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Curtis Condor biplane twin


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Got on with cutting wing ribs again today so that I now have a full set of ribs for the upper and lower wings. It took a bit of time to work out where to cut the wing tube holes to allow for the dihedral on the outer panels. And then how to accurately cut them. In the end I made a simple jig and used the appropriate drill bit from my 1 - 6mm x 0.1 drill set (1.4mm; 2.8mm; 4.2mm; etc) as spacers to position the rib to cut holes in the right place. Seems to have worked, but it is when the wing is built we will find out for sure.

20201115_163415.jpg

ribs with holes.jpg

Edited By David Ovenden on 15/11/2020 16:00:22

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Thanks Eric.

Actually, in a strange sort of way I quite enjoyed it. It has been some while since I last cut out ribs by hand. Luckily the wings are parallel chord so I was able to do most of the ribs from only 3 ply templates. Once the templates were made it was reasonably quick to cut the ribs themselves. There is a certain pleasure in selecting the right sheet of balsa; trying to get the most efficient placement of ribs on the sheets to save waste; and in seeing the pile of finished ribs build up as you go.

The thing I dislike most is making wing struts and interplane struts (and fairing them ) and I'm not much looking forward to planking the engine nacelles either!

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This morning I set about modifying the design of the tail surfaces. The rudder and elevators are shown on the plans as being solid balsa 5/8" thick. This had to be changed, firstly because of the current balsa shortage and secondly, to save weight. I am using a 1/16th sheet core with built up structure either side. Strong and light.

This afternoon I started on building the elevators. I was able to use the scrap wood from cutting the wing ribs to made the (very small) half ribs for the elevator. Feels good using the "waste" balsa to build the model. I think in the past I would probably have cleared the bench and thrown the offcuts in the bin!

new plans tail.jpg

elevators.jpg

Edited By David Ovenden on 16/11/2020 15:59:51

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Sign of the times David, I made some ribs for a Sea fury I am busy, with they all had jig tabs on which have been cut off and kept instead of binned. it will be a faff but most of them will make ribs for the ailerons. Those old designs were fond of using solid balsa for the rear end I've always built them up for economy and weight saving.

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I spent a couple of hours in the workshop this afternoon. I managed to get the structure of the fin mostly done and make some progress with the rudder. Still something of a mystery how I'm going to build the tail end of the fuselage onto the rudder. It goes where the curved dotted line is at the bottom .Something to look forward to?

20201117_164155.jpg

Edited By David Ovenden on 17/11/2020 15:56:02

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The propellers I ordered arrived today. A pair of 10x6 3-blades and a pair of 11x7 3-blade. They look pretty good in terms of being about right for a 30s biplane. Whether they are super efficient we will have to see.

11" is the maximum diameter that will fit between the engine nacelles and the fuselage. I think the 11x7 will work best with my 790kv motors on 4s lipos. However I may try the 10x6 on 5s to see which works best.

20201117_173619.jpg

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Not sure if there is much interest in this project. But I thought posting progress might help to keep me focused and maintain the momentum..

Little more progress today. Ribs added on elevators and rudder and some sanding done. Also cut out the core for the tailplane and some ribs. Hope to get it finished tomorrow.

fin & rudder.jpg

tailplane.jpg

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Jeff, Yes biplanes are very addictive . To answer your question, not my first twin, but my first biplane twin. I built a sport twin a while back. It was a Doublet built from a Denis Tapsfield plan. That had two 25 2-strokes in it. Flew nicely but I sold it after a bit.

Also had a Black Horse Mohawk (electric) and a GA Monospar (also electric) that I bought 2nd hand.The first flight of the Monospar was "interesting" as it had been designed and built with opposite rotating motors. Different thrust angles each side. When I bought it it had both motors working in normal rotation. On take off it veered violently to the left. Just managed to cut the power and level up before it got to ground level. Phew!

I have decided that the Condor will be electric as the nacelles are just too small to squeeze in four stroke engines, plus tanks and servos.

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As a biplane addict myself (currently refurbishing a Flair SE5a and contemplating an Antonov AN2) I'm certainly interested.

I like the technique of a 1.5mm sheet core, stiffened with ribs on each side as a stiff, light structure for tail components. Easier to make than a fully built up component as well.

Geoff

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another silent viewer here

lovely work so far David, don't be disparaged by lack of comments, sometimes that just means we can't think of a better way to do anything you're posting pictures of!

good to see you've done your best to help stave off the balsa shortage by not using lashings of 1/2" sheet for the tail surfaces laugh

are you sure those enyas cannot be pursuaded into the nacelles?

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Posted by Nigel R on 19/11/2020 08:28:18:

another silent viewer here

lovely work so far David, don't be disparaged by lack of comments, sometimes that just means we can't think of a better way to do anything you're posting pictures of!

good to see you've done your best to help stave off the balsa shortage by not using lashings of 1/2" sheet for the tail surfaces laugh

are you sure those enyas cannot be pursuaded into the nacelles?

The problem with the Enya 53 (or even a Laser 70) is that (too much) of the cylinder head will stick out from the cowl and the nacelles are really small so there is not enough room for a decent size tank even with a micro throttle servo. The last thing you want with a twin is to run out of fuel! I will keep all the rib templates. IF the model flies well on electric I might build another modified lower wing centre section to accommodate a pair of four strokes - there was a later version of the Condor 2 that had slighter bigger cowl and longer nacelles. Then I could have the best of both worlds. For the time being its enough to build one!

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Bob,

I'm using some carbon tubes as wing joiners. I have 12mm joiner on the front spar (in 14mm carbon tubes in the wing) and 8mm on the rear spar. Its only for the tip panels as the centre section with motors is in one piece (3 piece wing). There will be functional rigging wires too, so its rather overkill but I felt they would beef up the wing without adding sheeting and extra spars. It will hopefully be a robust system that will make sliding the outer panels on easier and less fiddly. We shall see.

I did have a Royal P6-E kit but sold it some years back. Lovely kit, but I just had too many projects (like the Condor) to realistically ever get round finishing it.

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I take it the joiners are tubes? I have some solid rod from a Carbon-Z Cub joiner that I thought should be up to the job for the mainspar area, I think it's about 10mm diameter. Maybe a 6mm rod on the rear spar. I really can't deal with a mass of wing and strut bolts to assemble a model at the field these days so it's plug in wing panels or it ends up another wall hanging face 1.

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Like Bob, I have boxes of wood pieces too small to be of further use ... and then find they are useful and usually save hacking into a full sheet for a small amount. When I'm building from a kit I avoid thrwing anything away until its finished and, even then, a lot goes into the aforementioned boxes.

With the current balsa situation, it's even more worthwhile.

Geoff

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Bob, The front ones are 12mm o/d (10mm i/d) tubes. The rear ones are 6mm solid rod in 8mm tubes. The sizes were determined by what was available from HK (not much) and what could be accommodated in the wing ribs allowing for dihedral on the outer panels.

I can't imagine that your 10mm solid rods wouldn't do just fine. The Carbon-Z cub is designed to be "chucked about" after all.

Edited By David Ovenden on 19/11/2020 16:15:05

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