Rotor Pitcheron Scratch Build UK - Page 4 - RC Groups
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Jan 30, 2018, 03:45 PM
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I will be doing it the traditional way as per the plan.

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Feb 04, 2018, 11:59 AM
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Wing Tubes - Preparation

I spent a lot of time thinking about how best to install the wing tubes. I decided to bore through the cores instead of cutting a channel in the cores and embedding the tubes in splooge. I donít know why; maybe I will use the splooge method in my next pitcheron projects (Orca and Axle).

I made a dihedral tray out of 9mm (3/8") MDF with some aluminium to prevent it sagging (See photos 3 and 6). The tray is set at the correct dihedral angle relative to the boring tube.

The brass tube is 8mm ID and 9mm OD.
Feb 04, 2018, 12:02 PM
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Wing Tubes - Results

The system worked beautifully. This is one situation where making multiple models paid off. After spending so much time tooling and setting up, I rattled off six cores in only a few more minutes more than it would have taken me to do two.

My only regret is that I only got one degree dihedral per panel because I had to provide a safety margin to avoid tearing the top or bottom of the cores. With the splooge method I would have got more dihedral because I would not have been worried about tearing the upper or lower surfaces of the cores.

I had to pin the cored-out foam cylinder because static electricity would attach it to my hand and I couldnít get it to sit still otherwise.
Feb 04, 2018, 12:04 PM
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Root Ribs and Sub-ribs

I made plywood by epoxying two 3mm (1/8") sheets of the offcuts I had from the fuselage. I regret this because the plywood is really hard and sanding it flush is going to take time and patience.

To drill the wing tube holes in the blanks I tacked them together in sets of three. However, I traced the parts individually so that each piece of plywood belongs to a specific core. Root ribs were band sawed and disk sanded to the trace line so that they stand proud of the core and the sub-ribs were sanded small so that they are slightly recessed. Splooge will make up the difference.
Feb 04, 2018, 12:41 PM
Yes, ALL your money...
winchdoc's Avatar
Originally Posted by Kenneth Paine

My only regret is that I only got one degree dihedral per panel
Thatís plenty dihedral for a Rotor. 1-2 degrees is all you need.
Feb 04, 2018, 12:51 PM
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Thanks Winchdoc. It is good to know.
Feb 04, 2018, 01:56 PM
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I set mine around 3/4” up on both wings and it is plenty . Looking great Ken
Feb 04, 2018, 03:28 PM
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Ward Hagaman's Avatar
Nice jig!
Feb 05, 2018, 03:27 AM
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Thanks Joe and Ward.

It is good and motivating to have veterans like you two and Winchdoc chipping in with advice.

Kind regards,

Feb 12, 2018, 04:24 PM
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Fiddly Bits

I cut the slots for joiner and wing drive pin sub ribs undersize and made some small sanding blocks to open the slots up.

I also sanded all the sub ribs undersize so that they would not protrude above the core surface.
Feb 12, 2018, 04:37 PM
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Sanding the Root Ribs

The root ribs were cut oversized with the intention of sanding in situ to fit.

I protected the foam next to the ribs with 3M Magic Tape. I drew lines on the tape to indicated when to stop sanding. I started sanding with 80 grit and when the Sharpie lines started to get scuffed finished with 200 grit. Tape on one end of the sanding bars kept them from scoring the cores while sanding.

To avoid knocking the root rib off the core, it is better to pull the sanding bars onto the core rather than push them towards the root.

The technique works really well, so much so that I canít feel any step between the foam and the ply root rib. The only problem is that the ply root ribs are so hard it is going to take me ages to do all six panels.
Feb 13, 2018, 11:26 PM
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Ken Stur would be proud of this effort! Keep it up kenny
Feb 14, 2018, 05:04 AM
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Thank you Joe.

Everything is a first for me on this project. One does one's best.

Kind regards,

Feb 14, 2018, 05:16 PM
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timmig's Avatar
Looking GOOD!! One of my FAVORITE all time flyers!!
Feb 14, 2018, 07:07 PM
Originally Posted by winchdoc
Thatís plenty dihedral for a Rotor. 1-2 degrees is all you need.
Is dihedral needed at all for twisty wings? Redoing wings for my Samurai and wondering if I need it?

Originally Posted by Kenneth Paine
When I was cutting my tail surfaces I had noticed some mild ridging on the cores towards the tips. I attributed this to my 1/32Ē plywood templates not being smooth enough, so I applied some aluminum tape onto the templates in the hope that this would help the wire better glide over the templates. This did improve things for the tail surfaces but had an unexpected consequence for the wing panels.

I thought my first wing core was going to be a good one as the wire exited the blankís trailing edge for the second time but I was in for a surprise. The aluminium tape sucked so much heat out of the wire that at the ends of the core that the wire ripped through the foam where it was in contact with the templates while in the centre it over-burned the core with very bad ridging because it was hotter and travelling too slowly due to the drag and tearing at the ends of the core.
I just experimented using .016 sheet aluminum from K&S as template material since I was out of phenolic or laminate. I was pleasantly surprised how easy it was to form with scissors, small file, and 320/600 emery paper. They cut really well with no temp loss that I could detect. Actually got the idea from the Flight Test guys website.

Any ideas on a good pivot point for the wing rod on twistys? RG14 foil. Sorry for the hijack and great work on your scratch build!

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