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Sukhoi su-26


Jamie sawyer
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Thanks Martyn. I'll be posting some pictures later on the covering of the fuselage and electronics installation. Wee bit boring really but all helpful. That link you posted is a good one. I ordered from them and will be again for some 6mm carbon control rods. I've never built something of this size but it's infectious lol.

Thanks for the comment thumbs up

P.s my root rib depth is 95mm at the main spar so I dont know if going for the biggest aluminium tube is the best hence the question. I was thinking along the line of a 25mm tube but does that seem undersized ??

Jamie

Edited By Jamie sawyer on 23/12/2013 09:38:34

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Hi Jamie

Thrust me - this is all VERY interesting - I am also a largish scale newbie as well and also taking the same route that you have = scratch design and build so I am very interested to see what wood material sizes and types you will be using, choice of servos, linkages, electronics, covering materials etc.

The way I am looking at the wings is to consider the weight, multiply by the max 'g' force expected - I guess about 8-10g (say 10g) and then build my wings to support a progressive load increase from the tips through to the centre. This should work fine for progressive flying loads, but would not be so good for an unplanned landing.. so need to add a safety factor out at the tips - which is what you would do anyway.

95mm - almost 4" for those who cant think metric - is huge isn't it! If you want to look at some ideas that the Free Flight glider (F1A) flyers use - they get wing loads at the centre of about 40kg at launch using a wing in a wing that my be about 12-15mm thick. Originally they used very high carbon steel about 8mm diameter - not piano wire, but these are slowly being replaced by solid moulded carbon joiners - about 12mm square from what I can see. The benefit is that these can be tapered allowing a proportional reduction in strength away from the root and then they blend into the bound carbon structure.

25mm tube - my thoughts are what are you going to put inside it? My guess is that it (and the wing structure) should need to support about 100kg Many years ago I built a 12 foot span slope soarer. It had 3 x 8g wing joiners and I used to bend them significantly every flight performing just basic manoeuvres (loops etc). It made me realise just how much load there is at the root of a large model.

Good luck

Martyn

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Well I'm no engineer or scientific gienius so I hope I get it right Martyn wink..

The wing root is pretty thick but it is 1/3rd to scale and Id guess the full size aircraft would have a wing thickness of around 3 inches. Thinking about it like that doesn't make it seem so thick really.

The wing build up is quite technical and I have deviated from plan slightly bearing in mind the plan that I am using states its for a 55 inch model and my one will be 103 inches. It's quite a significant difference.

My wing build up is as follows.

2 Main spars at 1100mm long 3/32 sq Cyparis

They will be sandwiched between 2 1.5mm ply sheer webs out to Rib 3 and just past it. Ribs 1, 2 , and 3 will be made from either 3mm Lite ply or 1.5mm birch ply. These 3 ribs will be the main section of strength to the wing carrying the aluminium tube and threaded rods. There will be a final 8 ribs out to the tip from medium balsa all in 3/16 or 1/4 inch thickness. Leading edge will have a balsa medium strip and false leading edge. Trailing edge will have the same build up but rein foced where the hinges are to be fitted. I've also been installing a good sized square of 1.5mm birch ply where the horns are fitted. Everything I have done up till now is P.V.A white glue except the hinge gluing where I have epoxied them in with 60 min epoxy. Wings will be 3/4 sheeted in the end top and bottom with 3/32 medium balsa.

My servos Martyn are Hex Tronik HX12K High speed metal geared servos....15 kg @ 6v and .13 sec/60 deg.I've 2 on the elevator and I will possibly have 2 on each wing but I'll decide that later....I've never used them but I have been told they are good. If I'm not happy with them then I will be removing them and replacing with a Futaba (Futaba) is my pet love laugh but everyone to there own lol

My under carriage is coming from an ebay site which I cant find right now but they are a carbon fibre company and do large scale under carriage sets for up to 1/3rd scale rc at a very affordable price. Think from memory it was about £60 for my set.

