Extra 300 S ARTF with different design

[Vecchio Austriaco]

Christmas has passed some weeks ago, so I think it is time to start building what Babo Natale (Father Christmas in Italian) brought..

It is an Extra 300S ARTF kit made by Graupner. Wingspan 1600mm, powered by a 60 2stroke or 90 four stroke IC engine. Why this model?

 

 

 

I have to go back in time a little. Last summer I watched an airshow in Austria where I was fascinated by an Extra 300S, and so the idea was born to build this plane as a model. Who is interested in how it will look should have a look into my albums, where you can find the pictures in the folder airshow Dobersberg.
But back to the model. I looked for a decent plan and purchased one. A rough calculation showed me that the cost of building the model would be higher than that of an ARTF, and my self confidence in building from plans with all the pieces to cut out was not too high, so I decided to buy the rather cheap Graupner kit - as I think a product from this company should fly properly.

 

Sorry for Mrs. Wagstaff - I removed her from the cockpit and started to remove the shrink foil cover.

All the nice original cover removed

 

 

What is very good is the fact that all the hinges are secured by little metal bolts (which look a bit like sewing pins to me). This may be good for everybody but not for somebody who wants to change the design. These pins are glued in with cyano acrylate and cannot be removed without destroying half of the model. So I had to find a workaround.

>> 

 

Using abrasive paper to open up the gap between fin and rudder

 

 

The workaround is to cut the new foil at the positions where the hinges are and push it through the gap between control surface and wing or fin. I found that Graupner did a really nice job as all the joints were so tight fitting that it was impossible to put the foil through. I had to open the gaps to some tenth of millimetres by the use of abrasive paper. This makes the straightforward job of covering a fin to a nightmare. This work needs precision in cutting of the foil and a lot of patience. Just to give you an idea of the timing: Covering the tail fin only needs one whole evening.

As covering material I use Top Flite, not because I like it so much, but because it was available at the local shop in the right colour. It does not shrink too much, I have the feeling the materials I used some 25 years ago were more "forgiving" (or I was better at this time).

 

 

I am happy with the result so far, the fin has been changed to its new colour.

 

 

[Stephen Grigg]

Vecchio,youve given yourself a task and a half,congratulations on your perseverence in changing an ARTF to a different looking model of you choice

[Vecchio Austriaco]

Thanks Stephen, did not get very far yet - hope your congratulations were not too early. 

 

Yesterday was a bad day as Alex the crazy heli guy (my son) shared the work table with me so in the end I was working more on his heli maintenance then on my project. Then it happened that I set the iron temperature too hot and burnt a nice hole into one side of the rudder - so no progress at all. 

 

Today I could catch up a bit, the tail section has it base colour and I started to look at the wings. On the first one the old covering has been stripped already and I have to open again the gaps between controll surface and wing. 

 

Lets have a look at the engine: I decided to put an 91 four stroke engine into the model. Graupner recommended an engine from OS but I thought of a cheaper one, coming from planet hobby (P.H., same as Magnum, Chinese copy of the OS 91) 

 

the engine on a test bench 

 

The dimensions of the cowl  do not allow a 90 ° installation, otherwise it would stick out of the cowl quite a bit - more than I like it.

 

So I will go for inverted.

 

Doing so the fuel tank center is too high - and I have the fear of flooding the engine. I changed the tank position on the test bench already and tried it but the fuel was dripping out of the carburator so I will make an extension to the carburator turbe to put it higher up.

 

Also I am not happy with the exhaust system - the real plane has the exhaust pointing down, more or less at the end of the cowl. This will require a 180 degree turn of the silencer and at the moment I am searching for a tight flex tube of either aluminium or stainless steel to make this happen.

 

VA

Edited By Vecchio Austriaco on 27/01/2010 22:19:05

[Vecchio Austriaco]

Last weekend was flying weather so the progress on my project is rather limited. But the problem of the carburettor position has been solved (I hope so as I did not test it yet) by making an extension tube. If you are interested in that go here http://www.modelflying.co.uk/forums/postings.asp?th=36225

 

VA

[Vecchio Austriaco]

Just a quick progress update - I have changed one of the wings to the new design while the old one is still in its original cover. 

