The air speed indicator requires some tubing that goes to the pitot tube and static ports. Previously I wrote about the static port installation, you can read about that here. This article covers the tubing for the pitot tube. I decided to use the removable pitot tube kit, sold by Leading Edge Airfoils, so I can remove the pitot tube when removing the wings.
I thought that putting it out the leading edge of the wing would look nice, trouble is I already built the wings so installing is not going to be a simple task. I created two wood blocks, one to fit inside the wing just below the leading edge stringer and another to fit in the outside of the wing to support the pitot tube mount.
The inside block was threaded to match the pitot tube mount. I added CA glue to the wood as I tapped the threads to ensure the threads remain strong.
The only access hole in the leading edge is where the strut mounts are located so that’s where I decided to mount it. I cut a hole in the leading edge ply and epoxied the threaded block in place.
All of that was done about a year ago, now that the wing is covered in fabric and painted, time to finish. I first run the vinyl tube inside the leading edge from the root to the access hole. There I slid the tube through a 3/4″ deep well socket, then the plastic nut and out the threaded hole.
The outside wood spacer block was slid over the pitot tube mount and then the vinyl tube was slid over the barbs on the mount.
The mount was threaded into the wing, I had to ensure that the vinyl tube inside the leading edge was rotating too instead of rolling up into a knot. Now for the hard part, I used some long forceps to get the plastic nut started on the pitot mount. To tighten the nut I dig around my junk drawer and found the perfect tool, an old useless screwdriver. After a trip to the disc sander and vice it now looks like this.
My newly designed wrench fits into the hole on the side of the socket allowing me to turn the socket about 1/4 turn at a time.
I used my $20 USB endoscope camera hooked up to my phone so I could see if the nut was indeed fully tight.
I retrieved the socket using a magnetic pickup tool.
Next I made a plate to hold the quick disconnect.
Here I forgot to take a picture. Before I drilled that 5/8″ hole in the plate above, I had only drilled a small 1/16″ hole at the center. While chewing some gum I installed the wing so I could mark the center of the quick disconnect on the fuselage.
Grabbed the hole saw and drilled a hole in the fuselage side.
The vinyl tubing was cut to length, disconnect plate varnished and disconnect installed.
The 90° disconnect inside the fuselage was attached to the vinyl tubing that runs up to the AIS.
I’m using the same valved disconnects I used for the fuel lines. So I don’t have to worry about bugs crawling inside my tubing and clogging it while I have the wings removed.
The final result looks great, hope it works well too!
Various parts of the airplane need to be locked for safety or plugged to keep bugs/debris out when the airplane is parked and not in use. These locks and plugs are usually attached to a flag stating “Remove Before Flight.” I purchased some inexpensive, well made, keychains for my flags.
The BRS ( aka ballistic parachute ) came with it’s own flag. This is for safety because you do not want to accidently activate it. It does not have ballistic in it’s name for show, that rocket needs treated like a loaded gun.
The static ports are used to measure atmospheric air pressure and are integral to the air speed indicator (AIS) and altimeter. I bent a small piece of music wire that attaches to the keychain and doors snuggly into the static port.
Maybe not necessary but seemed like a good idea I got a small rubber stopper and eye bolt to make a plug for the exhaust.
The pitot tube, for the AIS, was a little more difficult to block because the tube can be removed. We not to plug the hole the tube goes in or the end of the tube when it’s installed.
Drilled a hole in the side of a 1/4″ aluminum rod to attach the form.
The rod can easily plug the pitot holder.
Added a piece of 1/4″ ID tubing, this will be used to plug the tube when it is installed on the airplane.
With the pitot tube removed the hole is easily plugged and looks nice.
When the pitot tube is installed the same flag can plug the hole. The only downside is that it does add a couple inches to the length.
The droop wing tips I got from TEAM had some flaws. A few voids here and there were no big deal but not fitting the leading edge was a problem.
