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Author Topic: Rolling P30 fuse  (Read 1701 times)
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mkirda
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« on: July 15, 2012, 04:19:36 PM »

So I have the parts for a Majestyk and want to start to build it.

I am assuming that rolling a fuse is not too different from rolling an F1D fuse, just larger - A form, some silkspan, wet balsa, some tape and let dry.
The only difference I am assuming - I imagine it easier and stronger to not edge-glue the balsa, but sand a taper in one edge, overlap to glue, then cut/plane/sandpaper the extra.

Am I missing anything?

Regards.
Mike Kirda
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danberry
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« Reply #1 on: July 15, 2012, 07:02:58 PM »

I just edge-glued my new one.
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Rewinged
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« Reply #2 on: July 15, 2012, 07:19:44 PM »

I rolled a whole bunch of balsa this past winter (about eight p-20 and P-30 fuses), to learn what worked for me, and what didn't.  I rolled my first fuse last summer, and while it came out fair, and I'm using it on a great flying P30, and wanted to improve.  Here are my thoughts.

Both edge overlap and edge-to-edge gluing worked fine on balsa sizes down to 1/32 thick.  For anything larger than 1/32 (My multiple efforts were with 1/32 and 1/20 sheets) I would definitely stick with the direct edge-to-edge.

Even with 1/32, I believe I will stick with edge-to-edge.  I will cover the fuse with spiral-wrapped tissue and dope, so it will be plenty strong.  My original fuse used an overlapped edge, per a John Kamla article on his Marie in the FFQ P30 issues.  However, I think the joint ends up shrinking differently than the rest of the fuse, and this is may be more pronounced with the overlap.

I use doped tissue on the inside, not silkspan.  There is some very lightweight Tyvek paper that I would like to try sometime, for a strong fuse that should withstand a blown P-30 motor, but I haven't done that yet.

Other than that, your technique is pretty typical.  I tried both tape and an Ace bandage.  Your skills are surely very high from F1D, but you have to be careful with the tape and soft wet balsa to not compress it too much.

My best fuse used 1/32 balsa, edge-glued,  I saw in the Digest that some P-30 flyers use as small as 5/8 diameter fuses, so I am trying that.  Not sure it is really big enough, but with a long-run motor I believe it will be, and it will be nice to put a little more weight and strength in the wing.  That fuse has not been covered externally yet.  The raw tube, with tissue, rolled, and glued, weighs 4.0g. I will wrap doublers at the nose and at the wing and stab mounts after covering with tissue.

--Bill

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mkirda
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« Reply #3 on: July 15, 2012, 11:28:44 PM »

The silkspan is used in F1D solely as a way to hold the balsa tightly to the form. It should also strong enough for this purpose in 1/20" balsa.

If you typically dope tissue to the inside, that would likely be before soaking and putting on the form, correct? No interference with the dope/tissue to soak and bend the balsa?
I had not intended to put tissue/dope on the inside.

So I'll edge glue the first one to see what it looks like.

Further question: 0.75" form - the circumference is a bit less than 2.4". When I cut and wrapped one tonight, there is a rather large obvious gap. The silkspan would increase the diameter slightly. Would you typically slice to width, roll it, then glue it up to close the gap? Alternatively in F1D some will wrap the wood around, then slice through it while still wrapped and glue there. Which would be most likely method here?

Regards.
Mike Kirda


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Tapio Linkosalo
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« Reply #4 on: July 16, 2012, 02:12:14 AM »

An old Finnish model building book (from 60's) described wrapping tubes for F1B, and I used that method for my #2 and #3 P-30 models, build in the early 80's. Major difference for F1D tubes is that the instructions suggest to cover and dope the inside properly before wrapping around the mold (obviously you cannot cover the inside after molding, but also the paper says that doping just one side starts to curve the sheet into tube). After inside is doped, the balsa is soaked and wrapped onto the tube.

I did my tubes from 1mm balsa with Esaki silk (fabric) both inside and out. Worked fine. For the next models I changed over to composite tubes though.

I have seen Burdov fuselages that are quite thin, less than 20mm in diameter. I feel that my current ones that are 22mm are about as thin as are practical for 6 strands of 3mm rubber though, even with this some bunching of the motor tends to touch the tube. This was quite obvious with the first attempts to use outside the tube -winding I tried earlier this year.
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Rewinged
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« Reply #5 on: July 16, 2012, 02:13:47 AM »

The tissue is doped onto the sheet before soaking.  It keeps the inside from stretching, so when it is all soaked in hot water the balsa naturally curls and gets you about halfway there.  The tissue/dope on the inside is protection against rubber lube, as well as adding a bit of strength.

I tried both cutting to width and cutting while on the form.  I found that cutting to width was fine when I used an overlap, but I preferred cutting while on the form for edge gluing.

