Fokker D.Vlll - GeoffS

[Geoff S]

I'm building Peter Miller's Fokker D.Vlll and getting on quite well (I'll add a few more photos shortly) but I'm slightly puzzled by the aileron hinging as shown on the drawing -

 

 

Obviously, it'll work but there's a big gap and I always try to avoid that.  Unless it's a scale feature but I can't see any disadvantage in centre hinging in a conventional way. Plus, I don't have any pin hinges that small but lots of both pinned and CA flat hinges.

 

btw, to get an idea of the scale the sheeting is 1.5mm and the shaded wood is 6mm stock

Edited April 12, 2023 by Geoff S

[PatMc]

11 minutes ago, Geoff S said:

I'm building Peter Miller's Fokker D.Vlll and getting on quite well (I'll add a few more photos shortly) but I'm slightly puzzled by the aileron hinging as shown on the drawing -

 

 

Obviously, it'll work but there's a big gap and I always try to avoid that.  Unless it's a scale feature but I can't see any disadvantage in centre hinging in a conventional way. Plus, I don't have any pin hinges that small but lots of both pinned and CA flat hinges.

 

btw, to get an idea of the scale the sheeting is 1.5mm and the shaded wood is 6mm stock

A bit untidy but I don't think the gap will be a big issue. However as drawn won't the aileron have more down travel than up ?

[Geoff S]

I don't know, Pat. I haven't built it yet but it looks like it should be the same each way.  I've built the centre section of the wing and mounted on the parasol supports on the fuselage but I'm part way through one wing and just thinking about the ailerons.  It's proving to be more difficult than I thought 🙂   To be fair, the build is described as being intermediate/advanced level but I didn't see that until I'd bought the drawing and associated articles from Sarik along with the CNC parts.

[GrumpyGnome]

A club mate has one and has the following record..... 2 flights, 2 bad crashes. I think he has some issues with wing/tailplane incidence, and centre of gravity. 

 

Luckily Mr Miller is nice and active on here so you can get good advice.....

 

(I'm 100% certain the issues are down to the builder and not the design!)

[Peter Miller]

Hi.  By all means use CA hinges. The ones shown are flat nylon similar in size to CA hinges but with a pin hinge  across them.

 

As for the gap. It doesn't look like anything that I drew up. I normally use a flat rear face to the spar on the wing and a simple V shape to the front of the aileron. Crude but simple and it works.

 

These plans were redrawn by R/C Model World and they never sent me copies to proof check. It seems that the draughtsman has added his own variation to the gap.  They do that sometimes. 

 

These days I submit plans as PDFs and get them back to proof by PDFs so I have them on file for future reference.

 

I do get plans to proof from RCM&E and I admit that sometimes I miss slight changes that have been made and also I miss some alterations made to the final drawing and the occasional mistake that I have made.

[Alan Gorham_]

I agree with Pat that the way the plan is drawn it looks like you will get differential aileron movement due to the fact that the horn is set back from the hinge line. It is distinctly odd and as Peter says, it must be a draughting error. 

[Jon H]

You would want more up than down anyway as an aid to prevent adverse yaw. Its not a fix, but it helps. 

[FlyinFlynn]

11 hours ago, PatMc said:

A bit untidy but I don't think the gap will be a big issue. However as drawn won't the aileron have more down travel than up ?

It looks that way but you also need to see the connection at the servo to see if the differential is offset back to equal there.

[Frank Skilbeck]

Here's mine on it's first flight of 2023 last weekend, been flying for almost 2 years now. Pretty sure I top hinged the ailerons on mine and it does have aileron differential. Trickiest bit of the flight is take off and the transition from tail down to flying attitude, if it's crosswind it gets a wobble on and can even tip over, same on landing you can do a real greaser of a landing and as it slows down it can get the wobbles and tip over. Take off and landing are best into wind with as little rudder use as possible.

 

 

[J D 8]

            You describe pretty much the characteristics of most early aircraft during take off and landing. Both best done directly into wind.

