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OK, with lots of other projects on the bench there's been some delay in me getting started. But started I have, so I thought I'd show you how I'm getting on and pass on any experiences so far (for what they're worth!)

Like most, and as suggested by Nigel, I started with the wings. Basically glue the bits togther - not too difficult!

 

tucano 1.jpg

 

CA is the recommended adhesive - I have to admit I'm not a big fan of CA for building and the wings were not a 100% positive experience. I find that CA grabs too quickly - giving no time to adjust anything. Its right first time or not right at all! Anyway the task was managed - but if you haven't done yours yet I'd strongly advise you at least consider using Aliphatic. Definitely CA is useless on the wing tips - I used epoxy here.

Wing shaping was as easy as billed. Rough shaping done with the David plane then coarse sandpaper to home in. Here's one of the wings in close up:

 

tucano 2.jpg

 

This just needs a final sanding with fine grade just to finish the surface. But we'll leave that to the pre-covering phase. One tip I can pass on. If you are using the woodpack - as I am - then the ailerons are pre-cut out. This is a bit of a pain to be honest because you oviously want to shape them along with the rest of the wing. I found that a strip of Duct Tape on the underside held everything in place fine:

 

tucano 3.jpg

 

So I could then just go ahead and plane/sand the top surface. As you can see I have cut the channels for the aileron torque rods and the rods themselves are bent up. So I just have to fit them and join the wings for these to be finished. I decided to make up the basic fuselage before doing that.

Next up was the tailplane. Simple construction, again I fitted the tips using epoxy - but not too much - its heavy! The assembly was then given a rough shaping - this time just by sanding.

 

tucano 4.jpg

 

OK, that the flying surfaces done - at least in rough - onto the fuselage!

BEB

Edited By Biggles' Elder Brother - Moderator on 09/04/2013 22:05:37

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So, on to the fuselage!

I thought the sides of the Tucano looked a wee bit flimsy, and problems have been reported I understand with both the nose and the sides on heavy handling. So I've opted to reinforce the fuselage side centre panels with some ply doublers:

tucano 5.jpg

Next, there is much talk on the Mass Build Chat about the line of the fuselage top being wrong on the drawing - which it certainly seems to be. This means its also wrong on the parts supplied with the wood pack - as obviously that's simply taken from the drawing! The long and short of it all, when you measure everything up - the top rear section of the fuselage is 3/8" too tall. So, it will have to be removed. Not a big problem, just mark it up carefully and cut. Here's a picture showing the sections to be removed:

tucano 6.jpg

With these chopped off we can proceed to adding F2 and F3 plus the doublers to the separate fuselage halves - being very careful as always to make two opposing halves and not two the same! Hands up if you've done that? Mmmm - that many eh! Me too!

Obviously the formers have to go in dead square if we are to end up with a square fuselage:

tucano 8.jpg

Now, I'm going to want to bend the sides of the upper fuselage in to make the Tucano shape - but those ply doublers will present me with a bit of a problem here. If I'm not careful they won't bend so much and all of the bend will be at the top. Not good. Solution? Add some grooves to the ply so it can take up a curve and will be about the same stiffness in the vertical plane as the balsa:

tucano 7.jpg

We still get the stiffening once its bent - but this way it will take up a nice even bend. We hope!

Now its time to bring the two halves together - just gluing at the bottom for now. Given the nice flat, straight, underside I'll do this the easy way using the fuselage jig.

tucano 10.jpg

The fuselage will remian in the jig now until the other formers are added, the curves glued in and the tail joined.

BEB

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Posted by Biggles' Elder Brother - Moderator on 09/04/2013 22:55:41:

Now, I'm going to want to bend the sides of the upper fuselage in to make the Tucano shape - but those ply doublers will present me with a bit of a problem here. If I'm not careful they won't bend so much and all of the bend will be at the top. Not good. Solution? Add some grooves to the ply so it can take up a curve and will be about the same stiffness in the vertical plane as the balsa:

tucano 7.jpg

We still get the stiffening once its bent - but this way it will take up a nice even bend. We hope!

