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Martyn K's Tucano


Martyn K
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I mentioned in an earlier post that I was building my Tucano with a built up wing and promptly put Profilli Pro to work

The outcome was a simple 10% thick NACA0010 sectioned wing.

An A3 printable set of wing sections can be downloaded from here

My master set of ribs were cut by Green Air Designs Ltd at (what I consider) to be a very reasonable price considering it was the master set. If you want a set cutting, yours should be (slightly) cheaper than my set £12.50 plus P&P.

Contact Greenair JET-SALES [[email protected]] to get a quote - mentio my name (Martyn Kinder and the layout Tucano 2013).

I have spoken to Nigel Hawes and he is happy that I publish this info - thanks Nige.

Here is what they look like.

pc030017.jpg

 

The salient details are: (repeated from my original post)

  • 1/16" sheet LE upper and lower to the main spar.
  • Some root ribs will be faced with liteply
  • All spars etc balsa is nice easy to get 1/4" stock. Tapered spars will be simply cut from sheet..
  • Using 1/16" webs up to bay 6 from the root
  • Wing rib spacing 57mm equidistant. 1" soft block wing tips to get that nice curvy tip shape
  • 1/16" x 1/4" cap strips from main spar to TE spar
  • Sheet ailerons and infil behind the TE spar. Keep the wood light..
  • I am not producing a fullsize plan, I am simply going to draw onto the shop plan to place the rib spacing.
  • Undercarriage, servo mounting etc - haven't thought about it yet..
  • Power - probably a .20/.25 size whatever I have got lying around at the time..

 

More to come but this will be slow as I now have 3 models under construction.

Martyn

Edited By Martyn K on 03/12/2012 22:22:08

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  • 3 months later...

March already eh..Better get a move on.

I have actually stopped pontificating and started work on the Tucano this weekend. However, an update. The 10% thick ribs that I originaly had laser cut have gone into the "recycle into a different model" bin and I am waiting for a set that are 16% thick. The main reason was that the section was just a little too slim for the construction method I wanted to use and I was worried that it may be a bit fragile. I have ordered the replacements, but still waiting...

So I have made a start with the fus. A couple of changes to suit an SC21 that I bought off eBay. Probaby the biggest change is the location of the formers and the change in material for the fuselage sides. I am now using 3mm balsa (instead of 3/16" )  but with 2mm liteply doublers from the nose to a taper behind the wing. I had lots of photos of assembly that made this clear - unfortunately, a camera memory card fault failed to record them..

So what I have done do far..

p3090008.jpg

The engine layout. This will set the position of F2 - now 6mm ply

p3100009.jpg

The nylon engine mount bolted to the already fuelproofed former with the non steerable nose wheel leg attached.

p3100010.jpg

The former glued in place and supported by triangle stock.. Note that the right thrust is built in by tilting F2.

Accepting that nearly a days worth of photos have been lost, these next 3 show where I am up to tonight as the two fuselage halves are glued together..

p3100003.jpg

The fueltank base is 2mm liteply that sits on top of the 1/2" lower triangle braces. The tank is a 6oz SLEC Red.

p3100002.jpg

from the top... A second balsa former (similar to F2) is located at the rear of the tank. Triangle section cross pieces behind the firewall, top and bottom.

p3100001.jpg

Finally, the rear former (F3 IIRC), is 2mm lite ply, its a bit flexible and will need cross bracing (6mm balsa), top and bottom.

 

That's about it - hopefully more progress during the week.

Best wishes

Martyn

 

Edited By Martyn K on 10/03/2013 22:41:14

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A bit more progress in the past couple of nights.

The triangle stock on the upper sides of the fuselage confused me. The fuselage is broadly trapezoidal (or mine is) in cross section. This means that the flats of the triangle where the top sheet is attached are actually tilted inwards. It gets worse when the sheet sides are pulled in behind the canopy. This meant I hadn't read something (I haven't actually read anything about this model yet) or I had some sanding to do. So I fitted the fin post and pulled the sides in last night - keeping it straight. I then planed and sanded the upper triangles this evening so there is now a flat edge. I reckon it needs about 1.5mm at the fin increasing to about 3.5mm behind the cockpit. Not a lot of effort but rewarding work. The upper decking is now glued to the nice flat edges. I tend to cut sheeting like this well oversize and then plane and sand it back.

The solitory photo:

p3120003.jpg

Other bits that have been done include the triangle stock upper left engine bay plus a triangle brace across the bottom of F3 to stiffen the lite ply former behind the cockpit. The tailplane has also been made up (sans elevators) and is ready to be glued in.

Everything strapped up and left to dry for 48 hours (I am out tomorrow night).

More to come.

Best wishes

Martyn

Edited By Martyn K on 12/03/2013 21:04:55

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Only a bit of progress this last couple of days.

