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Outdoor Free Flight Forum => Peanut Scale => Topic started by: Bredehoft on December 16, 2016, 01:08:22 PM



Title: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on December 16, 2016, 01:08:22 PM
I've been kicking this Peanut around for about 16 years.  In fact, I laid up one side back in 2001 or 2002 and then went no farther.  I decided to get back into building this as a personal challenge and re-drew the plan and laid out the parts for laser cutting.  This won't be a kit, just to see if I can do it and get it to fly.  I figure, if I can get a minute out of it, I will be pretty competitive in all but the highest level FAC Peanut contests (35 bonus points).

Liberties have been and will be taken since I am working on a small scale.

Here is the subject - simple because I will be challenged enough with the structure:

(http://www.volareproducts.com/files/goose/0000005279.jpg)

And the drawing, parts and nacelles ready to proceed (I started on 12 Dec):

(http://www.volareproducts.com/files/goose/GooseBuild01.jpg)

--george



Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Mefot on December 16, 2016, 01:13:31 PM
I'm looking forward to seeing this one take shape  :)


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on December 16, 2016, 01:17:09 PM
Working on the fuselage...

Notice there is a traditional motor peg.  I have gone back and forth with having the motors run back to a 5" wide motor peg or building a prop hook out the trailing edge of the wing.  I reverted back to the motor peg because I felt this is going to end up being nose heavy and any extra help I can get shifting the weight back would be welcome.

All of this structure is light (6-7 lb) 1/16" balsa, with the exception of a couple of 1/16" x 1/32" stringers.

One side:

(http://www.volareproducts.com/files/goose/GooseBuild02.jpg)

Fuselage at 90%:

(http://www.volareproducts.com/files/goose/GooseBuild03.jpg)

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on December 16, 2016, 01:24:34 PM
Here is the nose.  As you could see in the parts photo, I cut the nose pieces to basic shape.  I have the center hold to properly align them.  I stacked them and then glued the stack to the fuselage and sanded to final shape.  As you can see, I needed to patch in some balsa as I miscalculated the depth - or broke pieces out during sanding.  Once installed and sanded, I used a dremel to hollow out the inside, but I didn't take out very much as I didn't want to poke through - and I was worried about the stick structure.

(http://www.volareproducts.com/files/goose/GooseBuild04.jpg)

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on December 16, 2016, 01:38:46 PM
Wing build up:

Here you can see the wing starting to take shape.  I build the center section first, then started on the outer panels.  It is a little tricky and required a bit more preparation and thought before building.  The outer panels will be glued on for dihedral later.  I designed a double spar since I want the wing to be pretty stiff as the motors will be pulling against the wing.  I didn't take the lower spar all the way out, since the tips don't have that stress on them.  The nacelle is placed there to ensure proper rib spacing.  I'll be cementing the nacelles in place and needed a slip fit on them.  I show diagonals inboard of the nacelles.  I hope these will resist twisting.  I better not forget them!

(http://www.volareproducts.com/files/goose/GooseBuild05.jpg)

Here we are, up to date as of yesterday.  As I told my son, now all the difficult pieces remain:  the nose blocks, the 3-blade props (about 3.75" diameter), the spinners, the wing tip floats...

I completed the nose blocks after this photo was taken last night.  It is about 5 grams as it sits.  Now I am designing the props...

(http://www.volareproducts.com/files/goose/GooseBuild06.jpg)

We are up to date now...more progress and photos when it occurs.

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: calgoddard on December 16, 2016, 02:31:03 PM
George -

Wow a peanut seaplane!

I love the nacelles.

Nice work so far.

I will enjoy watching this build.


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on December 16, 2016, 02:44:19 PM
Wow a TWIN peanut seaplane!

Fixed that for ya ;-)

I forgot to mention the nacelles are rolled 1/32" balsa on a 1/2" dowel, already covered with tissue once.

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: MKelly on December 16, 2016, 02:53:09 PM
Really interesting build - please update as you progress.

Mike


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Copbait73 on December 16, 2016, 03:27:10 PM
Subscribe


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Don McLellan on December 16, 2016, 05:05:08 PM
Beautiful model George!  An all time favourite.

Don


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Crabby on December 16, 2016, 09:29:35 PM
It is so nice to see someone else who has a project stuck in time. Great looking Goose George...of course I am gonna ask about ROW?


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: fuzzywill on December 19, 2016, 12:49:55 PM
As always, great job George.  Can 't wait for updates.


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Starduster on December 19, 2016, 02:34:55 PM
I've said it before, and I'll say it again, you scale guys are in need of some serious professional help!

All kidding aside, I'm just in awe of what you guys do...



Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Sky9pilot on December 20, 2016, 03:18:17 PM
Really amazing George...in Peanut scale!!! I've loved this plane since riding in one to Catalina years ago!  I look forward to your progress.  Keep up the great work!
Tom


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on December 21, 2016, 11:50:46 AM
I've spent this time trying to figure out how I will do the props.  I had planned on building three-bladed props.  I had even gone as far as cutting out blade blanks from a clear, cylindrical, smooth-sided, plastic juice bottle.  I spent way too much time trying to fugure out how to build them cement them together in a hub, design a spinner, and so on.  I changed my mind

I just decided to go with some 4" Yoshida props.  First I trimmed 1/4" off each tip to clean the fuselage nose.  Then I sanded and scraped them down (from 2.1g for the pair to 1.6g).  Then I sanded off the ramp and the back nib.  I colored them black with a Sharpie.  Next was how to integrate a freewheeler and a spinner assembly.  Here is what I did.

In this photo you can see two things: 

1.  the 1/64" plywood backing plate that will be the base of the spinner.  I will be vacu-forming the actual spinner, but I need a base to glue it to when it is formed.

2.  the freewheeler.  I chose a Nason-style freewheeler.  I just tried these recently and find them quite effective and efficient - it will fit well in the small confines of the spinner (remember 1/2" max diameter on these motor tubes) and will automatically engage and disengage without me doing anything.  I made this with 0.015" music wire and a #72 drill through the body of the prop.  This light wire will be strong enough as I intend to use a loop of 1/16" OR LESS for the motor.
(http://www.volareproducts.com/files/goose/GooseBuild07.jpg)

Next I had to fill on either side of the prop.  This is some light 1/4" balsa trimmed down to 3/16" high.  These halves are fitted to each side and them cemented to the prop and ply base.  The finished discs will provide a base for gluing the spinner.

(http://www.volareproducts.com/files/goose/GooseBuild08.jpg)

(http://www.volareproducts.com/files/goose/GooseBuild09.jpg)

(http://www.volareproducts.com/files/goose/GooseBuild10.jpg)


--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on December 21, 2016, 12:04:14 PM
Here is how I did the nose plugs and final prop assembly.

These are simple laminations of 1/16" balsa, sanded to a slip fit in the tube.  I have added a small 1/164" ply disk to prevent the small Peck nose button from collapsing the balsa.  This nose button has a 1/32" hole for the prop shaft, but I will be using 0.025" music wire.  There will be a little slop, but not terrible.  I was aiming at keeping the nose light, as everything that is even remotely heavy is forward of the wing on this model.

(http://www.volareproducts.com/files/goose/GooseBuild11.jpg)

In this photo, I am showing that I sanding in downthrust into each tube.  The motors on the full scale are definitely pointing up above the angle of the wing.  I will be putting them in line with the wing, because pointing them down would just look bad.  So I added a little downthrust.  This might be the trickiest part of this plane.  Nearly all rubber models need more downthrust than I will be giving this one.  It might be a challenge to get this to fly.

(http://www.volareproducts.com/files/goose/GooseBuild12.jpg)

Here are the finished prop assemblies.  No, I haven't made the spinners yet, and yes, the nose blocks are still bare wood.  But you can see that the Nason freewheelers will be well inside of the spinners and will not interfere.  The props are tube-in-tube - well, tube-in-prop - I have put 0.047" OD thin-walled brass tubing in the prop to allow freewheeling.  The key here is to make sure the hole for the tubing is larger than the tubing and the tubing is slightly longer than the prop body.  This will allow the tensioned motor to pull back on the prop shaft (natural action).  The prop shaft will stop at the tubing, capturing it, but the prop will be free to spin on the tubing.

(http://www.volareproducts.com/files/goose/GooseBuild13.jpg)

Bonus points for identifying the CD on the desk...

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: tross on December 21, 2016, 12:46:39 PM
Hello George,

Good for you that you are finally getting this going. :)
Really neat. ;D
I'd be surprised if it needs any down thrust at all just off the cuff, with the wing and thrust up high and close to in-line with each other like it is.

These sorts of off-the-beaten-path subjects are always of interest.
A peanut twin to boot!

Tony

PS. Sorry. No bonus points this time. ::) ::)


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Mefot on December 21, 2016, 12:56:44 PM
I can't comment on the downthrust requirements but will hazard a guess at Quadrophenia for the CD !!! ;D


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on December 21, 2016, 01:33:12 PM
I can't comment on the downthrust requirements but will hazard a guess at Quadrophenia for the CD !!! ;D

Winner, winner, chicken dinner!

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Pit on December 22, 2016, 07:40:01 AM
George,
what a great project!  Don't see a peanut twin very often!

If I may make a suggestion, that "play" in the thrust bearing/prop shaft might well be fatal.  Precisely that was the bugaboo with my RIVETS, and only after getting the bushing crimped down to fit the shaft closely did the model start to behave (Thrust bearing bore 0.9mm, prop shaft 0.8mm - visible slop).

