[Lake Flyer]

Hi Phil, My motor is a generic O.S. 25. I am not sure which one as it has a carburetor I have never seen before. But then I never met a O.S. engine I did not like.
I believe I moved the firewall back about 1/4".
I am glad you mentioned C of G. I cut my spar slot where I wanted them and assumed that was the C of G. My spars are a little forward so I'll have to do some careful measuring before I fly. At the moment it appears I am just slightly tail heavy. The servos are in but I still have to install the battery, RX, and fuel tank. So I think it will come out really close to what it should be.

[Mad_Mike]

My turn for one of the wing jigs.
Laurie got it all figgered out so I'll leave his tape on there and copy it.

Here's hoping I can get the wing done as fast as Lake Flyer got his whole plane done.

[Balsaworkbench]

Originally Posted by Lake Flyer

Hi Phil, My motor is a generic O.S. 25. I am not sure which one as it has a carburetor I have never seen before. But then I never met a O.S. engine I did not like.

The first time I built one of these about 15 years ago I powered it with an OS 20 FP. It flew great until it got really hot and humid in the summer time. You guys in Canada should be OK with one of the less powerful OS engines because of the cooler weather. Since yours is a 25, even if it's one of the milder ones it will probably be better than my 20 was.

[Mad_Mike]

Well begun is half done.

Took me a while to work out how to get the dihedral braces in and sort out what to cut and where.
My big brace is going aft of the Basswood spar parts, I had to cut 1/8" out of the first 2 ribs to make room for it.
I'm putting the small brace in about 2-1/2" ahead of the TE, I cut the notches for that. I cut the ribs for the other panel at the same time.
I wanted to get all the ribs on the jig so I don't have to take the wing panel off until I flip it to do the underside.

[Balsaworkbench]

If you start with the wing upside down in the jig, you can put the landing gear block and bottom sheeting in place, then when you turn the wing over you can put the anchor block on top of the landing gear block, then install the top sheeting after you already have the entire landing gear business put together.

In fact, after you get the entire landing gear assembly assembled, but before you install the top sheeting, you can quickly flip the wing over and drill the hole, and then install the top sheeting. That way you are guaranteed not to accidentally drill through the top sheeting.

[Mad_Mike]

Thanks Rob, I like that better.
I can drill the block before glueing it in. I'll use the dihedral brace to get the angle right.

[Balsaworkbench]

The other reason to build your wing upside down and then flip it is because of the order in which you put the spars on. When you build a wing flat on the table you start with the bottom spar, tilt the root rib inwards, and then add the top spar, which is going to be a little bit too long. When you build a wing on a jig, you put the ribs in place, then you add the top spar and set your dihedral angle on the root rib. When you flip the wing over, if you started right side up, you will now be adding the bottom spar to the top of your assembly (which is now upside down) and it will be a little bit too short.

[Mad_Mike]

That makes sense.

Engineering question about the plywood half ribs that reinforce the LG block.
Do I need to fiddle about getting them glued in straight half way between the full ribs or can I laminate them to adjacent ribs?
Seems to me it would be stronger that way.
Our LG blocks go all the way to the third rib so each would have a plywood half rib.

[Balsaworkbench]

When I built mine I completely ignored the rib spacing on the plan because it didn't make any sense. I laminated the plywood to the balsa ribs, which I thought would make it stronger. Then I laid out what I thought was a sensible rib spacing scheme and the landing gear block placement was made to conform to the rib placement.

Come to think of it, I believe that I placed a rib at the edge of the fuselage on each side, which is about 1.5" from the root, then proceeded with the 2.25" spacing from there. The landing gear block hangs over the rib on each end. That layout is consistent with what I measured with my ruler on the finished plane a moment ago. My rib spacing is 2.25". My landing gear block is 5" long, and the inboard edge is 3.5" from the root.

[Mad_Mike]

For those who might be starting on the wing ...

Instead of trying to glue in the plywood half ribs between the balsa ribs I laminated them to the balsa ribs. I meant to put the third one an extra rib over but messed up on this side so it isn't.

While the wing is open I put a 4mm light plywood doubler in at the root rib(both sides) so I will have a thick part to drill into for the dowel.

It's easy to drill the LG blocks before they are in the wing but you need to bevel the center end first to get the hole in the right place. If you're fussy you can use the spar joiner to help get the hole at an angle but really, you can bend the gear wire a bit to make it all fit.

Also, the landing gear is meant to spring like a torsion bar so I will relieve the block sides(out at the downward leg) to let it bend fore and aft in case I hit a bump during one of my awesome landings. I will add reinforcement inside the wing at the hole.

The above is just the way I did it, if you think there is a better way please say so. Too late for me to fix mine but ...