on: September 06, 2012, 05:03:11 PM »

Ha! At last, my pig headed refusal to go electric looks like it may pay off! Sometimes, being an idiot pays off...

Pete: The PO2 would be fine for a Telco as drawn, if you can keep it light. If it was me, I'd go 10-15% larger for the 120. Then again, I have just admitted to being an idiot...

Cheers,

Dan.
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Phugoid
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« Reply #27 on: September 06, 2012, 05:59:32 PM »

te he, Grin very funny Dan I'm grinning as I type.....

Not many Idiots build models as nice as yours....

Cheers

Andrew
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Pete Fardell
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« Reply #28 on: September 06, 2012, 07:24:52 PM »

Thanks Dan. You're probably right, but I'm going to stick to the Telco and will try and keep it light. Not my strong point though! 
I've actually just put my 120 into my Chazal monoplane (which previously had another Telco but didn't look like flying with it). I'll let you know how that goes.
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danmellor
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« Reply #29 on: September 07, 2012, 12:52:33 PM »

You should be ok, Pete. I've just dug the plan out and it does look pretty light, especially the standard fus. version. Sliced ribs save a great deal of weight, too. They are are pain to keep in one piece whilst sanding/handling etc. tho, given my ham-fistedness...

looking forward to the build,

Dan.

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Pete Fardell
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« Reply #30 on: September 07, 2012, 06:30:06 PM »

I've never made proper sliced ribs like this really, although I've sometimes just cut the centres out of ordinary ones. What's my permissible swear allowance for making sliced ribs? Quite high I should imagine.

Off to Old Warden tomorrow: http://www.bbc.co.uk/weather/2640985
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sparkle
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« Reply #31 on: September 08, 2012, 04:29:23 PM »

 Wink  really interesting story so far. Anything on the building board to show us so far?
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Pete Fardell
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« Reply #32 on: September 09, 2012, 06:48:08 PM »

No, not a LOT to show yet, but as of this evening I've officially started at least. I always feel relieved once the first wood is cut and on the board as it means I can't change my mind again. I don't normally weigh much balsa first, but I'm determined to keep this light so went to the trouble of finding my least heavy bit of 1/16 for the sheet sides. As All my bits of 1/16 were different shapes and sizes, this involved quite a lot of calculator bashing!
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sparkle
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« Reply #33 on: September 10, 2012, 03:08:32 AM »

 Grin hi Peter, glad to see you have made a start. I agree, once the first wood is cut most of the anxiety is over. Looking forward to your progress!
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OZPAF
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« Reply #34 on: September 10, 2012, 06:27:14 AM »

I've just caught up with this Pete and am looking forward to your build. Well you be hinging the rudder? I thought as it is quite large it might exagerate the left turn effect under power.
John
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Phugoid
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« Reply #35 on: September 10, 2012, 04:11:45 PM »

Looking forward to seeing this one coming together Pete.

Andrew
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Pete Fardell
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« Reply #36 on: September 13, 2012, 05:12:49 PM »

Thanks, chaps. Yes, I will be hinging the rudder, John.
Not much more done, but two basic fuse sides are now ready to go together. Before I do this though, I need to build the rear U/C legs into one of the formers and want to check how this is meant to work. Pics of the relevant parts of the plan attached (and a paragraph from its accompanying mag article).
 It seems the wire is first stitched to the balsa former and then fronted with a 1/64 ply plate. I presume if this is the case then I should glue them together with epoxy? I've already picked Dan's brains on this and he's dug out his copy of the plan. He suggests adding another ply plate on the back of the former too, to strengthen it further and keep the stitches from cutting through the balsa. Any thought welcome, as I've not fixed wire to balsa by stitching through the wood like this before.
Thanks,
Pete
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danmellor
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« Reply #37 on: September 13, 2012, 05:20:44 PM »

Looking at the side view again, there doesn't seem room for the ply doubler and the wire u/c and still have the legs emerge in scale position. I'd be tempted to make the whole lower part of the former from ply, stitch the u/c to that and then add a few gussets for good measure, once the former was built in!

Cheers,

Dan.
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Pete Fardell
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« Reply #38 on: September 13, 2012, 05:37:10 PM »

I'm almost certainly being dense here, but I don't quite get what you mean about scale position. Won't the wire emerge from the fuselage underside in the same place regardless of whether the former's made of balsa or ply? And regardless of whether there's a facing plate on the wire? Or do you mean that the lower, ply part of the former is fixed just behind the balsa upper part, so that the wire comes out right under the former top.

