Toronto Electric Model Aviation Club Forum

Toronto Electric Model Aviation Club (TEMAC) => Building / Construction => Topic started by: Frank v B on February 13, 2021, 10:49:37 PM

Title: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 13, 2021, 10:49:37 PM
Started cutting out my next build.  The Dumas 30" span rubber power to RC electric conversion.  Bought the kit about 8 years ago from Michael Rogo at a TEMAC mini swap meet.  Thank you Michael. ;)
After cutting out the parts, studying the construction and checking some internet projects,  I have made the following decisions:

1) It needs significant strengthening everywhere.  Have come to the conclusion that Dumas rubber models were designed to be very good rubber models (read as "very light").  The construction is light and the wood is almost contest grade...for rubber models.  The three Guillow's models I have built (Arrow, B-25, DC3) prove that they are very strong and were probably marginal rubber flyers.  The overbuilt nature made them excellent RC conversions built as supplied (much harder balsa).  Very little strengthening needed.

2) It must have ailerons. The rudder gives a lot of adverse yaw when flown as a 3 channel. See this web report https://mrm1018.tripod.com/mikesparkslowindoorrcflyers/Bearcat.html

3) It will have retracts.  This is actually a very big model with lots of chord in the wing and depth to the airfoil.  See the GWS retracts in the photo (left side).

4) The inside box frame will be 1/16 balsa and not built-up per plans.

5)  This model will be heavy for a rubber plane but very light for RC.  It will not be overpowered.... or it will be over-powdered on the first landing.  ;D

6) Should I be tempted to add flaps?

Each part has been labelled and each plastic bag contains a sheet's worth of parts.

Frank

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: GuyOReilly on February 14, 2021, 08:01:15 AM
Quote from: Frank v B on February 13, 2021, 10:49:37 PM
Started cutting out my next build.  The Dumas 30" span rubber power to RC electric conversion.

6) Should I be tempted to add flaps?

Frank

Of course add flaps!! As if you needed to ask.  :D
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 14, 2021, 09:45:52 AM
After careful consideration* of Guy's recommendation this model will have flaps. 8)

F.

* one nano-second!
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 14, 2021, 01:01:47 PM
Quote from: Frank v B on February 13, 2021, 10:49:37 PM
Started cutting out my next build.  The Dumas 30" span rubber power to RC electric conversion.  Bought the kit about 8 years ago from Michael Rogo at a TEMAC mini swap meet.  Thank you Michael. ;)
After cutting out the parts, studying the construction and checking some internet projects,  I have made the following decisions:

1) It needs significant strengthening everywhere.  Have come to the conclusion that Dumas rubber models were designed to be very good rubber models (read as "very light").  The construction is light and the wood is almost contest grade...for rubber models.  The three Guillow's models I have built (Arrow, B-25, DC3) prove that they are very strong and were probably marginal rubber flyers.  The overbuilt nature made them excellent RC conversions built as supplied (much harder balsa).  Very little strengthening needed.

2) It must have ailerons. The rudder gives a lot of adverse yaw when flown as a 3 channel. See this web report https://mrm1018.tripod.com/mikesparkslowindoorrcflyers/Bearcat.html

3) It will have retracts.  This is actually a very big model with lots of chord in the wing and depth to the airfoil.  See the GWS retracts in the photo (left side).

4) The inside box frame will be 1/16 balsa and not built-up per plans.

5)  This model will be heavy for a rubber plane but very light for RC.  It will not be overpowered.... or it will be over-powdered on the first landing.  ;D

6) Should I be tempted to add flaps?

Each part has been labelled and each plastic bag contains a sheet's worth of parts.

Frank

This is a very interesting post with very thoughtful analysis.  I had always thought of adverse yaw as a phenomenon resulting from using aileron without coordinating rudder (especially on high aspect ratio wings), not from use of rudder without aileron.  The geometry of the rudder versus the roll axis is most intriguing.  A great troubleshooting example.  Thanks for this @Frank v B .