[Frank Skilbeck]

3 minutes ago, J D 8 said:

            You describe pretty much the characteristics of most early aircraft during take off and landing. Both best done directly into wind.

Yep my 1/4 scale Camel is exactly the same and once it starts to wobble all you can do is throttle back and watch it 😮, Flair D7 isn't as bad.

[Geoff S]

3 hours ago, GrumpyGnome said:

A club mate has one and has the following record..... 2 flights, 2 bad crashes. I think he has some issues with wing/tailplane incidence, and centre of gravity. 

 

Luckily Mr Miller is nice and active on here so you can get good advice.....

 

(I'm 100% certain the issues are down to the builder and not the design!)

 

I've had problems getting the incidences right as well.  I bound and soldered the parasol wing support then unsoldered/rebent/resoldered several times to get it right. It's not easy but the wing centre fits perfectly now and is at exactly 2 degrees incidence.  Similarly, I must have made an error when I built the sides because the tail incidence was a ridiculous 6 degrees.  I'm a poor builder but an ace bodger and it's corrected now and is also at 2 degrees.  Obviously CoG isn't yet an issue but I'm delaying building the cowl until I've finished the rest of the model and decided how far forward the motor will be.  I'll also be using a 4Ah 4s LiPo so that should keep the weight forward.

 

 

 

Front view of fuselage with centre part of wing attached.

 

 

Fuselage so far.  Most of the dirty marks are from the laser burns of the cnc cutting.

 

 

... and here's my bodge to overcome my building error. It won't be seen once it's all covered and, in any case, this is definitely a sport scale model not to be compared with the superb SE5a build currently being posted elsewhere.  However, the fuselage is straight and the incidence angles are correct as measured by my Robart incidence meter.

 

Just to complete the current state of the build, here's the wing half (third?) under construction.

 

 

 

 

 

[Peter Miller]

I must admit that, while it flew quite reasonably it was not my favourite model.

It also managed to give me a very nasty bruise through my jacket onto my fore arm.

[Geoff S]

1 hour ago, Jon - Laser Engines said:

You would want more up than down anyway as an aid to prevent adverse yaw. Its not a fix, but it helps. 

 

On most of my models I set down at about 50/60% of up on the ailerons.  Even on my Gypsy Moth it can be flown without using the rudder on turns though I usually do.

 

4 minutes ago, Peter Miller said:

I must admit that, while it flew quite reasonably it was not my favourite model.

It also managed to give me a very nasty bruise through my jacket onto my fore arm.

 

Now you tell me!  😅  I'm hoping to avoid the bruise!

[Frank Skilbeck]

Make surer you use good quality captive nuts in the wing, the threads stripped on one of mine and I had to cut a hole in the top sheeting to replace it.

 

One thing omitted on the plan is the dihedral, I looked at the full size and set mine up so the top surface is level, so you get dihedral on the lower surface as the wing thins.

 

Mine flies on a 3200  mah 3s and 13 x 8 prop, pulls around 33amps at WOT, around 380 watts, balanced fine on that.

 

Apart from caution on takeoff and landing roll out it's a quite a nice flier.

 

If it wasn't scale I'd say it would benefit from a larger rudder.

Edited April 13, 2023 by Frank Skilbeck

[J D 8]

34 minutes ago, Frank Skilbeck said:

Yep my 1/4 scale Camel is exactly the same and once it starts to wobble all you can do is throttle back and watch it 😮, Flair D7 isn't as bad.

   

 I like to think of the D7 as one of the first aircraft in the modern style with its thicker wing section, little external bracing and where the ailerons are taking over from the rudder as primary turning control.

[Geoff S]

Thanks, Frank.  I'm using the threaded inserts from Modelfixings and they seem pretty good.  One reason I'm using 4S is that the motor I have spare has a relatively low Kv so a higher voltage is desirable.  I expect to use something like a 12x6 but a 13x6.5 is an option but would be more power than needed, I suspect. We'll see in a week or three.

