Paul Lee - SQ2000 Project, Pierre SD USA

Click on images for larger view.
DOOR BACKSTOP - Still no hinges (actually half of the hinge material arrived about 12-17-01) but can get started on some things. Instructions are to leave door in place and use duct tape/wax/2glass plies /then cutout door and then remount the backstop made with tape/wax..... and then cutout. But I allways have ideas and don't mind trying something different to save time or improve things. I decided to cutout the doors first - well not completely, see below.

I cut around the door but left a few spots in to hold the door in place.
Use the slots to do initial sanding around the door opening (door will be removed and sanded later)
The magic stuff (clear plastic packing tape) is taped over the slot around door - mostly covering the door part to protect it from resin bonding.
... and then the tape is cut along through the slot..(bad photo).
and the portion outside the door is peeled off... hard to see the clear plastic.

Two 2" glass plies are applied over the frame with less than 0.5" of it reaching over door and then peel plied. When cured the few spots holding door can be cut and door released since the plastic tape cover on doors does not stick to cured resin.

Well... as of 11/24/01 still no hinges. Being able to put more time on the project than average builder but not having 5 to 10 years to do it, I cannot wait longer and have to get the door opened to do other things. So here is the K-Mart solution.

The problem with hinges on SQ2000, is that the door/body border is thin and distance must be left to clear accross the 5/8" weather strip from the slot so the only way to get hinges there is to have a surface mount strap type hinge that reaches sufficiently accross the gap and the hinge pin has to be higher on roof in order to open all part of door away from the body. I ordered a set of Velocity hinges (as seen below) but they are not long enough to reach across the gap. I know of some builders who have adapted the Velocity hinges and its recessed-into-the-roof style. There are two problems I see with that. First it would mean extending part of the doors into the roof line and going below ceiling inside - being 6' I need all the ceiling room. Secondly my over the top strap method does not disturb the roof ply strength. while the large cut-outs in the roof needed for Velocity hinge style may weaken the roof structure.

Hinges have to be mounted so that the hinge pins are in line - otherwise cannot rotate hinges properly on a curved surface. I aligned the hinge pins using clamps and a piece of plywood. Then measuring position and cutting hinge slots in the body, and covering the hinge bottoms with release tape, the hinges are floxed into place and then after curing removed for shaping to body. After shaping the hinges the machine screws are installed. NOTE: To hold the screws in place the inside part of the body (foam and inside layer)in the screw holding area is removed and then floxed to fill in the void. This provides an excellent holding area while not weakening the fuselage. Then the machine screw holes are drilled through that and hinge tightened. I intend to cover the hinges with some S2 glass plies for more reinforcement (and better looks).

Just an afterthought: Gullwing doors are by design more susceptible to wind dmage when open. The factory hinges are more sturdier than my Kmart solution. However in case of an accident with a door being hit or in a strong wind (or whatever)..., I would prefer the hinges being twisted or broken rather than fuselage damage. It would simply mean a trip to Kmart and some glassing and patching work. But with sturdier factory hinges, even with no fusealage damage, the twisted hinges would be harder to fix/align.

Finally RS door shown swung open. The method I used for making the back stop worked very well and saved time.
And both doors open.
The doors require inside reinforcement with foam and glass plies on rim. This is the part I hate - messy & fidgety. Shaping 3/4 foam to the surface is a unique challenge - especially when you got a curve like below and you dont want to distort the door shape with the foam back pressure. The solution was to slot some of the foam strips where the curve is extreme like shown below. The foam is bonded with 5 minute microballoon epoxy mixture to the door. The slots and gaps around the foam strips can be filled in later with microballoon slurry.
The foam strips are shown mounted below.
One problem with microballoons mix is that it allways runs. Instead I tried a 3 part mixture of microballoons to 1 part flox which held the stuff reasonably together without running too much.

One thing I wish is to have left the door window installation until after this point. It is really difficult to deal with epoxy spill over window part when working so close to windows with these reinforcement strips.

