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Old Apr 09, 2012, 08:17 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Build Log
Hauptmann Berthold's Fokker DVII

BUILD LOG - Rudolph Berthold's Fokker DVII

[Been out of action past svl months: 'torticolis" ("wry neck") --- have just sat around doing nothing. Doing better now.]

This is my fourth Fokker DVII R/C model. First was the one in 1968, a Guillow's conversion, using a TD 010 glow engine and a Bentert micro receiver, The 2nd was around 2008, using the early PZ guts. The third was in 2010, using the Flyzone Playmate guts.

This one will be the largest: 28" wingspan, 241 sq." wing area, around 70 grams AUW, and using the new Flyzone brick (from the Fokker DR-1) with the larger servos. The reason I now build larger is that I fly only outdoors, where there's usually prevailing winds, plus I build only SLOW flyers --- and they can't handle the winds unless they weigh around 60-70 grams AUW.

The build fotos/text won't be too extensive ---- I'll mostly show the changes made from my previous approaches I've posted in the past. You can follow my past build techniques in these URLs:

http://www.rcgroups.com/forums/showthread.php?t=1092247 ---- WW1 micros using PZ Cessna 210 guts.
http://www.rcgroups.com/forums/showthread.php?t=1205126 ---- WW1 micro gear using Playmate guts.(See Post #6 for details of DIY hotwire foamcutter.)
http://www.rcgroups.com/forums/showthread.php?t=1297361 ---- Need a different prop for Playmate motor.
http://www.rcgroups.com/forums/showthread.php?t=1319068 ---- WW1 Scratchbuilt with Playmate guts.
http://www.rcgroups.com/forums/showthread.php?t=1320300 ---- Playmate/Albatros-Gearbox Version 2.
http://www.rcgroups.com/forums/showthread.php?t=1374744 ---- Handley Page O/400.
http://www.rcgroups.com/forums/showthread.php?t=1405464 ---- The British BE2e.
http://www.rcgroups.com/forums/showt...light=billyjim --- Avro 504k
http://www.rcgroups.com/forums/showt...light=billyjim --- Sopwith Camel
http://www.rcgroups.com/forums/showt...light=billyjim --- "Porpoising Paradox"
http://www.rcgroups.com/forums/showt...light=billyjim --- SPAD XIII
http://www.rcgroups.com/forums/showt...light=billyjim --- SE5a - "Big Red"
================================================== ========
Here's another thread, a mini-review of the Marvy foam cutter:
http://www.rcgroups.com/forums/showt...ir+foam+cutter
================================================== ==
There's a nice bio of Berthold in Wikipedia .... here's the URL: http://en.wikipedia.org/wiki/Rudolph_Berthold

================================================== ========
Here's a full-size replica of the plane:

Bill
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Old Apr 09, 2012, 08:23 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Here's a 3-view.

Bill
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Old Apr 09, 2012, 08:36 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Here's some fuse build pics

The pics are pretty much in the sequence of the build.
One note on the paints used: Painting the box -- used Testors Model Master Spray Enamel Grabber Blue 2964, and Italian Red 2919. I don't know if I want to use those again --- they take considerably longer to dry than the Testors Acrylic in bottles, and I suspect they weigh more too.

Note the "spreaders" in the fuse. They keep the top of the fuse side spread apart far enough to match the width of the upper fuse section.

Bill
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Old Apr 09, 2012, 08:55 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
OK, here's the GB/motor mounted on the fuse

(Also the brick --- will explain that in a later pic.)

Bill
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Old Apr 09, 2012, 09:08 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Here comes the pushrod installation.

The only thing tricky about this is that the rods are installed into the BOTTOM of the servo arms, with the ends thus protruding thru the top of the servo arm holes. I then put a dab of epoxy on each of the rod ends. Why not the usual way -- installing the rods in from the top and protruding down below the arms? 'Cause I was worried there wouldn't be enough clearance from the top surface of the servos themselves. Also it would have been real ticklish trying to get a blob of epoxy on to the rod ends if they were underneath the servo arms.

Anyway, it works. .

Bill

Additional info about that brick: it's taken from a Flyzone Fokker DR-1, and it's a real upgrade from the previous FZ brick, In particular its servos are much more powerful and have a longer throw. Excellent!
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Old Apr 09, 2012, 09:26 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Now the flying surfaces.

Pics of the wing foam and tailfeathers foam.

Bill
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Old Apr 09, 2012, 09:30 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Now the struts

Note that I had to use TWO "splints" for each pair of struts -- 'cause the struts are so large.