Just a "heads up".

Pete


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: bigrip74 on December 28, 2016, 12:06:32 PM
George,

     I have enjoyed your Goose build, but the prop spinner process has taught me more to be able to finally make my airplanes with a spinner. THANKS.

Bob


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on January 09, 2017, 07:17:22 PM
It's been awhile since I posted.  I have the wing tip floats carved and covered - then I stopped.  This will be a white plane, and I usually do white planes with white tissue and no other pigment.  But the Motor tubes and the tip floats are balsa-colored, even after being covered with tissue.  I like the simple way to do things and have used spray cans in the past.  But there are a couple of things that prevent me from using them on this model right now:  1) sometimes they spray inconsistently, 2) the last time I painted white, it was very heavy, and 3) It's well below freezing outside and I have no spray booth indoors.

So...what to do?

I decided to break down and buy an airbrush and a compressor and paint.  Today, I tried it out.  I chose to use Daler-Rowney India Ink.  I read that it would spray just fine without thinning.  I practiced with the airbrush until I felt I could control the coating.  Then I tested on a piece of tissue.  I cut an 11"x11" piece and weighed it - it was 1.1 grams before paint.  After my test dried out, I weghed the piece again and it was 1.4 grams - so my paint was 0.3 grams - I am happy with that - and look how nicely it turned out.  It really makes the tissue white and is still a bit translucent.

(http://www.volareproducts.com/files/goose/GooseBuild14.jpg)

(http://www.volareproducts.com/files/goose/GooseBuild15.jpg)

I was so pleased with this test, that I decided to use this piece to cover the tail surfaces.

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on January 09, 2017, 07:27:56 PM
Before I used the piece to cover, I imported a Goose 3-view into my CAD program and sized it to match my pieces.  Then I traced over some panel lines and added the registration number.  Then I printed right on top of my painted tissue.  Notice the surface outlines are very faint - I don't want them to show during covering; they are only used for alignment of the tissue.  Also note that I carry the lines slightly beyond those outlines, just to make sure that the lines exist as I wrap the tissue around the edge of the piece.

(http://www.volareproducts.com/files/goose/GooseBuild16.jpg)

(http://www.volareproducts.com/files/goose/GooseBuild17.jpg)

(http://www.volareproducts.com/files/goose/GooseBuild18.jpg)

To me, these pieces really look good.  the white paint really brightens up the tissue and the nice sharp lines just stand out (I should have done the rib outlines in gray, not black).  I even found the Grumman Goose logo that is on the full scale plane and added it to the print file.

Now I can paint my wood parts, paint more tissue, and get on with the build.

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on February 04, 2017, 12:09:11 PM
Well, time to catch up.  There was very little activity on this until yesterday.  I will start with the spinners.  The thought of spinners has been causing me concern for a long time.  Yesterday, I jumped in with both feet.

I chucked up a 1/2" dowel in my drill press and sanded it down to the "appropriate" profile.  It is not quite scale, but affords a lot of room inside for the clutches.  Here is the plug on a base for the vacuformer.

(http://www.volareproducts.com/files/goose/GooseBuild21.jpg)

Here is a shot of the first spinner pulled in my vacuformer.  It is a chinese dental vacuformer and it works well for small parts (less than 4" long").

(http://www.volareproducts.com/files/goose/GooseBuild22.jpg)

here are the two spinners cut out and ready to install.  They look nice.

(http://www.volareproducts.com/files/goose/GooseBuild23.jpg)

And one fitted...

(http://www.volareproducts.com/files/goose/GooseBuild24.jpg)

next up: finishing details.

--george



Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on February 04, 2017, 12:17:06 PM
I decided I needed a couple of obvious details; you know, for a couple of detail judging points.  I found a photo of a Goose flying with fully retracted wheels - both the tail wheel and the side wheels stick out.  So I got some real light 1/16" balsa and cut out some wheels.  Also, the full size example I am modeling had some obvious spray strips on the front chine line, so I cut them out, too (out of a file card).

(http://www.volareproducts.com/files/goose/GooseBuild25.jpg)

Here is one wheel done compared to the raw cut one.  It has been sanded and marked with black and silver sharpies. 

(http://www.volareproducts.com/files/goose/GooseBuild26.jpg)

I think these two details really add a lot to the model.

(http://www.volareproducts.com/files/goose/GooseBuild28.jpg)

Next:  final shots.

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on February 04, 2017, 12:27:41 PM
So the model is virtually complete.  I only have to make the rear motor peg.  It will be aluminum tube - extending out the sides to the width of the nacelles.  There will be small hooks on each end to capture the rubber.  I plan on starting with stripped rubber, about 0.050" width for each motor, to start.

Here is how the rubber will exit the nacelles.

