Vicomte

Hey...

What angle incidence is fixed wing in your D.VIII ?

FokkerAce

Ben Buckle plans [1/6th scale] show 0 degrees on wing & stab, -2 degrees on thrust, 1.5 degrees right

What size is yours?

can dig out GTM or BUSA 1/4 scale plans if necessary.

FA[8D]

Vicomte

My D.VIII is in 1/5 scale;

http://pfmrc.pl/viewtopic.php?t=221&view=newest

CarreraGTSCS

My Feedback: (2)

FokkerAce- Have you built all three DVIII's that you mention?

Mike

jumpinjan

If you look at his (Vicomte) D8, you can see the decalage is negative. I have faced this problem back in 1968 when I build my D8
http://img411.imageshack.us/img411/9070/ostatuf6.jpg
It needs to be positive, right? As this picture demonstrates:
http://upload.wikimedia.org/wikipedi...6/Decalage.jpg
Jan

FokkerAce

Have built one each of the Ben Buckle and Balsa USA E.V/D.VIII. have one each of all three still in boxes.
[one of my all time favorite aircraft]

the GTM is still in it's box, but I'll get to it when life will allow.
have planes for two other clients on the board at the moment.

FA[8D]

ZoomZoom-RCU

Not necessarily Jumpinjan. I would recommend that he finds someone with the same kit and starts with the manufacturers recommendations and adjust from there. Some DVIII's however, benefit from some negative incidence. I've spoken with quite a few who have had them be quite beastly in performance, stalling on takeoff, wobbling, and tip stalling erraticly, that is untill they added in some negative incidence. Result, problem solved. I cant say this is what you should do with yours, once again follow the manufacturers specs for incidence and balance to begin with and see what happens. But I will say that my scratch built DVIII has from 1 to 2 degrees negative incidence, and it flys like its on rails, and handles sweetly to boot. So if you have issues, I'd go there first. Good Luck!

ZZ.

CoosBayLumber

My Feedback: (1)

The Ben Buckle kit was supposedly a copy of the plan done by Earl Stahl back in the 1930's. That was a low power A/C designed for free flight.

Presume that you are going radio. Most builders and designers indicate they want 2 degrees Max difference from tailplane to wing incidence. The B-B exceds this by some.

I have magazine plan for a D-8 circa 1959 and it indicates the more common two degrees incidence.

Wm.

TFF

I built a 1/6 scale one from MAN plans and it is a handful. Soon to add some neg to the wing. It will snap like nobodys busness. The airfoil is pretty thick and if one assumes that the bottom is at 0, the wing is at 0, you realy have about 4 Deg in there.

TKFOKKER

I guess I better get it right on my half scale before I fly that thing!! The wing is framed, but not mounted yet. Still have a lot to do before that accures. It is 5 inches thick at center. I plan on just following what Glenn did on his 1/4 scale. I will also compare his to my Ron Weis 1/3 scale which flys great as did my old scratched 1/4 scale I did in the 90's. We shall see!! Tom

FokkerAce

I think TFF has hit on it, that fat Fokker cantilever wing doesn't have a normal centerline. Also, the stab should have +3ish degrees, which is sometimes overlooked.....it's not flat!

FA[8D]

ZoomZoom-RCU

You guys are right Fokker ace and TFF. If you look at a cross section of that fat fokker airfoil, and draw a line from the center of the trailing edge to the center, (furthest outer part) of the leading edge, that IS the 0 degree line. And you will find that even if you mount the wing at 0 degrees incidence ( a good place to start) it will appear that you have included negative incidence already....but you haven't really! Tricky tricky. I think what most people end up doing with this design is using the flat bottom of the airfoil as their incidence line, and unknowingly are adding in huge amounts of positive incidence.....and the resulting snaps and bad handling follow.

ZZ.

PS. If you want to see mine in action, here is a clip. http://www.youtube.com/watch?v=0G2WGhrWOlk
TFF, you are right about some positive incidence in the horiz stab as well...its very helpfull.

jumpinjan

Maybe the neg decalage is required to off-set the upward pitching moment from the thrust vector? Have you D8 flyers noticed that you needed to apply a lot of up elevator on a glide (when you chopped power)?
My D8 was a 1/8 scale gas free flight model, so it had to be trimmed for glide and trimmed for power. The initial glide tests looked good, but the first powered flight was way out of trim. It would do loops, sometimes stalling and doing this about 20 feet from the ground under full power. It had enough flight time to qualify as an official flight (this was at the 1968 NATS). I had about 2-3 degres of downthrust too.
I have never flown an RC D8 model. Maybe its time to build another one?

Vicomte

I thank all for statements. Maybe this film still will explain something ;

http://video.google.pl/videoplay?doc...77048078&hl=pl

Prop Nut

My Feedback: (3)

I also added negitive incidence from what the plans show on my Balsa USA DVIII, about 2degrees. It still has a tendancy to tip stall if I am doing radical manouvers at very slow speeds (What double tapered wing wouldnt?) but that is more of a piloting error than the planes fault. Here is a flight video with a four stroke gasoline motor from Briggs and Stratton.

http://media.putfile.com/Fokker-DVII...-Stroke-Gasser

ZoomZoom-RCU

Geesh thats a gorgeous shot Prop Nut!