The upper decking has been carved and sanded and the tailplane fitted and double glued into place. Note the square to make sure its aligned correctly withe the fin post.

p3140005.jpg

It seems to be going together very easily - in spite of the changes that I have made to accommodate the i.c. engine that will be fitted.

The only difficulty I thought I was going to have was carving the upper decking. The reality was that it was dead easy. It took me about 30 minutes with a razor plane and coarse sanding block.

Apparently the wing ribs will be with me tomorrow or Saturday so I can start on the wing, but the next job will be the lower decking and the front hatch.

I am planning to locate the radio gear and servos (MG90S) above the wing rather than behind the wing as shown on the plan. However, before I commit, I'll get the CG checked. If its looking nose heavy then I'll put the servos in the tail and drive the elevator and rudder using short links.

More to come...

Martyn

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A bit of progress these past few days.. This is more of a photo diary - apologies...

I started on getting the engine mounted and the front fuselage carved to fit.

p3170002.jpg

Engine bolted in and front former (balsa) fitted..

p3170003.jpg

Cutouts for the exhaust and idle screw

p3170004.jpg

One thing I have had to do is shorten the canopy a bit. The blacklines on the fus (half way down the tank) show where the canopy should finish. However, I wanted a full length hatch so I have had to shorten the canopy by about 25mm. Model now renamed Shorter Tucanoish...

p3170006.jpg

I got everything in place then realised I had forgotten the throttle linkage. A deftly bent 22swg linkage wire running inside a goldenrod inner seems positive enough.

p3170005.jpg

Upper hatch carved and sanded.The one thing I should have done is offset the engine mount slightly to cater for the right thrust, the result is the shaft is about 3mm too far to the right. A bit of creative carving had hidden that but I must remember Pete Lowes advice next time.

Which brought me onto the wing. I had a new set of wing ribs cut by Mike at Greenair designs. As expected, these are perfect and far better than I could hope for. The section is thicker than the original set - now 16% thick if I remember correctly.

p3200008.jpg

Assembly is straightforward, the lower 1/4" square spar is pinned down followed by the 1" x 1/2" LE and 1/4" TE (Cut from sheet). All are packed up by the correct amount. Note that I use lots of elastic bands pulling it together until the glue dries.

p3200009.jpg

The LE is roughly carved/planed to shape and lower LE sheeting fitted.

p3210010.jpg

Wings joined up last night. I am using 1/16" ply braces across2 bays. I think that will be sufficient for a model this size.

p3220011.jpg

And finally tonight, I have added 1/8" ply U/C mounting plates and added the lower dihederal brace. The U/C plates will need a bit of local reinforcement. I'll worry about that tomorrow.

More to come.

Martyn

 

Edited By Martyn K on 22/03/2013 21:30:44

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Hi Phil

Have to admit, I much prefer them to electric. And as I buy all my engines off eBay, they tend to be much cheaper. I only paid £15 for the SC21 for this model.. I dont know whether it actually runs though but there is very little wear.

Martyn

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  • 4 weeks later...

Posts are a bit thin with this build - not sure why, progress has continued, just haven't been in blog mood for some reason. Apologies

Anyway - bringing this build more or less upto date:

p4050001.jpg

Centre section sheeting has been added - full width to the outer limits of the undercarriage plates and tapered on top. I don't like sudden discontinuities in structural changes and always avoid them if I can. You can see the ply undercarriage plates with captive star nuts that are epoxied in place. I don't want them coming loose.

p4050003.jpg

The MG90-S aileron servos sits on 3mm ply 'bearers' fitted between the ribs and then sheeted over with 1/16" balsa. They can be removed, but it would be a bit of a nightmare as I have got keepers in place where they join the 'Y' lead - somewhere under the sheeting.

p4050005.jpg

The wingtips are laimated from 2 strips of 1/2" balsa and carved and sanded to shape. Note the ailerons on the variant extend further out than the standard sheeted wing version. The balsa for the cap strips was a bit too soft, it has got rather bruised during the construction and sanding.

p4120006.jpg

Bare bones shot from the front, I just need(ed) to cut the ailerons and elevator.

p4120007.jpg

And from the rear.

I have actually got further that this now and have started covering it. Hopefully, it will be ready to fly within the nexy couple of weeks.

I still need to:

Fit the radio gear. The servos for the rudder & elevator will probably go in the rear fuselage as the model is looking nose heavy

Add the wing mounting plate in the fuselage. I have inlaid a ply plate in the wing as a load bearer.

That's about it for now. Hopefully another post within the next few days.

More to come

Martyn

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Once again Martyn, looks most professional. Normal expectations would be for this wing to be a lot more efficient than the flat sheet version. However, because that works far better than one would ever expect, it's a great opportunity to make an objective comparison. Of course, it is the only realistic way to enable retracts, although I see that you're not going that way this time. The change in mean thickness/chord ratio from 10 to 16% moves it even further away from the flat wing, so the comparison could be even more informing. This gets more interesting by the minute!

