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 Post subject: Cutlass Fins
PostPosted: Tue Oct 27, 2009 1:43 am 
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Paper Model Overlord
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Joined: Fri Oct 06, 2006 1:15 pm
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Location: Alameda CA
File this under: "Just Because It's One Piece Doesn't Mean It Has To Be Glued All At Once"

Building an F7 Cutlass I ran into the problem of how to keep the vertical fins airfoil shaped and, in particular, make the ventral portion of the fin a fatter airfoil (since it houses the retracted main gear). The fin pieces are simply two halves without any internal shapers or other devices to hold their airfoils.

The first model wound up with fins flat as the paper they were printed on. This at least revealed one of the immense advantages of paper modeling - if you don't like a result, print another sheet for another try.

The second try worked, and it demonstrates that simple as these models are, getting them put together nicely can sometimes be a Chinese puzzle of steps done in exactly the right sequence. Most of my finished models are 2nd and 3rd passes; the first pass usually winds up being fodder for the ""Don't Do It This Way" chapter of the How To manual.

The Cutlass fins have deep slots in their sides for sliding them onto the wing, and if these are cut out BEFORE gluing the fins together, they're not going to be aligned with each other, and the fin will sit on the wing askew.

So the first thing I did on my 2nd pass was leave the slots uncut. I put a curl into the fin halves to give them an airfoil, then glued only their leading and trailing edges together. Once the glue dried, I could fatten the airfoil by squeezing the leading and trailing edges toward each other.

Next I trimmed the tops of the fins to their finish edge, and also trimmed the leading and trailing edges both to shave off the glue bead and to remove slight mismatch in the halves. Removing the glue bead allows the finished edge to be colored with watercolor pens (and I couldn't color the edge before gluing becuse of the slight mismatch in the halves).

Now I had fins with good airfoil shape, with the ventral portion fattest (and as yet unglued). I cut the wing slot in one half, then simply followed its edges cutting the slot out of the other half. The fins would thus fit on the wing dead perpendicular.

Putting glue only on the upper edges of the slots, I slid the fins onto the wing and let them dry thoroughly. On the bottom, the unglued open ventral portions of the fins looked like small canoes resting on the undersurface of the wing. I filled these canoes with a thick layer of glue, firmly fixing their fat airfoil shape on the wing, and, again, set them aside to dry thoroughly.

Then I closed the ventral bottom edges of the fins, not all at once, but in three steps so I could control the developing edge and keep it straight. Finally, I trimmed the finish edge to remove the glue bead and slight mismatch, colored the edge and voila: airfoil shaped Cutlass fins with fat ventral sections big enough to house their gear legs.

I've spelled out all this detail not so much to help get Cutlasses looking good, but because the method demonstrates a larger principle: even though something may be one piece, treating it as if it were several separate pieces could be the difference between a model that looks like it was cut out of a ceral box and a model that, well, doesn't look like it was cut out of a ceral box.

Hope this helps.


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PostPosted: Tue Oct 27, 2009 5:18 am 
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Supreme Paper Commander
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Joined: Mon Sep 25, 2006 10:42 am
Posts: 3075
Location: Papillion, NE
Thanks Mark! That was very informative and points out the joy of the FG models. They may look simple (in many ways they are), but it is an art form to get them looking perfect.


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PostPosted: Tue Oct 27, 2009 5:33 pm 
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Paper Model Overlord

Joined: Fri Mar 30, 2007 1:29 pm
Posts: 600
Location: Maryland
dude, you should def take some pics!

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