Quandry!! Thick rib section

[Shakey Jake]

I am in the process of printing out the rib sections for a new plane. I've discussed this model before on the zone. his is a some what diamond shaped wing. It is swept back12" at the leading edge, and swept forward 3" at the trailing edge. Span is 50". I started by drawing a tip rib section of 6 3/4" which I then scanned into my computer. I then stretched each rib section to the desired length from that tip section. I let the depth of each rib section increase in proportion to the length.
My quandry is this. The root rib section is 22" long and the depth of the rib came out at 3". Does this sound like it will be a drag on a 50" wing? I'm not particularly interested in a fire ball, and would like to be able to slow this thing down pretty well for landings. I know this thick wing will give good lift, but am I pushing it a little here??
Thanks for any thoughts.
Shakey

[Sparky Paul]

Depends on how much power you're planning on.. a Speed 400 probably would get a hernia on a 3 inch thick wing..

[Shakey Jake]

Sparkey,
I'm planning to try a Turbo=10 on 6:1 gear drive pusher mounted mid wing. I'm trying something different to keep the weight down on this thing. I'm going to cover a very light weight skeliton wing structure with a thin foam and glass sandwich skin, which is extreamly stiff and yet light weight. If I can keep the weight down I think the T-10 will push it OK.
I'm just concerned that going from 7/8" thick tip section to 3" in a 25" run might be a little extreme. Would it cause any problems if I decrease the thickness at the root to around 10% from the current 13.5% section and leave the other sections as is?

[Sparky Paul]

Looking at a topview.. the taper ratio isn't good, relative to the Reynolds number, root to tip.
The tip could be made thicker to help over that situation..
There's a lot of area.. 725 sq.in. which can be more of a kite than a plane in a wind.
Having said that, here's one like the one you describe I've flown.. back in '63 with a .15, and in '91 with a 05, geared and direct...
25 inch root, 2-5/8" thick; 8 inch tip, 7/8" thick; 36 inch span.
594 sq in.
Very crashable airplanes... fingering out which point is the front is difficult when they get some distance away...and top/bottom is a problem..

[Shakey Jake]

The mod I'm working on has a fuse which gives it a total length of about 40". That should help some visually. I'm thinking of holding the center section (15") at a constant thickness of about 2 3/8". Would that be a mistake? The fuse will cover about three inches of that anyway.
The attachment below is rough but will give you an idea of what I'm up to. Dimensons include the elevons.

[Sparky Paul]

Well, a constant thickness on a tapered wing is a PITA.
Makes for breaks in the spars and sheeting. Better to keep the section percentage common along the span. Then everything fits in straight lines.
.
Where is the motor and the motor batteries?
.
You might have a serious nose-heavy situation with everything up front.

[Shakey Jake]

Sparky,
Just behind the large black bar (main landing gear spar) is a slot in the wing for the prop to swing in. The motor and gear box are mounted just in front of this spar. The battery pack will reside inside the fuse. Exact placement to be determined for proper CG.
The CG is way forward on this wing (about 8% to 8.5% just as it is on my other Simitar types. Being nose heavy is the last thing I worry about on these monsters. Even with a long snout on them I usually have to push the battery packs as far forward as possible to get them to balance, thats with a front mounted motor. This wing will have even more weight to balance out if I can't keep the weight down. The fuse may wind up being even longer than shown here. I won't know for sure until I finish the wing and do a test balance on it.
As for the sholder on the wing. I can make it without a break in the main wing spar, and the composit wing skin can be wrapped over it without a break of any kind except in the 1/8" foam core which will have to be cut at the front of the wing, but it's just filler for the composit structure anyway and adds no strength on its on.
Actuall this thing will be a plank from MAC to MAC and then taper from there on to each tip if I do it that way.
Anyway was not sure what the aerodynamic effect of this flat wing section would be but since I'm cutting a slot in the center section anyway the point may be moot. You can probably tell that I like to try unusual things.
Not sure what PITA means. Pathetic idiots terminal attempt??
;)

Thanks.
Flying backwards as usual,
Shakey