Guillows Fokker DVII conversion. - RC Groups
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Feb 17, 2015, 08:08 PM
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Rem Fodder's Avatar
Build Log

Guillows Fokker DVII conversion.


Thought I would kick off this build log with a bit of history about a very old Guillows kit that came into my possession about 30 years ago. It was a Christmas gift to a childhood friend that he received when we were about 12 years old, around 1973-74. I remember him showing the kit to me all proud to have it. To be honest it was way beyond our skill sets at the time to build. The kit sat for years, and as you can see the plans are severely yellowed on one panel and still show the black electricians tape he had used to hold them down to a building board. The kit came to me when I was in my twenties as his parents were cleaning out his stuff after he had moved on.

So now after reading about many Guillows conversions and with the advent of micro RC radio gear I thought I would give this old kit a makeover and build. This will mark the first time in 30+ years that I have attempted to build a wood kit. Since getting back into RC about 5 years ago, I have satisfied my need for RC flight with ARF's, I know I can hear the groans from some of you out there, but the truth is, the ARF's got me back into the hobby.

I'm still waiting for some of the components to arrive to complete the build, some micro servos and covering. The original covering is missing. I have on hand some Coverlite, but have never used it before and am somewhat hesitant to try it for the first time on such a delicate framework. I have done plenty dope and tissue coverings, so for now think this is how I will finish the project.

Pretty much all of the wood parts are present as are the hardware, and nose piece. I think I will take the time to cut all of the parts off of the patterns provided from better quality balsa that I have.

I do have a couple of questions for some of the seasoned Guillows conversion experts out there regarding the airfoil shape. Is it worth the effort to change the shape to a Clark Y airfoil on such a small model? Or is it just too little gain for the effort expended? Second question is in regard to the leading edge. Since I will be cutting new ribs will it be worth the effort to use a 1/8" square stock or 1/8" dowel for the leading edges? Also in regard to the wing, this kit shows no dihedral at all for the wing, to me that seems a bit odd for a free flight model. So, if I make this model a simple three channel, RET, should I build in dihedral or leave it flat and add some functioning ailerons?

Think I will leave it at that for now. I hope to start in a couple of weeks or so. Right now I have a giant scale WACO on the bench that is being converted from 30 cc gas to electric. I need to clear that one off the books before starting with the Fokker. Going from the very large to the very small, I must be crazy.
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Feb 17, 2015, 09:53 PM
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glewis's Avatar
An old WW series kit. I built a bunch of them when I was a kid. If they flew 50 feet I was thrilled!

A 1/8" square LE would be a good idea. You can cut a notch in the rib and put the LE strip in on the diagonal. Then sand the bottom of the rib up to meet the LE changing the profile to more of a Clark Y section.

The dihedral is marked in the note on the plan. 1" per panel on the top and 7/8" on the bottom. That's for free flight. I would go with about 1/2" per panel on the top and 7/16 on the bottom for rudder/elevator control. Or...

If you decide to cut new ribs you could add a tapered spar and make the wing tapered like the full scale. Not worth the effort IMO.

You can't go wrong with tissue and dope on a model this size. That's what I used on my WW series Camel. https://www.rcgroups.com/forums/show....php?t=1807720
I used a 8.5mm brushed motor in the Camel and it has adequate power. It is Not over powered. I did have to add nose weight, so it would have been better to have used a small brushless and a 2 cell. Might as well add useful weight....

Here's a pic of me holding a WW series DVII I built in 1965...
Glenn
Feb 17, 2015, 10:13 PM
Round engines & two wings...
WWI_Flying_Ace's Avatar
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Feb 17, 2015, 11:30 PM
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moscow580's Avatar
Hey Rem.

Long time no speak. How is the Dynam Waco?

I just bought this kit on EBay. Ready to watch.


Sean
Feb 18, 2015, 12:28 AM
This is what 2 HP looks like
Rem Fodder's Avatar
Quote:
Originally Posted by moscow580
Hey Rem.

Long time no speak. How is the Dynam Waco?

I just bought this kit on EBay. Ready to watch.


Sean
Yes long time. Been working on Sweet Virginia's big brother. Flown her quite a bit the past 2 years and had a blast. See picture.

This little project should be a lot of fun. I'm looking forward to getting stuck into it, the research to make this little bird fly has been very time consuming. Still, its good to brush up on some things like covering, weight reduction etc.
Feb 18, 2015, 08:17 AM
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moscow580's Avatar
Hi Rem

The Wacos look great. Are you going with ailerons on the DVII? I want to add ailerons but I am not sure whether to use a torque bar or micro inline servos. There is a great Se5 build on the site and he used torque rods and inline servos. The problem here is there are only ailerons in the top wing and the servo wires are kinda short.

I am working on the Sterling P6E first at 16". I will experiment there first.

Sean
Feb 18, 2015, 09:17 AM
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Rem Fodder's Avatar
Sean, the jury is still out on the ailerons for me. I ordered four 1.9 gram linear long throw servos with ball bearings from Horizon as there was a clearance price on them. I went with the extras in case I decide to install the ailerons. One thing that I am contemplating based on a discussion I had with a fellow that flew RC a lot, is to add an extra bay to the wings to increase the span by an inch or so. This would effectively add more wing area and change the wing loading. Which would help I suppose for the model to carry the extra weight of the radio gear and motor.

As for the rest of the guts for the model, there is a Park 180 2200 kv motor with 350 mah 2 cell packs (from my Blade 130x heli). The receiver is a Specktum AR6400NBL. Yesterday I picked up a 5.5 x 2 E-Flite prop from their Hyper Taxi. I was hoping that would work, if not I have some GWS 5x3 and 6x3 props on their way to try.

