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Author Topic: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6  (Read 1358 times)

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Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #15 on: February 16, 2021, 08:55:05 PM »
The top and sides of the formers are in place.  That's 30 of the 40 pieces.  The bottom of the formers are next.

Will let it dry overnight.  Am using LePage Fast Dry carpenter's glue*.  Works very well.  None of the pieces had to be pinned.

Frank

* Jack Higgins insisted I try it when it first came out and have used it since.
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Offline Andy Hoffer

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #16 on: February 17, 2021, 09:19:11 AM »
Fabulous @Frank v B !  It's a dead ringer for a stegosaurus.  I would stop right where you are!

Andy

Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #17 on: February 17, 2021, 03:24:00 PM »
Andy,

re: your  " It's a dead ringer for a stegosaurus".

How can you say that?  A Stegosaurus can only run, has no wings and can't fly.  My model will eventually have wings and will fly, however short.  The least you could have called it is a Pteradactyl* since it can fly.

P$hit, get it right Mr. Hoffer. ;) ;)

Frank

* from Wiki:  Pterodactylus (from Greek πτεροδάκτυλος, pterodaktulos, meaning "winged finger"[2]) is an extinct genus of pterosaurs, whose members are commonly known as pterodactyls (/ˌtɛrəˈdæktɪlz/). It is thought to contain only a single species, Pterodactylus antiquus, which was the first pterosaur to be named and identified as a flying reptile.
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Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #18 on: February 17, 2021, 08:55:27 PM »
Stringers on the fuselage.  Substituted the stringers and used them from an old Guillows kit.  These stringers were at least double the weight/strength for the same size.
The fuse looks a bit like a beached whale.  ;D

The wing is next.

Frank.
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Offline GuyOReilly

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #19 on: February 17, 2021, 10:21:07 PM »
Stringers on the fuselage.
The fuse looks a bit like a beached whale;D
Frank.

Wow, a Bearcat on floats !!  Add 3-COVID construction days!!
With flaps, it will takeoff off water in no time.  :D

Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #20 on: February 18, 2021, 10:37:23 PM »
Started the wing.

Observations:
1)  Too weak for RC powered flight. Tripled the balsa size of the leading edge, tripled the size of the bottom main spar, doubled the size of the trailing edge, added the trailing edge on the wing to take the ailerons and flaps.
2)  The dihedral break was weak. This plane has a flat center section at the fuselage and then has a small dihedral break outboard of that.  Overlapping 1/16" square spars are supposed to hold the break together.  I don't think so.  Two changes to fix this
i) made the leading edge continuous to the center.  Will fake the leading edge forward of the leading edge after the wing is off the building board. See photo 78
ii) made the new/added trailing edge of the wing (leading edge of aileron/flap) go through the center section.  This can be reinforced with plywood later.

Two things that stayed fixed with the plans:
i) the forward edge of the leading edge is per plan.  The wing saddle of the fuselage is fixed so this has to fit inside.
ii) the back end of the trailing edge matches the plan.  Same reason as above.

Starting the build
- pinned the bottom mid spar in place.  Double the width.  This will be used at the registration point of each rib since each rib has to be trimmed.
- prepped the ribs.  Glued the lightning holes back in place since in some cases the spars are higher than the bottom of the cut-outs.  Applied glue to both sides.  Note: if you do it to one side only, the rib will curl.  See photo 81

Will start the glue work tomorrow.

Frank

ps: Guy- no way for floats for an extra 3 days...... 'cause then you will want them retractible... for an extra 3 weeks!! and then I will have to go to the nut house. 8)
« Last Edit: February 18, 2021, 10:41:01 PM by Frank v B »
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Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #21 on: February 19, 2021, 05:00:31 AM »
An example of the adjustment to each rib. 

The toothpicks show the black magic marker areas that have to be cut out to make the ribs fit.
The registration point to keep all ribs in the same position is the front of the bottom spar slot (second toothpick from the right).  As long as these stay the same for all ribs, the wing high points and all upper spar slots will line up exactly as designed.

The upper spars will be increased in size but that will be decided when the wing is together but before it is removed from the board.
The new trailing edge of the wing rib where the aileron starts (second toothpick from the left) will have to go full depth of the rib but that will be done later.

This is definitely a case of "don't make a decision until you have to" because there are so many variables that need to be considered. (change in wood sizes, added aileron/flaps, retracts, dihedral, etc.).

Interesting exercise.