 

On the left side it is the new one - right the original one. 

VA

[Vecchio Austriaco]

went in twice for some reason.

VA

Edited By Vecchio Austriaco on 02/02/2010 20:59:40

[Vecchio Austriaco]

When I removed the cover from the second wing I saw that Graupner put in some surprise. The frame where the servo lid sits was broken. Obviously the person installing the lid used to much force when fitting the screws. 

 

I would have noticed it anyway when installing the servo, but without cover it is much easier to repair. A bit of cyano acrylate and treatment with sand paper and the problem is corrected.

 

Hope I can finish the wings today.
VA

 

[Vecchio Austriaco]

Wings are finally done. The control ailieron surfaces are so small that I allowed myself to use smaller servos than recommended. Graupner recommends standard size, I used Hitec 82. I had to make some adapter to fix the smaller servos but done in a way that I can change back to standard size if necessary.

Even the fuselage is not ready I had to put the parts together to see how the modell will look.

As you can see the cowl still need respraying - also the openings for the undercarriage have not been cut into the cowl yet.

 

In comparison to all my electrics it seems to be heavy. But you can hold it without beeing scared to turn it into woodchips  by holding it too tight.

VA

[Phil 9]

Well done. Its a brave man that strips the covering of a new ARTF.

 

Looks perfect so far

[Vecchio Austriaco]

Thanks -I didn't buy the most expensive kit for that reason... (there is always the possibility that it may not work...)

VA

[Sheldon Holy]

This looks very nice. I've done the same thing with a Richmodel Quickie. It's nice to have a model that looks different

[Vecchio Austriaco]

Today I played a little bit with the computer to get the necessary decals for my plane. I have started making the designs some weeks ago - so it was more doing the last little changes and corrections as well as printing and cutting. As basic material I used databecker adhesive weatherproof inkjet foil on an Epson Stylus photo 265. I checked the influence of glow fuel on this combination of foil and ink and I could not find any discolouring or swelling even after one hour of immersion. So I suppose I don't need any fuelproofing on these decals.

 

The only snag is that ink jet printers cannot print white - this would have made the job much easier by using transparent foil. To overcome this problem I had to use a red background color on white foil.

 

I printed a series of different red tones to find out the matching one and finally I am quite satisfied.

 

 

 

On the photos you cannot see where is the top flight monocote and where is the decal.

Of course - if somebody puts his nose close to the model he can see where the decals are - but an old friend said to me once - if the model is in 2 meters distance nobody can see it...

 

Cockpit and cowl are still waiting for their turn to get modified.

VA

 

[Vecchio Austriaco]

A little update about what has happened.

 

I tried to find the best position for the engine - actually it is clear that the main shaft has to be in the center - but the problem were the nylon motor mount parts. Due to the fact that I "lifted" the carburator up it was not easy to find a position where the carburettor was not in the way and I have access to the main needle. finally I found the position.

I also made a test-fit of the cowl, which has been resprayed and the openings are cut in.

I am quite happy with the surface quality  but unfortunately there is a nice difference in colour between the monocote and the cowl.

 

 

 

Here you can see the test fit from the front. I am very happy with the cutting for the valve box, it looks good, but it is too small. (currently bad access to the glow plug)

 

The original parts for the undercarriage are very stable aluminium parts, they are not only stable but also heavy and far avay from the real thing.

 

 

 

Unfortunately I was standing 2 meters in front of the prototype, so I know that the original undercarriage is from carbon fibre and also a kind of half circle shape.

So I looked into the market where I found those.

 

 

 

 

This undercarriage looks much more like the real thing, should be ok for planes up to 3 kg and I saved 50g of weight.

 

Saving weight: As I changed the wing servos I also changed the rudder and elevator servos.

 

 

For the rudder I found a HS85 MG in my collection, for the elevator two HS 81. The HS 81 have plastic gear, but I dont plan to touch the ground with the elevator (you never know...) and also I have some spare gear sets for them as I use them also in other planes.

 

Here you can see for the first time a bottom view of the plane.

