Simply Amazing craftsmanship! Awesome looking flaps, Man i can wait to hear how it flies

Randy how did u come up with the idea of the built up rudder does it have an air foil? or is it just one flat thickness? I would love to try something like that on a design I'm working on.

18oz, not bad usually i come in at 18oz when i do a single wing tip

I love how light those flaps are, but how do you plan to keep them from flexing under flight loads?  Got some CF tube buried at the hingeline?

Randy,
pardon me for climbing on the soap box with ya, I think the key is understanding the strength of the material you are working with.(which is what you are saying if I am correctly interpreting, ok so we have talked about this) Im gonna spell it out like I build now, simple,, you say it like you build, eloquent,,,,
the key is to make sure that the line of strength in the material is in line with the stress it is resisting. in other words, the grain direction is the strenght in balsa, by alternating the direction of the grain in a structure, like Randy does with his buildup method, instills strength, and torsional resistance by virtue of the multitude of grain directions in the structure to resist torque. Actually each peice ideally will resist motion in a tension mode since that is where the strenght comes from. hence the warren truss structure is strong because the lines of resistance counter the lines of stress. ,,,,,, Um oh yea, I said I was gonna be simple, I will stop there,,,,,,,
Ok Randy back to you,,,
bythe way, I like the belly scoop mucho better,,

Mark,

Yea, the scoop is better. With the gear mock-up I did, I set it on the table and it looks pretty cool. Still messing around with venting (as you can see). I am just short of the 1 to 2 ratio, so it will probably get another vent somewhere back there. I'm using an old differential equation that I picked up somewhere (probably college calculus) to figure areas. Fun stuff tried to measure a couple of those openings. 

Along the lines of what you were saying, I suppose I was effected a lot during college by a roomate I had. He was majoring in structural engineering. I helped with the design and building of his project for a bridge contest. You know, the old build a bridge, put it in a press and measure the stress it will take before it colapses? Anyway, he and I did EXTENSIVE reading on various materials and elected to use balsa. I have to admit that I was facinated by the fact that for the weight, balsa had greater compression and tension resistance than most any other material. And we won the contest, by the way, with a Warren truss, tied arch design. I think I still have that design in my mind when I'm messing with things like this.

Doug,

Good question. I think you can see in the picture that the flap standing up is unshaped, the one laying down is ready for final sanding. When I build these things, I lay the core down on a chunk of 3/8" think glass and tack it down in a couple of places with CA. I cut out the ribs, LE and end blocks with the bandsaw. Glue on all that, flip the thing over on the glass and glue on the other side. Then you get the flap that is upright in the picture.

To shape, I use a razor plane with the core as a reference line and plane down the ribs and end blocks using a sort of template to check. There is, admittedly, a lot of eyeballing involved. I use a long, thick ruler I picked up to check the lengthwize taper often.When I get the profile close, I use a long sanding block to bring it down to profile.

If the core is straight and relatively rigid, then it's pretty easy. It takes some touch, but isn't all that hard. I've done enough of these that I can plane off and shape both flaps in a half hour or so. But initially, when I was developing the technique I use, it seemed to take hours to do one flap. It works for me OK.

Hope all that's clear.

Warren,

Well that goes back to having a relative rigid core piece. That is probably the most scrutinized piece of wood in the whole enchilada. As I noted, I use a piece of "C" grain (in this case) 7lb stock with pretty consistent grain. I usually want a plank for this; something that could be used as a diving board. A lot gets cut away and so, the final weight of the core isn't much. But the structual rigidity of the inherent piece remains. By the way, the grain runs parallel to the trailing edge, not the leading edge. Haven't had any problems with it warping yet, but I imagine that the rib arch helps in that, too.

No building classes for me. I have too tough a time explaining what I'm doing as it is. A lot of this stuff is just accumulation of trying something, having it fail, sometimes spectacularly (read elsewhere about the USA- explosion), going back to look at the plans and figure out what caused the problem, figuring out a way to make whatever broke stronger by rearranding the structure rather than adding more structure (unless absolutely necessary) and trying again.

I'll try to take a couple more pictures of the flaps and elevators. I still have one flap and one elevator to shape. Got sidetracked with a new idea on building with a sort of prebuilt hinge pocket and I wanted to build a quite mockup to see if it worked (I don't ALWAYS try new idea on the actual airframe). Anyway, I'll see if I can take a couple more pictures of the before, during and after shaping.

One of the things that I get, uh, reminded of regularly is that I don't tend to do things half way. I get an idea, I build a full boogie stunt plane with serviceable finish to try out the idea. Probably not very bright on my part since half the time the bright idea is a non-starter. But along the way I get to test out a lot of structural ideas, finishing techniques, etc. And that is never wasted time even if the plane ends up as a hanger queen or parts carcass.

Great Lou, give all my secrets away!  How do you expect me to be mysterious if you tell them everything? 

Yea, I generally lay it down on the glass, plane then sand it to shape checking periodically with a straight edge (for spanwise taper) and a template for rib taper and, of course, liberal use of the Mark 1 Eyeball.

When I flip it over to do the other side I usually just use some scrap 1/4" plywood pieces up against  the core to keep the finished surface up off the glass and do the other side.  I do the finish sanding lightly by hand. I tooks some pics last night while I was doing the flap, but it was too late to mess with re-sizing so I could post them. Maybe tonight.

One note to all: I wouldn't expect anyone to build the way I do. I've sort of evolved the techniques I use over a lot of years; usually copying someone elses idea, then modifying it to fit what I wanted to do. Sometimes just coming up with an idea. Some things are probably harder than they have to be, but I'm comfortable with them and know I can get things light and straight this way, so I continue to employ such techinques. The hope here to just get folks interested in how they build stuff.

Hi Randy,

One thing to consider: with the pipe systems, it has become general practice around here (read that around Randy Smith! LOL!!) to not have any cooling outlets until the pipe outlet at the rear.  For whatecer reason (I don't know, I just do as I'm told! ) Randy had us close up our header cooling holes and all the others.  Now the air flows all the way down the pipe to exit.  And he says that's the only way to do it. ?? ?? ??  I rememer Ted having to put backing in the cowl to close up all those beautiful holes in one of his TPs.

Well, the control surfaces are completed and on (temporarily at least). I'll try to get the fairings on tonight and start getting the gear built. Once that's done, I do the final sanding and start slopping dope on. I imagine once the thing is in silkspan, it will go in the rack for a bit so I can get my Cobra fixed and refinished. VSC is only, what, 7 months away?

Randy:
I just kinda wish you had made this with an UPRIGHT ingine so you could REALLY show off all that pipe tunnel work!