compound curves in plywood

"Rich S." wrote in message
...

The end result was a smooth, compound-curved, thin, light, streamlined
shell of a body.

Hah! I thought I had one - just one - picture around here someplace. You can
see it at http://tinyurl.com/4xqyw

Rich S.

nafod40 :

BA-100 wrote:
Does the cedar strip technique you mention use multiple layers of
veneer? Presumably you need a form to wrap this around. Does it have
to be solid or can you just use formers, say, every 9 inches or so?
How do you clamp to get a good bond between layers?

A different build method from cold moulding. Does not use veneers.
Here's a great site on the strip-built approach.

http://www.guillemot-kayaks.com/Buil...ilt/index.html


OK, now i'm totally confused! Most canoes i've seen seem to have their wood
running at about 45 deg. This looks pretty much just like strip planking
any boat!
I used to build models like this, using strips of balsa from nose to tail.
I've never seen a full sized aircraft using anything like this. Most seem
to use either sheets planked on formers, like many thirties glider like the
Minamoa or other european high performance saillanes of the thirties as
well as the Albatross of WW1, or the Lockheed method. (And BTW, the guy who
says the dutch built stressed ply airplanes for the Germans is a bit off
course, Tony Fokker only built those things under duress, he hated them and
didn't design them, rather, he and his chief dsigner, Rheinhold Platz,
developed the steel tube fuse we all came to know and love, but I digress)
There were a few inthe late thirties, notably the Timm aircraft and one
odball little twin, the Langley which used something called the "Vidal"
method of contstruction which apparently involved about 5,000 sq feet of
veneer and god knows how much resin to make one airplane. Pretty litle
thing

http://www.aerofiles.com/langley-twin.jpg
http://www.aerofiles.com/langley-twins.jpg

As you can see, the unpainted versions clearly show a 45 on all the wood
visible. Presumably, the underlying layers al go 90 deg to each other.
You gotta love the way the did the cowls out of wood as well!

http://www.aerofiles.com/langley-twins.jpg There's little doubt but that
this airplane would be nigh on impossible to build at home, but surely one
of these must be able to produce the simple teardrop that is the Baby's
pod. By the way, on the original, the teardrop is pure. That is, the fillet
between the teardrop pod and the wing was not all one piece. That fairing
is added on afterwards and is non-structural, which,it seems to me, would
simplify molding the pod no end.

In article . net,
"COLIN LAMB" wrote:

I just looked at the fueslage of the Bowlus and it would be easily
duplicated using cedar strip techniques. Assembly is very quick with almost
no tools required, except for a saw to cut the wood strips. I did use some
mahogany in one of my canoes, just to try it, and it works fine. Because
the inside of the fuselage does not require the transparancy that the
outside does, you could even use one of the lighter and stronger cloths
(such as carbon fiber). This would result in increased strength and lighter
weight.

Now I may have to build one. The tube from front to rear could be
constructed easily using carbon fiber cloth rolled into a tube, or a
commercial tube purchased.

Colin

You might want to explore this site:

http://single-handedskiffs.com/pages/453349/index.htm

That is a sailboat constructed along the lines being discussed. What's
interesting and germane to note is the *loads* on such a boat created by
the rigging. Typical standing rigging (that which holds up the mast) is
tensioned to hundreds of pounds, so you can get some idea of the loads
created between the rigging pulling upward and the mast pushing down.

There are some notes about the resin system used (from West, IIRC) and
some strength testing done on sample panels.

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

In article ,
"Rich S." wrote:

"Rich S." wrote in message
...

The end result was a smooth, compound-curved, thin, light, streamlined
shell of a body.

Hah! I thought I had one - just one - picture around here someplace. You can
see it at http://tinyurl.com/4xqyw

Rich S.

Forget that. I want the four-foot long micrometer secret!

--
Alan Baker
Vancouver, British Columbia
"If you raise the ceiling 4 feet, move the fireplace from that wall
to that wall, you'll still only get the full stereophonic effect
if you sit in the bottom of that cupboard."

"Alan Baker" wrote in message
...
In article ,
"Rich S." wrote:
Hah! I thought I had one - just one - picture around here someplace. You
can
see it at http://tinyurl.com/4xqyw

Rich S.

Forget that. I want the four-foot long micrometer secret!

How much energy is wasted while coasting over a thousand foot downhill
course if one (of four) wheels is one-thousandth inch out of alignment with
the other three?

Instead of expressing the loss in some esoteric unit of measurement, express
it in terms of "equivalent to pulling the racer X inches sideways".

How many builders align their wheels using a micrometer?

Rich S.

