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STUPIDLY THIN / STUPIDLY FAST...?

Old 02-20-2012, 07:40 PM
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combatpigg
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Default STUPIDLY THIN / STUPIDLY FAST...?

That's gonna be the theme to this build. Make a plane that looks like it might not be big enough or strong enough to hold together for a ASP .12, APC 5x5 combo.
Keep it simple with a minimal amount of frontal area.
The wing was built over a 1/16" balsa bottom sheet. The main spar is spruce, the rest of the bits and pieces are strips of balsa. The spruce spar was shaped to taper towards both ends by marking the cut with a fine line marker, then bandsawing it. This is what established a "grade level" reference point so that I could sand the rest of the framework to a nice contour before applying the top balsa sheeting.
The wing is about 3/8" thick at it's highest point and tapers to 3/16" thick at the tips.
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Old 02-20-2012, 07:52 PM
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phatboy
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

SAWWWEEEEEET!
Old 02-20-2012, 08:02 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

That looks crazy light! I would have had to go with a CF arrow shaft for the spar though. Laminate some kevlar for the hinge line too.
Old 02-20-2012, 08:09 PM
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combatpigg
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

I did a wing like this a couple years ago for a K&B RISE .15 and used a fiberglass tube spar.
Old 02-21-2012, 08:40 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

The fuselage sides are 1/8" balsa and sanded to a taper at the aft end where the sides meet. I'm using 1/64" plywood doublers to strengthen the front end.
There is a balsa block sub-firewall that the plywood firewall is glued against.
The fuselage is being built upside down on the flat top deck.
The top deck is the "zero-zero" line for this plane.
I mark the edges of the stab on center as a target to hit while shaping it to knife edges.
If you really want to get extreme you can make a tool that slits the perimeter of parts like this so you can insert 1/64" plywood strips to create a perfect and hard edge.
The sides are tack glued to the top deck with drops of thin CA, then 1/4" balsa triangle stock gets glued against the sides and the top deck.
I won't know the final placement of the wing until the rest of the plane is finished as much as possible. This way you can arrive at a workable CG without needing any lead.
Old 02-21-2012, 09:33 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

What kind of stall would you expect with that sharp a l.e.?
Old 02-22-2012, 07:23 AM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

I expect the stall to happen with the "SWRs" right before touch down.....right at the same moment they tough alphalfa.
With the .049 - 061 powered SWRs, they have 120-150 square inches of wing area and range from 11 to 16 ozs. None of them ever come close to stalling and there have been a few times when they have had to be landed heading down wind.
If a certain magic wingload isn't exceeded, plus rigging them with conservative control throws like you would for any racer they begin flying just as soon as they leave your hand...even with just average power.
I'm not sure what the upper limit is for these flat airfoils, hopefully this attempt at a .10 sized racer isn't taking it too far....but that's the theme of this thread.
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Old 02-22-2012, 07:26 AM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Haha. Good one
Old 02-22-2012, 01:30 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Looks like a fun project!
Old 02-22-2012, 01:39 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

It's fun to just have a general idea of what you want but no solid plan.
The trick is to avoid working yourself into any corners, but if you ever do that's what razor saws and cut-off wheels are for.
I started out with the idea of building another "prop-jet" but later decided to forego the "aesthetics" and just go for a bare bones speedster.
Later on it would be fun to build a Pacer or Mach None type bird for a .10 sized engine and set it up to fly like a pattern plane with rudder included.
Old 02-22-2012, 03:52 PM
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ProBroJoe
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

I'm not sure what the upper limit is for these flat airfoils, hopefully this attempt at a .10 sized racer isn't taking it too far....but that's the theme of this thread.
You never know how far you can go until you've gone too far, right?
Old 02-22-2012, 04:08 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Howdy Joe....yep, everything seems to have an upper limit....except for how good homebrew can be made to taste.
If this air frame ends up sleek enough it will allow testing the Enya and ASP engines with more propellor choices and maybe engine mod ideas. The idea is to have an airframe that is less of a limiting factor than the power plant.
Old 02-22-2012, 04:44 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Lookin good as usual CP, looks like a good airframe for a Nelson 15.
Old 02-22-2012, 04:46 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Dang skippie SRV! Send him one
Old 02-22-2012, 04:56 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Sorry guys had to post a pic!
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Old 02-22-2012, 05:50 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

I love the look of the Mach none, CP, and even considered for a few minutes upscaling that plane to a 60 size bird. Not sure what I think about those funky wing tips though!