ZZ.

Prop Nut

My Feedback: (3)

Sorry it appeared so large I thought it would come out in a normal expandable window.

ZoomZoom-RCU

Dont sweat it....it looks nice. I love the AC color scheme in contrast with the trees. If you could only get some of the non scale stuff out of the background it could almost pass for a scale shot. So when are you adding your markings? I just got done with mine....now all thats left are the machine guns and the scale cockpit. I wanna fly it again first though to be sure I haven't "imbalanced" anything though.

ZZ.

Prop Nut

My Feedback: (3)

Thats an old picture, its done now.

export!

Well I'll take a chance and ask a question in an ancient thread. I just built a scratch 1/6 DVIII and the maiden was quite successful but once I got it trimmed and down I had noticeable down elevator trim. On setup I had mounted the elevator even with the straight lines of the top of the fuse and I shimmed the rear mounts of my wing to reduce the incidence of the main wing.

Bottom line it flew nicely. I'm thinking if I remove a bit of shimming I might be able to dial out a bit of the down elevator trim. Does this make sense?

Prop Nut

My Feedback: (3)

My DVIII also took down trim on the elevator (most of my WWI birds do) so I put some down thrust in the engine, Balsa USA (Dave) recommended it.

export!

Hmm Interesting. I do have some down and right but maybe I'll try a little more down. I really have to fly the plane a bit more on a calm day and see what happens under full power, no power, etc.

It's funny but the more I read about incidence and decalage the more confused I get. I understand all the terms but when you try to actually fix an issue by adjustments it gets a bit nuts.

ZoomZoom-RCU

Prop nut is right. Some down engine thrust is a good way to address it. You mention removing some of the shimming, and I'm assuming you are referring to the wing. This can be a method to address what you have going on with the elevator down trim, but with this bird, if its flying nicely the way you have the wing set, I'd leave that be and either do what prop nut suggested, or add som positive incidence to the horzontal stab. Most WWI craft need this (and use this) anyway, so its not a bad solution either. With the wing incidence adjustment, there is a fine line between a little and too much, and on this bird, you really don't want to go too far.

ZZ.

TKFOKKER

Guys
I ended up going 0 on my 1/2 scale, same as Glenn's kits.

rowarrior

Hello All,

I just wanted to post something about my 56" WS Fokker DVIII 1/6 scale with the purpose to help anybody that ever comes here looking for some info. I want to thank this forum, Airdrome RC and Ben Buckle for all the helpful tips. I was very nervous on the maiden flight, but it turned out great:

https://www.youtube.com/watch?v=m1bgcgB8f74

Allow me to share the info I obtained that is deemed to be ideal regarding INCIDENCE:

0 deg. at the wing compared with the fuselage datum
0 deg. at the axle wing compared to the datum
+2 deg. at the horizontal stabilizer compared to the datum
-2 deg. engine thrust compared to datum
+2 deg. right thrust

my plane ended up and flew at:

+1 deg. at the wing, with wash out with the tips at 0 deg.
+2 deg. at the axle wing
+1 deg. at the horizontal stabilizer
-2 deg. down thrust
+2 deg. right thrust

Having said that, the incidences I ended up with were very good for me and comfortable to fly with,

Now, some more info:

I used a Rossi 45 Nitro engine, way more power than what is recommended, but since my plane ended up with a 7.1 lb weight (no fuel) it was very heavy.

At this point, i worried about the wing loading, given that the Fokker DVIII does not have struts that go from the fuse all the way to the wing tips i feared the wings would collapse in flight or something...

After I did the math, I calculated a 31 oz/sq ft wing loading... I considered the axle wing as a flying surface, so I added its surface to the wing's surface when I performed the calculation. (wing and axle wing area divided by the total weight of the plane) . Mine were 545 sq inches (3.78 sq ft) and 7.2 lbs respectively.

Now, 31 oz/sq ft seems really high, and i think it is for an RC model but the real Fokker DVIII had also a considerable higher wing loading than its brother, the DVII, . I know war birds usually have a 20 to 25 oz/sq ft loading. However, there was no way i could shave weight off my plane, so with lots of fear, I flew it that way.

I have to say, my high wing loading was evident: the Fokker DVIII is not much of a glider, hence i did not even try to put it thru rolls or loops and I always kept my angle of attack low(as you can see on the video). I used the mixer AIL-RUD to compensate for adverse yaw at the very real possibility of tip stalling. Although I never felt it would tip stall, I felt my plane would be more than willing to. For what I read, most Fokker DVIII have this tendency. So be CAREFUL! an online calculator predicted that my plane would stall at 45 km/h, i dont know if its true, but i kept that info in my head the entire flight.


The plane balanced perfectly right at 1/3 of the Mean Aerodynamic Chord (or MAC), or in simple terms, right behind where the 2 frontal struts at each side meet the wing. It would be hard to get this bird nose heavy, but really easy to have it tail heavy. I had to use a lot (yes, lots) of ballast weight right at the nose, glued to the engine mount.

I think this info should be helpful to most Fokker DVIII planes out there. I will attempt pushing my plane more in future flights, but I hope this info comes handy to someone in the future.

Safe flights everyone.