Another Ozzie Extreme Composites 40% Extra 260 Build

[b0Bro's dad]

Tikka,

It's good to hear from you again. How's the weather up north, we're just coming into our summer flying season in Australia. I'm glad to see that you are still flying your Extra 260. Byron and I followed your build and I know that it got Byron interested in the X-treme Composites version. Thanks for your tips, they all help. It sounds like I need to go shopping for some 1.5 mm bearings and change the rudder pin over to carbon.

Cheers,
Ian

[b0Bro's dad]

I felt like fiddling today although it was all to a good purpose. I'm working up to the job of fixing the canopy into the canopy frame which I suspect isn't going to be as easy as it sounds. Of course I going to complicate the process by fitting an instrument panel which will need to installed after the canopy. Although there is plenty of room underneath the canopy frame, the 25mm flanges mean that I can't prefabricate a complete panel/coaming assembly. Instead, I'll need to make the parts individually and only glue them together when I've fitted them inside the frame. That means that I need to have the parts cut to the templates I made last week and dry fitted before I can fit the canopy.
I wanted a scale panel without being stupid about it but there isn't anything commercially available in 40% scale. No problem, I'd could build my own. I started by downloading the Extra 300 panel template from Extra Aircraft and scaled the image by trial and error before printing a 40% scale template showing the instrument panel layout. I then searched the net for aircraft instrument/guage/parts suppliers to find good images of the various instruments I'd need (it took a bit of seaching to find some of the engine guages). I did some quick calculations to work out the correct 40% scale dimensions for standard 3-3/8 in and 2-1/4 in guages and re-sized the images to scale before printing them onto photographic paper with a colour ink-jet printer. I individually cut each instrument from the sheet and layed them out over the template. I was pretty chuffed to find the images were correct scale for the template so my figuring must have been OK .
The next step was to transfer the template onto a sheet of feather light art board which I had sprayed light grey for contrast. Cutting the art board was pretty easy with a fine tenon saw and I finished to exact size using the face sander and a sanding board for the inside corners. I used art glue and a ruler to carefully fix each cut-out instrument in it's proper place. I then added a few micro-switches and circuit breakers from Dick Smith for effect. I made the main knobs from a carbon/aluminium arrow shaft with a carbon rod inner (gives a nice aliminium ring around the top) and cut the top off a Dick Smith plastic knob for the magneto. The finer ones were made from Nyrod inner filled with a toothpick and painted black. The knobs were all glued over the photo with a small dab of super glue. The finished product looks really good and weighs bugger all.
I have attached the photo sheets of the instruments correctly scaled to 40% just in case anyone else wants to spruce up their model, as well as the build photos.

[b0Bro']

Wow dad, that came out alot better than i was expecting! I like very much!

[Devo]

man that is a nice job....hey bobro you should take it to a scale rally....it will win first prize....excellent job...your dads a excellent builder

[b0Bro']

lol, i might have more of a chance winning a scale rally if i dont have to fly :S

[b0Bro's dad]

Another fiddly weekend working on the cockpit area. After a bit more thought, and with the help of some more cardboard templates, I decided that it would be too hard to fit the instrument panel AFTER the canopy was glued to it's frame. The main problem I would have would be the almost impossible task of stretching the coaming securely onto the upper side of the instrument panel and holding it in place inside the canopy while the glue dried. Although doing it first will make securing the canopy a bit more tricky, I needed to fit the instrument panel BEFORE I fitted the canopy.

I still couldn't prefabricate the whole instrument panel and coaming as one assembly because I wouldn't be able to fit it inside the canopy frame because of the flanges and the way the cockpit sides angle in towards the rear. I therefore started by making a 'frame' to hold the instrument panel coaming in the correct shape while still providing a gap around the inside of the frame for the later fitting of the canopy. I traced the curve from the top of the instrument panel on to a sheet of feather light art board, making the sides wider to fit the canopy frame at a point just clear of the fuel tank. I went through three prototype frames (art board is relatively cheap) before I got the shape of the top just right. I found that it needed to be slightly rounder at the edges and flatter at the top to get the required single axis curve on the coaming which is very slightly conical.

When I had the frames right, I used art paper to cut a template for the coaming which I made from 1 mm aircraft ply, steamed to the correct curve over a pot of boiling water. In the process, I discovered that a pair of large spring claps were just the thing to grip the thin ply and avoid scalding myself in the process. When I had the coaming holding the correct shope, I glued the centre frame to the coaming with slow set epoxy using lots of rubber bands and pins to hold the coaming stretched tight over the frame while it set. Although the pins etc were doing their bit, I found that I also needed to use a large furniture cramp to pull the sides in and stop the thin ply from warping around the frame. I left the whole assembly overnight to cure before spay painting the top of the coaming the same light grey as the instrument panel.

