My Fokker DVII Project

Maxim08 · 5 July 2008, 12:55 PM

Jeff,
As you are aware, some time ago I was able to spend a day with a pile of Fokker built ribs.
At that time we traced the outline and openings of each rib onto Kraft paper.
I have located the rib tracing that you refer to as Rib #1 being the inner 'doubled' rib on the lower wing.
My reference notes this as being Rib #11, counted sequentially from the port outer rib.

Here's a photo of what I had to work with. It is warped and beat up at the trailing edge. We applied gentle pressure to flatten it slightly to gain a more accurate shape.

I have taken the following measurements for you:
Unlike the OAW information, this is literally a doubled rib, 2 webs and 4 capstrips yielding a total width of 25mm.

Below are pairs of numbers starting at the leading edge of the front spar opening and ending with the trailing edge of the rear spar. The first number is the overall height of the web, outer cap to outer cap, and the second is the height of the spar opening. There is some variation caused by the fabric tape wound around one side of the upper and lower capstrips.

Front spar, front: 178mm, 161mm
Front spar, rear: 183mm, 167mm

Rear spar, front: 146mm, 130mm
Rear spar, rear: 132mm, 115mm

The cable relief holes are 25mm in diameter and each is 73mm up from the bottom of the rib. They are both 20mm at centreline from the edge of the spar opening. The front hole set to the rear and the rear set to the front. This gives an edge to edge distance of about 7-8mm from the spar cut out.
I hope that this will help you.
Regards,
John

Jeff Brooks · 5 July 2008, 06:09 PM

Quote:

Originally Posted by Maxim08

Jeff,

I have taken the following measurements for you:

Below are pairs of numbers starting at the leading edge of the front spar opening and ending with the trailing edge of the rear spar. The first number is the overall height of the web, outer cap to outer cap, and the second is the height of the spar opening. There is some variation caused by the fabric tape wound around one side of the upper and lower capstrips.

Front spar, front: 178mm, 161mm
Front spar, rear: 183mm, 167mm

Rear spar, front: 146mm, 130mm
Rear spar, rear: 132mm, 115mm

I hope that this will help you.
Regards,
John

Those numbers are very close to the Replicraft numbers ... maybe I am just missing something here ...

Jeff Brooks · 6 July 2008, 08:24 AM

John,
The number you posted ... they are at the spar and not at the 300mm back from the nose, right. then the rib must get larger than the 181mm.

Udo,
I didn't see it at first, but I do see it now. the 185mm separation of the two reference lines had me fooled into believing there is only 4mm difference form the Replicraft rib drawings and the Cash ... but looking more carefully, I see my mistake.

gipsymoth236k · 17 July 2008, 06:31 PM

John and Jeff,

First, thank you John for posting your photo and dimensional references for the original Fokker D.VII bottom wing's root 'compression' rib #11. Previously I had asked you for the width dimensions for this important rib, and now we have your given dimension of "25mm." I have some comments about it here:

1. It seems that Fokker D.VII BOTTOM wing 'compression' ("doubler" or "box") ribs are found to have been manufactured in at least TWO different widths, depending upon manufacturer and their design changes. My research documents include an original Fokker factory drawing of the bottom wing, and it shows the 'compression' ribs to be of "32mm" width, or more likely "32.4mm" width. I derive the "32.4mm" dimension by the design of two 'standard' 11.2mm ribs sandwiched together between a 10mm width filler capstrip (Cash research). The individual 'standard' ribs themselves are constructed of two 5mm square capstrips attached on both sides of a 1.2mm plywood web, thus giving a 'standard' rib width dimension of 11.2mm. On John's original BOTTOM wing 'compression' rib, he measured a width dimension of "25mm" vs. the expected 22.4mm Fokker factory dimension, as in the TOP wing's 'compression' rib design, which if carefully measured again will likely result in the given 22.4mm dimension, and not "25mm." Therefore, I believe we have found BOTTOM wing 'compression' rib widths in BOTH the 22.4mm and 32.4mm dimensions!

For TOP wing 'compression' rib design, research finds ALL D.VII contractors used two 'standard' 11.2mm ribs sandwiched together to construct 22.4mm wide 'compression' ribs, but this was not always true for the BOTTOM wing! Why are some bottom wing 'compression' ribs found to be wider at 32.4mm? This will be explained later...well OK, it's probably because of the observed fabric 'pull' distortion on the bottom wing's root rib, thus requiring a wider and stiffer box design vs. this unnecessary need in the top wing. BTW, the Fokker Dr.I Triplane design was this way too - using a wider wing root compression rib in the bottom wing's root rib vs. narrower compression ribs in the mid and top wing. This was likely designed to prevent fabric 'pull' of the bottom wing root ribs and avoid rib distortion (Neil Good's logical theory anyway!).

2. This and the other original D.VII ribs that John has shown us previously reflect a design difference in the rib stabilizing construction methods used by the D.VII contractors. In John's 'compression' rib we see evidence of two square holes on the top edge (only!) of the rib for the attachment of span-wize 10 x 10mm stringers running along all the rib's tops in two locations - the rib's center, as well as running span-wize aft of the rear spar. Now for a design difference! In Fokker factory BOTTOM wing drawings and in my photos of Fokker-built bottom wings, we find only 20mm wide cloth 'zig-zag' rib reinforcement tapes used, with no 10 x 10mm stringers. However, in Fokker factory TOP wing drawings and supportive photos, we DO find 10 x 10mm stringers used. It seems that Fokker-built TOP wings used 10 x 10mm stringers, but the BOTTOM wings used only 20mm cloth tapes for rib stabilization. I believe that O.A.W. and Albatros-built D.VII wings only used the 10 x 10mm stringer method in BOTH top and bottom wings, and it seems that Fokker-built wings MAY also have eventually switched to this method excusively as well, if John's photos are indeed of Fokker-built ribs!

