Building D VII bits

[snj5]

Happy Canada Day.
The more I read about the history of the Sopwith F.1, the more I am finding that Canadians in particular had a happy talent for its employ.
Best to all in the land of cold beer and cheap drugs, eh!

[Maxim08]

There have been a few details bothering me re both the seat frame and the stabiliser struts. Not serious 'I can't resolve this' issues but detail focused on accurate re-creating of correct parts.

To enable this I flew to the Canada Aviation Museum yesterday to look, again, at their D VII. I should quickly state that the challenges when dealing with this airframe is it's checkered and not completly documented history. Part of many visits have been to read the complete technical file regarding this aircraft which consists of 4 folders about 4" thick. Other aspects were the measurement and photographing of parts, assemblies and general arrangement.

Perfect VFR day and the 4.5 hr drive becomes a 1.4 hr flight via RV7. A few others tagged along and recieved a senior curator led tour of the interesting stuff the public doesn't generally get to see.



This is a Travelair 2000 with an OXX 6 engine. Really nice cowling, all cotton covering. It will be on public display in about a month.

While that's all interesting, the reason for going was validating a couple of points.

The first regarded the seat frame assembly. The plans that I was using were ambiguous at best re the rear transverse tube. It needs to be welded to the forward face of the upper clamp and not the way I have shown earlier. The second point was that common opinion indicates that the side frame triangles are fabricated and then slipped over the fuselage uprights before the frame is welded together. This concerned me because my frame was welded prior to working on the seat so the only alternative was to use four clamps that could be spread and then closed around the tube. The seat would work, but wouldn't be correct. Would anybody see at after covering? Doubtful but, wrong is wrong.

To my relief after double checking all my photos and looking at the CAM D VII it turns out that 4 clamps are correct after all. Is this a late production modification? Who knows but I can tell you that both the Ottawa, Fokker built D VII and the Knowlton, Albatros built version both use 4 clamps.

Lower clamp in Ottawa.



I guess I got lucky this time.

I will cover the other parts, stab struts and OAW panel layout, in later posts. Time to go and make something.

Regards,
John

[Maxim08]

Finally completed the stabiliser struts today.

Not taking my own advice and doing the hardest task first, I had previously shown the fitting of the flat metal forked component that attaches to the stabiliser. The other end uses a 4cm long threaded insert. I believe, but cannot confirm, that Fokker used a forged fork similar to the undercarriage leg to fuselage fitting. To ease both time and budget I am taking this (gasp) shortcut. After looking at a couple of originals, the only give away will be the rosette weld that stabilises the inner end of the fitting. These fittings are shown in post #2.

Here are the finish welded ends.



Forming the streamline around the threaded insert is a little blacksmith like, using both heat (oxy-acetylene) and hammer to coax the metal into a new form.

This picture shows the fittings mostly, but not completely formed. When finished they have a very small seam that is easy to run a welding bead along.
I gapped on taking another photo before welding. BTW, I didn't use the actual fitting to heat and beat around but substituted a length of equal diameter mild steel rod.



Above are the two sides. Note the different length and shape. This is because the threaded insert sits along the thickest section of the tube (minor axis) and there is more material on the trailing edge of the streamline than the leading.

I was planning on showing the beginning of making my tailskid but the two lengths of ash that I bought have a serious split that runs across them.

Right now it is 33 Centigrade (92F) with a relative humidity of 65%. Too warm for anymore welding. More latter.

Regards,
John

[Maxim08]

Another day in a week of record high humidity with temperatures hovering around 100F. Tends to put a damper (pun) on work particularly welding.

Ted, the wonder machinist, finished up a few parts that allowed me to trial fit the landing gear.

One objective with this project is to have the aircraft appear as authentic as possible and when compromises for safety and/or conformance come into the equation, to minimise they visual impact. This is noticable with many WW1 aircraft in regards to brakes. An earlier thread showed my wheel build and some of the decisions in the process. Here is a picture of the axle components involved for the low-vis brake system.



Here is a closeup of the parts for one end of the axle.