Also, I tried gluing while on a slightly smaller mandrel than the form I used for wrapping.  I succeeded in gluing the balsa to the mandrel after I was done with about 20 of the 28 inches.  Frustrated, I gave up gluing while on a mandrel.  For somebody with good skills, and/or a good glue-proof protection for the mandrel, it might work OK.  With later fuselages, I glued after removing from the mandrel.

Hopefully some people with more experience than I will chime in here.

--Bill
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NormF
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« Reply #6 on: July 16, 2012, 03:31:10 AM »

Most guys use "A" grain wood to roll a P-30 tube, but if you can get a "B" grain to roll you will have a much stiffer tube. Tried "C" grain but no luck! Works for indoor sticks!

- Norm
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frash
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« Reply #7 on: July 16, 2012, 08:45:54 AM »

The best instructions for rolling motor tubes that I have seen were by Jim O'Reilly in the NFFS Digest, Free Flight, a few years ago. I'll try to reproduce it from memory...

He cut the wood blank to its final dimension, but added some correction for the thickness of the wood to the calculated circumference. (If you are covering the inside with tissue, or silk, or something, this should be first.) Jim then formed the soaked wood around a form that was very slightly OVERSIZE (even for the wet, expanded wood) so that the edges did not touch. When dry, the curled but unglued motor tube was placed on a very slightly UNDERSIZED form, turned vertically, a section of tube slid below the end of the form, and glued with CA on the part extending below the form. Then more of the tube was slid down and gluing continued. You might not use CA for indoor tubes or you might spot glue and then make sure that your glue seam is good while not on the form.

Storing on the form for a few days after gluing may also be wise.

If you find this article, post it on Builder's Plan Gallery>Short Articles & Magazine Excerpts so that we all can benefit again from reading it. Thanks.

Fred Rash
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mkirda
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« Reply #8 on: July 16, 2012, 12:38:39 PM »

Thanks for all of the responses.
Funny that I see so many of the INDOOR guys over here too... Grin

I will probably just slide it off, edge glue with Ambroid, tape to hold it, then tissue/dope the outside on this first one I rolled last night.
I'll try the inside tissue/dope for the second attempt.

Regards.
Mike Kirda
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tctele
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« Reply #9 on: July 24, 2012, 05:53:33 PM »

My method. Cut to exact size place on tapered mandrel (F1G fuselage described), carbon fishing pole in most cases, place back on but push up by a few mm to give a 1mm gap. Tape and bandage on. Either wet beforehand or do on the mandrel and roll. Easy with .8mm balsa, I soak on anything larger. Don't worry too much with the bandage deforming the outside, once glued (Edge to edge on the mandrel with sellotape underneath) place back on the mandrel and wash with a damp sponge. This will lift out any marks.

Cover with tissue and dope on the inside prior don't worry about it curling, .25oz glassfibre on the outside when glued and dry and get 99% of the epoxy off by paper towel. I spray the outside with the lightest coating of 3M spray prior, roll the glass on and smooth with my finger until all the fibre is running true. Make sure your hands aren't rough or you'll lift fibres up. It's really easy to do.

My current coupe fuselage, now running on 14 strands 1/8" is 1/32" balsa with tissue and one layer of glass and weighed 4.5 grams. It's still perfect and no cracks.

I can cut and roll in less than 40'. Much quicker than a stick fuselage.

The key to doing all the above is the selection of the wood. As straight grained as you can get, try and get the grain running parallel all along the length. Most shop bought wood isn't like this so search carefully. Hold it up to the light when you buy. You want an even transparency with no dark spots. If there is the density won't be consistent. This is why I can roll a tube in less than 40', it's the wood.

For interest I've just rolled a coupe boom 610mm, not glassed yet mind you, 15mm to 9mm, .8mm balsa and it weighs 2.47 grams. It will weigh no more (Probably slightly less) than 1.5 gram more when done. No tissue on the inside. An average carbon boom weighs around 6 gram.

Tony

« Last Edit: July 24, 2012, 06:51:54 PM by tctele » Logged
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« Reply #10 on: July 25, 2012, 06:33:52 AM »

I did a couple of experiments with gluing the seam while the part was on the mandrel, and the easiest (for me) turned out to be using mold release wax on the mandrel - generously applied and well polished.  I also left about 1-2mm of the wood over the mandrel at the big end (when using a taper).  Saran Wrap has also worked, but is a pain to get on the mandrel evenly.

When the seam was dry, a light rap on the overlapped end has sufficed to pop the tube loose.  I have NOT tried it with CA.

Now to roll a REAL fuz for a  P-30.  I'll copy the one from a Pee Wee (IKARA) that I'm picking up (hopefully) next week.
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mkirda
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« Reply #11 on: July 29, 2012, 01:38:01 PM »

Feeling like I am 16 again...

It's summer, CA on the thumb, the smell of Ambroid in the air and Pink Floyd on the radio...
Second fuse done and first tailboom.

Mike

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