Another Ozzie Extreme Composites 40% Extra 260 Build

[b0Bro's dad]

Well guys, I finally got around to starting the build thread for Byron's new Xtreme Compostes 40% Extra 260. As with all things giant, we started with a very large and expensive box being delivered to Byron in Melbourne. The only problem is that Byron was just about to head overseas for five months holiday with his girlfriend leaving me, his dad, to build the beast ready for his return to Oz in November. I live in Sydney and the box was too big for the postman! We ended up paying a lot more money to get the model trucked up to Sydney where it was finally unpacked in my basement. First impressions were centred on the excellent build quality and coming to terms with the sheer size of the beast. My 23% Cap 21 and 3m gliders looked like toys next to it! We checked all the bits out of the box and were reasurred to find no damage and all the bits included extra aileron hinges that test flying has shown to be necessary. A full set of hardware was in included, individually bagged and labled for each application (eg. cockpit) but the quality of some of the smaller bits wasn't up there with the quality of the molding and I expect I'll need to replace most of the hardware. The wing joiner is a very robust and heavy peice of aluminium which I'll also need to replace with carbon joiners at some point. Given the price of the model at the top end of the premium market, I frankly expected better on the hardware front.
An unexpected bonus out of the box was, however, a full set of covers for wings, fuselage, stabs, rudder and joiner tubes. These almost made up for the hardware!
The honeymoon photos are attached.

[b0Bro's dad]

Before Byron left for his overseas trip, we sat down together and created his 'wish list' for the bits that didn't come with the kit or needed to be replaced. The full list is attached for those that are interested. We also got me signed up to the forum and walked through Tika's build thread and Tony's build photos. I have found these two sourses to be invaluable so thanks Tinka and Tony if you get to read this. By now, another major omission from the kit had become very obvious; it didn't come with a builders manual. I have got around this to some extent by downloading the manuals for the Xtreme Composites 33% Edge 540 and the Composite ARF 40% Extra 260. Together, these manuals gave me enough good advice to proceed with some confidence although I have already found that there isn't any real subsitute to long and earnest thought before reaching for the drill and saw. This isn't a model for the beginner and, as a pilot of full size aircraft, I understand what 20/25 g will do to any sub-standard building. Another major decision at this point was to purchase West Systems epoxy resin and ground glass reinforcing powder. In my experience 30 min/3 hr epoxy just isn't strong enough. I also lashed out on a Dremal tool and built a build table from two saw horses with plywood top covered by 8mm rubber mat. This has been one of my better decisions as it puts the model at a nice height for building, gives me all round access and protects the finish.
Photos attached.

[excelpoint]

Good start so far Ian. If there is anything I can help ya with just give me a yell.
Matt.

[b0Bro's dad]

Finally time to stop procasternating and start building. I had finished the repairs to one of my gliders that Byron had decided to land vertically in the trees (I hope he flys IMAC better than that) and had run out of excuses.
I thought I would start with fitting the undercarriage as an easy first step. I followed the Xtreme Composites 33% Edge 540 methodology (same manufacturer) of first making a paper template and using masking tape to tranfer the measurement onto the undercarriage legs. After double checking my measurements, I centre punched the marks and used my drill press to drill the four 5mm holes all nice and straight. The problem that became immediately obvious is that Xtreme Composites hadn't been quite so fussy when they installed the blind nuts which I now discovered weren't all quite on centreline or installed exactly vertical. Half a milimeter doesn't sound like much but it was enough to stop the bolt threads from starting. A bit of work with a small round file soon had it fixed but now two of the holes were elongated and allowed the leg to 'play'. Feeling distincly pissed off at this point, I decided to 'do it right' and filled the offending holes with high strength epoxy/ground glass and left if for 24 hrs to cure properly. I sanded the plugs back to level, remarked and drilled the holes in the right place. No more problem!
I now have to wait for 2mm carbon plate to arrive from Aerospace Composites http://www.acp-composites.com/ACP-CAT.HTM as the plate provided by Precision Aerobitics is too small. The reinforcing plate will spread the load evenly across the four bolts which might be a good thing as the whole attachment looks a bit on the fragile side (Byron had better practice his landings!)