To fix the front I ground out the seam on the wing tip. Some wax paper was taped onto the leading edge of the wing. Polyester resin was mixed up and new fiberglass added to the wing tip. Another piece of wax paper was placed on top of the wet fiberglass and rubber bands were used to hold everything in pace while the resin dried.
The edge of the wing tips are not straight so I decided to mount them, drill the holes and then trim the edge based on the path of the screw holes.
I marked a line on the wing 2″ from the end around the perimeter, this will be used as a reference to drill the screw holes into the fiberglass tip. The tip was mounted and clamped in place then measured 1.5″ from the line and drilled holes into the wing tip every two inches. This places the center of the screws 1/2″ from the edge.
I would drill a few holes, remove the tip and enlarge the hole in the fiberglass and then bolt it back into the wing and drill a few more holes. Once all the screws were in place I used them as a reference to mark a straight trim line around the tip then cut off all the excess material.
A 1/8″ plywood piece was cut and fit to seal the end of the tip at the aileron.
It is held in place with some fiberglass cloth and resin from the inside of the tip.
The tip did not match up to the aileron as you can see here. Not really necessary but I wanted a better look.
Using a thin diamond cutting blade on the Dremel I cut a slot at the back of the tip.
Then I used some polyester resin to glue in a piece of 1/64″ plywood that I pulled from my R/C airplane parts bin. This was a little tricky to get right because it can easily flare in or out if your not paying attention.
Once that dried I mounted the tip onto the wing and marked where I wanted the tip to end.
The plywood was cut along the mark, then polyester resin and fiberglass cloth was used to build up the tip to the proper thickness.
After applying some filler and sanding the extended wing tip looks great.
Filler was applied to all the other imperfections, the entire surface sanded and primer was applied.
A couple base coats of white were applied and finally the red top coat. Installed they look great!
One last modification was needed to the tips so I can easily remove the aileron with having to remove the tip. I modified the SHCS that hold the bearings on the ends of the aileron so I can install a safety pin so I know the aileron cannot fall off.
To make it easy to pull the pin I drilled a 7/8″ hole in the bottom of the tip directly under the aileron bearing and plugged it with a solid rubber grommet.
Installing the pin is not terribly difficult through the.
To cushion the bottom of the tank I got some 1/8″ thick neoprene. The best deal I found was sold as “tool box drawer liner.” I cut it so it is wider than the bottom so it wrapped up the sides a little then notched out the inboard rear edge to match the plywood.
The tank needed two holes, one for the drain and one for the fuel level sensor. I first drilled a small pilot hole then used a 1/2″ forsner bit. Never use a regular twist drill bit for this step, you will end up with a triangular shaped hole instead of perfectly round and the bushing won’t seal.
Then installed the rubber bushing.
At this point I realized this particular tank is too deformed to install the fuel level sensor because the top and bottom are curved inward so there is not enough clearance for the sensor.
Knowing these tanks do expand the first time they are filled with gasoline I had to stop the installation and fill this tank with gas and hope that resolves the problem. After a few days the tank was still deformed, so I sealed the tank and put a few psi of air pressure in it. The following day I removed the air pressure and let it sit with gasoline in it. After a few more days the tank is back to its normal shape and has held that shape for over a week.
Now I can install the fuel level sensor. I made sure that the sensor was about 1/4″ above the bottom of the tank and pressed it into the bushing.
I was concerned that the polycarbonate cover might bump the calibration switch on the sender so I cut a ring of plywood to protect the switch. I used some silicone to hold the ring in place.
The drain hole in the bottom of the tank was drilled and fittings installed.
Now the tank was installed into the wing. To hold it in place I purchased some tie down straps. They were way too long so I cut them shorter and heat welded the end so it does not fray. I routed then under the plywood and diagonal supports then over the top of the tanks.
The fuel line was routed from the elbow to a tee. Then to the drain and quick disconnect. This was not an easy task to accomplish without kinking the lines. It would have been easier if the quick disconnect was moved an inch or two forward but that would have made the quick disconnect higher which is undesired and more likely to get bumped by my elbows when sitting in the cockpit. Maybe cutting one barb off of the tee would help too.