BEB

Are you saying that the sides might not follow the curve of the formers? Interesting to see if it works. How thick are the doublers and will you run a fillet of glue in the grooves after bending?

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They are 1/16 ply Tony. What I am concerned about is sort of "differential bending" the balsa immediately netxt to the ply will be very likely to try to absorb a dissproprotionate amount of the bend - while the ply stiffened parts stay relatively straight.

I've used this technique secessfully before and its was shown to me by an old joiner.

Regarding in-filling afterwards, I'll assess this after the fuselage is together and if neccessary I can run some epoxy into the cutouts. But to be honest its not prooved necessary in the past. The doubler should still give pretty well full reinforcement along the length of the fuselage (which is the direction I am most cencerned about being potentially weak). While the former itself, and its joint with the side, will give me circumferential stiffness.

To aid the bending further I may thin the doubler slightly towards the former anyway. Suck it and see is the motto I think! smile

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mmmm Not bad for a days effort - you will be finished by weekend.

I used longer lite ply (3/32" )  doublers on my ic powered version (still WIP). I went from the nose and then tapered it ou behind the wing

Watching with interest.

Martyn

Edited By Martyn K on 10/04/2013 13:38:59

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BEB,

This is how you suck eggs!sad

When I saw the doublers on your fuselage sides I wondered if you could be generating a weak spot.

You have a vertical line step where the ply stops. This means that under strain, there will be a lot of stress concentration at that point, making it a single point of likely failure.

(On the same principle you use when you bend something over a straight table edge.)

I suspect that the model would be stronger if you attacked the ply with a sander and thinned it so that it peterd out gradually rather than the sudden step. Either that, or extended it a bit further, and ended it with a curve rather than a straight line

Plummet

Edited By Plummet on 10/04/2013 14:21:10

Edited By Plummet on 10/04/2013 14:23:22

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Hi Plummet,

yes I agree about the potential problem there which is why I suggested thining the doubler towards the former in the post two above yours. I've now done that - basically just shaved a taper onto the last 1/3 or so with a scalpel and then smoothed off gently with a sanding disc in the Dremmel. You can almost control the bend profile with it! Its like sculpting in reverse!

I'll show this in some piccies tomorrow.

BEB

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Oh, I forgot to mention. I've ordered the Tucano's motor. I decided on this GS item:

motor.jpg

An E-Power 2812 1180kV job maximum current 43A. I'll be using a 60A Black Mantis ESC that I have in stock. I've also ordered a new Rx for the Tucano - a Frsky TFR4 FASST job! I thought I'd give them a go! Tomorrow I'll be having a look if I can fit in one of my 3s 4000mAh batterries as an alternative to soldering up some new connectors to double gang two 2200mAh units in parallel.

BEB

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Good to hear that Olly. Well the motor has arrived - it will fit easily, but the mount is definitely going to be a bit of a squeeze! I've checked and my 3s 4000mAh Lipos will fit - again just!

So a bit more progress on the fuselage, sides now fully glued to the formers with the top bend in place. The stiffening ply was no problem in the end - once it was thinned a bit towards the ends. The tail has been joined up with the fin post in. Its model has a definite aspects of a "bitsa" - ie bitsa this and bitsa that! I had no balsa the right size for the post - and no hardwood either! So I had to laminate up two pieces of spruce. Still its a nice strong fin post.

tucano 12.jpg

The planed triangular strip has been added on the top of the sides and as you can see the rear top decking is also in place. I couldn't find any parts for this decking in the wood pack which was slightly surprising - so again it was a laminate up job as I had no 3/8 soft sheet in stock.

tucano 11.jpg

So that's the progress so far.

BEB

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Nice build so far, wish I had thought about that ply doubler tip - grooving to insure flexibility. I had quite a job forcing the sides in to meet F2 and F3. Actually you did not need to chop off the excess 3/8" from fuselage sides - you could have glued the 3/8 triangular stock on the inside top edge. A Nigel tip.