 

Next stage will be to finish the cowl openings - which means I have to think about the muffler position.  I have already an idea - I would like to have two outlet tubes in the same position as on the prototype. So far I am not sure if I will purchase a new muffler or if I modify the existing one. In any case I have to make a flex tube extension between engine and muffler.

VA  

Edited By Vecchio Austriaco on 23/02/2010 21:57:07

Edited By Vecchio Austriaco on 23/02/2010 21:59:38

[Vecchio Austriaco]

I didn't find a brass tube with sufficient diameter in my metal collection so I decided to modify the existing silencer. To do so I drilled two wholes at the position where I want the exhaust tubes and cut a 6x0,75 thread in.

The I made the 2 exhaust tubes from aluminium, 46x8mm. One side got 6mm 6x0,75 thread. on the vilible side I drilled a 7mm hole into the aluminium bar, so the remaining wall is 0,5mm. In the thread area I drilled 4.3mm.

 

I made also a test piece to see how flexible my tube is, I am quite satisfied, it can be bent to a very small radius.  The flex tube is silver sodered to the threaded brass flange.

 

The original exhaust tube of the silencer I closed by an aluminium plug, I made the plug conical (0,5° and pressed it into the hole.

 

now the whole thing is assembled.

 

And now Istart to think how to fix the silencer to the firewall or fuselage.

VA

[Vecchio Austriaco]

Now I had a look at the real thing and I see that the distance between the two tubes is too small.

So I will plug one of the holes and move one tube further away. But this is a job for tomorrow.

[Vecchio Austriaco]

After looking at the picture of the real thing I did not only change the distance of the tubes but I changed also their diameter as they where looking much too little with 8mm diameter. I went up to 10mm and now it looks better. Also I prepared the flex tube in the right length.

 

As you can see this time I did not cut the thread 100% vertical, but looking at the prototype I can see that also their tubes are all but straight. So I leave this little error.

The test fit is ok, the problem of how to fix the silencer in this position is still to be decided.

 

But today is flying weather here - so the Extra has to wait a little bit.

 

Edited By Vecchio Austriaco on 27/02/2010 07:19:11

[Vecchio Austriaco]

The flying weather did not last the whole weekend - after a sunny Saturday followed a rainy Sunday. Means a perfect building day.

 

I made support pieces for the silencer from aluminium, even I think it will not be that hot it looks better than wood. Unfortunately the 5mm aluminium sheet pieces I found in my scrap box where very close to pure aluminium - means very soft and hard to cut. I ruined 2 drill bits as they got just stuck in the soft material. But finally I made it.

 

 

Having finished these pieces I saw that I cannot fix them properly to the fusealage as the exhaust tubes will almost disappear in the cowl. So I decided to make a little support panel to put them on in the right place. Installing the support panel to the fuselage was a real pain as I did not have proper access to the screws - I could neiter see them nor use any tool to put the locknuts on. Even for my fingers there was not enough room so I stuck  the locknut on a strong magnet, which I stuck to a piece of  iron and tried to find the screw by "feeling" it. Actually not a bad idea, unfortunately the bolts and nuts of the landing gear were rather close, so the magent prefered to stick himself to those instead to the end of the nut.

 

One hour fiddling for 3 M3 nuts....

After having success I attached the flex tube to the engine, using the right force to get tight connenctions. When I fixed the flex tube to the silencer I broke off both exhaust tubes. As it looks I did not leave enough thickness in the area of the thread. Ok.. All out again, back to the lathe, now I used a bigger thread, 8x0,75mm. Not more than an hour delay and the new tubes are produced. This time I could use more force and did not ruin the tubes.

 

The light grey part is the support panel which is bolted to the fuselage in a 1 hour job.... Now all connections are tight as I don't plan to take the exhaust off again.

 

Finally I cut the necessary openings into the cowl to allow the exhaust tubes to look out and I put all together. And I have to say I am pleased with the effect. Looks like a little Extra.  Yes I know - the prototype has a 3-blade prop - mine is still in the post - so I did put on what I have just to make the photo.

 

 

[Sheldon Holy]

Nice job!

That exhaust looks great. As for the 3 blade prop - i use the Graupner ones, and i use the same dimensions as the 2 blade one. I often over prop engines on models like this, the seem to run better. It'll look brilliant.