After installing the cover panel I’m amazed at how well it looks.
Not much remains on the wings now. Grease aileron bearings, safety wire aileron bracket bolts, install wing tips and I need to get the rest of the wing polished so it shines like the tank cover and ailerons.
Long time since I’ve posted anything but I’ve been busy painting. So glad I built these wing racks, made working in this small garage so much easier.
The first wing wizard worked ok, after using it a few times I realized it needed some improvements. To start with the base needed to have less flex in it. So I used a 4×4 for the main cross piece and some 1×4 for the caster supports. A 4×4 was way Overkill but it was cheap and simple. Besides the extra weight adds some stability.
2″ PVC was used to connect the two bases, the bottom tee was notched to allow the rotation of the bases. The base was drilled in the center and a piece of PVC was inserted to fit up into the tee.
When rotating the wing, locking the wing in place is easy with the cam lock nuts from Rockwell.
To raise and lower each side I purchased a couple trailer jacks from HarborFreight and mounted them with some exhaust pipe clamps. Don’t get tempted to get a square tubing jack, you want the arm to rotate so you don’t have to remove the arm to clear the struts.
To hold the wing some soft carpet was combined with 2″ tie down straps to create a nice cradle less likely to damage the wing than the previous design.
Both wings easily store in my one car garage.
I did write down all the dimensions but have not taken the time to post it all here. The bases have the same measurements so should not be hard to figure it out from my original design. If you are interested in this information leave a comment, might motivate me to make a more detailed post.
Installing the wings, even with a helper, is a pain. While I can do it alone and it’s not that time consuming it can be frustrating and it’s really easy to damage the wings moving them around. I’ve been wanting to make this process easier since I built my wing carriers long ago and I finally came up with an idea that works!
I’ve basically built a set of sawhorses, on wheels, that transforms into a wing rack while the wing is resting on the sawhorses. Watch the video to see it in action:
Now, time to start building this, your gonna need some materials:
|2||2″ PVC pipe||62-1/2″||Main horizontal support|
|2||2″ PVC Pipe||12″||Main vertical support|
|2||2″ PVC pipe||1-3/4″||Reducer connector|
|2||2″ PVC pipe||3-1/2″||Rotator for base|
|2||1.5″ PVC pipe||25″||Vertical slider|
|2||1.5″ PVC pipe||6″||Arm rotator|
|2||1.5″ PVC pipe||20″||Lower arm|
|2||1.5″ PVC pipe||28″||Upper Arm|
|6||1.5″ PVC pipe||1-3/4″||45° connectors|
|2||1.5″ PVC pipe||3-3/4″||Bungee holder|
|2||3/4″ PVC pipe||3-1/2″||Bungee hook|
|2||3/4″ PVC cap||N/A||Bungee hook|
|2||2″ PVC 4-way||N/A|
|2||2″ PVC Tee||N/A|
|2||2″ to 1-1/2″ PVC reducer||N/A|
|2||3″ sch 30 cap||N/A||Mount to base|
|2||3″ to 2″ sch 30 bushing||N/A||Mount to base rotator|
|8||1-1/2″ PVC 45° elbow||N/A|
|4||1-1/2″ PVC cap||N/A|
|4||1-1/2″ PVC Tee||N/A||Arm rotator assembly|
|6||Wing Nuts||N/A||Replacement wing nuts for lawnmower handles|
|8||3″ casters||N/A||All must be casters, preferably locking too.|
|32||5/16-18X1″ carriage bolts and nuts||N/A||Attach casters|
|??||Various small screws||N/A|
|6||1×4 common board||44″||Base|
|4||1×4 common board||18″||Attach casters|
|2||1×4 common board||56″||Attach casters|
|2||bungee cord||4′||Flat cord bungee|
Note: Do not use “sanitary” fittings, they will not work.
Many of the PVC parts will need modified, a lathe would make most of the modifications easier. A mill would be nice too. I used a Dremel and a drill press.
