Another Ozzie Extreme Composites 40% Extra 260 Build

[b0Bro's dad]

Thanks Matt,

My basement looks kind of empty without the beast but it does now give me a couple of weeks to start work on building a plate for the engine and working out how I'll arrange the ignition/headers/throttle/batteries etc on the cone/firewall. I'm also fast coming to the conclusion that the best way to reinforce the undercarriage is to make the carbon plate a 'H' peice (in plan view) and install mountings for another four "up facing" bolts on the fuselage each side of the existing girder. That should spread the vertical load to three bolts on each side and provide a wider, more secure base to resist the torsional loads for the least cost in increase to overall weight. Your thoughts??

Cheers,
Ian

[excelpoint]

That sounds like it would work fine. Maybe a little overengineered but should work. Just remember that if and when he does pop the gear plate it may cause a fair bit more structual damage that way. If you just glass or carbon the plates in then it ill take most impacts but still pull away fairly nicely on a large impact.

[b0Bro's dad]

Matt,

I was intending to do some local glass reinforcing of the girder as well but I was trying to think of ways around cutting holes in the fuselage under a high stress point. I might be able to cut some holes in the frame and get under the girder that way, but it would be extremely hard to do a decent glass reinforcing job between the girder and the fuselage side that way. What I intend do using a wider carbon 'sandwich plate' is to extend the glass cloth reinforcing from the outside of the girder frame to new blind nut mountings I'll glass onto the fuselage side immediately in front of and behind the girder frame, making a much wider load bearing attachment. Of course the problem is, as you correctly point out, that it might just make a smash that much harder to repair. What I really want is to get the whole undercarriage mounting strong enough to ensure that the (easily replacable) undercarriage legs fail before the mounting. Without some detailed crash tests, it will probably take a judgement call on how much is enough here.
Thanks,
Ian

[excelpoint]

Sounds like your heading in the right direction. As you said its a judgement call on how much is enough. As they say " there are many ways to skin a cat"

[b0Bro']

LoL, where is the confidence in my landings! You both are assuming i will rip the guts out of her...

Dad, im confused what scheme you have chosen. The red bull plane looks really nice but has no red. Your star burst scheme has no yellow??

[b0Bro's dad]

Byron,

First of all, happy birthday and I hope that you and Natalie get to celebrate it in style. Lots of nice thoughts inbound.
On the other matter, I thought that you would have picked up on the 'prefered' and 'alternate' titles on the attached photos but, on reflection, I can see why you are confused. To clarify, the scheme being painted (actually as I type these words - I've just spoken to them) is the red and white 'starburst' pattern with one very big change. I have asked Colide-a-Scope to paint the underside of the wings and stabs yellow with black 'invasion' stripes in the same general arrangement as the attached pinch from the Xtreme Composites house scheme #2 (replace the red with black). The yellow from the house scheme will NOT go on the fuselage which will remain true to the scale white/red/black scheme shown in the photos.
An interesting aside to all that research was finding some photos of the original Extra 330 that your yellow 'Breitling' scheme was based on. I've posted them here to show how the semi-scale model can actually look better than the original.

Ian

[b0Bro']

Thanx Dad, have had an awsome birthday. Everyone has being buying me drinks all night so really ready for bed now.

I think Mick did the scheme on my extra 330L, if so he did a good job.

I look forward to seeing how the paint turns out opn the 260..

[b0Bro's dad]

Guys, after considering all of your very useful comments on the matter of strengthening the undercarriage attachment, I've come up with a plan that I'd value your thoughts on before I get too carried away. Essentially, my problem is that Xtreme Composites have put the attachment girder frame upside down from the point of view of spreading the landing loads and making it easy to reinforce. I don't want to cut a hole in the fuselage which leaves going in through the back of frame (the firewall restricts access to the front) as the only practical option for getting under the girder to strengthen the fuselage attachment points. There isn't much room on the frame so I'm thinking Step 1 is to drill 2 x 12mm holes, one each side, and use a paper funnel to pour a small amount of epoxy/ground glass 'slurry' into one side at a time and let gravity form a fillet at the fuselage/girder attachment. When I've done both sides that way, Step 2 is to use expox/glass cloth to reinforce the outside if the frame where it holds the girder and attaches to the fuselage, and to seal up the access holes I cut into the frame in Step 1. Step 3 is to make a top plate from 2mm carbon and file down the top of the frame so that the plate sits flush on top of the undercarriage legs. Then, rather than bolt the plate to new mountings, I'll permantly glass the plate onto the frame and fuselage sides, effectively making a fully reinforced carbon 'tube' for the undercarriage legs to slide into. This should arrangement should transfer most of the load from the bottom plate to the top plate which will now be properly tied to both the frame and the fuselage. A plus for this system should also be to prevent the undercarriage legs from flexing aginst the attachment bolts leading to 'crushing' damage to the fuselage as long as, that is. I properly glass the the top plate to the frame. It should also be reasonably light and easy to install.
All comments welcome.
Thanks,
Ian