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 15, 2021, 10:44:28 AM
Getting going....

- did some internet searches on flaps (size as a % of span).  Interesting result-  On each side, the flap measures 60% of span and the aileron only 40%, measured as the projection from the fuselage side.  Have drawn them on the plan.
- first change-  The kit expects you to build a rectangular inner frame onto which you glue the formers (4 pieces per former) to make the fuse round.  To heck with that.  Made the box out of 1/16" sheet.  I did the count- the current box uses 5 pieces.  As designed it needs 104 pieces.  I am trying to ride out Covid; not serve a life sentence!  ;D

Transferred it from the plans onto the balsa with the high tech dot/matrix X/Y axis method (plans over the wood and use pin pricks through the paper).  8)  Connected the dots.

Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 15, 2021, 11:51:26 AM
The inner fuse frame is finished.

F.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 15, 2021, 12:33:22 PM
Hey @Frank v B

Could you please redo photo #3456 with better focus? I am having trouble reading the print on the package just to the left of your epoxy bottles?

I'm sure it will offer great pedagogical insights into this project.

Thanks so much.

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 15, 2021, 01:00:51 PM
Andy,

No thanks.  Keep trying. :)


F.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 15, 2021, 06:20:56 PM
Stabilizer/elevator done.  Changed the design significantly to make it stronger.  The wood size was roughly doubled but the spacing was increased.
Once everything is dry, the rounded Bearcat stabilizer shape will be sanded into it.

Yes, the photo shows an oops in the leading edge (center).  When dry, I will cut it across and glue a piece onto the front.

F.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 15, 2021, 08:53:59 PM
Photo 62- Fin/rudder- the wood has again been at least doubled in size.  The original plans use 1/8" square balsa.

Photo 61 shows the de-oopsed stab.  Once dry, it will be cut back to fit properly.

F.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: GuyOReilly on February 16, 2021, 08:30:24 AM
Good Morning @Frank v B ;
Before @Andy Hoffer mentions anything about pins (one of is specialties) kindly note that in picture #61 the left red pin is quite correct; however, the right pin should be green: the white one should be at the back.

I love following your builds; such great work!
Guy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 16, 2021, 12:00:50 PM
Quote from: GuyOReilly on February 16, 2021, 08:30:24 AM
Good Morning @Frank v B ;
Before @Andy Hoffer mentions anything about pins (one of is specialties) kindly note that in picture #61 the left red pin is quite correct; however, the right pin should be green: the white one should be at the back.

I love following your builds; such great work!
Guy

Excellent work @GuyOReilly@Frank v B should consider himself blessed.  He cannot help but get this one totally right with his devoted staff of real-time super-diligent auditors on duty.

I will have more to say after I finish transcribing his pin codes to nautical, then to ICAO, then to Dutch, and finally to (sanitized) English. 8)

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 16, 2021, 02:29:01 PM
Guy,

Two white head lamps, red and green pins properly oriented into an arrow and a single white tail light.

Happy now? ???

Frank

ps: 15 minutes of my life I will never get back. ;)
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Michael on February 16, 2021, 03:15:48 PM
Nice project.

My opinion: no flaps. It's a small and light plane. The unnecessary weight, complication and installation won't contribute to a better flying experience.

Also, make the landing gear removable (plug-in). You'll probably be belly-landing the plane in the grass.

My rule: KISS.

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 16, 2021, 05:09:16 PM
Michael,

Yours is the view of a rational person.

Here is my irrational thought process:
- add flaps?  ... adds 2 Covid-busy days to the project even if I never deploy them.  That is good.
- add retracts- adds 4 days of Covid-busy tinkering.  Take off on wheels and belly land.  This is what Jim Spence taught me when he got tired of re-gluing ripped retracts every landing.  I use this approach with my Superportster all the time now.

The additional weight is easily overpowered with a brushless motor.