Mike.

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And got more gluing area! Drat - never thought of that! Ah well tis done how! Thanks for the kind remarks Mike. Yes the ply doubler has come out rather well in the end.

OK here's today's efforts - not a lot!

I've roughly shaped the back top fuselage - its only approx, lots more to do there yet, but it will enable me to check the fit of the tailplane and fin etc.

tucano 13.jpg

tucano 14.jpg

The reason not a lot got done today is that I have been pondering long and hard about the motor and how to mount it etc. Its going to be a very (very) tight fit! Anyway, I think I've worked it all out, step one is a "small" alteration to F1

tucano 15.jpg

I need to be able to fit the motor body through this former - and allow enough clearance for the fact that there will be 3 degrees of right thrust offset in place.

BEB

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Quick progress report,...

On closing up the nose I noticed that F2 was bending! So I've faced that with some ply. The front end is now closed up with F1 in place and the epoxy is drying as I type! I'm just in the middle of making the extension nose ring piece before I fit that.

The motor has been causing me a few minor issues. It comes with a very nice screw-on prop adapter - but the fixing screws are too short to attach it! Of course there is no documentation so no info on the thread size. I tried M2 - too small. I tried M3 - too big. So I guessed at M2.5. But of course I didn't have any M2.5 countersunk screws in did I!?

Anyway - ordered some from Modelfixings - late Sunday night and low and behold they were here this morning! I've found this several times with Modelfixings - very fast order turn round. Good company to deal with.

Anyway the prop adapter is now fitted to the motor and after I've attached the extension nose ring piece to F1 I shall start on installing the motor while I still have access without the top and bottom front decking in place.

I'll post some more piccies tomorrow.

BEB

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Well - shoehorning this motor in turned into the job from hell! There really isn't much room up there in the front of the Tucano!

First I had to perform some fairly drastic surgery on the spider mount - it was far to wide to fit into the Tuc's nose. So arms shortened and new mounting holes drilled.

Then I had a make a firewall of course - no problems there. Here is the firewall with the motor mounted to it.

tucano 16.jpg

You can see just how "modified" the spider has become if you compare it with the picture of the motor in an earlier post on this page! If it looks off-centre to you that's because it is 2.5mm off-centre to allow the drive shaft to exit on the centre line with 3 degrees of right thrust in place at the firewall. Here's another view:

tucano 17.jpg

I assembled the motor to the firewall prior to installing the firewall in the model. Two reasons for this; first while it would be just about possible to insert and do up the mounting screws and nuts in the model it would be very fiddly. Second I needed to be absolutely sure, while the glue was not set and everything was aligned (vertical and 3 dgrees horizontally), that the motor would clear the front ring without interference. Yes its that tight! Here's the motor in place with the epoxy drying on the firewall:

tucano 18.jpg

You can see that to get the motor in I've had to completely cut back the triangular strips along the top side of the bay - no way on earth would it go in with them in place. But I will be able to reinstate them (at least partially) before attaching the top decking.

Every build has a "crux", and feel that for me this was it for this model. I'm looking forward to some faster and easier progress over the next few days!

BEB

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BEB I couldn't agree with you more, I have had a dickens of a job fitting the F1A in place such that the spinner lines up with balsa ring giving a Clarence of 1/32 Phil's F1A has been much modified to get it into the correct position and Ive snapped off the tail post in doing so - another repair job before flight. The pic shows the motor in place before I tack glue in position.

Mike.

motor and f1a in place shimmed up.jpg

Edited By Mike Hardy on 23/04/2013 12:31:36

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Quick newbie question that I hope you don't mind me asking on your build thread...

I've not built a model with side-thrust before so can I please ask how you accurately work out the offset of the motor on the firewall to ensure it will have the correct degree of side-thrust and so that the motor shaft will exit the front of the model in the exact centre (presumably the front of the circular wooden ring shown in Mike's photo above)?