Top is the primary axle, a section of 4130 steel tube with a 2" (51mm) OD and 0.125" wall The original had a 55mm OD. Second is the intermediate spacer, once again, 4130 with an OS and ID to fit snugly within the primary and over the 'working' stub axle. Third is the actual 1.5" working axle. This is an inexpensive precision ground piece available from aircraft suppliers. Since I am using top hat bearings, the actual bearing surfaces have been polished smooth. To the right is the axle end cap. To the left of the axle cap is a short spacer turned from a section of the intermediate tube. Below the axle cap is the brake caliper mount with one caliper mounted. The short section is solid, mild steel bar which is push fit into the 1.5" axle. When all pieces are assembled, 2, 1/4" holes will be drilled and the centre core tapped for two locking bolts that will hold all of the bits together. This will allow for easy disassembly and replacement of any, heaven forbid, damaged parts.

Assembled.



Everything sleeved together nicely. Here are the axle and wheels, trial fit.



In this configuration the track is 1850mm. Kiger and Cash both show 1800mm while Rousseau shows both 1780mm and 1844.

I could reduce the track by running the caliper underneath the axle and out of sight. The challenge would be that, while I am only using one caliper per side, the mounts are designed for two calipers in case theory does not work out and I require increased braking force. If I move the caliper inboard then the second caliper would interfere with the bungees. Working with the theory that it is easier to shorten the axle than lengthen it, I will leave things as they are for now.

Next step will be to weld the intermediate axle spacer sections together. That is the intermediate spacer, the caliper mounting bracket and the short spacer.

When that is done the pilot holes for the locking bolts will be drilled.

Regards,
John

[Maxim08]

In the ongoing quest to start as many sub-projects as possible, today is turtledeck day 1.

The turtle decking on the D VII is combined with the rear section of the cockpit coaming. The coaming section is made of 2 thicknesses of 3mm ply with an additional 1.2mm ply skin that extends aft to the stabiliser. The 7.2mm thickness is reqired to carry the load of the pilot levering himself in and out of the cockpit. The front coaming is 1mm alloy. Will probably require 'Do not lean here' signage.

To start the process I built a jig for laminating the 3mm ply. This is from 1/2" mdf forming two bulkheads to support the narrow, rear top of the coaming and stub sections forward to maintain the curvature. The side rails are the only glued in place segments and provide purchase for the clamps.





I generally use screws to hold the jig sections together and not glue as most of these are for one time use and take up a lot of space. I do keep all of the unique jig parts, suitably labelled, in a knocked-down form, just in case...

I first laid out a template for the coaming section and trial fitted it to the fuselage. The actual cutlines were then traced on to the plywood. You can see the white bristol board template on the spar table in the back of the next photo. The shapes were quickly cut on the bandsaw. and the semi-circular offcuts saved.

T-88 was used on the ply and then the two pieces put together. T-88 flows slowly so it's good to 'rub' the pieces together to reduce the amount of float when they are being clamped on to the jig.



I do use thin ply scraps between the steel clamps and the wood. This protects the wood and helps to spread the clamping pressure. I don't use anything with the plastic clamps.

BTW, the semi-circular offcuts from the coaming sections have been glued together and will provide the 6mm wood that is required for the seatbase.

Regards,
John

[Maxim08]

In posts #1 and #12 I laid out some of the issues regarding the seat frame. Here is a photo of the final/revised/fixed layout at the upper port side clamp.



Remember that it is lying down in the jig with the top to photo right. Note that the clamp is not welded to the transverse tube but 'rests' on it. I'm having some challenges welding in the narrow V of the cluster that join at the front transverse so, no photo of that until I get it right!

Layed out, scarfed and glued the main section of turtle decking as well as rough cutting the 15mm x 15mm stiffeners (longerons?) for the deck. The decking is 1.5mm ply, slightly thicker than what is called for (1.2mm) but I couldn't find a supplier for the correct thickness and my thickness planer isn't wide enough to take a sheet of ply.

As usual, I made an allowance for final fit etc by cutting the wood oversize. Right now I suspect that I have only caused myself some extra work later. I don't believe that an extra 2 or 3mm would matter in this particular case.



