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| CHAPTER 7 - FUSELAGE EXTERIOR | |
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Fuselage exterior shaping begins with building up the aft end and creating the NACA scoop. Here the urethane blocks have been cut and micro'd into place. The wood and weights in the aft end are holding the vertical sides of the scoop in place. |
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I was a little confused about where the little triangular birch plywood pieces went. Well here there are - either side of the landing gear well. The landing gear will come out right above (or in my case slightly into) these pieces. |
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Sanding urethane is easy - toooo easy! Go slow and make sure you have a straight and long sanding spline. Here the right side is complete (left side of picture - remember fuselage is upside down). When microing the urethane blocks together - go easy on the micro on the vertical joints and on the forward end. As you sand the micro will break off in little pieces and gouge the foam. |
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To get a perfectly perpendicular and curved edge I cut a 1/2" plywood form. The edge of the urethane had numerous dings in it and I knew that I wasn't going to get the edge I wanted without a form and support. This worked great. |
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Trouble! If you read the archives carefully - unlike me - you will notice that several people noted that the forward urethane blocks were a little short using the plans dimensions and the result was a slight dip 4"-8" aft of the landing brake of about 1/4" in depth. This was unacceptable to me so I set out to correct it. |
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Here you can see that the sides have now been rounded. Again, whenever sanding or cutting away something - go slow. It's a lot easier to take off than it is to put back. Well fixing that dip behind the landing brake wasn't as easy as I had hoped. I didn't have any 1/4" foam so I thought I would try some pour-foam. It works - soft-of. It doesn't have as fine a cell structure as urethane and can come out looking like mange when sanded. I ended up hard shelling (a coat of Micro) over the top of it and sanding that down to level. I also used some to correct a little over zealous sanding on the corners. |
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Here the landing brake has been prepared. Notice that the build-up around the edge has been done using double sided adhesive foam instead of duct tape. The foam is exactly the right height and is easier to apply and remove. The backing is left on the exterior as a release when it comes time to cut the brake free. Note also the lines on the fuselage for aligning the layups - very important and makes the layups go faster. |
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The wood backing for the step. I was undecided on which approach I would use for the step - so I went ahead and put in the wood support - Oak too! (didn't have any spruce that size). I later decided to use the retractable step so I'm now carrying around a few ounces of wood that I don't need - oh well. |
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A good pivot is essential for the next 100 or so steps - well at least until you get the landing gear in. I chose to screw a 2x4 into LWX (Y? - the wood thingy inside the main spar cut-out). I then made the pivot out of 3/4" plywood that is screwed laterally into the 2x4. I also had a removable brace I could add that provided fore-aft stability when sanding and shapping. |
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Sides glassed - and peel-ply'd |
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Sides glassed - and peel-ply'd |
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When lapping onto the firewall (I think it says 5") - make sure you tape your screws that you installed in Chap. 4! |
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Hinges should be installed in Chap 7 as well - that way you don't have to cut the shoulder support later to get to that nut. Even though I used a straight edge and level on both hinges to keep them in the same plane and in line - I think one of them is about .05" out of line. I guess I'll find out how forgiving the canopy is in a few months. |
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Reflections Lots of "Micro" in joints that are going to be sanded is not a good thing. Try to get a tight joint with little micro needed to hold the joint. There will still be flakes of Micro that break off - but they should be smaller. User longer 1" urethane on the forward part of the NACA buildup so there isn't a dip behind the landing brake. That way the bottom of the fuselage will be flat until it gets to the landing gear well. Go slow on shaping - it is real easy to take too much off - and it is real hard putting it back on. Now on to Chapter 8 Shoulder supports, Headrests, and SeatBelts!! | |
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