With a bit of gentle coaxing, the coaming assembly was fitted in place and mated with the instrument panel in situ. When I was satisfied with the fit, I glued the instrument panel to the coaming assembly with more epoxy and pins, although this time the sides of the coaming were jammed between the instrument panel and the canopy frame and didn't need to be clamped. That was it as I won't glue the assembly to the frame until I've fitted the canopy. The limited freedom of movement fore and aft might be useful. The pics are attached.

[b0Bro's dad]

Shortly after I started this project, I purchased a 40% "Blue Bob" from Lite Pilots but he always looked a bit small in the cavanous cockpit. I kept looking and eventually found another 'acceptable' 40% Masters Life-Like scale pilot bust from H.P. pilot which promissed to be a bit bigger. When the bust eventually arrived courtesy of an extremely slow US Postal Service, I found that the Life-Like bust had a 'fatter' face but otherwise was pretty much the same size as Bob. The bust moulding was also a bit 'cruder' with less crisp detail and 'moulded' sunnies which I detest. With a bit of work, however, I thought he might be OK, and I had an old pair of Ray-Bans I could easily cut down to scale.

I started by using the permabit drum on the dremal to grind away the offending sun glasses and tidy up the detail. The moulding got a bit thin around his eyes so I filled the inside of his face with a thick epoxy/micro-balloons mix and let it dry over night. In the morning, I used the dremal to sculp some eye sockets and sanded the whole lot smooth before painting. Although all this worked out pretty well, and before I went to work on the Ray Bans, I decided that Bob would still be a better choice. Paticularly as the instrument panel now made the cockpit space seem less 'empty'.

Bob also needed some work. I started by grinding out the 'flash' and fitting two 3 mm ply plates to hold the blind nuts I will use the secure him in place. Although Bob doesn't weigh much, 20 g could still do some damage. I also found that Bob needed a booster cusion which I cut from a peice of 25mm styrene foam, painted to match his shirt. I cut the mounting plate from featherlight art board which I painted black. I wont secure Bob in place, however, until after I have fitted the canopy.

The Life-Like bust is available to anyone who can find him a good home for the cost of postage (you'll have to make your own sunnies). Pics attached.

[b0Bro's dad]

After a weekend sailing and taking Rebecca (18) Christmas shopping, I was hoping that fitting the new canopy was going to be relatively simple but no such luck.
I started by constructing a temporary 'gantry' from two chairs and taped stiff aluminium rods/angle to created some secure attachment points aligned with the edges and top centreline of the canopy. I intended to use clear packing tape to create 'handles' on the outside of the canopy and use light bungey cord to connect the 'handles' to the 'gantry' and hold the canopy firmly in the canopy frame. I could then gently push the canopy away from the frame and run a bead of Pacer Formula 560 Canopy Glue between the canopy and the frame and hold it with the bungey while it dried. The nice thing about this fixing method is that, because the frame is mounted on the fuselage, the canopy won't end up inducing any unwanted warps or twists in the canopy.
I cleaned off the work bench and laid down some bubble wrap to prevent any scratches. Then, I covered the old opaque canopy with Glad Wrap and seated the old canopy inside the new tinted canopy to mark the cut lines with a felt tip marker. It was a warm day and I didn't have any problems cutting along the outline using heavy scissors, starting a little bit wide and trimming to fit. All pretty simple, except I managed to drop the canopy off the bench (about 800 mm) and it split end to end!! Clearly the tint, or the unleaded petrol I had used to clean the canopy for tinting, three and a half months earlier had made the plastic very brittle. Just to be sure it wasn't a one in a million fluke, I stuck my thumb through a bit of the discard material and it just shattered (see photos). I also tried to break/tear an old canopy I had used as the original test application for the tint and remained as flexible as the day it was made. Even so, I'll be very wary about using VHT 'Smoke' SP-171 to tint my canopy's from here on in.
The good news is that the Hobbyman has spare canopies in stock for immediate delivery. Hopefully, I'll have better luck with canopy number 3.

