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Fiberglassing a large balsa nosecone...
#1
I'm in the process of building a 3 x upscale Estes Bandit (the classic K-48, not those horrible recent things!) with 4" BlueTube for the airframe. I have a glorious hand-turned balsa nose cone from Gordon Agnello of Excelsior, but the shoulder fits a bit loose in the airframe and the base diameter is a bit smaller than I would like. The obvious answer is to cover it with a couple layers of light fiberglass.

After much searching on the Internet, I didn't really find an answer that I liked, so I came up with my "own" technique that seemed to work pretty well. 

First, I marked three equally spaced points around the shoulder of the nose cone, and added one at the very tip. Then I grabbed my chalk line and snapped lines from the marks to the tip, dividing the cone into perfect thirds. So, this gave me the size of the fiberglass pieces that I wanted to lay up, but how do you turn a complex curved surface into a flat one? I tried wrapping paper around it and coming up with a template that way, with less than usable results.

Then my wife walked by and saw what I was trying to do and suggested that I try plastic wrap. I thought (to my self) what a dumb idea! I can't even get that stuff off the roll without it folding up on itself and ending up balled up in the trash. Plus, it would stretch at the slightest force and leave me with a distorted template. Of course, it worked perfectly. 

With her help, I was able to get an unfolded sheet of plastic off the roll, carefully lay it across the nose cone, and hold it there while tracing along the chalk lines and shoulder transition with a Sharpie. I then transferred the plastic wrap to my cutting table and cut along the lines with a rolling fabric cutter. This flimsy template was placed on top of heavy paper and carefully cut out using the fabric cutter to create a paper template.

This final template was used to cut out multiple layers of 1.5 oz. fiberglass cloth (again with the rolling cutter). I tried to cut about 1/8" bigger than the template to make sure I got some overlap on the layup. I taped the nose cone to some scrap tubing, mixed up some West Systems 105 resin with 206 slow hardener, poured the epoxy into a Tiny Trim-It Roller Tray Set that I found at the local Home Depot for $3, and rolled an even layer of epoxy onto the nose cone. The fine fiberglass cloth is very transparent when wetted out, making it easy to see the chalk lines for aligning the cloth, and to see where I needed to roll on more epoxy. The first three pieces went between the chalk lines, the next three pieces were centered on the chalk lines to offset the seams. I ended up putting on four complete layers of cloth, and it went on like a dream. Any big wrinkles that tried to form were fixed by tugging on the closest corner of cloth, and small wrinkles and bubbles were easily rolled away with the mini-roller. Even the very tip looks pretty good, but it will take a bit of trimming and sanding to get it perfectly smooth.

I decided to do the shoulder separately, so I'll probably just do a single layer of heavier cloth there. A couple coats of primer and it should be ready to go!
Let us create vessels and sails adapted to the heavenly ether, and there will be those who will not shrink from even that vast expanse. - Kepler to Galileo in 1610

NAR 86500
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#2
Photos man...


Bill Clune L3 | NAR#88583
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