CMAD Small Wonder build pics

[KRProton]

I noticed a little resin deposited on the ends of the joiner pockets, so I just used my piece of wood with sandpaper to take down that resin.

Now that the stabs are fitted and the joiner fitted to the elevators, time to drill the holes. This procedure always concerns me because I don't want to mess it up and get the hole misaligned or cut into the threads in the joiner, but so far so good on all the other planes before this one. I'm not excited about the prospect of using a threaded hole in an aluminum part to guide a drill bit, but again, this way has worked every time before and I don't know how else to do it...

With the stab halves pressed tightly to the fuselage, make sure the joiner is centered laterally in both elevators. This time I used a clamp to hold the joiner to the other elevator. A 3/32" drill will suffice, but instead I used a little smaller drill that I have with my 4-40 tap set. It's a .087" drill where a 3/32" drill is .094", so with the smaller drill I figure there's less chance of cutting any threads out of the joiner.

Holding a piece of wood on the top of the elevator (so as not to drill into yourself!), use the hole in the joiner to guide your drill at the correct angle and drill the hole.

Remove the stab and enlarge the hole. I believe a 1/8" drill is typically recommended for a clearance hole for a 4-40 screw, but I used a 7/64" drill instead.

Tim

[fizzwater2]

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

Tim

Remember the little springs that were in the fuel line in the Cox Babe Bee engines and their ilk? Kept the line from collapsing where it was bent?

I wonder if we could find some little stainless steel springs (guess they wouldn't have to be stainless, but it might keep them from corroding) to slip into a fuel line when it has to bend like this, to do the same thing - keep them from collapsing, especially down behind the engine where you can't see it.

Found this place with a quick google search, there are probably others. .088 dia is just under 3/32, might slip into a fuel tube. Several lengths available, I just looked at 1" for the heck of it.

https://www.springsfast.com/products/co ... 03-010-032

[KRProton]

The holes in the tops of the elevators require counter-sinking for the heads of the screws. On this model I was able to just turn the countersink bit by hand to get a suitable hole.

I also added a drop of thin CA in the countersink to harden the area.

Now I'll assemble the stabs to the fuse with the joiner and move the elevators up and down to see where there is interference to make sure I get enough throw. 1/4" is way more than needed (in my opinion), but if you can get that much or about that much you'll be assured the joiner will not be topped out in the hole and you're not binding anything in the system (including the elevator servo).

Tim

[KRProton]

Use more sanding tools and/or a small file to clean up and open up the holes for the elevator joiner to get the throw. I suppose it's not a major crime if you cut into the top of the stab fillet, but I try to avoid that so the hole cannot be detected from the outside.

It usually helps that list little bit to chamfer the top of the trailing edge of the joiner just a bit.

Put it back together and check the throw.

Once you have everything right, check to see if the elevators are even with each other. I just eyeball the tip ends of the elevators to see if they are even with the stabs. I suppose this isn't perfect because it's not necessarily guaranteed that the stabs are perfectly the same incidence, but, well...

Usually I make note of which way the joiner needs to be bent, remove it from the model and use two crescent wrenches to bend the joiner, but on this plane they seemed so secure in the elevators and the pockets seemed so robust that I simply used my fingers to bend the joiner while installed in the model. It took only a couple "tweaks" to get them "perfect."

Tim

[KRProton]

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

Tim

Remember the little springs that were in the fuel line in the Cox Babe Bee engines and their ilk? Kept the line from collapsing where it was bent?

I wonder if we could find some little stainless steel springs (guess they wouldn't have to be stainless, but it might keep them from corroding) to slip into a fuel line when it has to bend like this, to do the same thing - keep them from collapsing, especially down behind the engine where you can't see it.

Found this place with a quick google search, there are probably others. .088 dia is just under 3/32, might slip into a fuel tube. Several lengths available, I just looked at 1" for the heck of it.

https://www.springsfast.com/products/co ... 03-010-032

Interesting!

Tim

[KRProton]

Felt like mounting the wing next, but not exactly sure where the wing bolt holes are supposed to be. I guess this must have been one of the first Small Wonders available and looks like there are some modifications to the exact wing bolt hole locations. For the front holes, looks like they realized after the fact that the holes must move inward due to the fuselage being narrower than the Too Sweet (as this is the same wing as a Too Sweet). Not quite sure what's going on with the rear bolt hole locations.

Because of my uncertainty about the wing bolt hole locations, I thought it would be a good idea to fit the belly pan which may help me decide where to drill the rear wing bolt holes.