 

Sheldon

[Vecchio Austriaco]

Hi Sheldon,

 

I ordered one size smaller as the recommended 2-blade prop. The 2-blade for this engine should be 13x8 - so I ordered 12x8.. And of course I ordered 2- otherwise it will break at the first bad landing.... Murphys law....

By the way  - also I ordered a Graupner one as the nicer props are all starting at bigger sizes.

I will see - if the engine revs are too high I will order a bigger one. But this will take time as I am far away from having finished the model (dosn't matter - i like building... )

VA

Edited By Vecchio Austriaco on 28/02/2010 20:44:25

[Stephen Grigg]

Coming on very nicely Vecchio,like the way you tackled the Exhaust

[Vecchio Austriaco]

This evening I installed the fuel tank where I allowed myself to put in a 2-way filling valve which reduces fiddling with tubes to one only (overflow tube needs to be opened during filling). Also I made a needle extension, just using a small hex key. This has the advantage that it is proper steel and because of its hex form it cannot slip when it is clamped to the original needle.

 

After that I didn't want to start something serious now as I will travel for the rest of the week so I just took out my wifes kitchen scales to check the weight of my bird. And now I am a little bit unhappy. It showed me 2800g (battery, canopy and lower wing cover added) and according to the instructions it should be 2500g. Somebody may say this is due to my exhaust extension, but this gives me only 50g plus in comparison to the original set-up. The engine -yes - I use a 91 instead of the 60 - but if I look into the OS data and the data of my magnum the weight difference is only 30g.

 

Also - you may have noticed higher up in my blog I use small servos - alone from this fact I should save 170g. And I have changed the landing gear from aluminium to carbon - should save 50g. So may be the weight written on the instructions was somehow the whish of the designer but not the reality.

 

Hope our landing strip is long enough to bring that heavy turkey to a halt in time....

 

Checked with my sons Angel 50 which has the same wingspan, it weighs 2900g. So in the end the difference is not so big as I thought.

 

I also checked the COG for the first time.

 

The plane is front heavy, this comes from the 4-stroke engine. If I put the battery as far back as possible - in the picture I just put it into the canopy - it should be ok to balance it without extra lead. Not to forget that I think also of a pilot - this guy may help a bit. But I think in the end together with the fuel I will be at 3000g.

VA

[Sheldon Holy]

Hmm. you may want to go down in pitch, and up in diameter to a 14/6 Graupner 3 blader as the 12/8 will mean it'll be slooting around the sky, lots of torque reaction when you throttle up, it'll only want to fly fast with that prop.

 

Sheldon

[Vecchio Austriaco]

Bach to work again - but the next trip will start on Monday and delay the work again.

 

I finished the throttle servo connection and sprayed the second colour at the cowl. The white lines I plannned to do like on the rest od the plane - with white adhesive oracover.

 

On the picture you can see also the hole for the needdle and the fuel valve.

I sprayed also the landing gear and the wheel covers, My son did not agree at all that I sprayed the carbon parts as he said you could see the carbon structure also on the prototype.

Looking at my photo collection I could not see any carbon so I sprayed it blue like the cowl.

Also the 3-blade prop and the spinner arrived in the meantime, the spinner is a nice piece made from aluminium, but he he will not help to get the plane lighter as I have the feeling it is rather heavy.

 

The front view looks good and I am rather happy with my progress.

 

Next step will be the glow plug extension - I think I am old enough not to fiddle around at the bottom of the plane to find the position to plug in the glow plug heater - so I invested into a glow plug extension. Found one at Lindinger.at, for 4,90 €. You get 2 different glow plug adapters (different diameters), the extension cable with a mass connection and the glow plug connection on one side and a coax socket on the other side. A second cable contains the coax plug and croco clamps to connect to the glow battery.

I will install it tomorrow.

VA

 

Edited By Vecchio Austriaco on 11/03/2010 22:28:28

[Sheldon Holy]

Lwts hope it flies as well as it looks good!

 

It'll be amazing then

[Dusty]

Very neat  job! Well done... Will look even better in the air