Back to building:
- sorted out all the formers.  To get the round shape, each former has 4 parts (top, 2 sides, bottom).  40 pieces in total.  Argh!!
- the formers on the top have been glued onto frame box.  Note that I have glued the lightning hole of the stab mount back inside.  Prefer the strength over the weight saving.


Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer 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
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: GuyOReilly on February 17, 2021, 10:21:07 PM
Quote from: Frank v B on February 17, 2021, 08:55:27 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
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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)
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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


Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 20, 2021, 02:26:59 PM
Quote from: Frank v B 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

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

Great thread.

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B 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
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 21, 2021, 12:31:28 PM
Quote from: Frank v B 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

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
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: bfeist 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.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: GuyOReilly 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...
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 21, 2021, 06:50:46 PM
Quote from: GuyOReilly 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...

Hi @GuyOReilly,

I thought you'd never ask!  I am actually assembling an illustrated encyclopedia entitled The Many Faces of @Frank v B

Watch for it at Bookstore Spijkerman (De Bergen district in Eindhoven), Boekenberg (also in De Bergen), and Bookstore Van Piere.  It will be full of great ideas for your next aircraft pilot mannequin.  8)

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 21, 2021, 10:14:29 PM
Installing the retracts

Approach- do all the fiddly stuff on one side to get it to work, then copy it exactly on the other side.

To reduce the rib compromise from 3 to 2 ribs, I made the landing gear 3/4" shorter than the plans and used wheels one size smaller.

The Bearcat has a very high stance on the wheels so by reducing it, it looks more normal.  The clearance is still enough to be able swing a 9" prop.  My guess is that I will be using about a 7-8" prop.  Have not decided on the motor yet.  Will do it when I have an relatively accurate flying weight.

Frank

Andy, I am not changing anything.  If the depth of field is perfect and the resolution is perfect you will be able to read everything.  That would spoil the challenge. ;D
Guy, Andy doesn't build anything because it would lead to you and me making his life difficult. ::) "I'm in the revenge business". ;)
Ben, I am not changing anything because that would involve reprogramming my brain.  Never a good outcome expected.  ;)
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: GuyOReilly on February 22, 2021, 05:03:46 PM
Quote from: Frank v B on February 21, 2021, 10:14:29 PM
Guy, Andy doesn't build anything because it would lead to you and me making his life difficult. ::) "I'm in the revenge business". ;)

So @Frank v B does that mean operating cannons and machine guns or bomb drop?   ???

Guy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 22, 2021, 10:45:57 PM
OOOOOOHHHHHHHH!!!  Looks good.

Just had to spend 15 minutes to make the wing fit.  Had to do it to figure out where the retract servo could be installed.

Both retracts are in place as are the retract servo rails.

Frank

ps: Guy- MAAC rules don't allow anything to be fired from a model airplane.  Tempting as it may seem at times. ;)
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 22, 2021, 11:28:40 PM
HEy @Frank v B

Love the attitude tape on the tail!  :D

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 23, 2021, 10:46:30 PM
YYYESSSS!!!!  The retracts are in and working. 
They work surprisingly well....coming from a skeptic who thinks all retracts are sent to us from a greater power who is ticked off at us. ;D

Notice the servo (Hitec HS-55) is sticking out from the bottom.  The wing still has to have the rounded bottom added to follow the round bottom contour of the fuselage.  Those stringers will cover this servo bottom.

Next- making some wheel wells so the wing structure is not open to everything.
These retracts will have taken three building days to install.

Will attempt to attach a short video of some retract cycles.

Frank

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 24, 2021, 08:31:54 AM
These look great @Frank v B .  I presume you will fly gear up (belly landing) until the gear-stripper runway is replaced at TEMAC!  8)

Looking forward to your landing gear cinematography!

