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Building Tips and technical articles. => Building techniques => Topic started by: Tim Wescott on February 02, 2022, 09:48:33 PM
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So I've fallen in love with a plane, and want to do a semi-scale stunt of it, with a big molded fuselage like Paul Walker and Igor Burger have been doing.
But it's a racy sort of thing, and the fuselage is banana-shaped. I'm forseeing all sorts of issues with the molding process -- basically, I just can't envision where the balsa will want to go, or, if I cut slits in it like you to with a convex-convex fuselage, whether it'll make things better or worse.
Has anyone attempted this? Did you succeed? Did you do anything special?
PDF of the start of the plans posted.
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Tim,
I have molded balsa top and bottom blocks and have an old Top Flite molded fuse P40 and Peacemaker kit. The technic goes back to Al Rabe so you might want to research some of his work, also Bob Hunt has done a lot of this.
One approach to complex shapes would be to form the center part of the fuse from sheet balsa kinda like a box fuse for this part, then add pink or blue foam blocks to shape the rest. Once you have it carved and sanded to shape use light (1oz ish) fiberglass cloth to cover it. You could then melt out the foam (spary gasoline or acetone over it) or if you built it in two half's hollow out the foam blocks leaving say 1/8" wall under the fiberglass.
Let us know how you do this.
Best, DennisT
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You could buy / build a CNC router and carve it... I have a project router I have never finished and it's times like this, I seriously consider getting my tail out there and getting it done.
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Tim, several planes ago I molded a 3/32 balsa fuse that requires a complex shape in the engine/cowl area and it turned out good. I did the "slit the balsa and overlap it" technique and found that to work just fine. Once overlapped I then cut the extra wood away and glued the slits together, then glassed the area from the inside. Keep in mind that I molded the fuse in a right side/left side configuration then joined the sides after the shells had dried.
It was a very good and light ship and I really enjoyed it 'til I sold it and the PA61 so I could justify my PA 65.
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Tim, several planes ago I molded a 3/32 balsa fuse that requires a complex shape in the engine/cowl area and it turned out good. I did the "slit the balsa and overlap it" technique and found that to work just fine. Once overlapped I then cut the extra wood away and glued the slits together, then glassed the area from the inside. Keep in mind that I molded the fuse in a right side/left side configuration then joined the sides after the shells had dried.
It was a very good and light ship and I really enjoyed it 'til I sold it and the PA61 so I could justify my PA 65.
That one is definitely badassednesscooleruleo to be sure..
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Tim, several planes ago I molded a 3/32 balsa fuse that requires a complex shape in the engine/cowl area and it turned out good...
Yup. I've done one molded balsa turtle deck, which ended up well. I'm being inspired by the local top fliers that are doing warbirds with big molded fuselages -- my big worry is that the fuselage has a lot of curvature to it lengthwise, with some undercamber in the back (it's in the drawing I included).
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That one is definitely badassednesscooleruleo to be sure..
Thanks Mark!
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Cool looking plane Tim.
This should help with the visualization of your banana concept. H^^
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Cool looking plane Tim.
This should help with the visualization of your banana concept. H^^
That wasn't the paint scheme I was contemplating, but if I run out of ideas, I'll run with it!
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Hi Tim,
Make a sacrificial styrofoam plug. Soak the balsa for many, many hours and just go at it with loads of elastic bands to hold the balsa against the plug.
Unrelenting pressure from the bands forces the balsa to submit.
Later you can slice up the plug to get your cross-sections.
Attached is an image of DC3 nacelles.
Did I say you need lots of elastic bands?
Steve
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I know the basic technique, and have used it -- all of once. It's the negative 3D fuselage that has be worried.
BTW: I go off of Bob Hunt's instructions, and use Vetwrap or an Ace bandage. He specifically mentions that something like rubber bands can make marks in the balsa. Dunno if that's happened to you, but...
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I know the basic technique, and have used it -- all of once. It's the negative 3D fuselage that has be worried.
BTW: I go off of Bob Hunt's instructions, and use Vetwrap or an Ace bandage. He specifically mentions that something like rubber bands can make marks in the balsa. Dunno if that's happened to you, but...
Bob is right.