MegaTech R/C Real World Helicopter Series Uživatelský manuál stáhnout pdf (Strana 49)

Glass cloth will not take

to sharp corners, so I filled

these with a mixture of resin,

chopped strands and a thick-

ening agent. A generous

layer of this mixture will pre-

vent any cloth from showing

through. It also helps to flat-

ten out any irregularities in

the compound. Use only air-

craft-grade epoxy; it's much

easier to work with and it

leads to better results.

Immediately following

the resin/fiber mixture,

I applied the layers of glass

cloth that would form the

mold. I try to minimize the

amount of resin; the cloth

reaches its maximum

strength once it's completely

soaked. Any excess resin

only adds weight. The first

layer of cloth can be laid on

the mixture with almost no

resin at all. I added subse-

quent layers of cloth until it formed a rigid mold. For small items like

this, I stick to a wall thickness of %2 to % inch; this requires approxi-

mately five layers of 1 -ounce cloth. I always let the cloth cover a fairly

wide area (about 1 inch) around the plug, as the second half will be

formed against this and will require trimming after the moldings have

cured. This photo shows the final stage of the first half of the mold.

|=| When the first half

had fully hardened,

began the second half

of the molding. Never

remove the molding

from the support or the

first half of the molding

from the plug in the

early stages; patience

is the key to this

process! I carefully

removed the blade from the support and cleaned off any excess

clay. This photo shows part of the newly formed flange in black,

with all of the clay still stuck to the blade and flange. Thanks to

the release agents, it was easy to remove.

Next, I used a Dremel saw to cut

off any excess cloth. To ensure a

proper fit, I drilled some 1/8-inch

blind holes into the flange,

spaced about 3 inches apart.

This will act as a lock when form-

ing the second half of the mold.

Commercial pins are available as

well, but for small items like

these, I generally stick to this

method. Once again, I liberally

treated the plug and flange with

release agents before moving

on to the next step.

l For the second side

of the molding, I

simply repeated all of the

previous steps. Here, I've

just applied the glass cloth

to the molding compound

to begin forming the second

half of the mold.

When they were fully

cured, I drilled the

moldings through while

they were still attached

to the plug; this ensures

maximum accuracy.

I then trimmed off the

excess cloth and

separated both halves

from the plug. For the

first splitting, I normally

use some warm water

to dissolve the PVA; an old credit card carefully placed in between

the flanges can also be beneficial. Never use metal tools or brute

force! Usually, the plug just falls off. In this photo, I had just

removed the two halves from the plug.

Because you must close the mold while the cloth is still

wet, it is essential that the cloth fit the molding exactly.

Pictured here are two layers of 0.4-ounce cloth together

with a non-woven surface cloth. The black shoelace is, in fact,

carbon roving, which I later laid around the blade's perimeter.

Making the actual

prop is basically

just a variation of

the molding

process, beginning

with the application

of the wax and

PVA; the primary

distinction is in the

outside coating.

Though gelcoat is the most common choice, you can also use a

good quality epoxy-based paint. I brushed on two coats of yellow

Hobby Poxy. Once it had hardened to the point that it was sticky, I

brushed in some slightly thickened resin.

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