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Normal Topic Bamboo Skewers for area that need added strength. (Read 328 times)
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Re: Bamboo Skewers for area that need added strength.
Reply #2 - Feb 22nd, 2020 at 11:57am
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Saw this post and reminded me of using round reed in place of bamboo, given that bamboo is tough to bend as seen in Alfakilo's post. As I remember, Tom used this material for the stringers in his Roland Walfisch and I ordered some to use for stringers on the Marcoux Bromberg. When it arrived it was rolled pretty tightly so I went to work to straighten it and stuck it in water for a couple of hours and found it relaxed very well, so well I could tie it in a loose knot. The down side of this stuff is it comes in a life time supply.  I dug out the wing tip template for my Culver Dart and bent some. The process is same as laminating wing tips with balsa strips.

The following pics are:
1. Reed dry with the template
2. Reed wet and starting to wrap on the form
3. Wrap complete
4. Reed off the template

There is some spring back but nothing that cannot be pushed back into place during glue up.

Hope this helps in some small way.
Mike
  

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Reed_Finished.jpg

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Re: Bamboo Skewers for area that need added strength.
Reply #1 - Feb 19th, 2020 at 11:04am
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I've been experimenting with bamboo as a replacement for balsa, more of a desire to try out 1930s building methods than anything else.

For certain, bamboo is really durable, much more so than any balsa technique.

My experience with working with bamboo is at odds with some aspects of that article. Bamboo can be bent using some form of heating, but I've found that the bent piece will not hold its exact form because it tends to relax a little. By itself, not a big deal since we can overbend it a little so that it 'relaxes' to the shape we want.

I've found that the heating method is not as simple as it seems. I agree with some sources that suggest steaming is not the best approach. Most references involve applying heat directly to the wood, the most common example being the soldering iron. This works but for me is awkward to use and easily scorches the wood.

Here's what I use now. I have a hot plate that I use for heating vacuform plastic. I like the hot plate because it lets me control the temperature. I cut a small (2" by 3") piece of sheet metal from the left over sheet that I used for my magnet building board. I clipped that to the hot plate heating coil to provide a larger heating surface area. I stripped a 1/16" bamboo stick and sanded it flat on opposite sides.

Then I cut a form from 1/8" sheet for my wingtip, stab, etc and taped one end of the bamboo stick to the edge of the form. I set the hot plate to a low temp setting to start with (I'll increase that a little if the bamboo isn't bending well). I think the bamboo bends easier if wet and is less prone to breaking as well, and so I boil the sticks a little first.

To bend the stick, I place the taped end edge on the hot plate and slowly roll the edge of the form as the stick slowly bends. I use a little pressure but not much, just enough to get a solid contact between the bamboo and hot plate. Practice makes perfect and I'm still learning this black art!!

Some additional thoughts. Bamboo is heavier than balsa so use thin strips (I think 1/16" is probably the max needed). Thinner is better. Old plans that show bamboo tips seem to show very thin strips.

When thinking about how to attach tissue to this thin strip, I had one of those "light bulb" moments. Back in the day, most folks glued the tissue on dry in small pieces using dope or banana liquid (liquid adhesive similar to dope without the smell). Gluing a piece of dry tissue to the bamboo strip wasn't difficult since there was a minimum of tissue adjustment. Probably still can be done wet but the narrow gluing surface will require extra attention.

I'll post some pics as soon as I can!
« Last Edit: Feb 19th, 2020 at 9:06pm by alfakilo »  

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Sky9pilot
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Bamboo Skewers for area that need added strength.
Feb 12th, 2020 at 10:00pm
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Found this tip from Rick Pendzick's "I.T. Corner" in the FACN JAN-FEB 2020 issue.

I have been working with bamboo skewers for areas that need extra strength. I have found  my razor plane works well. With a little effort I can make a half round leading edge or working both sides, a flat stick.  The wonderful thing about bamboo is how easily it is bent and once formed it will stay in that exsact shape.  When making rounded wing tips the length of bamboo that requires heating is a few inches long.  So the method of using a soldering iron just didn't heat a long enough length of bamboo.   So I tightly wrap my bamboo stick in aluminum foil.  Then heat about 4 inches of bamboo  over a flame.  The aluminum foil prevents the bamboo from scorching.  It does not take long for the bamboo to turn soft, almost rubbery.  You must immediately move to your form.  In only seconds the bamboo cools back to a stiff stick.  With care you can re-heat and re-form.

It might take you a few tries to exactly form the bamboo shape you wish, but bamboo skewers are cheap and easy to get.  Also, save the bamboo shavings from your razor plane.  I soak them in water and straighten  to dry.  They are excellent reinforcdement for broken balsa sticks and can be used to strengthen any weak spots.

Have fun -- Rick Pendzick

Also here's a link that Alfakilo posted on a source of flat bamboo sticks approximately 15" long for those longer needed areas:
https://www.amazon.com/gp/product/B0739LZQWL/ref=ppx_yo_dt_b_asin_title_o01_s00?....

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