[Alan Gorham_]

1 hour ago, Jon - Laser Engines said:

You would want more up than down anyway as an aid to prevent adverse yaw. Its not a fix, but it helps. 

Sorry, that's wrong. Several full size biplanes including the Tiger Moth incorporate mechanical differential and they definitely have a small amount of down aileron movement and a much greater degree of up movement. 

[Geoff S]

4 minutes ago, J D 8 said:

   

 I like to think of the D7 as one of the first aircraft in the modern style with its thicker wing section, little external bracing and where the ailerons are taking over from the rudder as primary turning control.

 

I acquired a copy of the Profile Publication 67 on the D.Vlll (only £4.99 posted but it has 'two shillings' as the original price!).  Reading that it seems Fokker was something of an aeronautical genius as well as being a top class designer her test flew his own creations.  The Kaiser was lucky to have him.  He did pioneer thicker section, minimally supported wings but it wasn't without risk - early D.Vlll had some serious wing failures apparently due to inferior materials.

 

[Geoff S]

4 minutes ago, Alan Gorham_ said:

Sorry, that's wrong. Several full size biplanes including the Tiger Moth incorporate mechanical differential and they definitely have a small amount of down aileron movement and a much greater degree of up movement. 

 

Isn't that what Jon (and I) said?

[Jon H]

8 minutes ago, Alan Gorham_ said:

Sorry, that's wrong. Several full size biplanes including the Tiger Moth incorporate mechanical differential and they definitely have a small amount of down aileron movement and a much greater degree of up movement. 

 

Im with Geoff. didnt i just say that? More up than down as down increases induced drag and up reduces it causing an adverse yaw out of the turn. Reduce the down, reduce the drag rise. 

 

In any event, having been fortunate enough to have a go in a tiger moth i can confirm the differential effect is not enough to do away with the rudder. 

[J D 8]

                   Also had a go in a Tiger and agree with the above. It took designers in the UK longer to move from thin wire braced wings than other nations.

[Peter Miller]

My father was shot down by a Fokker DVII. from Von Braun's Jagstaffel.  in a DH 4.   Mind you as observer and rear gunner he had an official score of 6 kills.

 

On another point.  Back at the time my DVIII came out there was a chap in Ebay creating pictures combining photos etc to create works of art.  He used my photo of my model in flight for one of those.

 

[i12fly]

9 hours ago, Geoff S said:

 

I acquired a copy of the Profile Publication 67 on the D.Vlll (only £4.99 posted but it has 'two shillings' as the original price!).  Reading that it seems Fokker was something of an aeronautical genius as well as being a top class designer her test flew his own creations.  The Kaiser was lucky to have him.  He did pioneer thicker section, minimally supported wings but it wasn't without risk - early D.Vlll had some serious wing failures apparently due to inferior materials.

 

I think Reinhold Platz was the inspired designer rather than Fokker, but Fokker was the man with the money and knew how to push his staff..... and take the credit. Both were self taught through experience. 

Regarding design, a bit like Reg Mitchell and Joe Smith....   Reg Mitchell was very good at selecting his staff.

 

[PatMc]

I believe Fokker & Platz were influenced by Junkers in using thick wing sections in order to produce a fully cantilever wing. The D. VII wings were designed to be fully cantilever & flown without interplane struts but pilots were unnerved by the wings not always remaining parallel under even normal flight loads so struts were fitted to the production aircraft.

 

Re aileron differential/adverse yaw ; the Wright Bros were aware of it before their first powered flight, they used coupled rudder to compensate from the first fight on.

OTOH some fighter pilots deliberately flew into combat zones with some rudder (& opposite aileron) to induce a yaw in order to disguise the true direction they were flying in by a few degrees. The idea was to cause the opposition to misjudge their aim. It was successful to the extent that some pilots were said to have used the tactic during dogfights in the early days of WW2.