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Hi Colin

My models always look a lot less professional when viewed close up.. nerd Thanks for the kind words all the same.

I originally went for 10% thick section to try and keep it more in line with the originals flying characteristics. However, when the ribs arrived I realised that I would need a lot more wood to keep the wing stiff - which would have added more weight etc. The 16% thick ribs looks about right for this model.

Probably the most significant change is that my section is symmetrical, the original flat bottomed plate had an implied +ve incidence through not being symmetrical. I suspect that I will need a couple of clicks of up to counter for this. I am also hoping that I can get a slower approach/glide through using a thicker wing section. I did aerodynamics at colllege and I am aware what happens to the airstream over a flat plate when the AoA goes up and the airspeed drops. (I appreciate that the original Tucano airfoil is not a true flat plate, but it is very thin).

What I cannot argue with is the original flies very well, in my humble opinion far better than theory should say so..

It will be an interesting comparison. Two of my club mates are building (more or less) standard Tucanos and of course we have the Greenacres Fly-in where I can crash mine in public.

Martyn

 

Edited By Martyn K on 19/04/2013 15:01:44

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Hi Martyn.

I follow your logic. The 16% symmetrical is guaranteed to work I reckon, this plane is going to fly well. The conundrum is as you suggest, why does the flat plate wing defy logic, (also how much bigger could it go before it didn't work so well)? Looking forward to seeing you at Greenacres, although my worry isn't crashing in public there, it's crashing in private somewhere else before I get even get to Greenacres! A very real possibility.

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I have that as a real problem. There was some talk about having a re-run of last years Vintage Fly-in which was a bit of a none event due to the lousy weather.

It will mean that I have to get a move on and get my totalled Astro-Hog 25 back in a flyable state.

Martyn

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Hi Ian/Colin

I bought the one from MHS. Fitting it was really easy, I had to shorten it from the back by about 25mm as I needed to leave access to the front hatch. It was wat toolong and also too tall

I trimmed the front first then located the front and rear using map pins and drew around the outline that I wanted using a felt tip pen. I then cut is down using a pair of sharp scissors and then finished off the edges with the sanding block. I think it looks OK. Much better than my poor effort on the Curare.

Martyn

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  • 2 weeks later...

Bringing it up to date.

I mentioned in my previous post that I started covering it. I have actually chosen the 2011 display colours..

Tucano 2011 Display

I can forsee lots of 2012 colour scheme models for some reason.

My interpretation:

p5020006.jpg

It's not quite right, not enough blue at the wing root but too late to worry about it now. You can see that the canopy is also too short - sacrificed for the fuel tank hatch.

p5020001.jpg

and

p5020002.jpg

The underside is very simple and contrasting:

p5020003.jpg

All covered in Dark Blue and Silver solarfilm with trim cut from Solartrim. I cut the roundels using a home made compass cutter. The red centres were very tricky, the larger circles were very easy and I made them all concentric by feeding each circle onto a pin using the compass point hole as a reference. The large areas of colour were marked out a piece of cardboard using a steel rule on its side as a french curve (by bending it). when happy, I cut the card out and used these for templates. The only really tricky area was around the fin where the red is linked from top to bottom. I didn't quite get it right on the RHS, but didn't spot the error until after the trim had 'set'.

The silver solarfilm has been a nightmare. Basically, I just could not get it to attach. Or rather, it would attach and then delaminate when cooled. It may need recovering sooner rather than later. I tried lots of different temperatures etc, I suspect it may have been a duff roll.

A bit more detail:

p4290005.jpg

The servo tray is very simple as all servos (except throttle) are mounted by the moving surfaces:

p5020004.jpg

Back end:

p5020005.jpg

Ailerons and u/c mounting

p5020007.jpg

The pretty curves around the front end have been sacrificed to get the engine in place.

I have a couple more jobs to do. The main u/c legs are too long - they need shortening by about 25mm must have been a mis-measure

The spinner is the wrong colour and size. Need a different one.

I need to finish off the throttle linkage and fasten the battery and receiver down.

However, I am away for a week from Friday so it will be done when I get back

AUW = 1.3Kg dry

Best wishes

Martyn

Edited By Martyn K on 02/05/2013 09:58:48

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Martyn , that model will look terrible in your hangar, you would be better off paying the postage to Australia and i will take her off your hands to save you the embarassment of turning up at the field with a model you have built and covered yourself. cheeky

Really looks the biscuits, top job. Oracoverangry??? used once still have a little bit left, you have just reminded me to burn whats left.

bbc

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I agree, I am deeply ashamed embarrassed... there are so many little tweaks I could have done to make it better, but never mind - it's only meant to be a fun flyer not a full scale jobbie.

The CG needs sorting as well, it's about 25mm back from the LE at the moment so some tail weight will be required - hopefully not too much.

Oz is just a bit too far too fly it unfortunately. The tank range will be about 10 minutes.. nerd

Thanks for the kind words

M

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