[b0Bro's dad]

**** Matt, that was quick! I'm still writing cowling, undercarrige and canopy stuff.

[excelpoint]

Good Idea with the carbon plate Ian. I had an aluminium plate on the Giles. The Comp ARF 260 I just finished has the undercarrige mounted underneath the plate which helps a bit. Does the extreme do the same?

[b0Bro's dad]

Next step was fitting the engine cowling that comes in two peices; a top and a bottom peice. The kit came with 10 x 3mm cap head bolts and blind nuts and 8 x small bullet head wood screws. I didn't like the thought of what all that vibration would do to wood screws and the cap heads didn't look 'right' so I headed down to Witworth marine (I sail a 505 dinghy when I can get Byron and his brother away from girls/aeroplanes) for 2 dozen bullet head 3mm x 12mm bolts. Next was a trial fit using tape to hold the whole thing in place but this wasn't too sucessful as the cowling moldings naturally want to 'spring' apart. I did get it in place long enough to note that the back face of the cowling (where it attaches to the fuselage) wasn't absolutely true. I was a bit wary after my experience with the undercarriage so I decided to fit the top half to the fuselage first and then 'adjust' the bottom half to fit. It sounded like a good plan but it ended up not being one of my better decisions! The top half went on easily but when, I tried to fit the bottom half, it was obvious that the whole cowling assembly was pointing slightly high. When I pulled the top down to mate with the bottom, I got some buckling along the join seam (see photos).
Back to the drawing board. It was clear now that the problem was the back face and a much better way of tackling the whole thing was to first join the top and bottom peices before lining the assembled cowling up on the fuselage. I also decided to fit a 12mm wide strip of 3mm birch plywood inside the lower cowling to stiffen the join and provide a base for the joining bolts. This process worked much better although I discovered the need to join one whole seam before doing the other side and only then to align the front bolts. It was a slow job fitting a couple of bolts at a time and removing the cowling again to drill on a firm base but it was worth it. Again, I found that using a peice of masking tale to mark the centre worked well and stopped the drill bit from wandering on the hard surface fibreglass. Doing this in the right order was much easier. After that it was a simple job with a sanding block to true off the back face and trial fit the whole cowing onto the fuselage. Next was the fiddly job to epoxy all of the nuts in place and let them dry. I used five Nylock nuts in strategic locations to ensure that, even if the rest of the nuts vibrated out, the cowing would not come adrift in flight. I ended up having to re-glue a couple of nuts where I had also inadvertantly glued the bolt to the nut (!!!) but it all worked out well in the end.

[b0Bro's dad]

Matt,

The Xtreme Composites has a built up carbon 'girder frame' built into the bottom of the fuselage which has the blind nuts already fitted. The undercarriage legs bolt onto to this frame from the top and I'll fit the carbon plate across the top of the legs making a sandwich. I think that I will still have to reinforce the undercarriage frame for torsion loads by fitting two or three 3mm ply 'joiners' between the firewall and the undercarriage.

[excelpoint]

Thats exactly the same as my 260 except that the legs mount from underneath. After having a few composite planes(7 between me and Dad) with that setup i would highly suggest laying some carbon or glass cloth over the joins and onto the fuse. After you have fixed a few you start to realize what they need. I found with the legs mounted on top if you have a bit of a hard landing the weight of the plane pulling up on the blind nuts from the top always split the mounting plate because you are only pulling up on 4 points(blind nuts). The Carbon plate would help that. On my Giles I ended up cutting an access hatch above the plate from the underside of the fuse and glassing the whole plate in with 1200g of chopped strand mat. I left the hatch as an inspection point. I swore that if i ever had another Composite plane that mounted the gear on top I would cut a hatch straight up.