Is it simply a case of using a protractor and ruler to work it out? It's something I can see myself messing up slightly. Will it make a huge difference if it is a degree or so out to either side (Presumably a few washers under the motor mount could correct this)?

If there's a post or aticle that already covers this then just point me to it

One quick question that's become 3 questions, ah well, hopefully you can help. Ta muchly.

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Hi Ian,

no problem asking the question at all - that's what the Mass Build is all about!

No it doesn't matter if it is a little out, the 3 degrees is a fairly nominal and standard offset. Experience over time has taught us that that is the sort of offset that will correct for torque pull. So, while you don't want it miles out its not a big deal if it comes out a little bit off.

People will have their own ways of doing this - please feel free to add suggestions - but I will tell you how I do it.

First you have to accurately mark two lines on the firewall;

  1. the first is a horizontal line giving the vertical location of the thrust line for the motor - you get this off the plan, its dotted line shown going through the motor outline and spinner.
  2. the second line is a vertical line marking the geometric centre of the firewall - just a vertical line down the middle.

Now we have to get our calculator out and do a quick sum. The motor can't be placed in the centre of the firewall - ie it can't go at the intersection of the two lines we have just drawn. It has to be offset to one side, so that when canted at 3 degrees it will exit the nose in the middle. Attach the mount to the motor then measure from the front of the prop drive washer to the back of the mount - ie the length of the motor plus the mount. If possible do this with a venier calipler. Suppose this length is 50mm, now work out 50 x tan(3) on your calculator. The result is the horizontal distance you have to offset the motor by so that when the firewall is canted over at 3 dgrees the drive washer will be on the centre line. In my case that distance was 2.5mm - which is pretty typical.

Now mark a new vertical line on the firewall 2.5mm (or wahtever distance you work out) to the right of the centre line (as viewed from the front of the firewall). Where this line crosses the horizontal thrust line is where the centre of your motor has to go. You can see this offset in the picture below;

tucano 16.jpg

Now the next thing I do is take a piece of 1/16" ply and cut a rectangle - in this case about 80mmx40mm. Be very careful and use a "square" when cutting so you are confident that the sides of this rectangle are at square to each other. Now do a calculation the same as above - take the length of the long side of the ply rectangle - say 80mm - and multiply it by "tan(3)" on your calculator. Mark a point this distance down from one short edge of the rectangle and draw a lengthwise sloping line from the far corner, along the long side to your mark. This line will be at 3 degrees. Cut along the line. So now you have a ply template - one long side is square to the sides, while the other long side is tilted at 3 degrees. I can put a photo of this up later if its a bit confusing. We will use this as a "sighting tool" to align the firewall with a Mark 1 Eyeball!

I now put the model in a fuselage jig, for two reasons - first it holds the model still while I'm fiddling, second by alinging the fuselage such that one of the length wise red lines on the jig goes straight down the centre I have a datum point for the centre line.

Put the fire wall in the model. Jiggle it to about the correct "forward/abackward" position. Take your ply sighting tool - align the straight edge with the fuselage jig cross lines and the jiggle the firewall to line up parallel to the sloping side of the sighting tool. Don't forget to put a square up against the back of the firewall to make sure its vertical. Now look at the drive washer - if you have marked everything out and cut accurately it should be bang over the fuselage jig centre line.

Assuming all is well, lightly mark the top surface of the fuselage on both sides with the firewall position. Remove the firewall and mix up some 1 hour epoxy - you are going to want "adjusting time" here! Apply epoxy to the inner fuselage sides - in line with your marks - then insert the firewall to the marks. Clamp up lightly.

Now squint at it from all angles. Is it vertical? Get that square up against the back face of the firewall. If not vertical then tweak. Does the 3 degrees look right? Check with your sighting tool - lift it off - check again. If not right - tweak. Is the drive washer right over the centre line? Is the drive washer the right distance forwards?

Basically you just work around and around these combinations until you are happy. You have about 15 minutes with 1 hour epoxy before it starts to stiffen up.

