Extra Super Bettini

[Vecchio Austriaco]

From a club-mate I purchased a kit which has been made in Italy and has slept some years in a loft. It is a kit in rather historic style, as I built them some 25 years ago. The wings and the tail are cut styrofoam covered with abachi wood and the fuselage is made from FRP.
 It should be the model of an Extra 260 but I have my doubts if I look at the shape of the cowl.

 

wingspan is 2050mm,

length 1750mm.

weight approximately 6,8 kg

recommended engine 30 to 35ccm

 

Now that I have the beast at home I had a closer look at it.

The quality of the wings is good, the space for the wing tube, for reinforcement, servo installation and also the ailerions are milled out of the sandwich construction.

What I don't like is that they didn't use any premilled parts - all balsa parts are standard rectangular. So a lot of balsa dust needs to be created.

The hardware pack is rather poor and so is the plan and the instructions.

 

There is a plan in reduced size but without any measurements. This plan shows part numbers which are also mentioned in the instructions and which are printed on the balsa parts.

 

Some unnecessary details as how to fix the tail to the fuselage are up to the phantasy of the builder.

 

So in the end I ask myself "WHAT ON EARTH HAVE I BOUGHT?"

But on the other hand - if this thing ever flies I can really say that I did some work.

 

Tomorrow is the 1st of May or as we call it labour day -and the weather forcast is bad - so I will start doing some labour and produce some balsa dust in my garage.

VA

Edited By Vecchio Austriaco on 30/04/2010 20:45:11

[Vecchio Austriaco]

As mentioned last Friday - the weather was not the best - but good enough to let the grass grow like mad in the garden 

 

Finally I found some time and started some work - looking a bit at the tail. Instructions asked to reinforce it in the middle with two stripes of birch ply - which needs quite a tricky cut - as you have to remove the wood on one side and the styrofoam but not on the other. To get the thing done I used my circular table saw, a device which I will need quite frequently for this model.

 

I am a bit disappointed that the tail of a model of this size doesn't have any profile - even if it doesn't matter if it comes to flying - it looks better.

 

Speaking about the size - When the tail was done I couldn't resist takeing this photo. 

The tail has the same wingspan as my old slowflyer. 700mm

Time to go back to the garage to see what comes next.

VA

 

 

 

Edited By Vecchio Austriaco on 02/05/2010 15:20:27

[Chris Card]

A very interesting build in prospect here Vecchio.  Shows how easy we have it these days compared to the challenges of yesteryear.  And I suppose a kit like that was viewed as the easy option when compared to building from plans.

 

I'm not sure I agree with you by the way about a profiled tail not affecting the flight characteristics.  I've always found models with profiled tails to be far more progressive and less "grabby" in pitch changes. 

 

Be sure to keep us informed of the ways you find around the problems  

[Vecchio Austriaco]

Thanks Chris

It is still not too late to change something and I was playing already with the idea. I still have some cutting wire as I did once the wings for my gliders myself so I could even make a tail using the same technology as used for the original one. And there should even be some old books with profile coordinates on my shelf. Or I could build it up from Balsa - which may be the lightweight option.

In any case I have the rest of the week for thinking over the possibilities as I am currently at the ARTF paradise (In China for business reasons).

I will take my time for this build, as I have enough ARTF's for flying during the weekends. 

[Vecchio Austriaco]

So my ARTFs are not helping -no flying weather. At the moment all the good weather went to the UK I suppose. Here it is raining every day. And I switched on the heating again. In Italy in May!  

But this gives me more time to build and to think.

 

As I cannot get the comment of Chris out of my head I really looked into my old Eppler profile book. Nothing useful there. So I looked into the internet. And I found some interesting stuff. Dr. Quabeck's profile collection. Seems to be some serious work.

http://www.hq-modellflug.de/koordinatenframe.htm 

Sorry - site is in German. But I don't think it is difficult to find the right profile if somebody wants to. There is a selection of profiles also for tails and fins, so I think of rebuilding the tail now. It will be the HQ W07 - it is a little thicker in the middle than the "board type tail" but this will allow me to make it dividable - so the transport will be easier.

