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Nov 19, 2014, 08:23 PM
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Build Log

My Bob Wallace Fokker V.23


Looking for an interesting project I ran across a Fokker V.23 Short Kit by Laser Design Services (laser-design-services.com). Having enjoyed building their Short Kit of Bill Effinger/Berkeley Cessna 170, I thought this looked interesting. Included with the kit and plan was a reprint of an article by Bob Wallace, the designer. Turns out the V.23, a mid-wing monoplane, never made it beyond the prototype phase. And that prototype was apparently destroyed in WWII. Anyway the kit was relatively inexpensive, looked pretty simple and if I managed to get it built it would definitely be the only one of its kind at our flying field.

The kit sat under my bench for several months while I had other projects under way as well as living life which takes up some time. If you are interested, the article was from the March/April 2005 issue of RCM and the Plan is #1342.

As of today I have the wing construction nearly completed, just wing tips, ailerons and covering to do yet. Here are the photos so far. The original design called for a foam wing covered with 1/16 inch balsa sheet. But Laser Design Services provides a built up wing design which I used. So that is what you are seeing here. One thing that struck me is how thin this wing is. At the fuselage it is only an 1-1/8th inches thick and at the wing tip it is only about 3/8th inch thick. That seems pretty thin for a 48 inch wingspan.
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Nov 26, 2014, 09:47 AM
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Fuse Progress


Got the fuselage pretty well framed. Also have the tail feathers roughed together. Learned something important for future builds. The elevator halves are supposed to be joined together with a 3/16 hardwood dowel. Well, I couldn't find one so decided to use a bamboo barbecue skewer, seemed pretty rigid. Bad choice. though it is fine in "stiffness", it is NOT fine in twisting strength. The two halves feel like they are joined with a rubber stick! Probably not good for a fast combat plane!

I decided to embed the aileron servos into the wing as the photos show. Used trimmings from vinyl siding for the mounting plates for the servos.
Dec 12, 2014, 03:22 PM
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Battery Sizing


Receiver Battery Size. This deals with both battery capacity and physical size and became an issue for me while building the Bob Wallace Fokker V.23 which has very limited space in the fuselage for the receiver, servos and battery. I have on hand a small 750mAh battery consisting of five AAA cells which is perfect physically. The question is whether it is OK capacity wise for a typical day of flying?

Like most people I went to the manuals and Internet to do some research on current drawn by my receiver and servos. I was unable to find much. They all specify a voltage range but give little helpful information on current requirements. Also, looking at discussions in groups like RCgroups the prevailing opinion which, by the way I agree with, is to use the largest battery possible. You never know when you may need the extra capacity. No one said much if anything about the minimum sized battery you might be able to get away with!

So I set up my own test to simultaneously measure battery voltage and current using a couple digital multi-meters, a 2000mAh 4 cell NiMH battery, a Spektrum AR8000 (with satellite) receiver and five Hitec HS-81 servos. Here are my test results.

Receiver only: 60mA @ 5.4v
Receiver and one servo, resting, no load: 70mA @ 5.4v. The servo draws 10mA resting
Receiver and one servo, rapid movement of control: 400mA @ 5.3v. Servo draws about 340mA when in motion
Receiver and one servo, with simulated load (pressure by my fingers!) : 250mA @ 5.4v
Receiver and five servos, resting, no load: 100mA @ 5.38v
Receiver and five servos, all rapid motion: 1300mA @ 4.8v

It looks to me like the worst case would be when all five servos are under load, about 1250mA. So if you had a fifteen minute flight with all five servos under constant load you would consume about 313mAh of power. It is very unlikely that all servos would be under constant load all of the flight. The throttle one, for example, would experience very little load most of the flight. Here are some assumptions to try to estimate the real demand for a 15 minute flight:

Throttle, 20%, 13mAh
Ailerons (two servos) 50%, 63mAh
Elevator, 30%, 19mAh
Rudder, 20%, 13mAh

Total: 108mAh

So I would use about 15% of the capacity of my 740mAh with a single 15 minute flight. It appears I might safely get three or four flights out of a charge. Unless I learn something more before flight time Iím going to proceed with the 750mAh battery in my V.23.

Anyone have any suggestions?
Dec 12, 2014, 03:28 PM
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Progress Update


Making progress on the fuse and tail section. I was held up deciding on a color scheme as I needed to cover the tail feathers so I could install the hinges and determine the locations of the cranks for both the rudder and elevator. After looking at photos and talking it over with my son I decided to go with Monokote Cream material and color. I think it will look good. So tail feathers are covered, hinges installed, along with control rods and servos. All that allowed me to close in the rear part of the fuselage.

