Aeroworks 42% QB 260 on a diet

[bodywerks]

Those of you who know me know that I am a stickler for weight, and it appears that I will be no different with this plane.
The plane is the Aeroworks 42% Extra 260, and we are already familiar with what type of plane Aeroworks offers, as well as how they fly, etc., so I won't really go into a detailed "review" type build. Instead, I just want to show some of the things I do to drop a little weight off my planes.
For this plane, I am not as concerned about wing loading as I am pure thrust to weight. The plane has plenty of wing to nicely support 42-44 pounds, but at that weight, vertical becomes a little limited, especially in the upper classes of IMAC and in windy conditions, and in density altitudes above 5,000 feet. I have heard of this plane built as light as 37 pounds (claimed weight, on stock mufflers) and as heavy as 42.5-43 pounds(cans and full equipment), so I really don't know where I will end up at this point, but I will be satisfied with anything under 40 pounds.
Engine will be the proven DA 150. I was going to wait for the 170, but the 150 has been working well up to now, and it is a powerhouse on Greves, so that will be my powerplant.

[bodywerks]

Let's take a look at the gear to shave some weight. Interestingly, Aeroworks provides CF wing and stab tubes as well as tailwheel in this kit, but the stock gear is aluminum, and replacing it with CF is going to be one of my biggest weight savers. What I did here is a mock up of the gear, cuffs, gear cover, and axles on the stock setup and weighed it. You can see in the pic that this came out to 1 lb., 12.1 oz. If one were to purchase the CF gear and simply bolt it on, it would result in about a 8.5 ounce savings. I took it a few steps further by shaving even more material off the CF gear, installing PSPmfg. titanium axles, taking a dremel to the gear cover, and not even installing the gear cuffs. You can see in the pics the total weight - a 12.4 ounces savings overall! This alone will be one of my biggest weight loss numbers of the whole shibang.
I am leaving the wheel pants alone, and I opted to use the stock wheels that came with the kit, as they are pretty light already, at only 2.75 ounces each. TBM has wheels that would save another 2 ounces...

[bodywerks]

Now on to the hatch. Unfortunately, probably over half of the hatch weight comes from the super thick canopy, and there's no real way to lighten that without redoing the whole hatch. The canopy alone probably accounts for about half the total weight of the hatch. Still, there were places to remove some excess lumber, and I did just that. I only dropped a little over 4 ounces, but it still contributes to the big picture - in just two areas on the plane, I have now dropped over a pound.
You might be able to see in the pics how I drew out what I wanted to remove. Two hours later and a face full of sanding dust and here I am:

[bodywerks]

Man, I went to TOWN on the fuse today! In fact, I was so much on a roll that I forgot to take before pics, but I did get the before weight:

[bodywerks]

I got to looking at the front end of the fuse and, while I know it has to carry the brunt of almost all loads placed on the plane, I really saw no need for a 1/2" thick front fuse former! So that was going to get some holes put in it for sure.
Then, a common practice when building a Carden or other kit, is to skeleton the engine box a bit. The upper part of the box is 1/4" thick, the sides are 3/8" thick, the bottom is 1/8", and the engine firewall is about 1/2" thick. All I did here was enlarger the already existing holes on the top and sides(the top had a 1/8" hatch that I will not be using), and then I drilled a big hole in the firewall in the center. Again, this is pretty standard operation stuff when building a kit for light weight.
The fuse also had a rudder and radio equipment tray built into it. Since I will be mounting my rudder servos in the tail, and since I plan to mount my batteries and other equipment higher up in the fuse (this will help achieve a better vertical balance - something that is often overlooked, but can affect how true a plane flies), I cut those out. I did this on my 75cc QB Extra with no problems and with no auxiliary reinforcement needed. And once the wings are bolted on, they seem to stiffen up the fuse, too.

[bodywerks]

More pics. Notice the front fuse former thickness at the bottom of the fuse - way overkill, IMO.
Here, you can also see the big holes in the sides of the front fuse former and the engine box. I left the bottom alone for now, and probably wont touch it even after I mount the throttle servo. You will also see in one of the pics that I removed part of the tray where the tank would have mounted, as well as the cross-beam usually found right above the wing tube socket. I plan to mount the tank on the CG, so this stuff didn't need to be there:

[bodywerks]

with a weigh savings of over 3/4's of a pound, I think it was worth it...

