Model Forum / Radio Controlled / Air Models / April 2007

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c.air&q=scratch+building&qt_g=Search+this+group>

-- pinpricks through the plan
-- copy the plans, place upside-down on wood, brush
    acetone over the back, rub, lift carefully
    (Careful!  Copying can introduce distortions in
    the x-axis, the y-axis, or both.)
-- copy the plans, cut out sections, rubber-cement to
    the wood
-- trace plans, cut out tracing paper, rubber-cement to
    the wood
-- copy onto card stock, cut out parts, trace onto wood

Try both.  I like a fine-tooth bandsaw myself. I cut
outside the marks and sand down to them, more or less.
YMMV.  Whatever works for you is "best."

For a simple design, you can cut stacks of ribs, sand
to final shape, and cut notches while still in a stack.
Tack-glue, pierce with nails, bolt the stack together ...

For more complex wings, you can make a root and tip template.
stack the stock in between, have at the stack with a razor
plane & sandpaper.  Gently sand a perpendicular surface
on each rib afterward.  You might want to mark the low
(good) line with a pen so that you don't inadvertently
spoil the piece by sanding too much off.

Sin bravely.  Then let us know what worked!

"One observation is worth 10,000 expert opinions."

                Marty

I like to trace curved shapes onto plain white paper with a pen, cut it
out, and trace around the template with a pen onto the wood.  Then cut
the wood out, erring on the side of being oversized.  Then sand with a
sanding block and compare to the plans repeatedly, until it's just like
the picture on the plans.

When dealing with straight edges and angles, nothing beats measuring the
plans and transferring the measurements onto the wood using a ruler.

I make ribs one at a time.  I make a master rib, then trace around it
and rough cut the rest of them.  Then I hold each rib against the master
in one hand while shaving the extra balsa off with an XActo knife in the
other hand.  It sounds time consuming, but it's pretty fast when you get
the hang of it.

A lot of guys use rubber cement to attach paper to the wood, etc, but
that's just extra steps if you ask me.  Even if you glue paper to your
parts you're going to sand and compare the part to your master plan
anyway, so why not just do that without all of that copying and gluing?

By the way, what plane are you going to build?

I'm also a woodworker.  I've found that a hacksaw blade on my band saw
gives fairly smooth cuts in balsa, modeling plywoods, and even foam.
For small cuts or thin material, I use a surgical scalpel.  They are a
little sharper than a modeling knife and the blades are cheap if bought
un-sterile, by the 100 pack.  My table and scroll saws just cut too
aggressively for my liking, regardless of the blade I use.  Finally, if
I want to use a power sander (bench or palm) I have to use a really fine
grit (150 or finer) to avoid taking off too much stock, too quickly.
Experiment - you will quickly find what suits you.

Good for you -- scratch building is the way to go.

I usually transfer parts to wood using the pin-prick method.

For straight wings I make a master rib of plywood & use it as a
template.  There are a number of ways I've seen recommended to hold the
rib to the wood -- I just glue a strip of coarse sandpaper to the master
rib, and cut carefully to not dislodge the master from the rib.

For tapered wings I make a pair of master ribs & cut a stack.  I leave
the (excessive) taper in the ribs, then sand it off after the wing is
assembled with sanding paper on a long (one or two feet) bar -- this
gets _everything_ straight.

I use a coping saw for balsa thicker than 1/8 inch, and for plywood.
Sometimes I use a knife for thin plywood, but it _always_ breaks the tip
of the blade.

Get an X-acto knife or the equivalent, and buy blades by the 100.
Replace them often, and _always_ start with a new one for a critical cut.

I print on a laser printer, turn teh paper over and rub dope thnners
through. Printed wood results.

Razor saw, scalpel and permagrit block to sand it.

The message <1170885567.538314.131540@v33g2000cwv.googlegroups.com>
from "Kevin R" <datafry@gmail.com> contains these words:

A method I have used for accurate copies is to scan the plans using
Photoshop and a good scanner, the error is approximately 1mm in 36''
which can be absobed quite easily, scan a secttion of plans then when
you do the second scan overlap the first at an identifiable point so you
have a reference to match the two sheets to and so on.
Align the two sheets with a good straightedge such as a 1'' wide 36''
steel rule or strip of metal then glue the sheets together at the edge
and then compare the tiled sheet to the original, once you know you can
make accurate copies all you need do is scan a pattern or whatever and
print it then cut the print out and stick it on the wood. I have been
using this method for a long time with scale sailing ship models of
large warships like Constitution and Victory etc and never had problems
with distortion or inaccuracy worth bothering about.
One method I had to use because of the bad state of the plan was to
print on tracing sheet then place these over the top of the original
plan to match them before fixing them together, once assembled I laid
the tracing over a sheet of white paper on my drawing board (yes! some
of use antiques still use them.) for clarity, this allowed me to work on
the plan without causing damage to the original,

                                       regards,                       Terry

Kevin I do have a power point presentation on gang sawing ribs made by
me and James Taylor renound builder.
send me your e-mail address and I will send you the presentation.  Doc
Ferguson

Having built a few planes from just plans I have settled on the
following....

Save your pizza and cereal boxes !

Cut them up to obtain nice, flat sheets of cardboard and store them.

Put cardboard (that you carefully saved) and carbon paper under the
plan. Put plastic film on top of the plan. Trace around the part with a
ball pen (leaves a nice sharp line), the plastic protects the plan.

Cut out the shape that has been transferred onto the cardboard and use
this as a template to mark the balsa.

A French curve, or one of those flexible strips that can be bent to any
shape is handy for tracing around curved parts.

For wing ribs I normally use the above method to make a thin plywood
"master" template.

Once parts are cut gently sand until they match the part on the plan.

I use a scroll saw a lot and find it invaluable.

Making your own "kit" from a plan is very satisying.

Reg

I make templates for curves like ribs.  To make the template, I use a piece
of hardboard, or something like that.  I lay the plan over the hardboard,
and prick the plans with a pin, about every quarter inch, more when the
curve is sharp,less when it is straight, or close to it.  I then take the
plan away, and connect the dots with a French curve, cut on a band saw, and
sand to agree with it laying on the plan with a drum sander, or disc sander.
The sticks I just lay over the plan and cut with a razor saw, and then use a
miter sander to true it up.

I use a product called See-Temp. I purchased it from a vendor at the
Toledo show years ago and now am ready for a new supply. I believe he
advertizes in one of the model mags. I did a web search and found two
places that sell it.

http://www.woodcraft.com/family.aspx?FamilyID=5866
http://www.seetemp.com/

These are the two. The stuff I used is a milky color but I see the
first link has an orange color. Anyway, take a look and once you use
it you will not use any other method.