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 24, 2021, 06:04:57 PM
Here is the video of the landing gear cycling.  It was attached to a GreatHobbies servo cycler and a 4 cell RX pack.
Thanks to Oscar for modifying the video so I could post it. 

https://youtu.be/omgaX4zl0U4

Frank

ps: There is no truth to the rumour that I want to build a Trireme using this technology.   ;)
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: sihinch on February 24, 2021, 06:34:46 PM
Could the pilot not decide about whether to land Frank?!  ;D
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 24, 2021, 06:49:53 PM
Simon,

Indecisiveness kills when flying. ;)

The video show pre-programmed go-arounds. ;D

F.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on February 24, 2021, 07:15:42 PM
Hi @Frank v B

So, if I understand this correctly, you hold the starboard wingtip, turn on the retracts, confirm that they are flapping properly (I assume at a much more energetic pace than that shown in the demo video), and then launch the plane into the air.  How many watts do you get per flap cycle?  Brilliant concept really:  just slow down the flapping when you want to land, then lock them in the gear down position just before touchdown.  Eliminates the whole ESC, motor and prop thing which just add weight and complexity.

Hats off to you Sir!

Andy

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on February 27, 2021, 08:58:30 PM
Gotta keep going.  Am doing the small stuff to get closer to the finish line.  A couple of decisions made:

- sheeted the bottom of the wing around the retracts so the covering can adhere to solid wood.
- attached the wing with two nylon bolts, one in the front, one in the back.  two reasons: i) This is really a mid-wing model.  The fuselage below the wing requires the wing be lifted straight up to remove.  It cannot have a dowel on the leading edge because it requires the wing to fit in at an angle. Hypotenuse issues.
ii) a bolt at the front and the back makes the wing a significant contributor to the strength of the fuse.  The wing acts as a brace.
- Landing gear covers- found a way to make the landing gear covers fit to the retracts.
- added corner braces around the edges of the ailerons/flaps.
- Magnetic battery hatch- started making the magnetic battery hatch at the bottom of the nose.  It will be sheeted, not open stringers.
- the bottom of the fuse under the wing will be sheeted and not open structure with stringers.  In case it needs to be hand-launched or belly landed.
- added spar braces around the dihedral joints.

Will probably start covering the model in the next few days.

F.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 04, 2021, 10:39:13 PM
Have been chipping away at it.  Just started the final sanding before starting the covering.

Next assignment:  Power plant!

Weighed the parts:
- wing, incl. retracts, wheels, aileron, flap and retract servos (4)          5.1 oz
- fuse (incl rudder and elevator servos)                                              2.7 oz
- tail feathers                                                                                   0.6 oz
- Rx, 12 amp ESC, battery                                                                 2.1 oz
                                          Total                                                    10.5 oz

Still to come are the motor, motor mount, cowl, covering, canopy and pushrods in the fuselage. 
This plane will be safely below 16 oz.

The motor would have to be around 100 watts.  Will go through (a deep dive of) my collection of brushless motors. ;D

Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 06, 2021, 02:50:14 PM
A deep dive of my BL motor cupboard brought out a speed 400 equivalent brushless motor.
The match shows it to be about 110 watts on 3 cells (12 amp continuous).  It is also a very light motor.  I don't think it is a robust motor so no prop strikes allowed.

Done in the last day:
- installed the pushrod housing for the elevator and rudder.
- installed the motor.  It is a firewall mount (not X mount).  Put an X mount around the shaft and built a balsa box so it would come out of the cowl properly.
- made the cowl.  Cowl magnet and registration pin installation is next.
- made the tail block- the fuse part that comes to a point where the former and stringers end.

The covering can start after dinner.

Frank

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on March 06, 2021, 05:50:53 PM
Quote from: Frank v B on March 06, 2021, 02:50:14 PM
A deep dive of my BL motor cupboard brought out a speed 400 equivalent brushless motor.
The match shows it to be about 110 watts on 3 cells (12 amp continuous).  It is also a very light motor.  I don't think it is a robust motor so no prop strikes allowed.

