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[ATM] growing and weaving a tube
I think sonotube is a handy material to have around.But it's weight is
a factor.The size and weight we are talking about here would be a bit much
to backpack.
Mark brings up a good point.It is indeed possible to have a properly glued
joint be stronger then the rest of the piece.Most joint failure comes from
3 things,
1.thermal failure,trauma,and design flaw.A well designed joint that is
assembled with the correct adhesive should withstand anything but a nuclear
exchange.
When I was living in Florida,(1970's)I would visit a local sailboat shop in
N. Palm Beach.The hulls for these $10,000 per ft. works of art were hand
laid fiberglass.A 'plug' was formed and the hull laid up on this piece.Some
of the forms were very intricate to say the least.This topic reminds me
that a ships hull is very much like a telescope.Few things are square,never
on the level,and constantly moving.The idea of laminating a tube with all
the beef in the right places,(joints,bosses etc.) it would be very strong
indeed.The idea is to 'grow a tube',much like trees grow around boulders in
the mountains.The forms should be made very carefully out of wood.A table
saw and router would be the principle tools for this.However hand tools and
some patience should do as well.And to stiffen real thin sections or to add
metal where you really need it,add metal.Brass,SS, or alum parts can be
'cast' right into the process.So when you get into the assembling
process,the material is there for you,and it shouldn't corrode.Boat
builders use 3 types of cloth: mat, it looks like a doormat or enlarged
screen.has great strength,roving,a bit more refined to smooth out the form,
and chop cloth,looks like bits of thread in a cloth.Many auto-body shops
use this for places like rocker-panels.A series of layers of mat,
roving,and resin are used on boats to give it the indestructibility the
older wooden ones could not.Finishing the work can be accomplished by using
wood veneer,or star-charts under a coat of,clear gel or gel coat.This is
the top layer of any boat hull or bulkhead.A scope with a 3/8" thick
tube-work made like this would be strong and stiff enough for most scopes
under 24",OK I'm guessing that approaching 24" could require more
under-pinning and strut work.Now here's the down side.It takes some
hard,sticky work,and it won't be cheap.You need to have a good filtered
breathing mask and work out of doors.You will be working with acetone and
other fun stuff that is anti human until it goes off.The forms need to be
accurate.BUT all the steps are simple.A well-thought out plan and a partner
are a plus.You may wish to do this in halves.Then fit the 2 pieces
together.If you can understand positive and negative shapes,your ahead of
the game.
For the less intrepid,I'd stick to the apple-ply club.Use chop cloth in
strips for all joints.You can wrap cloth around a strut for added
strength.Round tubes made of 16 gage alum can be made much stronger by just
1 layer of fiberglass and resin.Thin 1/32" .032 2024 alum is very easy to
roll.Another idea is to spin an octagonal tube.Ok, NOW Ron's on drugs! But
think a minute.Build a form on a 3/4" steel shaft with a hand crank.Use it
like a lathe to wind a fiberglass or kevlar thread on to the skeletal
form,(use lots of mold release).Keep a couple of guys busy mixing and
brushing on the resin as you wind the octagonal,or round tube.The first
wind can be straight while the next can be spiral.I should think a very
thin,very strong tube can be had with this method.You can very the layer
over critical areas where you want extra support. This is a low tech
approach anyone can do with a few things from a local hardware store.The
form can actually be the baffle system and interior rib-struts of the
tube.If you could use a black linen cloth as a first piece tacked onto the
ribs,it may serve as a light dampenner.The outside can be finished as
described earlier.I'd try it on a small scale first to see just how much
hot air I'm suggesting here.I cannot imagine this has not been tried
already.If I can come up with this stuff,there must be hundreds ahead of me
who already have.I'am sure there are some blanks to be filled in to make
these processes work.My intent here is to get you to just think about the
possibilities.
regards, Ron
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