It appears that the 'stringer' method used in the BOTTOM wing also caused the single triangular-shaped vertical rib stiffener location shown in the photo to move slightly aft from web center to accommodate the centered stringer hole located there.

OTHER REPORTS:

To add to this, I have an original (but inaccurate) French report showing "35mm" widths for (top and bottom wing?) 'compression' ribs, and "12mm" for 'standard' ribs. The American McCook Field report shows 1.25" (31.75mm) for TOP wing 'compression' ribs, 13/16" (20.6mm) for BOTTOM wing 'compression' ribs, and 7/16" (11.1mm) for 'standard' ribs. The American report seems to reverse the width differences between top and bottom wing 'compression' ribs!

Jeff - One of your dimensional problems is that your capstrip dimensions were taken from the early REPLICRAFT drawings which then reflected the incorrect Fokker (from the C.I rib design) capstrip dimension of 6mm square vs. the originally intended D.VII's 5mm square capstrip dimension. This correction to 5mm capstrips has all been recently corrected and updated on the latest version of these drawings. Also, the C.I ribs had 32mm diameter internal brace wire holes cut into the ply web, whereas the D.VII design had 25mm diameter holes. I have the Fokker factory rib drawings for both airplanes to support these dimensions.

Details, details...

Regards, Gary Sewall

Jeff Brooks · 21 July 2008, 05:28 PM

Hi all,
Just thought I'd drop a quick post. I am busy finishing up the Doubler ribs for the bottom wing. I will post pictures of the ribs later.
Here is a picture of my boy climbing into a static display at the Geneseo Airshow. He had to bring his cap & goggles to the show.

Here is one of the five throttle quadrants I have, this one in my plane. The handles are Cherry. I made the knobs by turning a piece of Cherry dowl on the drill press, using sand paper to reduce the size. The mixture knob, according to the Funcke drawings is approximately 45mm long, 8mm at the attaching point, and 16mm at the round end. I couldn't justify buying a wood lathe for just these five parts. The hardware holding it together is just temporary till the AN stuff gets here.

wd6bor · 21 July 2008, 07:39 PM

I've been reading different threads related to building a Fokker D.VII and saw references to Gypsy Queen engines as a possible substitute, with Pavel in B.C. using one. The thread about Mercedes alternates was closed so I'm posting this here. Have other people on the list looked at the Gypsy Queen 70 engines for sale by Wallaby Air Tours in Australia?

Darrel

I just tried to post the link but I haven't posted ten times yet so it wasn't allowed. It looks like they have ten or eleven engines and spare parts for sale, although I don't know if it is a current offer.

womenfly2 · 22 July 2008, 05:22 AM

Very nice Jeff! Excellent work.

Looks like your boy will have one gift on his Christmas list ....

Dear Santa, I would like a F4U Corsair for Christmas, dad is already building a Fokker D.VII for me ...

Handsome son you have there.

WF2

P.S. It looks like a W.A.R. Replica 1/2 scale Corsair, think the company changed hands but plans still available. I have a set.

Der Grüne Flieger · 22 July 2008, 06:18 AM

Quote:

Originally Posted by wd6bor

I've been reading different threads related to building a Fokker D.VII and saw references to Gypsy Queen engines as a possible substitute, with Pavel in B.C. using one. The thread about Mercedes alternates was closed so I'm posting this here. Have other people on the list looked at the Gypsy Queen 70 engines for sale by Wallaby Air Tours in Australia?

Darrel

Darrel,

I have a GQ30 and am going to put it into my build. My opinion is it's a good substitute for the Merc for a number of reasons.

Pavel is really the guy to talk to about the GQ70. Before I bought my 30, I was looking hard at the 70 because it is more available. I decided the GQ70 was too big, but Pavel said I was dead wrong. He took off some unneeded engine components to save weight and reduce the size to make it work. I recommend you PM him and get a conversation started.

Good luck, I look forward to seeing your build on the forum.

Phil

wd6bor · 22 July 2008, 06:50 PM

Phil,

I guess the question now is where to start looking for a Gypsy Queen, and then where to get the parts and information to rebuild it or have it rebuilt.

Thanks for the reply.
Darrel

buck toenges · 22 July 2008, 07:44 PM

I was told that the gipsy 70 was too big for a DVII replica. Then I saw what Pavel is doing. It would be nice for Pavel to chime in on what he expects out of the gipsy 70. How much does it weigh versus the 30? I assume he won't try and get full throttle so he can push a big prop. Sounds like the 70 is more plentiful and isn't it supercharged?

Not to hijack the thread but my Gq 30 at Roger Freeman's place is finally getting the attention it deserves. Seems that the main problem now is that the throttle bodies need to be revised because the engine can only get to 1600 rpm. Roger thinks the throttle body guys didn't figure out the requirements quite right.

Later, Buck