Good luck with your build and let me know to a link when you start as I would like to follow it to

Jamie

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Ok I have been a busy bee again with finishing the wood work and sanding. The fuselage has been fully covered and access panels fitted with there T nuts.

wp_20131223_001[1].jpg

This was the only part of the air frame that needed filling.. It was very superficial but needed it for peace of mind for me at least lol

wp_20131223_003[1].jpg

Ocean Blue has gone on here and a Duck grey is on the underside. I love the colors laugh

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Hi John. Its in the 4th and 5th post down at top of page. The DLE 111 I think will be the decision. Think it has a pitts style muffler to go with it.. The U.C and Cowel are next to be sorted on the list. Then I will be buying an engine. I can carry out a lot of ground testing with the fuselage while the wings are being built.

Prop will be a wooden 27 x 10 I think 2 blade. Full size is 3 blade but I'll not be taking that road I don't think.

I'll need to weigh it again. I'll give an update on that tomorrow.

Jamie

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wp_20131224_003[1].jpg

Here it is in place and screwed on. The Rudder is ply reinforced along the underside for all this so its not going to pull the screws unless I have a hard landing. I've installed another saddle clip onto the trailing edge. I haven't done it yet but I think I'll need to weld 2 washers on in place each side of the aluminium plate....either that or a wheel collet to stop the piano wire pushing up against the rudder when the tail bounces which it is bound to at some point. My bending skills of piano wire aren't the best but it will function just fine.

wp_20131224_004[1].jpg

Jamie

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wp_20131224_005[1].jpg

Here is a picture of the threaded rod right through both ribs on the fuselage side's. Just in case I didn't explain myself properly earlier. Its 1 piece of 6mm M6 threaded rod passing straight through in 2 places. You can see a very large washer on the inner wall of the fuselage to spread the load.

wp_20131224_006[1].jpg

There will be no give at all which may be a mistake if this aircraft comes in with dumb thumbs but the way I see it it is better than the wing falling off at 500 ft lol.....The ribs will literaly need to be torn out of the wing for unwanted wing removal!! .........Adding an Aluminium wing tube joiner right through at the main spar location all should be well I hope.

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Posted by Rich2 on 24/12/2013 19:55:51:

Excellent Jamie, that fuselage is huge!

Looking forward to the rest of the build...

Rich

Thanks rich. I'm glad some people are enjoying the updates on the build. It is actually encouraging me along more that you relies. Thanks for the reply and yes the fuselage is a monster. Its huge even without the motor and cowel fitted. That will add another 250 mm to the length of it smile p

Jamie

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8 Lbs ben, good guess though. The DLE engine comes in at 6.3 Lbs so total weight including engine will be 14.3 Lbs. Its looking like I may manage to keep the full finished Fuselage under 17 Lbs. That's well under the maximum 40 Lbs weight finished air frame. At a guess the wings will be 3 Lbs each so a predicted 23 Lbs flying weight is a kick ass weight with a 100cc flat twin up front that puts out just over 56 Lbs of thrust laugh providing the CoG comes in ok I'll be delighted even if it does push to 25 Lbs of weight....

Any way Santa Duties are calling lol.

Hope everyone has a good day on the 25th (Tomorrow )

Jamie

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  • 2 weeks later...
  • 2 weeks later...

Hi Cymaz, I have done some bits and pieces on the fuselage but not a massive amount. I'll post a reply over the weekend about it. Undercarriage is on and wheels fitted. 6mm push rods installed on elevator feathers and rudder closed loop connected and up and running. The fuselage is ready for the engine plant but just after Christmas its a wee bit difficult financially. I'll order the wing materials in February and crack on with the wings during that month. I'll maybe be a wee bit tempted to spend a wee bit of coin this weekend lol....

My Pc is giving me a bit of trouble online to with junk advertisements. It's doing my head in and need to get my dad to take a look at it.

Jamie

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  • 6 months later...

Hi I haven't added any update on here for ages and for those who were following the thread I most definately haven't abandoned the build but just set it aside for the summer as I am building an extension on my house and it has swollowed up all my time and resources but I will be continuing with it as the nights draw in. Bigger house = more room for planes :-D

Jamie

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