One interesting issue there was that the fuselage was twisted a bit. I was also concerned about alignment, that the rudder was on the centerline and aligned down the centerline. So I rigged up a jig from a piece of 1x6 some wood scraps and clamps. Worked very well - I guess the maiden flight will prove that!

I'm concerned about battery and receiver location. The fuselage is pretty cramped. Would like to put a 2000mAh battery in but it takes a lot of space and is heavy, making location even more critical. I may go with a 750mAh one that is much smaller and lighter.

Sketched out the landing gear wire plan. It'll be pretty similar to the one on the plan but a little different to make it easier for me to make.
Dec 21, 2014, 10:37 PM
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Nearly Finished


I have a web site with a page dedicated to this project where I'm posting photos and keeping a log. The link is

http://www.huyettm.net/fokker-v23-ww...ale-plane.html

The short story is that it is nearly finished now. Here are a few photos.

I purchased a Micro-Mark Mini Wire Bender off the Internet which made fabricating the landing gear from .032 in. wire almost easy. I would recommend it to anyone who needs to bend piano wire for landing gear. It's a deal at $20. I still need to actually install the fabricated landing gear on the plane.

Still awaiting the 3-1/2 in. vintage wheels for it. Ordered off eBay. The last significant thing to do is to fabricate a cowl. I was about to just skip it until my wife looked at it tonight and said it needs one!

Finally, I checked the weight and CG and it comes in just about as specified on the plan, 2.5 lbs with the CG very close to the point specified on the drawing and as indicated by the CG calculator at

http://adamone.rchomepage.com/cg_calc.htm

I'm pleased with the way it is turning out so far!
Dec 23, 2014, 04:13 PM
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Almost done!


Like a lot of projects there is always one more thing to do! Looking at the photos I realized I had forgotten to build the sub wing, the little wing mounted on the landing gear between the wheels! I also discovered that the landing gear was one inch too narrow! So today I corrected the narrow landing gear and built and installed the sub wing.

I also installed a fueling valve between the tank and the engine. Now I think all I need are the wheels for which I am still waiting.

The photos show the "finished" airplane with some old wheels I found in a box. I printed the emblems on Avery 8556 Full Sheet "clear" label sheets with my inkjet printer. Will be interesting to see how they hold up.

Now I need warm weather and sunshine....
Last edited by Huyettmeh; Dec 23, 2014 at 04:15 PM. Reason: Corrected some text
Dec 24, 2014, 12:03 PM
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Construction Completed


Today I finished all construction on this plane by adding three black stripes on the bottom of each wing to help in keeping track of it in the air. Then I checked and adjusted the travel on all the control surfaces including putting 50% expo on each. All seems to function smoothly and properly. So now it goes on the wall hook until flying conditions arrive in a couple months - hopefully.

This has been a fun project. I find that I really enjoy scratch building from plans (as with the micro-fokker eindecker or from short kits from plans. There are a lot more issues to think through and more room for creativity than when you build from a kit. I like kits too! Laser Design Services ( http://store.laser-design-services.com/) does a great job on their short kits and Bob has quick to answer any questions that I've had along the way, which weren't many. Based on my experience I recommend his work.

I'm on the prowl for my next project - after I repair my Cessna 170 (https://www.rcgroups.com/forums/show....php?t=2060032).

Merry Christmas!
Dec 24, 2014, 12:41 PM
Balsa breaks better
Thermaler's Avatar
Quote:
Originally Posted by Huyettmeh

So I would use about 15% of the capacity of my 740mAh with a single 15 minute flight. It appears I might safely get three or four flights out of a charge. Unless I learn something more before flight time Iím going to proceed with the 750mAh battery in my V.23.

Anyone have any suggestions?
I would use the largest battery that would fit instead of a small battery and lead to bring it to balance.
Better useful weight than dead weight.

Joe
Dec 25, 2014, 08:25 AM
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Nice job!

Jim
Dec 26, 2014, 01:00 PM
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The Windshield


One More Thing... Never done? Discussing windshield ideas with my son last night after Christmas Dinner I said I couldn't find any cement that would effectively stick to the plastic I tried to use. He suggested carefully sanding the edge. Then the idea came up of cutting a slit at an angle in the cabin top with my #11 Xacto knife and carefully pushing the little piece of plastic into that slot, then cementing in place with thin CA. So I tried that this morning. It worked very nicely! Here are a couple photos showing the result. NOW I'm all done with construction...!


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