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Author Topic: round fuselage  (Read 780 times)
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SolarCyclone
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« on: April 06, 2016, 02:36:01 PM »

Looking for info on how to build a light round tapered fuselage. Any materials/styles considered. Anyone know of plan or info showing methods of doing this on a competition power FF?
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USch
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« Reply #1 on: April 06, 2016, 04:46:07 PM »

Round, tapered booms can be made old fashioned with balsa, say 1/32" for rubber models, 1/16" for heavier models or 2 layers of one of 1/32 or 1/16.

The first thing you need is a tapered former to the dimensions your model has, max. diameter, min. dia. and length. Many times you may find and use a billiard pole, a piece of a fishing pole. Or you can make a former from hard balsa or turn it from aluminium, depending on the skill and machinery you have available.

Once solved the problem of the former you choose a nice straight grained balsa sheet and treat it on one side with dope and glue on jap paper. After drying you cut the sheet to the dimensions needed (slightly longer and 1-2mm larger than the actual size. Soak it in water for an hour and put it on the pole, holding it with a wrapped cloth ribbon. Cloth ribbon because in this way the water can evaporate trough the cloth! If possible put it in a warm place, better still sort of oven at 40-50°C for a few hours. So the balsa will hold the round shape. Once dry, slip off the balsa from the former, put a strip of adhesive tape along the former so the balsa will not stick to it during gluing. For gluing balsa booms I use cellulose cement in small amounts and glue in small lengths.

To finish I give the tube a light sanding (always on the former), dope it and cover it again with jap. This gives light and stiff tail booms.

Other materials to use are a combination of balsa and glass/carbon cloth. Instead of the final jap layer you may use a 25g/m^2 glass cloth and epoxy resin. Or build the whole boom from carbon cloth or unidirectional tape and epoxy. That's a completely different story and is hard to compress into a reply.

Urs

PS: just reread your post and you ask for a power model, depending on size (1/2A or F1C) you will need 2 layers of balsa.
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faif2d
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« Reply #2 on: April 06, 2016, 05:23:41 PM »

A workable tapered form can be made using a steel rod (dia at the smallest size required) and a LONG tapered triangle of brown paper like wrapping paper.  After you have this wrapped around the steel rod dope it well to both hold the paper in place as well as help prevent adhesion to the balsa wrap.
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« Reply #3 on: April 06, 2016, 05:43:05 PM »

SolarCyclone:

What size model?  For larger Power models .15 and up, consider one of the ready-made pylons that Matt Gawain sells.  These are professional made (by Matt) tapered carbon fiber tubes.  He advertises in the classifieds in the NFFS Digest.
Let me know if you can't find ad and I'll dig up.

The only problem using a pool cue as a form for rolled balsa tube is some cues are not straight taper.  See my Duration column in November 2015 Model Aviation for another method.

Louis
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ddock
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« Reply #4 on: April 06, 2016, 05:52:21 PM »

Find the 'Hummingbird' article by Charlie Caton...Model Aviation Mid 80,s I think.
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Hepcat
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« Reply #5 on: April 06, 2016, 06:52:35 PM »

Solar Cyclone,
I stopped flying power in 1950, added to which my memory will only recall the name of a person or model about three days after I need it.However there are enough people on HPA to fill in the details.  About five years ago, maybe a little more, a fellow Timperly Clubmate, (Huh) built a large gas model, about 6 feet span I guess, and started to win all the Vintage gas competitions.  I keep wanting to call it 'Pencil Bomber' but that may be just my befuddled mind making assumptions from the long, tapered,circular fuselage.  I am pretty certain the plan was in a magazine and 'Australia' keeps nudging my memory.  There was a narrow track, two wheel, undercarriage right at the front bulkhead.

I don't want to be rude when I say don't forget that if you want a Light, Strong round fuselage you forget all about billiards cues and make it quite a large diameter.  The model I am talking about had a simple structure.  The side view of the fuselage was cut from sheet balsa as a 'keel'.  Semi circular bulkheads were glued either side of the keel and the bulkheads were then planked.  Don't forget if you model is a large one, as my friend's was, that a circular fuselage, with exhaust goo and a bit of wind needs a firm place to hold it.
John
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billdennis747
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« Reply #6 on: April 07, 2016, 01:49:13 AM »

Flying pencil?
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Soc
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« Reply #7 on: April 07, 2016, 03:24:20 AM »

The design is Alan Kings work and became known as the flying pencil.
The plan was published in the aero modelling pages of the 'Aircraft' magazine, probably in 1951.
I've just been scanning parts of editor Jim Fullarton's scrapbook of the column, but I didn't scan that page.
The design was very successful and a number of others imitated it with variations including high thrustline versions.
The Pencil came in three sizes and I think some used a crutch as the basic element rather than a keel.
Hepcat is right about the formers and planking.
Power loading here was 8oz per cc, more than the FAI loading of that era, so weight was not a critical issue.

Sean

But don't give up on moulded tubes. While billard cues are too slim for a big power model, these days telescoping fishing poles are readily available and cheap. One of these furnishes a range of tappering forms and in my experience two or three layers of suitable sheet balsa backed up with a layer of glass fibre makes a very strong relatively light basic tube.
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Hepcat
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« Reply #8 on: April 07, 2016, 03:06:23 PM »

Thank you Bill and Sean for giving my memory a helping hand. Perhaps it stirred my cogs because a little earlier they churned out the name of my Timperly friend who built the Flying Pencils.  It was Richard Wykes.
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Tmat
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« Reply #9 on: April 07, 2016, 05:23:03 PM »

There is another way to make "moulded" fuselages that has not been mentioned that was shown to me by Dave Sugden (long time Canadian FAI power flyer).
You screw two planks of soft pine (or similar) wood together with the split on the vertical axis. You then carve the form to a suitable shape. I used an egg-like cross section with the bottom fatter than the top and the width was smaller that the height. The form was split and wet balsa was wrapped around the form using bandage and allowed to dry. The balsa was removed from the form (the form had been sealed with dope and waxed before hand) and a layer of fiberglass cloth was applied to the inside. Epoxy can be used or dope or whatever you prefer. The "shells" were placed back on the forms and the balsa was trimmed flush with the flat surface of the forms. Then the forms were screwed together again and the balsa was glued together at the seam. The outside was sanded smooth and glass cloth was applied to the outside. Then the balsa "tube" was removed from the form. A very stiff and light fuselage was the result.

Tony
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JohnOSullivan
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« Reply #10 on: April 07, 2016, 05:52:23 PM »

I flew with Dave Sugden quite a bit from 1968 to 1971 and admired his circular cross section fuselages.
I later in my modelling career developed a fibre glass moulding technique for RC gliders which I detailed in my web site http://www.windandwavemodels.com/rollfuz.html
I have used this technique for models from 40" slopers to 15 ft cross country sailplanes and has worked well for all sizes.
Nowadays, I have become more lazy and am content to purchase ready made carbon tail booms.
Talking of Dave, in the late 60's he had developed a Tachometer, based on a slide whistle. It was a 1/2" diam plexiglass tube with a whistle mouthpiece and a sliding piston insert on a rod which was slid back and forth to produce a tone corresponding to the tone of the motor. It was calibrated from his piano and could work from 8,000 to over 24,000 rpm. He gave me one and it is only in the past few years that I have misplaced it.
I kept in touch with Dave and his wonderful wife June up to about three years ago when they moved into a retirement home in Oshawa, but now have problems contacting them.
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John O'Sullivan
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