[excelpoint]

Another thing to do Ian is to allow about a 3-5mm gap between the leg and where it enters the fuse. The legs will flex a fair bit on a not so good landing and damage the fuse if you dont. May not look as nice as a tight fit but looks a lot better then a squashed fuse side.

[b0Bro's dad]

The cockpit frame is a light molding that deforms very easily and is hard to work with. I started by deciding that I would use four bayonet fittings to align the sides with the fuselage and two 5mm carbon pins to hold down the top front. I also decided to ditch the supplied 3mm x 12mm cap head bolts and use 4 x Dubro 4mm nylon wing bolts to hold down the canopy. I figured that the canopy will be on and off a lot and the wing bolts give better purchase and are harder to loose than the tiny cap heads. After having another read of Tinkas's thread, I started by using epoxy/ground glass to fill the fuselage behind where the pins will go. This will provide a good bearing surface and hopefully prevent the carbon pins from making the holes bigger as vibration does it's thing over time. Next up, I epoxied a strip of 3mm x 12mm birch across the top of each supplied T peice bayonet to space the bayonet in from the fuselage side. I then marked the slots on the canopy frame and cut them out by using a 3mm drill at each end and a dremal, finishing and trial fitting as I went with a flat rat file. Next up was making and fitting the two pins from 5mm carbon rod. I cut the pins to length with the dremal and finished them with the face sander. I also used the face sander to make a flat in the end of each pin for gluing it to the canopy frame. The angle here was quite critical as the frame/fuselage interface is about 45 degrees from vertical and I needed to give enough angle to be able to slide the frame onto the pins while still being flat enough to prevent the front of the canopy frame from rising under air loads (a whole lot of lift in that canopy). Drilling the frame at an angle for the pins took some patience but I made it easier by making a jig from a peice of hardwood and drilling against that. Again the masking tape was used to mark the centres and stop the drill bit from wandering. I next epoxied the four bayonets and two pins into the canopy frame and set it all aside to cure.
After it was dry, I used the frame and a steel ruler to acurately measure the slots on the fuselage. These were drilled and cut out with the dremal as for the frame except a word of warning; I was very careful to make sure I didn't have my eyes on the same plane as the dremal cutting tool and just as well. It shattered without warning and sent sharp bits zinging past my head!!! The slots were carefully enlarged with the rat file to ensure a perfect fit between the frame and the fuselage. This wasn't quite as easy as it sounds because the pins at the front meant that I couldn't sit the frame properly into the fuselage and I couldn't drill the fuselage for the pins until I had slotted the fuselage for the bayonets. In retrospect, it would have been easier to fit the bayonets first and do the pins later but it worked out all right the way I did it.
After elongating the slots to take the rotation around the pins required to assemble the canopy to the frame (12mm at the front bayonets and 6mm at the rear), I was ready to mark and drill the fuselage for the two pins. After very carefully marking the fuselage, I used a 3mm drill aligned at the correct angle to make pilot holes and gently and very carefully used a round file to enlarge the pilot holes to get the perfect fit.
Last job was to make scabard fittings to take the canopy bayonets. I made these from hard 3mm balsa on the inside (against the fuselage), 3mm x 12 mm birch spacers, and 3mm birch ply on the outside, being careful to leave enough room for the rotation. I used the face sander to trim the balsa insides to get a perfect fit and the right angle against the fuselage and, when I was happy with the fit, epoxied the scabards into the fuselage. I used some scap 3mm balsa and rubber bands to hold the scabards against the fuselage while the epoxy cured (see photo). When dry, I temp fitted the frame with masking tape and marked the bolt holes on the outside fuselage sides and drilled a 4mm hole through the fuselage, bayonet and scabard in one operation. I then fitted bolts and epoxied the blind nuts to the inside of the scabards. I was very happy with the way this bit turned out.

[b0Bro's dad]

Matt, that sounds like good advice all round. Thanks.