BA-100 wrote:

Does the cedar strip technique you mention use multiple layers of veneer?
Presumably you need a form to wrap this around. Does it have to be solid
or can you just use formers, say, every 9 inches or so? How do you clamp
to get a good bond between layers?


http://www.oneoceankayaks.com/Kayaks.htm

The web site I was looking at for a kayak.

Yes to your question of formers Their plans give you full size former
layouts that you cut out put on the plywood and cut the formers from there.
They then attach the formers to a central beam and proceed to lay up the
wood strips using whatever wood to get the design they want mostly cedar
with mahogany for designs. after they do the top half they cover with
fiberglass and epoxy. They then remove from the formers (you did use
waxpaper on the formers right?) and fiberglass and epoxy the inside.
They then repeat with the bottom side. Then you fit the two sides together
and apply fiberglass tape and epoxy to both inside and outside of the
joint.
Basically instead of using foam for a core they use wood strips.

As soon as I finish this KR-2 in my garage (about another 10 years) I'm
going to start on my Cape Ann Double Kayak!

John

COLIN LAMB wrote:

I have taken my canoe through
rapids, over small water falls and survived collisions with rocks. The
same technique should work for a lightweight aircraft.

Colin

Dang your brave I wouldn't want to do that in my airplaneG!!

Question: Does the cedar strip technique you mention use multiple layers of
veneer? Presumably you need a form to wrap this around. Does it have to be
solid or can you just use formers, say, every 9 inches or so? How do you
clamp to get a good bond between layers?

Response: Some of the cedar strip boats that I built were made from 1" x 6"
cedar planks, which means they were about 3/4" thick. Then I ripped those
planks on a saw (table saw, band saw or radial arm saw - whatever is handy).
This will give you long strips that are about 3/4" wide and 1/4" thick.
Cedar is used because it bends easily, looks good and is light. Stations
are built conforming to the curved shape you want. Each station is about
12" to 16" apart. Wax paper or tape are put over the plywood forms. The
first strip is installed, and following strips are glued adjacent to the
first step. The strips are stapled onto each form. Alignment between
stations can be assured by clamps over the strips you are gluing. The glue
does not matter, becase no strength comes from it. You can butt joint each
piece. Although some perfectionists angle the edges of the strips going
around a curve, it is not necessary. If there is a slight opening, epoxy
will seep in and make the structure stronger. The cedar simply replaces
foam, and the strength comes from the layers of cloth and epoxy resin.
Carbon fiber is stronger and lighter, but would cover up the beautiful cedar
strip finish, but could be used on the inside. Obviously, the application
and strength of the epoxy will control the strength of the overall
structure, but it can be quite high. The strength requirements for the
fuselage of something like a Bowlus would be quite low - but there would
obviously need to be some method of attaching the wings to the fuselage and
spreading out the stress of the lifting point.

However, the pod itself could be created similar to a cedar strip kayak. My
17 foot cedar strip kayak weighs about 50 pounds and I made no effort to
save weight.

One other process, which could be used is a process developed for the HK-1
Hughes "Spruce Goose" It is built of laminated birch. As I understand the
process, the it was plywood made in the shape required for the aircraft and
known as Duramold. The aircraft companies made a number of small boats
using the same process to perfect it. The Evergreen museum no doubt has
some information on the process.

The inventive can replace the Molt Taylor Aerocar of yesteryear with a
Glider/kayak. When making an outlanding, simply land by a lake ro river,
remove and store the wings and tail, and paddle home.

Colin N12HS

"COLIN LAMB" wrote

I have built a number of cedar strip canoes and kayaks, and the process is
simple and beautiful.

The same technique could be use for aircraft. I have taken my canoe
through
rapids, over small water falls and survived collisions with rocks. The
same
technique should work for a lightweight aircraft.

One problem is that for an airplane, there are bunches of point loads, like
the spar, engine, and landing gear. There are also some wicked bending
moments involved. If you canoe breaks, you go swimming. If you airplane
breaks, you......
--
Jim in NC

"One problem is that for an airplane, there are bunches of point loads, like
the spar, engine, and landing gear. There are also some wicked bending
moments involved. If you canoe breaks, you go swimming. If you airplane
breaks, you......"

No question the point loads are a big issue. However, it is the same issue
for those who build epoxy airplanes - because that is what a cedar strip
boat is really, an epoxy boat with a cedar core, instead of foam. All of
the cautions against cedar strip aircraft would apply to foam/epoxy
airplanes - yet there are a number of successful creations flying around.
The main difference is that you have to paint a foam/epoxy job because foam
is not intrisically beautiful - wood is.

I am not sure I advocate building a twin engined cedar strip fighter, but
the original query was regarding a Bowlus. It has no engine and the
strength demands are not nearly as great as a 10 G fighter.

Colin