Old 02-22-2012, 06:24 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Those Nelson .15s look like great investments for lots of fun..!
They look light enough to work well in a pretty small design.
That's a nice photo of the Mach None. Somewhere I've got a short kit. The kit comes with foam wing cores, the canopy and not much else.
Old 02-22-2012, 11:47 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Here's some details of the controls.
The elevator joiner wire is made from a scrap piece of 2-56 pushrod. The brass arm is cut from K&S stock they sell at the hobby store, then silver soldered to the wire.
The aileron control wires are 2-56 pushrods bent to form torque rods. They are coated with thick bearing grease and get buried in a mixture of epoxy and sawdust.
This gives a nice, slop free install.
The ailerons get sanded to match the tapered wing after they've been installed on the wing.
I cover the planes with the control surfaces installed.
The next step is to build the cowl for the engine. After the cowl is made, then I'll be able to get the wing placement nailed down so that the CG is correct.
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Old 02-23-2012, 05:07 AM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

CP

Where your aileron controlrods come up out of the TE, how are you keeping the epoxy out of the area at the bend?

andrw
Old 02-23-2012, 07:11 AM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?


ORIGINAL: combatpigg

The aileron control wires are 2-56 pushrods bent to form torque rods. They are coated with thick bearing grease and get buried in a mixture of epoxy and sawdust.
This gives a nice, slop free install.
I have used saw dust and epoxy as a filler were I needed some strength. But never as a sleeve for torque rods. Neat idea. The saw dust I used was what ever was in the shop from wood working projects. Sometimes I have added balsa saw dust , ends up much smoother.
I use plenty of torque rods but have always used metal tubing or plastic as sleaves.
Nifty idea. I will keep that one in the mental tool box.

Old 02-23-2012, 07:33 AM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?


ORIGINAL: Andrew

CP

Where your aileron controlrods come up out of the TE, how are you keeping the epoxy out of the area at the bend?

andrw
Andrew, I mix the epoxy / sawdust stiff enough so that it isn't a problem. Otherwise you could stuff little chunks of foam rubber into the trenches.
Mixing the epoxy with sawdust might also cut down on it's ability to freeze the torque rod if the grease barrier is deficient.
flyinagain, I think the epoxy bearing idea was introduced by a guy with the screen name "Clean" or "Mr Clean"...who hangs out mostly at the SPAD and combat forums.
It's been one of those ideas that a lot of guys here took an immediate liking too and have used.
Old 02-23-2012, 09:47 AM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?


ORIGINAL: phatboy

I love the look of the Mach none, CP, and even considered for a few minutes upscaling that plane to a 60 size bird. Not sure what I think about those funky wing tips though!

No need to scale up a Mach None. Just order a set of Mach-1 plans from Model Airplane News. That's what the Mach None was derived from. The wingtips of the Mach-1 were just cut off straight. The Mach None has "funky" tips because the airfoil isn't a symmetrical one.

Old 02-23-2012, 06:02 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

Cowl Day.
I've made quite a few 1/2A cowls this way and can say that I get a little bit better at it each time I do one.
The important thing is to take good measurements because garbage in really does equal garbage out. Any mistakes can be fixed, but you are looking at wasted time.
I use spray adhesive to glue the foam block to the firewall and carefully tape it off with clear packing tape pieces.
6 oz cloth is lightly misted with spray adhesive, smoothed out over the foam "mold" and then saturated with medium CA using a latex glove finger for your "tool".
Sand the high spots and apply a second layer
I applied a 3rd layer, but it was 1.5 oz cloth.
Use a holesaw running backwards to open up holes.
You can use a hacksaw blade with a point ground onto the end to use as a digging tool to hog out the foam plug when it is time to seperate the cowl from the fuselage. The cowl will attach to the sides of the firewall with #2 screws.
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Old 02-23-2012, 06:24 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?


ORIGINAL: combatpigg

Cowl Day.
I've made quite a few 1/2A cowls this way and can say that I get a little bit better at it each time I do one.
The important thing is to take good measurements because garbage in really does equal garbage out. Any mistakes can be fixed, but you are looking at wasted time.
I use spray adhesive to glue the foam block to the firewall and carefully tape it off with clear packing tape pieces.
6 oz cloth is lightly misted with spray adhesive, smoothed out over the foam ''mold'' and then saturated with medium CA using a latex glove finger for your ''tool''.
Sand the high spots and apply a second layer
I applied a 3rd layer, but it was 1.5 oz cloth.
Use a holesaw running backwards to open up holes.
You can use a hacksaw blade with a point ground onto the end to use as a digging tool to hog out the foam plug when it is time to seperate the cowl from the fuselage. The cowl will attach to the sides of the firewall with #2 screws.
That is an impressive piece of cowl work. What is "spray adhesive" exactly? Like contact cement?
Old 02-23-2012, 06:36 PM
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Default RE: STUPIDLY THIN / STUPIDLY FAST...?

It is aerosol contact cement.
3M77 is a good example, but kind of expensive.
There are cheaper cannisters at Walmart, but 3M is hard to beat for reliability.

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