[bodywerks]

Here's another area where one can realize a significant weight savings - hardware selection:
Now, I obviously wouldn't say it is worth it to got to these lengths if you are not going to try to keep the rest of the plane as light as possible. But if you are trying to look at the bigger picture, like I am, you can see that being more creative with hardware will also pay off.
The first pic below is almost identical to what Aeroworks recommends to attach the engine. They provide aluminum stand-off spacers and recommend Fender washers on both sides of the firewall. You then bolt everything together with steel screws and a lock nut.
What I did, was make my own stand-off plates out of end-grain balsa, capped with 1/16" birch ply, with the grains around the holes soaked in thin CA to harden that part of the wood. I did this exact same setup on an 85cc single and it was rock solid. However, in order for the balsa plates to be successful, you MUST glue them to the firewall with epoxy or gorilla glue.
Also, I replaced the steel 1/4-20 bolts with 6mm titanium bolts (about half the weight per volume as steel), and used blind nuts instead of regular nuts and a washers. Doing this results in the need of a shorter bolt, which reduces weight, but I also cut the bolts to exact length, so I reduced the weight even further.

[Twizlair]

Nice work so far nick will be lookin in again latter to see how she comes out.
jeramy

[bodywerks]

That's probably it for the major weight savings of the airframe. I put the wings on a scale and they tipped it at 3Lb., 2 ounces each - Ouch! Unfortunately, the only way to drop a significant amount of weight would be to tear all the covering off, and I still want this to be more of an ARF build than a kit build, so I might throw some lightening holes in the root rib and that's about it. On the bright side, the included CF wing tube only weighs 7 ounces - that is so light it actually has me wondering if they forgot to add some layers of fabric
Later, I will post my CG-mounted tank install and pipes install. Already thus far, though, you can do the math - I have taken a little over 2 pounds of weight out of the airframe alone. And I still have a good bit of weight to lose in equipment selection, too!

[bodywerks]

Here is a mock up of the engine installed. Notice that the blind nuts are screwed in instead of having teeth. I like it this way because you don't have to worry about the blind nuts coming out, and also because you can install the screws at an angle and the screws will actually help to keep the blind nuts from crushing the wood as you tighten the engine mount bolts (see pic below).
As I said, this is a mock up. prior to permanently installing the engine, I will soak the firewall around the blind nuts with thin CA, and also glue the stand-off plates down. Then I will safety the bolts with safety cable to ensure they never even think about coming loose.

[bodywerks]

I was reluctant to post these pics, as I purchased the 50mm header drop recommended in the Aeroworks manual and they turned out to be the wrong drop. This caused me to have to hack up the back of the fuse, because the shorter drop resulted in an overall longer exhaust. I do like that they put the pipes higher up in th fuse to reduce rotational mass, but I would recommend the 70mm headers for a simpler install.
One reason I wanted to post these pics is to show off the pipe mounts. They are lightweight mounts from Tony Russo (Dalton Aviation) and fit the Greves like a glove!
You will notice that the forward mount is removable. I had to do this to make the pipes removable. If I had used the correct drop headers, I would have been able to cut the stingers shorter and might have been able to do without the removable front mount.
You can still use this setup as a guide for installing pipes on the 70mm headers. Everything will be similar, except the mounts will be lower and you shouldn't have to cut anything out of the back like I did. However, if you use a DA 170, you need to run the full-length headers instead of the 9-3/4, so you would likely have to do something similar to what I did:

[bodywerks]

BTW, I got those pipe mounts from Desert aircraft. They have two different styles for the Greves - these are the lightweight units. If your kit does not come with Greves pipe mounts, don't waste your time trying to make your own when you can get those for a very reasonable price.

[bodywerks]

If you remember from some previous pics, I removed some material from the fuse to allow for a CG-mounted tank. Here's how that turned out.
It is very lightweight and was a simple install - just carbon rods, a little ply, and a little foam and zipties to hold it down. It is VERY important that the rods are not just cut to length and glued to the insides of the fuse! Holes needed to be drilled through the plywood and the rods then slid into place. I then simply held them there with some CA. This way, when the tank is full with 3 pounds of fuel and you're pulling 10-15 G's, you are not relying on a glue joint to hold the tank in place - you would either have to break the carbon rod or rip the plywood, which is not likely to happen...

[xtra330]

looks good! Keep it up.