CMAD Small Wonder build pics

[KRProton]

Got myself a CMAD Small Wonder, so here's some pics...

So, I was working in my basement (where I spend lots of time working on laser cutter jobs) gazing over at my Q40 collection. I'm down to four planes. Probably a better position than many, but four is only one more than three and three more is only one more than two! Winter is nearly upon us, so in a bit of an unnecessary panic I texted Tom Scott to see if he had anything in stock. He had a Small Wonder with my name on it! Just what I wanted - all-white so I could paint it (or not!). Two days later it showed up at my door!

A few minutes later I had the tail tubes cut and the stabs in place so I could see what she was going to look like. Cool!

The fuse seemed really light and the glasswork is awesome, but I already forgot to weigh the fuse. Maybe before I get too far I can weigh it and subtract the weight of the mount and ring that is on the back of the firewall now.

Tim Lampe

[KRProton]

First thing I usually do is enlarge and clean up the edges of the opening in the fuse for the radio compartment. I also cut holes in the fuse at the front and back of the wing. Smooth the edges with like 320-grit sandpaper so they're nice and smooth.

Tim

[KRProton]

Okay, now the engine mount; Mike Helsel already had a Small Wonder and I know he ground a circular notch from the engine mount to accommodate the fuel cut tube. Since this airplane uses a 1-3/4" spinner the whole front end is a little slimmer than planes with a 2" spinner (like the Too Sweet it replaces), so there is no room around the engine mount for a cut tube. Lonnie Finch showed me how he put the cutoff in the middle of the engine mount, and I know some do it this way, but I thought the cut wire and guide tube running up to the middle of the firewall would interfere with the fuel tank. Also, I usually mount the battery to the back of the firewall so a fuel cut in the middle of the firewall wouldn't work for me.

To further the discussion, I wasn't too excited about the prospect of cutting a chunk out of the engine mount, so even before I got the plane I was dreaming of clever (?) ways to concoct an internal cutoff. I know this has been done before too, but when I got to looking at it, the idea of an internal cutoff seemed more difficult than I had first thought. I really just wanted to plow ahead with something that was simple and familiar. And when I got to looking at the Jett mount, well, it already has a notch cut there anyway for the other fuel fitting location, so cutting a circular notch didn't seem so bad.

So I got out the Dremel and the carbide cutter and went to work. I cleaned it up with a small sanding drum. It took only about five minutes and I was on my way! Not sure if this is advisable by Dub or not. Guess I'll find out!

Obviously I relocated the fuel fitting to the other location and sealed the other hole with a 6-32 set screw and the same glue I used for the firewall (shown in a following post).

Tim

[KRProton]

Okay, now to make the hole in the firewall for the fuel cut tube. I'll use the Allan Booth type that the plane came with...

Of course, the hole for the cut tube cannot be drilled square to the firewall because the nose is in the way. I guess the hole doesn't HAVE to be perpendicular to the firewall, but I'd rather it was. Plus, you know how hard it is to control a drill bit, so my alternate method is to burn a hole with a 3/8" K&S brass tube...

Heat the tube with a torch and there you go. Took about ten "passes" to get the hole the desired depth. Then I drilled a pilot hole in the middle of the burned hole and enlarged with a drill to accommodate the bottom part of the cut tube...

Tim

[KRProton]

For C.G. purposes, I want to mount the battery as far forward as possible. I've had good luck in my other Q40s mounting my packs to the back of the nose ring with Velcro, so now this is my go-to method. I make a disc from 3/16" balsa and glue it into the ring. Oops...somewhere along the process of test-fitting I realized that the ring needed a small notch for the cut tube as well.

Okay, glue the Velcro to the back of the ring and disc. When test-fitting, I guide a couple pieces of wire through two of the engine mount holes, slip the ring onto the wires from inside the fuse, guide the ring up to the back of the firewall, then use an extra-long screw in the 3rd hole to catch the 3rd screw hole in the nose ring. Turn the screw to draw the ring up to the firewall, then remove one of the wires and replace with the next screw, then the next screw.

The factory engine cutout needed only minor enlarging around the engine mount lugs to accommodate the engine.

Tim

[KRProton]

Okay, time to mount the engine!