There were no cut lines on the belly pan, so I made a rough template from paper as shown. I used the template to mark a rough cut line on the belly pan, then used curved plastic-cutting scissors (from my Kyosho days!) to cut off the biggest pieces.

Tim

[KRProton]

Once the belly pan was trimmed enough to fit into position under the template, I marked the rest of the cut line on the belly pan and continued to cut, fit and trim. Eventually I moved onto finer trimming with sandpaper.

Once the belly pan was pretty much finished, I sanded down any small bumps and rough edges on the top and bottom for a good fit and a nicely-finished piece.

Tim

[rocket]

Are you doing a Korsen Hole for the elevator linkage?

[KRProton]

Hi Ray.
Yes sir, that's my plan. Already have the hole drilled and the "flag" set up. Pics to come...

Tim

[KRProton]

Okay, time to drill the wing bolt holes in the fuselage and wing;

I made 1/16" pilot holes where I wanted the holes to be. The location for the front bolt holes was obvious and marked. I wasn't sure about the rear holes. Looks like the original hole locations had been filled in for some reason, don't know why. I like the rear bolts slightly forward from the usual spot where the wing will be a little thicker and robust. So I went 7/8" forward of the trailing edge and about 1" out from center.

I used double-sided tape to hold the wing in place so it wouldn't move while drilling the holes. This method works only if there is a good fit between the wing and the saddle as is the case on this plane.

I use Kevlar string with tape to equalize the distance between the tips and the tail to make sure the wing is square. (For lateral positioning I just visually aligned the middle of the wing with the seam on the fuselage.)

I have a wood block with a perpendicular hole I drilled to use as a jig, but it works only on flat surfaces such as the rear wing bolts. I drilled the front holes with only my eye for guidance for holding the drill at the correct angle (perpendicular to the bottom surface of the wing where the bolts go in).

Drill the holes with a #7 drill.

Tim

[KRProton]

I got this countersink setup from McMaster-Carr. The countersink/drill combination makes for perfectly circular countersink holes. Without a drill to hold the countersink on center, the hole seems to wallow out. I got this idea from Jim Allen. Note: Always drill the countersinks shallower than you think. When you go to tighten down the wing the heads of the bolts always seem to sink in farther.

After drilling and tapping the holes in the fuselage I added thin CA to the threaded holes, spritzed on some accelerator, then re tapped the threads. I used to do this two or three times, but anymore I find that just one application of thin CA seems to work fine.

Tim

[KRProton]

Okay, truth in advertising and ya gotta take the good with the bad;

I went to bolt the wing onto the fuselage with my perfectly drilled holes. The rear bolts went in easily, but the front not so much.

The front holes in the fuselage were displaced about 1/8" aft of the holes in the wing. How could I have gone so wrong? I think what happened was, when I went to enlarge the holes in the wing, I must have held the drill at the wrong angle.

Okay, I filled in the front holes with my last little bit of Loctite 9462, allowed to harden over night, then re drilled new holes this morning. I used K&S brass tubing "sleeved" together to guide an 1/8" drill, then a 5/32" drill, then a 3/16" drill and finally the #7 drill for tapping threads in the new holes in the fuselage. Starting with smaller drills would assure that the drill wouldn't just fall into the old holes.

This time the wing fit well and I'm back on track.

Tim

[KRProton]

Here's a couple photos of the belly pan sitting on the wing and with the wing bolted to the fuselage.

Tim

[KRProton]

Just a quick check-in here. Been too busy building to pause to upload progress and photos, but plenty to come. For now I'll skip ahead though; our power has been out all morning due to maintanance somewhere down the line. I have enough light to finish this up. I'm going flying down at OJA tomorrow (Saturday) with Trey, so I'm taking the opportunity to finish this enough to fly.

It C.G.s a smidge ahead of what's typically preferred, but there is no tape on the tail. If any ballast is needed back there it won't be much. At this stage it's under weight too, and that's still with all the excess RTV and saran wrap while poting the wing (though no wing tip weight).

The plan is to get to OJA tomorrow morning and pull the wing in the afternoon, clean up the RTV and fly!

Tim

[fizzwater2]

Tim- the CG stand is intriguing. I see the dowels are slightly sharpened, and are those divots or holes in the little ply pieces?

Do the ply pieces stick to the wing temporarily with some 2-sided tape or something?

How stable is that small bottom piece on the workbench?

Thanks,
Gordon