(Sorry if that's about as clear as mud!)
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tross
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« Reply #39 on: September 13, 2012, 05:39:47 PM »

Pete,

Are we sure that the wire isn't glued and laced to the ply before the ply is installed?
Or does that cause too many other issues.


Tony
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Instructions: Step One...Assemble the pile of sticks shown in pic "A" to look like the model airplane shown in pic "B"........
OZPAF
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« Reply #40 on: September 13, 2012, 07:37:57 PM »

Pete,
I think I would vote for 1/64" ply either side of the balsa and then stitched through the lot.
Tony's idea would also work but  may need that facing to be 1/32' to take the load.
John
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danmellor
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« Reply #41 on: September 14, 2012, 10:14:51 AM »

Sorry Pete!

What I meant was that in the side view, the wire appears to be attached directly to the front of the former. If the former is ply faced, the wire will be displaced forwards by the thickness of the ply.

Dan.
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Pete Fardell
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« Reply #42 on: September 14, 2012, 02:04:39 PM »

Thanks guys. I'm with you now, Dan. You're right; it does look like that. I think I just assumed the wire was between the ply and balsa. Anyway, I shall make sort of a stitched ply and wire sandwich and let you know how it goes!
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danmellor
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« Reply #43 on: September 14, 2012, 06:07:42 PM »

I'd  be tempted to make a balsa/ply/balsa laminate, sew the u/c to that and adjust the former position so that the wire still emerges in the correct position. Don't you just love fiddling about with stuff like this??

Cheers,

Dan.
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Pete Fardell
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« Reply #44 on: September 21, 2012, 04:46:39 PM »

In the end I put a bit of ply on both sides of the former, pre-made the needle holes with a pin and hammer and then sewed (and epoxied) the wire on. Seems quite sturdy.
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Pete Fardell
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« Reply #45 on: October 10, 2012, 04:58:56 PM »

Barely enough done to be worth posting again really, but by putting another pic on here I at least feel like I'm making progress. I found that I had managed to skew the fuselage a bit when I decked the rear section  Angry. Actually a lot. Maybe the wood I used for the longerons was a bit too supple. Anyway I've skewed it back again to something like square by sneaking in an internal diagonal cross brace. Luckily as it's not to be rubber powered I'll get away with this (hopefully).
Oh well, on to the next bodge then...
Of course these battle worn PO2s aren't meant to look too neat! Roll Eyes
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Yak 52
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« Reply #46 on: October 10, 2012, 05:13:57 PM »

Looks good Pete. Do you have any pics of the motor and installation? I'm a bit green on CO2 so I'm watching and learning  Cool
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Pete Fardell
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« Reply #47 on: October 22, 2012, 10:29:23 AM »

Not much plan detail on the motor fitting, Jon. I'm also pretty green on CO2 models and shall certainly be asking Dan the man about motor installation presently. Have to finish the nose block first though, which goes onto the fuse before the engine firewall. I'm also about to start soldering the rest of the U/C. NOT my strong point, so any very basic advice on solder, flux, copper wire binding etc. would be VERY welcome at this point!
Pete
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danmellor
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« Reply #48 on: October 22, 2012, 12:19:33 PM »

Hi Pete,

Nice to see progress is being made! I have to force myself to venture into the attic once the thermometer drops...

The only "trick" to soldering is cleanliness! Polish all the wire with a small file or emery paper and then try not to touch it again before soldering. This is easier said than done when you have to bind the joint! I use thin copper wire stripped from old electrical cable, although some get on with fuse wire better. Dab a little flux on the joint, wait until the iron is really hot and away you go!

Apply the hot, tinned iron to the joint and wait until it's hot enough for the solder to melt and flow without touching the iron.

Good Luck!,

Dan.
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PeeTee
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« Reply #49 on: October 22, 2012, 02:54:14 PM »

For binding wire I can recommend telephone cable. There are 4 or 5 conductors, each one screened so it's a bit of a pain to liberate the wire. However, the pukka stuff is tinned already and solders easily. It's probably a bit too thick for very small models but I like it.

Peter
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