First though, I had to enlarge the holes in the firewall just a bit to shift the engine mount over about 1/64" to get the spinner perfectly centered on the nose. Other than that, the firewall was perfectly parallel with the nose.

I always pot the engine mount with Loctite 9462. It provides over an hour of working time and does not flow, so it's great to work with. I applied a thick film to the back (front?) of the engine mount ring and to the back of the engine mount. Before installing, I also applied some 9462 around the front of the firewall and made a smooth fillet with my finger.

Don't forget to glue the guide tube for the throttle cut wire into the throttle cut tube, install the whole show, clean up as best as you can, drop the mike and walk away!

Tim

[KRProton]

Got a few minutes in the shop tonight...

Made a pattern for an engine mount brace. I'll make one out of carbon fiber and glue it in next.

Two options for the fuel line routing; The first has the feed line from the tank going directly to the angled fitting on the outside of the mount, and the cut line from the needle up around the top engine mount beam, through the fuel cut and to the engine. This wasn't my original intention, but it's how Mike did it. (But I didn't position the hole in the fuselage optimally for this method because it wasn't my original plan.)

My first idea was the second one two photos; with the main feed line from the tank looping down around the needle, through the fuel cut, down inside looping back up to the needle fitting. This idea is the cleanest looking, but I'm not so crazy about the tight radius where it loops back up to the needle. I think it'll be okay and I think this is the way I'm going to go.

Tim

[fizzwater2]

is there room to wrap that one around the mount beam so you can reduce the radius (and chances of kinking) on that line?

[KRProton]

You mean wrap the line from the tank around the bottom engine mount beam?

That's the way I do it in my Too Sweets/Sweet 1s, but there's no room between the bottom beam and the fuselage on this plane.

Tim

[KRProton]

Modified my fuel line routing slightly - just shortened it a bit...

Tim

[KRProton]

Here's my engine mount brace from 3mm carbon fiber. Would be easier to do the thing where you thread screws into the end of the mount and pack it with epoxy and chopped up carbon fiber strands, but I just like this way better if for nothing else other than appearance.

Painted a piece of carbon fiber with white paint, etched the pattern with my laser cutter (I can cut G10 fiberglass - takes about six passes raising the bed a smidge each time, but it definitely will not cut CF), then went to work with a cutoff wheel, then a dremel with a drum sander, then my little table belt sander (in the rain!). Made two because there was just enough room on the cf sheet.

Tim

[KRProton]

Roughed up the inside of the nose area a bit, then more Loctite 9462 to glue in the engine mount brace...

Tim

[KRProton]

I weighed the fuse as it is now in this stage of assembly (with the engine mount/engine mount ring, cf engine mount brace, throttle cut tube and guide tube) and it weighs 13.22 oz. Then I weighed similar parts (including screws) and it all came out to 3.06 oz, so I reckon the fuse alone weighs about 10.06 oz. The wing (as supplied out of the box with the carbon spar joiner tube) weighs 17.62 oz. and the stab halves (not including the cf spar tubes) weigh 2.10 oz.

Summary:
Fuselage: 10.06 oz.
Wing: 17.62 oz.
R&L stab set: 2.10 oz.

Tim

[KRProton]

First thing I did when I opened the box was fit the stabs. The cf tubes were a little tight which is typical. Whenever this happens I just roll some 250-grit sandpaper and slide it in and out of the holes until the tubes will go in. Takes just a few minutes.

I also usually true up the root ends of the stabs a little to perfect the fit to the fuselage. Well, I never get a perfect fit, but it's a little better and very good anyway.

If you take down the stab halves a bit (or even if you don't), make sure the elevators don't interfere with the fuselage. If necessary, sand down the ends of the elevators for a little clearance.

Now that the stabs are fitted the way I want time to install the machined aluminum joiner. First mark the fuselage where it needs to be cut to allow the joiner to pass...

Tim

[KRProton]

I can never remember which the joiner goes in the elevators. Leave one of the screws in the joiner and fit it into one of the elevators. Then you can see if you have it in correctly or not. Once I've got it, I mark the joiner so I will easily know which way it goes as I proceed with assembly.

The 1/16" Dremel carbide cutter is a must-have for composite work. Carefully rough-cut the openings on both sides of the fuselage for the joiner.

Tim