For some reason when the door is cut out the door shape loses a bit of the curvature and does not conform exactly to the fuselage. Puting a strap on the door when the reinforcement glass is curing helps to put the original curve back.
The door knob stem was on the short side. Instead of using the extra stem nut to tighten door cam to position, I shortened the cam height (my small metal lathe is a real help here) and installed a set screw to lock the cam into position instead. That left sufficient stem to attach the inside door knob.
Door lock sleeves making: Factory send the wrong size sleeves. But they are easy to make out of steel tubing. I wanted closer tolerance so used my handy lathe to bore the tubing with undersize ID. Sleeves are shown floxed into place on LH door. The distance of sleeves to fuselage frame must be the thickness of the inside part of weather strip. Best way is to have the door pin in the sleeve and the outer sleeve pressed against a piece of weatherstrip while floxing. A pice of weatherstrip is shown (black smudge in photo) on the upper right side.
Before floxing/glassing outer sleeves, with the door in place and the pins in, the outer sleeve is pushed into the fuselage with a small wooden wedge. That ensures a tight door fit.
I also intend to put a small metal guide for each door as found in automobiles so that the door goes exactly in position where it should.
I made a set of door cam studs with two two ended threads and a non-thread section for the door push rods so there will be less wear than using simply threaded rod. The door pins from the factory were longer than necessary (extra weight) and such sharp points were not needed.
A good way to install the door pins for minimum length is to fit them in the door with cam in closed position and the pins into sleeves almost as far as they will go (fourth photo in this group). Then I rotated the cams into open position and marked the door pin cutoff size - then hacksaw, grinding, sanding pins tips.... The third photo here shows the alternating over/under door rod positioning required since the cam pins interfere with each other's rods in open position. The rods are easy to shape - the ends are simply squeezed flat with a wise and holes are drilled for the cam pins and door pins.
NOTE: Floxing the door cam stud threads before installation onto cam makes an excellent thread lock so that the nuts do not work loose.
Door strut mounting: The gas strut mount is held in place with a small wooden spacer away from the door weather mount while the flox/glass is curing. For even gas strut mounting only one of these should be mounted/cured first - the strut mounts on the door can be glassed both right away and all in one session using a small clamp over the mount and glass plies. As mentioned before, the fuselage halves were not perfectly matched so that mounting the strut door mounts at recommended position would make doors look lopsided in the open position. Instead, only one side is placed (along with both door mounts) and then after curing the other strut door mount can be positioned so that the doors look even when open. I found that such "symmetric" height appearance required left door mount to be placed about 1 inch lower from recommended position.

I also do not like the doors so high in open positon as it is harder to reach for closing in seating position and so will probably replace the struts with slightly shorter ones.

And finally door mechanisms are in place and both doors are self supporting. (The stool is not holding up the fuselage - it just hapens to be there.)
08/09/03 late update.
One of the nagging problems was the doors would sag somewhat and would essentially require "a little manual lift" into place when closing. I thought about making a striking plate / plunger guide like found on cars but until now could not figure a convenient spot for mounting it to make sure it does not get in the way or cause a bruise/injury. I finally settled on the lower front door outside position a few inches above the inside door closing plunger. The illustrations below may be left or right side since one was curing when working with other.

The striking plate is made up of 3/32 x 3/4 x 1 steel plate with some winglets attached (welded) for glassing from inside. It is fitted from inside into the 1/2 x 3/4 hole and the extra protrusion cut off and sanded. The striking plate extends about 7/8" into the fuselage. To have the plunger slide properly out of the door its axis and the the striking plate surface is parallel to the door cutout line and faces front of the aircraft - and not perpendicular to the outside surface (the surface is not parallel to hinge line). The outside plunger assembly is made up of a 1 x 3/8 x 3/8 keyway steel rounded a little at one end - it is jammed into correct position by a small wood wedge - and a 1 x 1/8 plate steel with a bigger hole near front/bottom. The plate is bent to match fuselage curve at gap and taped over the plunger and floxed (using Wal-Mart fast super-poxy) into position, then taken out and fill welded in the gap. The final streamline shape is about 3.75" long and the front part just covers the square hole. If doing this make sure you get the orientations correct (remember that the motion is perpendicular to the line of the hinges) otherwise the result may jam up when trying to open the doors. The square plunger should be at the bottom of the striker plate hole ( because it goes UP when opened) and flat/square against the striker plate surface. A little fiberglass cap is glassed from inside over the hole to keep any drafts out. After painting the result should be hardly noticeable being fairly small by comparison. The modification helps the door line up perfectly and a little grease in the hole will make things last. Some of you visual perfectionists may not like the small protrusion but other alternatives I see as tremendous amount of work and not really working better. The location of the device helps to support the door in a balanced way.

04/12/06 PostBuild Note: During flight I found that it was very easy to open the doors. Here is a simple way to make a door lock. Drill a 3/32 hole through the front, top cam/tube combo in the door closed position. A (whatchumacallit) clip is simply inserted into the hole which stops the doors from opening accidentally. The chain is plumbers brass chain.

Return to main page