The craziness continues!
My continuing flirtation with Aviation:
I've purchased a 90% complete Mitchell U-2 Flying Wing!
(Which in Aviation math usually means, 90% is left to be done.)
Manufacturing a new Nose
The original nose was unfinished and the shape was totally unacceptable. I never had any intention of using it but I didn't want to insult the seller, even though he wasn't the builder, so I was going to bring it back to Colorado with us. Either it didn't get put on the trailer or else it didn't get tied down before we pulled out. Either way, it didn't make the trip home!
|I decided to mold the nose
over a plug rather than cast it from a female mold.
To build a nose plug we start with a piece of 2 in x 2 ft x 8 ft house insulation foam and cut it into 6 pieces to give us a stack that is 12 inches high.
|The pieces were sprayed with contact cement and then left stacked under some weights - 70 lbs may not have been enough weight.|
|Next comes the art! After going out to the field to scribe the angles of the fuselage (the straight lines) on our block, we laid out the side profile I wanted for the nose.|
|Then we laid out the top profile that I thought I wanted. This was the first idea but it was changed twice before we settled on a final shape.|
|Working on the hot wire
The profiles were traced from the block and transferred to 1/4" thick MDF which was then cut and sanded to the final dimensions.
|The first two cuts with
the hot wire. Both of us were needed to make the hot wire cuts so
there was no-one available to take a picture of that process.
Basically, Norm held the block and I pulled the bow along the template free-hand. Note there aren't any position lines marking the templates. It worked out better than I thought it would.
|All four hot wire cuts are
complete. We took the nose plug out to the field and tested it for
fit against the plane - we had missed and were oversized in one direction so I had to re-cut
We keep these sections to use as saddles or "beds" to protect the plug during the cutting and sanding steps.
|Rough shaping - using saws, hand planes and sand paper.|
|The finished plug, ready to check dimensions and then lay-up the carbon-fiber part.|
|Fit- up looks fine but the
angle maybe off slightly. I think we will be able to
"shift" the part enough to correct the small angle error.
The front deck shown is the one I rejected - another one is acceptable but not done yet.
|Finally! A test part is under the vacuum bag.|
(on the left) I decided to pull the fiberglass lamination off of the plug
to check it for fit up on the plane before continuing with the expensive
carbon-fiber laminations. Everything looks good at this point - but
then we noticed the damage to the plug from our struggles to remove the
See the vertical streaks that we had to fill? They were caused by the thin, flat shims we pushed between the part and the plug.
This was considered a test part to prove the plug but it appears to hold some hope of becoming the actual nose piece. Two carbon laminations (one at a time) are coming up!
|Rolling out one of the two carbon layers prior to prepping it for the vacuum bag.|
|With the cowling complete, the nose's internal former is fit-up and clamped before being epoxied to the nose.|
|At last, the two pieces are nearly complete as the epoxy between the nose and it's former cures.|
|Once the epoxy is cured there will be some touch up reqired and the final clear-coat (automotive) for UV protection.|
|Here is the side
view. Here the two parts are separate pieces but while I was working
on them a friend had walked through the
hanger and commented that he thought the two pieces
were one piece. After he left I suddenly realized that he might have
suggested a solution to a nagging mounting problem. Before his
comment I hadn't thought about fusing the two parts to make one piece but
after giving it some thought I've decided against it.
The nose has to be removed in order to be able to truck the plane down the highway without exceeding the highway load width requirement. So ease of attaching or de-attaching is important.