 

To bring the profile to paper I had to think a bit - but then I found quite an easy solution without investing in to any extra software and without typing 2x260 x-y values into the computer. I uploaded the data direct into excel - made an xy graph out of it - removed al background, grid, axes, description and so on, and saved the picture in a bitmap file.

 

This file I uploaded into my little non professional 15 Euro drawing program (Serif drawplus 6) where I converted it into a polyline - so I can print it in every size I need it.

 

The weekend will be used for wood shopping - and if I get enough money back from my travel expenses I think also to look for an engine. This should be 30cc glow -

but I saw a 26cc petrol 2-stroke engine which is light in weight and should have the necessary power for this plane.

[Vecchio Austriaco]

Back from the shopping and back from another business trip. Those trips give me time to think about how to make things and sometimes I make some drawings in the middle of the night so that I can remember later.

The decision to change the tail is done, also the necessary drawing. But before that I would like to see the wings in place. For such a large plane the original plan suggested to install the ailerons with flat hinges, so you would have a nice gap. This is not what I like. So I took some wood and played around with my circular saw to cut out a negativ parabolic shape.

Of course I started with a small trial piece - and when this was according to my thoughts I made the same on the two pieces needed for the two wings.

 

The balsa block below is necessary to have enough material for the installation of the round hinges.

 

The positive side (the aileron itself) I made with a balsa planer, a negativ form to check the shape, some abrasive paper an a lot of patience.

 

Here you can see a test fit.

 

For the balsa blocks it was necessary to cut out the styrofoam from the wing.

 

looks easy but it is a tricky job.  

Tomorrow we will see if the whole arrangement is working.

 

 

Edited By Vecchio Austriaco on 20/05/2010 22:51:21

[Vecchio Austriaco]

As I have it announced yesterday I did go on a little. The hinges are not yet glued in (they will be glued on one side and clamped on the other) but the balsa profile with the negativ shape is in its position, glued in and with plainer and abrasive paper I gave it the right shape. in the picture the wing is left and the control surface right.

 

As you can see the result is amazing. The remaining gap is about 0,5mm or less.

 

The only real gap is where the hinges are located - this little whole will be visible - but only if the aileron is on its extreme positions.

 

Here you see the aileron in position up - in the extreme position the gap is zero.

Quite late here on the continent - so tomorrow I will continue. This time with some work on the lathe - as I need some small device to clamp down the hinges.

 

 

 

[Vecchio Austriaco]

Was lazy last weekend - and it was flying weather also.

But now I can go on.

The mentioned device to clamp down the hinges is quite simple as I just made a tube with a small flange. Inside the tube I cut a M3 thread. The tube is glued into the wing above the hinge (some photos further up you may notice that I glued balsa blocks behind the hinge position). In the tube I put a hex set screw.  

After a test fit I applied some cyano glue into the hole where the hinge goes to strengthen the balsa and to avoid that the hole will widen while the hinge is clamped down.

In the picture you can see the tubes, and one of them is already glued in position.

 

Later - when the wing will be covered I can close the holes with a piece of oracover and they will be completely invisible.

 

In the meantime I found better hinges which have already a hinge pocket (Robart - purchased in the UK last Friday). Those are slightly smaller than the ones I used so I will keep them for the tail and rudder.

Edited By Vecchio Austriaco on 30/05/2010 16:56:50

[Vecchio Austriaco]

Time to go on with my project. I am fighting still with the wings - before I can finish them completely I have to think about how to fix them to the fuselage.

 

As mentioned before the instructions are not the best.

 

The wings are fixed using an aluminium tube which runs in an FRP tube. So far so good, but we need to keep them in the the exact position and we need to fix them to the fuselage.

The instructions said to use a 8mm wood plug for the position and use some ringscrews which look like the plugs used by UHU adhesive some 35 years ago.

 

So I don't like both solutions. As I found some aluminium bars in my metal box I made the accessories myself. Some may think this is crazy, but I like doing it.

 

Here we are.

Some aluminium plugs for the position and 6mm screws to fix the wings to the fuselage.

 

So now it is time to glue in the wingtube.

 

This work needed some pation to find the correct position, as I would like to have a plane which flies straight.