[b0Bro's dad]

After a very busy period where work and family commitments took priority over building Byron's Extra, I finally got back into my workshop to do the fuel tank.

Unfortunately, the model is still at the paint shop and (you were right Glenn) they think they might need to revise their quote . Still, it looks like I'll get a quality paint job when they finally get around to finishing it. The carbon wing joiners from PCB Composites in NZ, and the 14 x Hitec 5955TG servos from Precision aerobatics all arrived this week. Hopefully, that's it now for the bits on backorder and my credit card can have a bit of rest

Building the fuel tank assembly. First up was sorting out the plywood bits that came with the kit and cleaning them up with the face sander, chisel and flat file so they all fitted snuggly for a dry assemble. This took only a little bit of work with the tongue and slots and nothing to worry about. Next job was to laminate the two undertray frames which was easily done with epoxy and weights to get a good bond and keep the frames straight while the expoxy cured overnight. Then it was superglue to hold the bits in place and more epoxy to build the tray. When the epoxy was dry, I glued the tray onto to the frames with more epoxy. After the tray assembly was dry, I mixed some epoxy/micro-balloons and used my finger to build up a fillet along all the joints and fill some gaps where the slots where too big for their tongues. All dry and an all over sand and tidy up. The only word of caution with this assembly is be patient as the tray will warp if it isn't built 'flat'. I can definitely recommend doing it in stages.
At this point, I noticed that the 4mm holes in the undertray frames for the cable ties didn't line up with the 4mm slots in the tray sides. This didn't worry me as I had already decided to use 20mm velcro straps instead of cable ties to secure the tank and I had to widen the slots with a chisel and flat file anyway. Hopefully you can see what I mean from the photos. After that, it was an all-over fuel proof with thinned epoxy (just warm it up by putting the mixing jar in hot water).
While that the fuel proofing was drying, I assembled the 50oz Dubro fuel tank according to instructions and making sure that I used the 'gas' components. The only tricky bit was soldering fine wire 'retaining rings' at the ends of the brass tubes. I did this by making two turns of fine copper wire around each tube, cleaning the lot with bakers soldering solution and using a hot iron to 'run' the solder around the joint. I used side cutters to trim off the wire ends and a file to remove the sharp corners. After doing one end of each tube, the brass tubes were all pushed through the stopper assembly and the whole exercise was repeated to put rings on the other ends of the brass tubes.
Getting the Tygon fuel tube over the rings was a pain in #$%&*% but perserverence won in the end. I used 2mm cable ties to hold the Tygon on the brass tubes behind the rings and the clunk. I inserted the assembly into the tank, making sure that the vents sat flush against the top of the tank (I cut v notch in the ends of the Tygon), and that the clunk moved freely and couldn't catch on anything. Tighten the stopper screw and the tank was done.
The only job left was to glue some 3mm foam rubber into the tray to absorb some of the vibration and cut the velcro straps to length. That was it, and fuel tank assembly all done.

[The Hobbyman]

Dont be too harsh on em Ian, it is a BIG job to paint one properly, rest of the build is looking good!

[b0Bro']

looks good dad, I see you decided to go with the three fuel lines in the end. Such a pain in the arse to set up but worth it.

Cant wait to see the paint job, hopefully they havnt revised the quote to much

[RTK]

	Quote: Originally Posted by b0Bro's dad
	Step 1 is to drill 2 x 12mm holes, one each side, and use a paper funnel to pour a small amount of epoxy/ground glass 'slurry' into one side at a time and let gravity form a fillet at the fuselage/girder attachment. When I've done both sides that way, All comments welcome. Thanks, Ian

I doubt the epoxy will stick, there really is no way of getting into that area to sand and clean it. Doing the outside area will work fine.
As long as you don't hit any gopher holes or slam it into the ground you should be fine with out any mods.