Done in the last day:
- installed the pushrod housing for the elevator and rudder.
- installed the motor.  It is a firewall mount (not X mount).  Put an X mount around the shaft and built a balsa box so it would come out of the cowl properly.
- made the cowl.  Cowl magnet and registration pin installation is next.
- made the tail block- the fuse part that comes to a point where the former and stringers end.

The covering can start after dinner.

Frank

Hi @Frank v B ,

Ijou reallij should sell tickets for events like this.  Ijou could make a pile of gilders and paij for replenishing ijour RC goody stash manij times over.  To saij nothing of the entertainment vaijue.  Ijou might want to consider posting a IjouTube clip of ijour next dive!!! 8)

Andij

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 08, 2021, 06:47:08 PM
Finished the nose area
Photo 06- the nose with the motor and cowl in place.
Photo 07- battery hatch (left) and cowl removed.  Both are held in place with registration pins and magnets.
Photo 09- motor built into the nose.
Photo 10- the bottom of the nose with the cowl and the battery hatch in place.

Bad news: Due to a technical glitch (stupidity?) I cannot post the pictures. My Commodore 64 is having problems. ;)
Good news: Andy has nothing to critique. ;D  Peace at last.

Have started covering.

Frank


ps: for those of you who wondered about my silence for the last week.  I could not find my camera in the car.  Found it today looking for wire to Lipo-start my car.  :)  It had slipped under the passenger seat.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on March 08, 2021, 07:05:20 PM
Quote from: Frank v B on March 08, 2021, 06:47:08 PM
Finished the nose area
Photo 06- the nose with the motor and cowl in place.
Photo 07- battery hatch (left) and cowl removed.  Both are held in place with registration pins and magnets.
Photo 09- motor built into the nose.
Photo 10- the bottom of the nose with the cowl and the battery hatch in place.

Have started covering.

Frank


ps: for those of you who wondered about my silence for the last week.  I could not find my camera in the car.  Found it today looking for wire to Lipo-start my car.  :)

C'mon @Frank v B !  Tell us where you found it!!  8)
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Michael on March 09, 2021, 07:32:37 PM
Quote from: Frank v B on March 08, 2021, 06:47:08 PM

Bad news: Due to a technical glitch (stupidity?) I cannot post the pictures. My Commodore 64 is having problems. ;)

Frank


It's not you. I can't post images either. I think there's something wrong with our website.
I've notified our 'web-master'.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 09, 2021, 08:24:45 PM
Michael,

The best news I have heard all day.    ;D


Frank

ps: as you can tell I have very little faith in my technical ability.  Ben is going to blame Andy again for his high resolution photos. ;)
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 09, 2021, 11:11:17 PM
Thank you Michael and Ben.

The pictures for the post at the top of the page attached without a hitch.

Feeling good again.


Frank

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on March 10, 2021, 07:45:41 AM
Looking good @frank.  Seems like a such a shame to cover such beautiful wood work.  How about clear or at least transparent covering?  8)

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 10, 2021, 10:25:45 PM
Andy, your last post is starting to sound like a compliment... are you OK?   ;D

The wing is covered on both sides and the ailerons and flaps are covered as well.

Note the small gold pushrods coming out of the trailing edge near the root.  These are the pushrods to activate the flaps.  They come out of the bottom of the trailing edge.  The push-pull action of these pushrods activates the flaps.  The reason: this plane may have to belly land to save the retracts so it cannot have exposed control horns, servo arms or pushrods.... and I did not want to use torque rods.

Still have to cover and add the landing gear covers.  Note the picture of the top of the wing.  There are 3 servo wires coming out (aileron "Y" harness, flap, retract).  A busy wing.

Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on March 10, 2021, 10:34:13 PM
Quote from: Frank v B on March 10, 2021, 10:25:45 PM
Andy, your last post is starting to sound like a compliment... are you OK?   ;D

The wing is covered on both sides and the ailerons and flaps are covered as well.