After fixing the correct position with some cyano glue I used wood pieces which I laminated with some glass fabric and glass rovings into the wing.

Here you can look inside - not totally nice but stable (I hope)

Edited By Vecchio Austriaco on 14/06/2010 21:39:43

[Vecchio Austriaco]

Having the wings in place the first time my enthusiasm for this build dropped to zero. There was a gap between the last rib of the wings and the fuselage. I found out that the place where the wings contact the fuselage have an angle of about 10 degrees. So what to do?

 

I made another end rib from plywood and gave it the 10°shape with a planer and abrasive paper. Much faster written then done. Having the cosmetic ribs in place and the wings again on the fuselage I saw another disaster. The wing tube was glued in slightly misaligned. I don't know how it happened, but i could clearly see that on one wing I had a space between fuselage and nose and on the other between fuselage and the end of the wing. I measured several times the position of the tube with a tape measure from tail to the end of the tube and it was fine. But obviously it wasn't.

 

So what to do? the wing tube was very fragile - so no way to get it out without breaking it, especially as I used the glass rovings as mentioned before.

 

There is always a way out - I decided to make a new wing tube. Some thin PE-foil wrapped around the aluminium tube, 2 layers of glass fabric, a bit of epoxy resin and some patience. As I didn't have enough of the last ingredient I put the aluminium tube into the oven and put it on 50°C. After 3 hours my new wing tube was baked and as good as the old one.

 

Now I could grind out the old tube and move the position of the holes to correct the error.

The new tube was glued into position again with some rovings to be sure of the connection.

Doesn't look so bad for a home made tube.

 

The aluminium tube used by Bettini is of some interesting quality. If you have it in your hands you get imedeately grey and also in contact with the FRP tubes it sticks leaving grey marks inside. I tried to polish it, I tried to grind the inside of the tubes a big bigger, and finally it is acceptable - but still stiff. To get the wings apart I need a screwdriver to move the first bit and to get better access.

 

After my tube adventure I had to move all holes a little bit by use of a file  - so what was nice and fitting before is now all oval

 

But finally the wings are on.

Here you can see my homemade aluminium screws doing their job for the first time.

 

To center the wing in horizontal position I made aluminium plugs and bushings. A carbon tube keeps the bushings in place and avoids that the fuselage may be deformed by the wings in case the pilot hits something during landing. (I don't trust the pilot as it's me)

wings are on finally and the full size of the monster can be seen. I tried to measure the position of the wings to the fuselage - all seems fine and I can think of the next steps.

 

 

[Vecchio Austriaco]

As the weather is really bad here I go on building. Now that the wings are almost done (the servos have to find a home still) I have to look at the tail. Further up Chris told me that a flat board is not only looking bad but may also fly bad.

 

So I decided to build up the tail - and it should have a profile. It will be a HQ W07 - as described above. Before fiddling with the scalpell to cut out the balsa I have to get the drawings on the wood. I know there has been a lot of suggestions in this forum how to do that. I am a lazy guy - and it has to be quick. The drawings I made with my 15Euro CAD - so having them already on the computer I decided to use textile transfer paper to get them to the balsa.

 

First you need the drawings - once done I rearranged everything to use both the transfer paper as well as the wood in an economic way.

 

Don't forget everything has to be in mirror image when printing.

 

The red line in the middle is just to know where  to cut for the 10cm bals sheet. My printer doesn't like it too much when I go close to the edge of the paper, so he told it to me by making some ink spots...

 

After that I took out my small iron I normally use for Oracover and ironed the printing to the balsa. This may create some steam as the wood is not at all dry. Also the wood may bend a little but it is not too bad.

 

 

In the end you have the printing perfectly transfered to the wood - of course there is also a thin transparent plastic film on it - but this doesn't distrurb me. I am quite happy with the result - but now comes the fiddly part. I have to cut the shapes out. And for that I didn't find a clever solution...

 

 

Edited By Vecchio Austriaco on 20/06/2010 16:35:58

[Vecchio Austriaco]

The solution (not so clever but working) was to cut out the ribs with a scalpell and finish with fine sand paper.

