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Author Topic: Reeds and lost foam questions  (Read 427 times)
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fred
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« on: August 01, 2017, 05:31:17 PM »

Was reading the old threads and was fascinated by Tom Arnold's Me262 build.
 First I've seen of  'Reeds' as Formers. 
Wetted these  seemed to form tight radii  formers on a Blu foam fuse plug.
 Wonderous :-)
Where can one source these?
 Also the blue foam was melted out of the built surrounding balsa fuse.
 When I try melting out blue foam .. I get a horrendous mess of blue goop.
 Definitely not, the looks like there never was any foam there results.
 Is there a technique to this that I'm entirely unaware of ?
 Thanks..
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Greg Langelius
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« Reply #1 on: August 01, 2017, 06:28:47 PM »

Amazon Craft Flat Reed. https://www.amazon.com/s/ref=nb_sb_noss?url=search-alias%3Daps&field-keywords=craft+flat+reed&rh=i%3Aaps%2Ck%3Acraft+flat+reed

Back in the 1950's I was apprenticed (under ten years old) to a WWI (German) Vet who was a chair caner. We would go out to Flushing Meadows Long Island, NY. and pick bull rushes. They were dried in the garage workshop, then split lengthwise into 1/8" strips. These were soaked in water, woven, anchored with dowels driven into holes near the outer edge of the chair seat and back. The dowel holes were connected by a 1/4" groove running around the line of holes, and a 1/4" round cane was pressed into the groove to hide the dowels.

Nowadays, they sell woven cane. It's not the same.

Greg
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Sky9pilot
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« Reply #2 on: August 01, 2017, 06:41:55 PM »

I believe Tom Arnold used the round reed that is approximately 1/16 diameter.  I believe he used laquer thinner to dissolve the foam.  I used his process on my Grumman Goose build. Click Here

I bought the round reed (a lifetime supply) at Walmart here: Click Here

Tom
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fred
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« Reply #3 on: August 01, 2017, 07:11:56 PM »

Thank You.. gentlemen .. all.  
Your  Links open up a world of possibles
 I had 'deduced' that those reeds were 1/16th.  Although width... a bit larger doesn't seem as a problem though
Never even considered Wally world.. 'till now .
 
 Was concerned about the Gooey residue mess that dissolving Blue foam creates.
 Worried cuz that's what happened in my previous efforts.
 The linked techniques work well then ?
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ZK-AUD
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« Reply #4 on: August 01, 2017, 07:19:20 PM »

Wonder whether the form was wrapped in glad wrap /saran / clingfilm before the wood went on.  Or even a condom come to think of it.  Some of our NZ ones should be good up to Coconut scale  Grin
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Sky9pilot
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« Reply #5 on: August 01, 2017, 09:18:02 PM »

No wrapping of the foam form.  You want to be able to dissolve the foam at a later time.  Grin Wink Cool
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tom arnold
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« Reply #6 on: August 01, 2017, 11:13:56 PM »

I always wondered if anybody else had tried the lost foam method and there are, indeed, a few wrinkles that come up. You are right, Fred, the foam really does not "dissolve" into solution----it transforms from foam into a blue jellyfish of plastic. You want to have a opening in the forward part of your fuselage (think of a P-47) for the glob to drop out as you dunk it vertically. I use a 2' long, 4" diameter PVC pipe as my vertical bath and slosh my form up and down a number of times to rid it of the the blue goo. I pour the used laquer thinner back into the cans but down at the bottom of the pipe solidifies what used to be the foam. It is a plastic floor there now!

When you glue the balsa stringers onto the reed formers (or the overlap joint of the reed formers) many times the CA glue will heat and melt a little spot of the foam at the joint and it will stick to the inside of the reed former even after you have successfully washed the main foam form out. It dries like a little blue spot and sometimes you can chip it out with a needle nose pliers but most of the time it stays. It really is annoying from a cosmetic viewpoint but it is all covered up with tissue and only you know of it. I have tried laying strips of parchment paper underneath the overlap glue joints of the reed to keep it from sticking and it works.

Actually, the wrapping of the form with plastic wrap sounds interesting---I wonder if it would trap the blue goo inside and all fall out? It would take a couple of minutes longer as the thinner could only work from the inside of the form to the out. My only concern is that the heat of the CA glue may attach the plastic bag to the inside of the framework and now you would really have a sloppy problem. Tom (skypilot 9), it looks like you may have done that with your Goose...did it not work?  There is another trick to keeping the blue gobs off and that is to rub the form with plain old cooking oil. It soaks into the foam and really sort of disappears but there is enough oil on the surface to repel the glue. It, of course, disappears with the thinner bath too.

Acetone and laquer thinner does eventually melt CA glue but it takes a lot of soaking and the bath we do is over long before the joints ever get weakened.

« Last Edit: August 01, 2017, 11:27:49 PM by tom arnold » Logged
Greg Langelius
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« Reply #7 on: August 02, 2017, 10:23:00 AM »

Another material that can be of some use is the tiny 1/16" bamboo dowels. They can be obtained cheaply as the main component of bamboo place mats (like he ones intended for rolling sushi, but longer dowels).