I have lots to think about before the wood shavings start flying, and certainly welcome any and all suggestions.

The little Peashooter sounds like it would be a very interesting project for such a tiny airframe.

Neil
Feb 18, 2015, 11:21 AM
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moscow580's Avatar
Hi Neil

You definitely have this thought out. I am on the same page with the Brick electronics. I picked up some good stuff here on RC Groups.

I was actually thinking of going with the UMX Beast setup, which is similar to the 130x (my 130 needs tail straightening ). My Hawk will be set up like the UMX Spitfire or the like. I am not against splitting some wires to extend the servo wires on the inline servos.

I am definitely going to follow your lead. It is going to be a fun build. If it goes I have the PT-17 waiting in the "wings."

Sean
Feb 18, 2015, 12:46 PM
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Rem Fodder's Avatar
Speaking of PT-17's, I picked up a Herr Engineering 28" Stearman just a while ago during a warehouse sale. I will convert it to electric power as well. My trouble is that there is just simply not enough time in the day to work on all these kits! Will you do a build log on the P6E? I was confusing it with the Boeing P-26 Peashooter. I have always liked the look of the Hawk, such a classic '30's era biplane.
Feb 18, 2015, 02:42 PM
Is it suppose to do that?
moscow580's Avatar
Hi Neil

Yeah. I am going to do a thread. I was told by Joe Malinchak at AMA to do it over at micro scratch build. I might put it here since it is scale.

I love the Hawk. I have my Dad's 1/4 scale one and always wanted to build it in smaller scale. The Tower Hobbies 43" is just to much money.

Sean
Feb 19, 2015, 08:59 AM
Registered User
Cool build w interesting story! The B&W photo is neat! Look at the clothes line in the background, too!
Feb 19, 2015, 09:41 AM
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Rem Fodder's Avatar
Glenn, I read your build thread on the Camel last night. Well, that was quite an effort you put forth trying to do the covering. My hat goes off to you for your perseverance. Beautiful build by the way. Are you still flying it?

I have an Electrifly Camel and ended up packing quite a bit of extra dead weight into the nose to get it to fly correctly. In a way I know the efforts you went through to get it trimmed. However, my Camel flies very nicely now that its trimmed, but it too is throttle sensitive. It will climb without any input from the elevator once throttle goes past about 60%. All of my bipes do it, its something I have become accustomed to.

The micro servos arrived yesterday and I manged to get a few minutes to bind the AR6400NBL to my transmitter and test out a servo. I'm happy to report that everything is a go at this point for the radio gear.

As for the airfoil shape, I came across this PDF file on Clark Y shapes on another Guillows thread. I'll post it here, not sure if it will open on the thread at this point.

Sean, will look forward to seeing your P6E progress. Hopefully I will have some time to make progress on the DVII before the spring craziness starts around our little hobby farm. Once the ground thaws out the work around here grows in a exponential manner.
Feb 19, 2015, 10:02 AM
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glewis's Avatar
Yep, still flying (and trimming) the Camel. Last change made was the addition of another 2 degrees of down thrust to calm the throttle pitch coupling. As you know it will always persist, but this model was severe! I don't have room for any more down thrust now, the prop will hit the cowl. I would have to remount the motor and that's too much trouble. I'll just fly it the way it is and get used to it as you have.

I have a couple more kits of the laser cut reproduction WW series from DPC Models to build, someday...

Cool, your radio gear is squared away.

If you notch a '>' into the leading edge of the ribs the square LE strip can be raised a bit in the profile leaving a tiny bit of extra wood on the bottom of the rib. This extra is sanded away to add some Phillips entry into the profile making it more of a Clark Y section.

The airfoil profile used in these kits works ok, but is speed/pitch sensitive to gain max altitude during the limited rubber motor power curve.
I left the profile as is on my Camel and changing it might have improved the pitching.

Glenn
Feb 19, 2015, 05:40 PM
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Rem Fodder's Avatar
Glenn, I did try extra down thrust on my Camel as well. Right from the get go I added extra down thrust from the kit design based on others experiences. I never did fly it as per the kit design for down thrust so have nothing to compare by. An additional shim was placed over what I started with and I think that is where it has stayed. One thing I have not tried is to mix in some down elevator to throttle to take out the climb. I understand that as airspeed increases a lifting wing will generate more lift which must be compensated by trim to prevent unnecessary climb. Makes me wonder about our model bipes, they really do fly much faster than the full scale aircraft we try to emulate, even when they are flying slow. Perhaps it's a no win situation?

I will have a good look at those Clark airfoils over the weekend and compare them to the actual Guillows shape and see where the differences lie. If they can generate a little bit of extra lift, that might be useful. It wouldn't be too difficult to make them, a couple of ply wood patterns to sandwich the rough outs of balsa and a bit of careful planing and sanding should be able to turn out a whole set within a reasonable time. What are your thoughts about adding a bit of extra wingspan to these designs? Can you tell I was one of those kids that always had to take his toys apart, see what makes them tick and try to improve upon the design?
Feb 19, 2015, 06:28 PM
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glewis's Avatar
Not sure if the Clark Y would generate more lift. I suspect the thicker profile should at the expense of increased drag. The main benefit is the reduced pitching moment as speed increases. The thing about the Guillows airfoil is the thickest part is so far back shifting the center of lift aft.

I was one of those kids too.
If it's not broke, take it apart anyway just to see how it works. Then when it does break, I'll know how to fix it... I tell people it's an engineer thing and they wouldn't understand....


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