 

After last weekends success with the homemade FRP tube another thought came into my mind. As I want the tail removable (tail span=700mm...) I will need tubes also here. I checked for the odd materials and I couldn't find any matching tubes. So why not - I will make them myself.

 

As connection rods I found a carbon tube which once had to work in a Multiplex Acro Master - the Acro Master went but the tube survived.  And also a 6mm cabon tube which I purchased in a weak moment.

 

So yesterday I made 3 tubes out of different materials - which was not my plan. I wanted to make 2 tubes out of glass fibre reinforced plastic - but the glass fabric told me that it is ok to go around 30mm (the wing tube) but it didn't like small diameters.

 

I could manage 10 mm (the Acro Master tube - see above) but 6mm was impossible. So different materials are to be found: My first choice was  - toilet paper. Works great, takes the resin like a sponge and gives a semielastic tube with a rough surface. (it has to be glued into the fusealge anyway - so a rough surface may help).

 

The second choice was printer paper. It doesn't take the resin that easy, but with a bit of patience it works. It gives a rather stiff tube with a smooth surface.

From top to bottom:

 

the Acro Master carbon tube

the 6mm carbon tube

the toilet paper tube

the 80g/m2 printer paper tube

and finally the glass fabric tube.

 

Now I have the necessary basic materials to go on with the tail design.
 

Edited By Vecchio Austriaco on 21/06/2010 20:14:02

[Vecchio Austriaco]

Knowing now the diameter of the tubes it is possible to drill the holes for the tubes into the ribs. I have seen in some forum post that there are tools existing which just cut with a thin wall tube into the balsa.

 

Having a lathe and a collection of scrap metal (this is what my wife calls it) such a tool is done in minutes. found some silver steel which is pretty hard and therefore not easy to machine but it should also keep the shape well. I made a tube leaving a wall thickness of 0,2mm and gave it a sharp edge. Cuts like a razor blade.

 

works not only on balsa but also on ply. (thin - lets say up to 2mm)

Finally a set of ribs is born. You can see that my textile transfer paper is working perfect on balsa but less nice on ply (end ribs - bottom of picture)

 

[Vecchio Austriaco]

Just to give you a sign that I am still alive -

the tail didn't come out as expected, first of all because the centre tube was too big. Means the ribs came out too fragile and some of them broke during assembly. So I need to change the tube to a 6mm design. I already made the drawings and I have just to iron them to the balsa but there are a few other important things going on at the moment - so not too much progress at the time. Also we had a lot of flying weather these days, so I need to keep the every day models up and running (today I stalled my YAK 54 into a corn field - not too much damage but a few hours it will need...).

 

But one thing I did was looking at the design of the bird. As I will move to UK in a short time it must be something British. So what is available? First of all the Union Jack, then we have also the English Lion. Putting both to one model this ist what comes out. (again done with my 15€ cad software...)

 

If the lion looks familiar to you - yes it is the same as you can find it on some brand of british eggs. So let's call it the egg lion.
So thats the update before I go into my holiday, this year UK, which has two highlights - first I will sign my new contract and second I go to Yeovilton to see the Yeovilton Air Day 2010.

Next update in August. VA

 

 

 

Edited By Vecchio Austriaco on 04/07/2010 15:54:22

[Sheldon Holy]

looks very nice!

Great job on building too, i hope it flies well! Are you sure that is an Extra 260? The cowling is all wrong, just as you pointed out.

 

Sheldon

[Erfolg]

Vecchio

 

The graphic is very imaginative and also impressive.

 

I am very concerned regarding the high level of skill and technique displayed regarding the fabrication of the hinge mechanism. It is hard to believe that a sparky, can have that much skill.  Models where so much time and effort have been committed are not suitable for flight, most are wheeled oniy for club static competitions, will yours be risked to anything but perfect conditions..

 

Erfolg

 

Erfolg

[Vecchio Austriaco]

The Austrian sparkies have to learn how to hold a file, to work with a lathe, milling, aluminium casting, galvanizing, welding and even to work with FRP before they are allowed to create any sparks. Some of these skills I have not forgotten and they come in very handy for my hobby... Jokes aside, some of my study colleagues have difficulties in changing a light bulb 

Will it fly - this is not a question as I have already purchased a nice 45cc petrol engine.