[b0Bro's dad]

The silly season makes it tough to find time for building but, with Byron up for the weekend (allegedly to oversee my work!!), I finally got back to working on the beast. We started by doing a wiring plan and full centre of gravity calculation listing the weight and moment of the airframe and all of the componants. We aimed to get the CG on the centre of the wing tube which appears to be almost impossible with 4 servos in the tail unless we move the engine forward another 30mm, which I wasn't prepared to do, or add 370 g ballast. After talking to a few people who have flown this plane successfully with 1 X hitec 5955TG in each tailplane half and 2 x Hitec 5955TG in each wing, and getting all sorts of assurance that Byron will NEVER try and 3D this model, we decided to start by saving the weight (we can always put in the extra servos if find we need them).
With that decision made, we found that we could mount the Emcotec DPSI 2001 RV power expander in the cockpit just behind the wing tube and far enough under the back of the fuel tank mount to easily plug in the RX/servo leads. We started by making a paper template which we transferred onto 3 mm birch ply. We cut the ply to shape with a tenon saw and finished with the face sander. We glued two 12 mm square balsa spacers to the edges of the mount and used a hole saw to cut two cooling holes under the centre of the power expander, and two more holes on each side for the wires. We needed to shape the front of the spacers with a round file to fit neatly against the wing tube and protect the edges of the wiring holes with grommets or fuel tube. The power expander was mounted above the mounting plate on 7 mm silicon fuel tube "spacers" slipped over nylon bolts and held together with nylock nuts. We glued some pads and loose fitted some 2 mm cable ties under the mounting plate (to make the wiring easier later) and epoxied and clamped the plate in position under the fuselage side frames with the front edge hard against the wing tube.
Job well done.

[b0Bro']

Finaly it was my turn to have some input to build. Only on my first day here we spent most of the time arguing about where stuff was going rather than any actual building. I wanted everything up front of the wing tube but Dad assures me that he has calculated the CG to be spot on and we can afford to have things more aft. Never the less I had to give in, after all he is funding the project. I dont think he will let me move the engine forward until the test flights prove it.

So while Dad was busy making the tray for our power expander I set to work on putting the servos into the tail stabs. After fiddling around for a while I found out that the servo cut out was too small. That was an easy fix with sand paper glued onto a long right angle aluminum rod. Fitting the servo was very frustrating because it had no hatch and was very difficult to get into the area. However with some home made tools I finaly got the servo into place and set to sticking the swb arm through the gap and screwed on with our home made long screw driver. Only now I find out that the arm is sitting up againts the gap and not centred.

Take two - once I got the servo we had to pad it out with 3mm strips of ply. I measured this would put the arm bang on centre. And it did thank god!! Once I had the swb arm screwed back in it was a little tricky screwing up the bolt on the back. Dad custom built a long spanner for me that I could stick down the stab and onto the bolt. I was able to get a small allan key in through the gap and tighten her up. Job done.

Also, Mental note to self: Measure every servo arm in the gap, because I just assumed the other stab would be the same. I quickly found out that I didn't need to pad out the servo on stab two... it only put the servo arm up against the other side of the gap ghrrrrr, was messy getting them out again.

[b0Bro']

Adding the servos into the wings was alot easier to my relief and mostly because of the easy access via the hatches. As I predicted the servo cut outs were too small and needed some sanding, the same as the stabs. A tad back-breaking as I was constantly bending over the wing.

After learning my lesson with the stabs, I measured where the servo arms would stick out the bottom of the wing and made sure everything was on-centre. I found that both servos needed to be padded out, one more than the other. I should also mention that we are only going to use two 5955tg on each aileron.

Screwing the servos in was alot easier than I thought it would be. Mostly because we used an awsome little screwdriver / ratched that Dad picked up from Jcar electronics. It let me get the all important 90 degree bend down the hatch and onto the screw heads.

[w1dry]

Hi there. I too have a 42% Extreme Extra 260 that I am putting together. I wonder have you done your equipment install and if so could you take some pictures of the layout and installation of matchboxes etc for the rudder and ailerons. Also could you describe how you put the servo wiring in to the back of the plane. Also did you use a Pull Pull system on the rudder or did you mount the servos to the rear of the plane?

I am following you suggestions to a tee and they are all just super. I thoroughly enjoyed reading your article. I currently am putting the cowling together with the ply strip on the bolt line. The landing gear are in and I have one servo in one of the elevators.

Also how did you screw in the aluminum tubes for the elevator? Did you replace the aluminum tube with Carbon Fibre? How about the wing tube? It is pretty heavy! Well carbon fibre work or is it too weak for the spar?

I plan to use a Kroma 180 for power plant with just mufflers. I want to keep it simple.

Any additional detail in construction would be greatfully appreciated.

Best regards,

Michael Wyman
AMA L-777
IMAC 777