Again, Amazon. https://www.amazon.com/BambooMN-Brand-Bamboo-Placemat-Rolling/dp/B0021Y69HG/ref=sr_1_9?ie=UTF8&qid=1501683605&sr=8-9&keywords=bamboo+mats.

Greg
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RalphS
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« Reply #8 on: August 02, 2017, 11:06:09 AM »

I used a light density blue foam master but made the laminated formers from 1/32" balsa, soaked in water and fitted into the location grooves, holding with masking tape.  When dry, these were laminated in situ using pva glue, again using masking tape to hold.    

The stringers were attached with pva to the formers and held in place with bits of masking tape and pins until dry.  When all the stringers were fitted and the glue had dried I poked out the blue foam with various pointed tools rather than use a lot of thinners and the subsequent mess. This dry removal was easy to do.  It gives a clean, light job and I would use the method again on suitable models.  I have shown these pictures before somewhere on this site but repeat them as I can't find the previous post.
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Sky9pilot
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« Reply #9 on: August 02, 2017, 12:29:14 PM »

I didn't wrap my foam with plastic wrap.  I didn't have access to the blue foam, mine was the pink insulation foam in the 4'X8' sheets at Home Depot.  I laminated the foam for the proper thickness for the fuselage of the Grumman G21a Goose.  I left the nose block off so the foam could be removed through the nose once it started shrinking.  I used a wall paper tray the first time to soak the fuselage in.  The pink foam did what Tom said, re: melting some foam under the cya glue joints of the reed and stringers.  Once the foam shrank from the reeds I just use a pair of needle nose pliers to grab the foam and pulled the foam out through the nose.  Worked well for me. I did have to add some cross members to firm up the fuselage at the wing saddle and where I grasp the model to hold for launching. But I liked the process.  I've also used the reed to make round formers for fuselages on some jet models which builds very light and just form the reed around foamboard patterns instead of laminating 1/32" X 3/32" balsa. Then placed on a ladder jig to build the fuselage. 

It's a fun process and reminds me of building solid models in the past, carving and sanding the foam to shape.  By the way.  If you'll rub the foam down with a dryer sheet it keeps the static down and the foam dust doesn't stick all over everything as much.  Just rub the foam down from time with the dryer sheet to keep the static on the foam at a minimum.
Tom/Sky9pilot
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Starduster
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« Reply #10 on: August 02, 2017, 12:36:30 PM »

  Some of our NZ ones should be good up to Coconut scale  Grin

Heck, I could fabricate a Jumbo scale....
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fred
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« Reply #11 on: August 02, 2017, 01:11:18 PM »

Great stuff Guys !
Every post gives serious information.  
I've been 'doing this' since 1960 and I'm still learning 'all new' stuff....Thank you all... again.
  
Tom: yes my previous  foam melting was clumsy with iffy outcome.
 Will try all that you suggested...it seems to work.
 
I have in the past  wrapped BFoam with saran wrap for applying an epoxy glass layer in attempts for a Monocoque
 Worked OK.. but my epoxy cured out as rubbery,  could almost turn the thing inside out... grrr.
  A year later it's now semi rigid, albeit still uselessly flexy tho.
Alegedly West Systems goop is better at this...@ 100$ for a min quantity .. unlikely to test it
 Suspect Poly Resin /fiberglass would have been a  better choice.  No rigidity issues there.
 Only a tale though, not today's issue/focus.

Perhaps the " NZ condom " could be the answer.
Or a party balloon.. aren't they the same thing?

 Considering a 24 ~28" span model so possibly the Reeds might not be ideal strength?  
None on hand either.  Lotsa 1/32 nd for laminating tho.
 Initially considered a series of  Formers as plugs for laminating hoops onto.. But the elegance of a complete fuse shape amazed in it's direct simplicity
Intrigued by the accuracy/consistency of applying subsequent  stringers, Sheeting? whatever... when all is Accurately placed /anchored on a plug.
 No subsequent sanding stringer/plankings, etc. paper thin in attempts to get the inevitable stragglers all in line/smoothly faired in.
 Did think about insetting /carving  rebates  in the foam plug for laminating formers into. Bit fiddly and unsure if worth the extra work.
It's presumed advantage being that every subsequently applied bit of wood would then be backstopped by the plug.
 For a very good consistency.. Or not?
 Bamboo sticks intrigues Not sure how one would bend up a ~ 2" diameter circle though..Heat? Water Soak ? Big hammer :-)
 
Only problem .. so far.. Is that; being the Dog Days of Summer... not the  ideal season to spending days inside fiddling.
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ZK-AUD
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« Reply #12 on: August 02, 2017, 02:24:20 PM »

Here's another idea that completely avoids the whole latex love scenario - how about carving the form in a series of blocks around a master or 'key' block,  - the blocks then being removed one at a time out the front.

Here's a rough sketch of what I mean based on Ralph's Lysander (very interesting to me at present!),  and an idea of the sequence of block removal.

I think you could tack glue the blocks together for carving purposes and then split them and hold together with tamiya tape or similar while you get the formers around
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