 

 I will not waste the money for this investment.

 

 

The real question is WHEN WILL IT FLY

 

Instead of bulding I sneak to the UK for some job intervies...

 

I will try to improve myself and will cut out this afternoon the tail ribs for the second time. (easy decision, we have blue sky but gusts of wind up to 50km/h....)

 

By the way Erfolg - have you ever seen that one ? It was also a lot of work but it flies almost every weekend...

 

Edited By Vecchio Austriaco on 24/07/2010 12:05:01

[Erfolg]

Vecchio

 

I had not seen the thread, again very interesting.

 

You mention making your own decals or transfers.

 

I think it is usually accepted that in the UK no suitable printer film exists. The Overlander product seems to be less than adequate.

 

Is there a film that provides professional results in Austria or Italy.

 

If you come to the UK, be prepared for weather, rathere than Summer or Winter for that matter.

 

Erfolg

[Vecchio Austriaco]

The product I use is Data Becker inkjet film weatherproof, glossy and adhesive. it is a white PVC film in A4 sheets, not too thin, but for the smaller Extra with 3,4kg it doesn't really matter... As all the product description of this printer foil is in German, you may be right. Comes from a shop called Mediaworld or Mediamarkt (same group, name changes in differnt countries) There is also a transparent version, but for some reason the transparent version has some fuel issues. But for electric it may work as good as the white one.

By the way - not only the paper also the ink counts. I use Epson Claria photographic ink.

 

Didn't check at Dixons or similar shops yet - I will have to update my knowledge about material sources in the near future.

 

Be prepared for the weather - By the way - was in UK 3 weeks ago and got a nice sunburn....

VA

 

Edited By Vecchio Austriaco on 24/07/2010 15:38:24

[Erfolg]

Ahhh yes that will have been summer

 

We have had quite a good year to-date, last year however, just a few warm days, the rest either wet or cold, terrible.

 

Will you continue yodelling when you come here? Cross bows are generally not approved off, certainly shooting arrows of children's heads, is a definite , no, no.! Unless that is you have a fully developed safety case supported by method statements, current safety inspection certificates for the equipment and a risk mitigation study..

 

I do find it surprising that there appears to be little suitable papers/films and ink here, I cannot see the market being smaller. It could just be that I am not in the know.

 

Erfolg

[Vecchio Austriaco]

No fear Erfolg - my yodelling - or rather swearing - is restricted to the moments when my model hits the odd tree at the end of the runway...

And the crossbow I leave in Switzerland - those are the precision shooters...

 

But I think I should turn back to my model- its rib cutting time. So no Whisky before this job is done...

[Vecchio Austriaco]

Back with this build after a short break (10 month?). I was not happy with the new ribs so I made them again and again. Set number 5 was accepted and I started to build the stabilizer. To get it warp free I made the stabilizer first without the hinges – the lines where to cut are printed on the ribs.

> >

As I want the stabilizer removable I made some little threaded aluminium flanges which allow clamping the stabilizer halves to the carbon tubes .

After everything was dry I cut the ribs and put in the half circle shaped bars which are connected with 3 Robart hinges each. I also cut off the inner corners for the rudder movement only now as this makes building easier. The part finished stabilizer including the carbon rods shows 30g less than the original on the scales.

Told in a few sentences – but it is the second weekend I work on the stabilizer… Next candidate on the list is the rudder. Also the rudder supplied with the kit is a flat sandwich part so I will do the same as with the stabilizer.

Edited By Vecchio Austriaco on 16/05/2011 08:27:06

[Simon Chaddock]

Vecchio

Superb work.

 

I do like your 'engineering' approach - not 'can I do this job' but 'how do I do this job' - brilliant!

[BalsaBasher]

Your attention to detail is impressive.

 

Well done.

[Vecchio Austriaco]

Thanks guys - there are others on this forum who build much more precise and even much quicker..... Just to mention one - Danny and his 1 day Webbit.

(I build slow so that the destroy rate matches the building rate