Frank
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Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #22 on: February 19, 2021, 09:50:28 PM »
Building the wing

The left wing has all ribs glued in place. (photo 84).  The new trailing edge is in place.  Next I will have to build the ailerons/flaps before removing it from the board.
The right wing- all ribs are fitted but not glued. (photo 85)
The close-up of the ribs show the fit and taper of the wing. (photo 86)

For the eagle eyed.... the second ribs from the center of the wing are cut and bent so they follow the fuselage taper.  Visible in photo 84.

The main next steps:
- glue in all the ribs
- build the ailerons/flaps while pinned to the board
- set the dihedral breaks by cutting the LE, TE, and spars and installing the upper spars.
- remove from the board and tackle the retracts
- re-inforce everything (dihedral breaks, wheel wells, LG mounts, etc.) and finish all other details (wing tips, flap and aileron movers/servos).

Frank


« Last Edit: February 19, 2021, 09:54:47 PM by Frank v B »
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Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #23 on: February 20, 2021, 01:17:07 PM »
Building the ailerons/flaps.

Photo 88- all the spars are glued in place so the wing is rigid.

In order to create the angle the leading edge of the ailerons/flaps, I pinned a pieces of 1/8" wide balsa to the board to fill the gap.
The balsa spacer is visible to the right of my hand holding the leading edge of the flap/aileron.  Photo 87.
The two clamps hold a piece of 3/16 balsa wood used as a doubler to strengthen the wing in that area.

Frank
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Offline Andy Hoffer

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #24 on: February 20, 2021, 02:26:59 PM »
Building the ailerons/flaps.

Photo 88- all the spars are glued in place so the wing is rigid.

In order to create the angle the leading edge of the ailerons/flaps, I pinned a pieces of 1/8" wide balsa to the board to fill the gap.
The balsa spacer is visible to the right of my hand holding the leading edge of the flap/aileron.  Photo 87.
The two clamps hold a piece of 3/16 balsa wood used as a doubler to strengthen the wing in that area.

Frank

F3 (Fabulous Focus @Frank v B ) !!  I can even read your fingerprints!!

Great thread.

Andy

Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #25 on: February 20, 2021, 03:10:36 PM »
Another compliment from Andy.  He's getting soft in his old(er) age.

Making the aileron and flap.
- since the full ribs were fitted earlier before the ailerons were cut in, the back end of each rib met perfectly with the trailing edge.  To make these cut-off ribs fit, I measured back from the trailing edge and cut the angles.  Glued them in place

Also visible in the pictures are :
- the double ribs at the fuse, between the aileron/flap and the tip.  I used 1/32 wood as a spacer.
- two flat plates for the control horns.
- the split between the flap and aileron was moved inboard about 1.5" so the wing would be thicker and the aileron servo could move inboard one rib bay.

Frank
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Offline Frank v B

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #26 on: February 21, 2021, 10:58:09 AM »
- cut out the flaps/ailerons
- set the two dihedral breaks outside of the flat mid-section.  Does that make it Polyhedral?

Letting it cure.  Will then go around adding braces, gussets, some kevlar to strengthen the wing.

F.

ps: took this picture on purpose so Andy can spend hours analyzing the tools/equipment in the background. ;D
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Offline Andy Hoffer

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #27 on: February 21, 2021, 12:31:28 PM »
- cut out the flaps/ailerons
- set the two dihedral breaks outside of the flat mid-section.  Does that make it Polyhedral?

Letting it cure.  Will then go around adding braces, gussets, some kevlar to strengthen the wing.

F.

ps: took this picture on purpose so Andy can spend hours analyzing the tools/equipment in the background. ;D

OK @Frank v B .  It's time for your lesson on image resolution.  If we're going to get into psychoanalyzing you based on the contents of your shop, you really need to max out the image size to allow less grainy magnification at the viewer's end.  @bfeist graciously allows 1000kB max per image.  Your last image, #3491, is only 234 kB, so if you could bump it up to say 950 kB it would be greatly appreciated.  (You don't want to get too close to 1000 kB or the system will reject it).  That will allow me to identify the nameplates on your tools, especially the heirloom pieces, and we can go forward from there.   Scheveningen!

Andy

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #28 on: February 21, 2021, 04:33:05 PM »
File size isn't the same as image resolution. I think what Andy is asking for is that you save the images at a higher resolution. You can do this without coming near the file size limit.

Offline GuyOReilly

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Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
« Reply #29 on: February 21, 2021, 05:46:42 PM »
@Frank v B , do not let @Andy Hoffer  comment on your pictures, rather let him show us what he is building...