(http://www.volareproducts.com/files/goose/GooseBuild29.jpg)

Here is a little surprise.  I expect this to climb to 12.5g with the motor peg and probably additional tail weight.

(http://www.volareproducts.com/files/goose/GooseBuild27.jpg)

And a couple of "beauty" shots.  It is not perfect, but I am happy with it so far.

(http://www.volareproducts.com/files/goose/GooseBuild30.jpg)

(http://www.volareproducts.com/files/goose/GooseBuild31.jpg)

Maybe Thursday, I will see if it flies.  I'll be nervous testing it indoors...we'll see if I can get over that.

--george




Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Copbait73 on February 04, 2017, 12:52:03 PM
Looks great George.


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Mefot on February 04, 2017, 12:53:17 PM
This is shaping up to be a fine looking model. Looking forward to seeing it in flight  :)


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: flyfac on February 04, 2017, 09:50:06 PM
Impressive build, George, especially at peanut scale! 

Looking forward to flight reports.

You planning on selling plans for this one?  ;-)

Best,

Scot Dobberfuhl
Forest Grove, OR


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: tom arnold on February 08, 2017, 12:23:19 PM
Beautiful job, George. A peanut twin is beyond my sausage fingers and I love to see one built. I have a question I should have asked earlier, though:

In making the Nason clutch, is the clutch wire the same diameter as your shaft wire? or smaller? Also how in the world do you make such and tight and tidy opposing bends in the clutch wire? In other words, I can make bend #1, then slide it through the bearing tube (or drilled hole in the propeller, as the case may be) but making the SECOND bend always comes out poorly. Normally, I have to grab the wire with a needle nose pliers at it's exit from the bearing tube and use another pliers to make bend #2. The problem is the short length of the wire that was the pliers gripping area now allows an awful lot of fore-and-aft slop that makes the final tweaking to make sure the bent "dogs" catch more difficult and usually a spinner won't go over my attempts. So to see you pull this off with a peanut twin spinner is pretty stunning.

My prop shafts are the standard .047 diam wire and I bend the clutches from the same stuff. I tried using lighter wire for the clutch but often it would bend under the torque I would use for a 24" span model (just for background info).


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on February 08, 2017, 02:33:57 PM
Hi Tom,

I think that is 0.020" or 0.025" wire on the clutches.  I just bend it against the prop.  Since it is so fine it bends easily.  Also, since I am using fine rubber, I don't need overly strong wire.  I think I stated I used 0.025" for the prop shafts?

By the way, I have put in a few test flights on single loops of 0.050" rubber.  I got it to start to fly.  It required nose weight, down thrust, and down elevator.  I guess I got some part of the design or construction wrong  ;)  Anyway, I got a fairly stable flight that curved across the yard, avoiding some pine branches, but it didn't avoid them all and tumbled to the snow-covered ground, undamaged.

Real testing tomorrow indoors.

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: tross on February 08, 2017, 02:53:57 PM
I guess I got some part of the design or construction wrong  ;) 

Not necessarily.
It flew so I say you did it right. ;D
Seriously, these little buggers are sensitive as you know, so it looks great and flies. :D


TR


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Ray_K on March 20, 2017, 10:37:15 PM
3-20-2017

Great model George, I love it, to bad it won't be a kit, I'd buy one.

Outstanding job George!

Cheers, Ray K.


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: David Lofthouse on March 29, 2017, 08:30:30 PM
George,

Outstanding.  I really enjoyed reading this thread.  A quick story about one of these with pistons in it. 

I was taking flight training at a college in Michigan.  One of these birds had been donated to the school through a government program.  It had been wrenched on and played with by the AP guys for over ten years, bird poop alone should have kept it from flying - I mean it was rough, inside and out.  When the government donation statute ran out, it was sold.  A couple of fellows showed up with tool boxes and started working on it.  Two weeks later, that machine was was leaking oil all over the place, had wheels that barely held air and only the most critical systems were operational.  After a couple of test flights, they flew it to Alaska for a fish hauling operation.  I remember it had a distinct smoke trail coming off of the port engine as they went out of sight.  I did not hear any more about it.  I assume that it made the trip and is still hauling fish to this day.  A tough airplane flown by guys with nerve. 

Neat airplane George, good luck with the flying. 


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on March 29, 2017, 10:38:52 PM
cool story.  I will be testing this on Sunday, if the weather holds.

--george


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: rgroener on May 03, 2017, 01:08:33 AM
George, any news of your great looking Turbo Goose?
I would love to see it in flight or hear how it flies.

Roman


Title: Re: Personal Build - Grumman/McKinnon Turbo Goose
Post by: Bredehoft on May 03, 2017, 07:05:36 AM
no, not yet.  We have had wet weather here, with standing water on the flying field - and while this is a model of a seaplane, I prefer not to get "that" scale!

--george