Next task is to trim the 1.5 mm ply decking to fit to the coaming and then glue it all together.

Regards,
John

[Maxim08]

Working away but failing to post so here's an attempt to catch-up.

After finish welding the basic seat frame, it's a good idea to clean up the inside of the clamps so that they will slide nicely. Part of the downside of good penetration on a weld to thin metal is lumps and bumps on the back. This was quickly cleaned up using a Dremel with a 60 grit sanding drum.



The last pieces required are the two seat shell braces that attach to the forward transverse seat frame tube. While I made these for another D VII two years ago, and even posted the final results on another thread, I was darned if I could remember how they were formed! Basically you need to flatten a tube so that a bolt can go through the seat shell and brace. Therefore, the brace needs to be flattened at one end in such away that the tube is only distorted on one side and straight on the side bearing up against the seat. A few wasted tubes latter it came back to me.

Here is the basic setup with the tube clamped to a steel topped table. I used a small 'V' block that helps keep the clamp in place.



The tube is heated with an acetylene torch and then delciately hammered into shape. I used a 2" diameter piece of steel bar and a dead blow hammer for this.





End result.



Next the ends will be radiused with a file and seam welded, the hole will be drilled and then the tube cut, fit and welded to the seat frame.

Regards,
John

[Maxim08]

I should have mentioned in the last post that forming the tube with heat and hammer is a three handed job. I now have a new assistant, my wife, something we both thought would never happen. This may be part of a change for both of us brought on by the discovery that, while she hates to boat, drive or motorcycle with me, she really enjoys flying in light aircraft. Maybe the D VII will end up as a two seater.

Parallel to the seat frame project is the making of a seat shell. A few years ago I made three or four flat metal seats using a template created from a drawing by Charles Cash. One of the shells had the lower flanger formed by bending and shrinking. What was needed was a wood seat platform and forming the flange around the perimeter of the shell to complete it.

The wood portion was simple as I already had a wood master that had been used before. Offcut 3mm ply from the cockpit coaming had been glued together earlier to a 6mm thickness and the rest was straight forward: tracing the seat outline, cutting on the bandsaw and then sanding.

With the wood section in place, I clamped up the seat onto the bench ready for forming the lip. The lip provides a considerable amount of stiffness to the shell and I founsd earlier that for me, it was better to lock the seat into its final position prior to forming the stiffening lip.



The above picture was taken after some of the roughing had been formed but should give the basic idea.

I used two forming bucks, one from an inexpensive body kit of hammers and forms and the other being the ball end of a body hammer. FYI, the ball has about a 7/8" radius. For a hammer I use a tried and true Craftsman plastic/rubber mallet.



While the initial bend was quickly done with an old set of seaming pliers (probably not really necessary) the rough work used the body buck and the plastic hammer end. After roughing the flange out all around and ensuring that the seat was still true in the jig, the real work was done by slowly working the lip with the rubber end and the ball hammer. Tapping quickly and not too hard in a series of runs around the complete perimeter seemed to work best. When ever I was over zealous and left a depression, it was fixed by putting the ball under the low spot and hammer to either side which, with sufficent force on the ball will work the spot up.

Before hammering:



After:



Here it is in place in the frame.



The black plastic clamp is holding the aluminum angle stiffener that runs along the front of the seat squab. Like most well engineered pieces it performs two functions, to prevent the seat cushion from sliding forward and to stiffen the front edge of the seat, something that's necessary when you put your weight on the seat climbing in and out.

The small black mark on the side of the seat shell is the approximate location of where the tubular seat brace will bolt to the shell.

More later.

Regards,
John

[Jeff Brooks]

John
what type wood did you use for the seat bottom?

I made a few of these seats, and found that the 1/4" 12 ply birch was the best! no deflection when stepping on the seat to get in!

[Maxim08]

Jeff,
I used 6mm (1/4") Finish birch ply for the seat. It's actually two layers of 3mm, 5 ply glued together which I guess means that it's 10 ply. My template is 1/4", 5 ply mahogany which certainly flexes more than the birch.
How's the upper wing coming along?
Regards,
John