Bill
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Old Apr 09, 2012, 09:51 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Pics of the finished model

Purists will note that the subwing (the little wing between the wheels) is narrower than scale --- I did that to give more strength to the landing gear design

Also note that the prop saver needs to use TWO rubber bands -- when I tried only one the prop flew right off the propsaver. .

Bill
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Old Apr 09, 2012, 09:59 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
The stats and the maiden and trim flights

Here's the stats: w.s. 28", wing area 241 sq.", AUW (with 180 Hyperion) 71.5 grams, wing loading = 0.297 grams/sq."

The maiden: a little problem with "porpoising" ... 'cause I forgot to follow my advice: never try a maiden with "normal' elevator setting --- always use enough "down" el to keep the plane from a successful R.O.G. Then gradually crank in more UP elevator with each ROG attempt --- until it finally does take off. Then adjust trim to give a nice gentle "float" flight.

After adjusting the elevator trim the old DVII flew like a champ: crawl'ed around the field like a WW1 bird should.

Hope to get some video later on --- have to finish building my head camera -- maybe in a week or two.

"Brech ein Bein!"

Bill
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Old Apr 09, 2012, 10:07 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Couple more pics

Here's the motor and exhaust (from a plastic kit) I used to model my build, which used foam for the motor and balsa for the exhaust.

Also the "winged sword" side decal, I swiped from a paper plane website.

Bill
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Old Apr 09, 2012, 10:34 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Comments on the propsaver

What a GREAT addition to micro R/C. By using a propsaver I no longer have to worry about 1) bent prop shafts, 2) gb/motor ripping out of its mooring, requiring re-epoxying, and then hoping to maintain the previous thrust angles, 3) saving prop tips from being chewed up.

So next build I'll dispense with the carbon-fibre 'firewall' mount, and dispense with the four screws needed to mount the EP Brush-8 gb/motor. I'll be able to use just 2 screws and mount the gb/motor in a small piece of 1/32" plywood, which I'll epoxy on to a 5mm black depron "bulkhead" -- easy peasy.

OK, two tips:
1) buy your propsavers from David Lewis (dlewis@homefly.com) -- order "ps-15-4" -- "prop saver, 1.5mm bore x 4mm bore" quantity 4, cost for them including s&h = a mere $11.20. And the service is fast!
2) when you get them in house hand ream out the front of the propsaver shaft hole with a bit that's approx. 1.42mm -- that will give you a tight fit for the entire propsaver when hand pressed on to a 1.5mm shaft (I also put a dab of epoxy inside the saver shaft.)

One more tip: for my next build I will use a modified HK GPS-8 gearbox (same as HK's "EP Brush-8 gb). It will replace the bronze bushings which are pitiful with high quality roller bearings. Here's the skinny (from Curt): buy Align part AGN-H25082T(681ZZ) 2mm deep bearings, for the front bushing replacement, and AGN-H25060 1.2mm deep bearings, for the back bushing. These are sold for the T-Rex 250 heli. You'll need to move the spur gear slightly to compensate for the 2mm front bearing. These bearings should give a real boost to the gb/m thrust hopefully.

Bill
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Old Apr 09, 2012, 11:10 PM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Forgot to mention throttle settings

Needs >50% throttle for ROG, ~45-50% to cruise, 50% or more to climb.

Bill
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Old Apr 10, 2012, 05:15 AM
billyjim
Cullman, AL
Joined Jun 2007
914 Posts
Couple more points

Landing gear: because of the increased weight of this size plane, next build will use 0.025" music wire instead of 0.020" --- the sprung axles can't take it -- they deform -- if there's any kind of hard landing.

The prop is a GWS 7035 -- the gb/motor handles it fine -- as long as I'm not trying to fly WOT. I think if I tried WOT I'd burn out the motor FET.

Bill
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Old Apr 10, 2012, 07:33 AM
Registered User
Gulf Breeze, FL
Joined Jul 2006
2,887 Posts
Wow, Bill...that's one magnificent thread you're authoring. I really appreciate the time and effort you take to share your expertise and creativeness ...now I need to find a couple of hours to study all the details you presented.

Gene K
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Old Apr 10, 2012, 07:33 AM
Registered User
Centreville,VA,USA
Joined Apr 2001
3,932 Posts
Bill,

Awesome job! Love the details you showed on the struts, I think the hardest part of these WWI birds. It came out great. Though that foam you use for the fuselage seems to have a lot of grain and makes it harder to finish.

How does the 1mm hold up on the wings? I only use it for tail areas

Again very good job.

Pete
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