Once you are really happy that its: vertical, at 3 dgrees and the right distance forward - pinch up the clamps a tad - do one last check just to be sure that nothing has moved - and relax!

You don't have to use a fuselage jig, I do because its convienient. A straight chalk or crayon line along your building board with some cross lines at right angles would do. And of course there are those "old hands" who will just say "for an average size motor its two washers under the lefthand support" And I'm sure they are right! But I prefer to be confident and work it all out. Its my way!

Hope this helps. When I get home I'll try to remember to post a couple of photos that might assist - one of the ply sighting tool I made for the Tuc and one of it in use on the model.

BEB

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Wow, what a fantastic amount of info, thank you! Some pictures of the "sighting tool" in use would be great if you have some, no worries if not though. Have bookmarked this page in my "RC Useful Info" folder as I get the feeling I will be referring back to this page on more than one occasion!

On the downside, it does seem you have proven my old maths teachers right in their insistence that doing things such as calculating tangents would come in handy after school (Managed to make it 16 years without pressing that "Tan" button though!).

Thank you for the imperial measurements too Bob smiley

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OK, update. Its been a bit busy this week so not a lot done. I've re-instated the triaangular side pieces and tidied up the front a bit. I've also cut the top and bottome parts out ready to go on. And finally the ESC is fitted - another shoe-horning job.

tucano 19.jpg

Shown from above and front, and now from the rear:

tucano 20.jpg

And before anyone asks - yes I am concerned about overheating - there is not only not much room there's not much air flow either! I do plan to use the dummy turbine exhausts as air outlets - fingers crossed it will be enough.

Finally I promised Ian a photo of the sighting piece I used to line up the front - well I've really struggled to get a close up shot that is in focus - and failed - but here's my best attempt with apologies in advance - I'm no photographer I'm afraid!

sighting gauge.jpg

The square long side is at bottom while the 3 degree slope along the top face.

BEB

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Too windy to fly today so I got a couple of hours in the workshop this afternoon. I had a another job to do as well so the Tucano didn't get all of my attention - but I did make some progress.

First up - yesterday I made a discovery. The nose of the Tuc had been bothering me for a little while. The problem is that the nose former, F1, is exactly 2" diameter - but the spinner is a 2" spinner. This means that from F1 forwards the nose would have to be a parallel tube. I was concerned that this wouldn't look so good!

On examining the drawing I realised the problem - F1 on the plan is 21/8" diameter! The F1 in the plan pack is undersized. What to do? I could just leave it - but it would nag me all the time. So I decided last night that I would put a collar around it to make it at least a little wider. So I stripped a length of 1/32 balsa and put it in soak overnight. Once really wet I would be able to shape it around F1 as shown in the picture below:

 

tucano 21.jpg

 

I know its not much - put it will keep me happy! I couldn't use 1/16 strip beacuse I'd already brought the sides in - it would stand proud of the side. Fortunately I had left just a little bit of the side sticking out from F1 - enough to do this anyway. We'll see how it works out when I start shaping the nose.

Next I needed to check that the direction of the motor rotation was right - before I effectively seal the wiring to the motor behind the glued in top and bottom panels (I'm considering not having a hatch here).

 

tucano 22.jpg

 

So, with a new memory allocated in the 8FG for the Tucano the Frsky Rx was bound and a battery connected. Set up went fine - direction of rotation is good. One slightly worrying aspect, the prop driver seemed to be running very slightly eccentric. The can itself was spinning true. I double checked and the prop adapter is securely home and square against the front face of the can. Something to keep in eye on and look at again when a prop is fitted.

Next up the top decking was fitted into place:

 

tucano 23.jpg

 

And here is a view from underneath showing the surfaces there ready to receive the bottom decking, once that is in place I can attach the nose ring and start shaping up the nose.

 

tucano 24.jpg

 

BEB

Edited By Biggles' Elder Brother - Moderator on 28/04/2013 21:06:34

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