Note the small gold pushrods coming out of the trailing edge near the root.  These are the pushrods to activate the flaps.  They come out of the bottom of the trailing edge.  The push-pull action of these pushrods activates the flaps.  The reason: this plane may have to belly land to save the retracts so it cannot have exposed control horns, servo arms or pushrods.... and I did not want to use torque rods.

Frank

Hi @Frank v B

The trepidation with which I approached this afternoon's sojourn at the field with you today manifested itself in some very bizarre behaviour.  Please accept my sincerest apology for such an uncharacteristic complimentary outburst!  8)

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 12, 2021, 10:45:25 PM
Getting there.

Glued the stab in place.  The photo shows the fin/rudder taped with a triangle to make sure it is 90 degrees while the glue dries.
One of the tail cone triangles is glued to the bottom of the fin/rudder on the port side.  Will let the glue cure overnight.

Frank

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: sihinch on March 13, 2021, 08:04:35 AM
Looking good Frank!
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 13, 2021, 08:17:38 AM
Thanks Simon.

You know this one has to fly better than the ones you and I bought from Hobby King about 7-8 years ago. ;)
That was a classic example where the cover was much better than the book.....of blank pages.  ;D

I still love the look of this plane.  Raw power and function verses the aesthetics... and performance.... of the Spitfire.


F.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 14, 2021, 10:41:17 AM
Everything fits.

The tail wheel.  Well, it is square but castoring.  The aluminum tube is partially exposed.  It goes all the way to the stab and is raked backwards.  Notice it is off-centre because I did not want to break the bottom stringer.  To trap the shaft, I soldered a bulge onto it (see photo 18), sanded it until it just fit inside the tube and squeezed the tube with pliers to trap the tail wheel assembly (photo 19).  Yes, a square wheel for a square pilot.

All the servos are connected to the moving surfaces.

Notice the landing gear covers!  Cool.  I will correct the "toe-out" of the port landing gear visible in photo 20.  If anything, there should be "toe-in".

Next steps
- The trim stripes, including the "this way" arrows as Guy requested. This way up.  This way forward. ;D
- my daughter is going to custom match the paint on the plastic cowl. I just picked any can of blue spray paint for my attempt.
- going hunting for a plastic cockpit.  It was missing from the kit.

Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 14, 2021, 12:30:49 PM
Cockpit shopping completed.  Nothing at Dollarama.  Found a package that would work at Home Depot.  The blister pack of a gate handle.  The cockpit on the plan showed 6" long and 2" wide.  This will do.  I invoke the 50/50 rule.  Photo 23 and 25 are of the package as bought.

Weigh-in

Weighed the whole thing now that it is covered and ready to fly.  Total weight is 16.1 oz.  Including the battery, RX and ESC. 
Not bad for a 30" wingspan plane with ailerons, flaps and retracts.  That gives it 150 watts per pound.  More than enough to fly..... unless you are Ben Feist or EdEdge.  ;)

Frank

Oh, yes... gate handle for sale.  Cheap!
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on March 14, 2021, 12:36:13 PM
Fabulous @Frank v B .

Just needs a Frankian Manikin.  8)

Looking forward to the maiden flight and portrait session.

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 14, 2021, 04:46:11 PM
Canopy in place.  Installed with 3 screws, then the edges glued with 5 minute epoxy.

Looks like a Bearcat canopy built by the guy who built the BF 109 canopy.  The corners give it away.

Trim on the canopy is car detailing tape from Canadian Tire.

F.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 14, 2021, 10:39:58 PM
When cleaning up after this build, I found two sheets of stickers.  Immediately applied them.

Photo  29 - the "this way forward, stupid" arrow on the wing
Photo  30 - the "this way up, stupid" arrow on the tail. The book in the background (right) is for Andy's background analysis of all posted photos.  Yes, you can borrow the book. :D
Photo  31 - the fuse stickers. 

Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: GuyOReilly on March 14, 2021, 10:44:53 PM
Bearcat looks FANTASTIC!!
I too would like to borrow that book... Once @Andy Hoffer is done reading it.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on March 14, 2021, 10:52:20 PM
@Frank v B I am SO flattered that you chose to feature my first initial so prominently on the tail of your Bearcat (photo 3530).

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on March 15, 2021, 09:37:50 AM
Quote from: Frank v B on March 14, 2021, 10:39:58 PM
When cleaning up after this build, I found two sheets of stickers.  Immediately applied them.

Photo  29 - the "this way forward, stupid" arrow on the wing
Photo  30 - the "this way up, stupid" arrow on the tail. The book in the background (right) is for Andy's background analysis of all posted photos.  Yes, you can borrow the book. :D
Photo  31 - the fuse stickers. 

Frank

Thanks for the book reference @Frank v B.  My kids were traumatized right from birth.  They found out that they had my DNA, and there was nothing they could do about it! The book is yours @GuyOReilly !! 8)

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 15, 2021, 06:44:30 PM
Took some quick photos of the stickered airplane.

Looks good.  Passes the 50/50 rule in spades.

Frank

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on March 15, 2021, 07:34:49 PM
Truly beautiful @Frank v B !  Anticipated maiden flight?  Portraits (I can provide some more expansive backdrop paper!) ?

Andy

Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on March 15, 2021, 08:44:19 PM
Thank you Guy and Andy.

Anticipated maiden flight?  Yes.  It will fly, however short the flight may be. 
When?  When can't you make it to Rogo Field?   ;) ;)

Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: GuyOReilly on June 28, 2021, 10:34:57 PM
Quote from: Frank v B on March 15, 2021, 08:44:19 PM
Thank you Guy and Andy.

Anticipated maiden flight?  Yes.  It will fly, however short the flight may be. 
When?  When can't you make it to Rogo Field?   ;) ;)

Frank

Hello @Frank v B ;
You picked a good day for the Maiden Flight, I will be in Montreal on Canada 🇨🇦 Day...
@Andy Hoffer please ensure you record that event for posterity and those of us unable to attend.
Guy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on July 01, 2021, 05:22:48 PM
It flew today and was remarkably stable.  The retracts worked fine.  Took off on wheels but belly landed with gear up on purpose.  Unfortunately the battery was not charged so it ran out of fuel after about 30 seconds.

Andy took photos so he will post them later.

Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on July 01, 2021, 09:20:02 PM
A great show by @Frank v B 's Bearcat.  The best part was when it was chasing its tail! Frank's P-51 and V900 made special guest appearances.

With extensive coercion I was able to get Frank to provide a reasonable facsimile of a human being in the photos of him.

Way to go Frank!  ;D

Andy
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on July 01, 2021, 10:43:14 PM
Guest appearance by @Frank v B 's V900 at the Bearcat Maiden Flight event.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: BJROB on July 02, 2021, 08:00:31 AM
Wow fantastic flight.
Pictures were ok too.... just kidding great pictures.
And the P51 flying with a broken flap. Dragging in tha air.
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Frank v B on July 04, 2021, 02:20:01 PM
Flew it again today and the motor pulsed again after two circuits on a fully charged battery.
The ESC was hot.  I suspect it was an overload protection feature.  The ESC was an Electrifly 12 amps.
Will replace it with a 15 amp+ one.

The take-off was brisk.  The plane is fast and very controllable.  I may reduce the prop diameter by 1/2" or so.

A very nice plane.  The retracts are great but still belly-land it on the grass to avoid ripping them out.


Frank
Title: Re: Frank's Dumas Bearcat RC conversion- 30" span- Covid build #6
Post by: Andy Hoffer on July 18, 2021, 10:32:34 AM
For the longest time I couldn't figure out how @Frank v B managed to get his mini-planes to do 200 mph with a Speed 400 (equivalent) on 3S.  Then I realized it's all in the special "wings" sauce he mixes with his 5-minute epoxy!  ;D

Andy