Wing to fuse fairings - RC Groups
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Nov 09, 2017, 06:33 PM
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Wing to fuse fairings


Evening all. Iím framing up a Sig Astro Hog. Wings and fuse are pretty much done. Plans call for 2 balsa blocks to be formed/carved to blend the leading edge to the fuselage. Any tips or trick that may shorten this process or make the process more accurate? I can see this is going to require a lot of trial fitting.
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Nov 09, 2017, 07:34 PM
Gravity sucks.
mrittinger's Avatar
Pics? I may have a hint if I can see what you mean...
Nov 09, 2017, 08:59 PM
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david.ingham's Avatar
I found I could make the rear part of the wing fairing of my little P40 by curving a piece of paper. There must be more high tech materials that bend smoothly. I was surprised that it wasn't a compound curve.
Nov 09, 2017, 09:26 PM
Registered User
Sand and form these 2balsa blocks to blend the contour of the fuselage to the LE of the wing, then glue in place on the wing. Nose of airplane is facing down.
Nov 09, 2017, 11:15 PM
B for Bruce
BMatthews's Avatar
Oh, THAT sort of fairing. I think most of us were thinking of the wing root fillet.

It's simply a matter of blending the wood to fair in line with the chin block. It's a bit of wood working tooling but a good tool for this would be a wood chisel. With it you can cut into those blocks from the shaped chin block and make the line follow well. And the wood chisel gives you the control you need to end the cuts when it starts to contact the lower wing sheeting.

You CAN do this with a longer bladed carving knife as well. But you'll want to use a good eye with a point light source in the distance and off and on check that the shape follows the chin block with a small ruler.

And with the idea in mind that these filler blocks are supposed to be extensions off the chin block before you shape the fillers be sure that your chin block and generally the nose section is carved down to your final desires so the filler blocks do indeed extend the lines off the chin block.
Nov 10, 2017, 08:52 AM
AndyKunz's Avatar
I like to lay up layers of 1/16" or 1/8" soft balsa on the bottom of the wing. This gives me a good fit without any concave carving. Sanding the outside edge to flair nicely is much easier.

Andy
Nov 10, 2017, 08:57 AM
Registered User
Wrap the leading edge of the wing with course sandpaper (80 grit). Run the block up and down the paper, till it meets the curve of the wing. Attach the wing to the fuselage and continue till the leading edge of the block meets flush with the fuselage former. Next sand each block to make the center joint close. Glue the blocks together and the sand the outside until it matches the fuselage width and a pleasing shape. Now, glue the blocks to the wing and sand the top of the blocks flush with the bottom of the fuselage.

On mine, I glued these blocks to the fuselage (not the wing), with about a 1/32" gap between the wing surface which allowed me to sand the final shape with the wing removed. There were some final finish benefits as well.

But yeah, shaping the blocks over sandpaper that matches the shape of the wing is the best way to get the job started.
Nov 10, 2017, 01:18 PM
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david.ingham's Avatar
. .
Last edited by david.ingham; Nov 10, 2017 at 01:24 PM.
Nov 10, 2017, 02:03 PM
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Thank you for the hints. I was leaning toward the sandpaper thing. Good reminder on finalizing the chin block profile. Mine still has a little ways to go. This airplane requires a lot of fitting.
Nov 10, 2017, 07:23 PM
Gravity sucks.
mrittinger's Avatar
I use one of these to get it close...itll match the shape of the wing. Transfer the shape to the block and carve airfoil shape, then draw-sand to get nice perfect fit. I got it from Harbor Freight.
Nov 10, 2017, 08:37 PM
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Quote:
Originally Posted by mrittinger
I use one of these to get it close...itll match the shape of the wing. Transfer the shape to the block and carve airfoil shape, then draw-sand to get nice perfect fit. I got it from Harbor Freight.
What is it?
Nov 10, 2017, 11:23 PM
Gravity sucks.
mrittinger's Avatar
The red parts slide, so you press it into an object and the other side gives you the exact shape to trace from. It's a really handy little gizmo!
Nov 11, 2017, 01:24 PM
B for Bruce
BMatthews's Avatar
Look up "contour gauge" on you tube for what it does. The steel wire version is way too stiff to use for model building in foam and balsa but perhaps this plastic version is better by needing less pressure to get the "pins" to move.

I was assuming that you'd managed to fit the blocks to the wing already. But if you still need to do that as well then roughing them out with a carving knife and then using MichaelR's wrapping of sandpaper around the wing to do the final shaping is a great idea and one I've used quite often for the same job
Nov 11, 2017, 02:42 PM
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Quote:
Originally Posted by BMatthews
Look up "contour gauge" on you tube for what it does. The steel wire version is way too stiff to use for model building in foam and balsa but perhaps this plastic version is better by needing less pressure to get the "pins" to move.

I was assuming that you'd managed to fit the blocks to the wing already. But if you still need to do that as well then roughing them out with a carving knife and then using MichaelR's wrapping of sandpaper around the wing to do the final shaping is a great idea and one I've used quite often for the same job
I agree.
Nov 11, 2017, 05:11 PM
Gravity sucks.
mrittinger's Avatar
I generally use the contour gauge to cut the wing shape in, then I draw sand by pulling the sandpaper ,( grit side toward filler part), between the part and the wing. perfect fit. Works great for sanding wing saddles for tight fit!


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