Let’s start at the bottom and work out way up.
The ends of two 44″ boards need notched to accept the 18″ boards. The notch in the 18″ boards starts 4″ from the end. I glued the there pieces together.
The rear two 44″ boards have a small notch cut in them to clear the 18″ boards. This board was glued and screwed to the back side of the platform.
The front 44″ board also needs notched but it needs to be lower. This board was added as a modification so some pictures might be missing it.
Before gluing this board I pre-tensioned it with some twist to counteract the off-center weight when the wing is in the storage position.
If your wondering why the board is pre-tensioned look at the picture below.
The casters are bolted to corners and the 3″ PVC cap is bolted in the middle.
Grab the two 2″ tees and cut a notch for the wing bolt that goes 90°. It is ok to go more than 90 but if you can make it exactly 90 you will be happier with the end result. Remember to make a right and left version, the tees should be mirrors if one another.
Now grind out the inside of the notched part of the tee until a 2″ pipe can easily rotate within the tee. Now glue the 3-1/2″ long 2″ pipe into the 3″ to 2″ reducer. Once the glue is dry insert it into the tee, ensure it freely rotates when fully inserted. Now mark the center of the notch onto the pipe. Drill a hole, use a small chisel to make the hole square for the carriage bolt.
The carriage bolts for the wing nuts need modified a little bit to better match the contour of the pipe. A vice and a file made this pretty easy.
Grab the 12″ long 2″ pipes. Cut a slot in them, this will be the height adjustment. I used my drill press to drill a line of holes then used a file to produce what you see here.
Grind out the inside of the two 2″ to 1-1/2″ reducers until a 1-1/2″ pipe easily slides through the adapter.
You can now assemble the main part of the base.
Set the PVC base into the caps. Now adjust the base rotation wing nuts. The vertical boards on each caster platform should be facing each other.
Once adjusted to your liking use some small screws to attach the reducer and cap.
Now get two of the 1-1/2″ tees and notch them for the wing nut. Again remember to make a right and left. The length of the slot is not too important, I made mine much more than 90° but depending on how much rotation you need you might want to do something different.
Now grind out the inside of the tee until a 1-1/2″ pipe easily rotate inside the tee. Go ahead and glue the 25″ 1-1/2″ pipes to the tees. You might be tempted to cut square hole for the adjuster, but wait till later when you can better align everything first.
Now take the remaining PVC parts and build two candy canes, again be sure to make a right and left.
The 1-1/2″ long PVC pipe needs a notch cut in it so the bungee cord can exit the pipe. The “cap” will slide over the end and is secured with two small screws.
A board was cut to create a flat platform for the bottom of the wing. I used a 2.5″ hike saw to notch the end and a 45° bevel wad added with the router.
The board was drilled and counter sunk then attached with some drywall screws I had laying around. Then it was covered with some self adhesive pipe insulation.
To adjust the tension on the bungee, wrap the cord around the hook before inserting it into the pipe. I did need to bend the hook a little too make it narrow enough to fit into the pipe.
Now you can assemble everything and mark the locations for the adjusting bolts.
A few weeks ago I ran across an article taking about aircraft bolts that answered lots of questions I had. One thing that concerned me on my airplane is that some of the bolts appeared to be too short. Turns out I was right, some of the bolt sizes on the plans are wrong according to general aviation practices. I suspect this was done to save weight.
The article mentioned above suggested that there should be at most one thread inside the hole, the bolt must go all the way through the nut but if there are more than three threads through the nut the bolt might be too long. I also looked up what the FAA says which is in AC 43.13-1B chapter 7.
7-37. GRIP LENGTH. In general, bolt grip lengths of a fastener is the thickness of the material the fastener is designed to hold when two or more parts are being assembled.
All bolt installations which involve self-locking or plain nuts should have at least one thread of the bolt protruding through the nut.
Armed with proper knowledge I looked at the bolts holding the aileron brackets. As you can see the AN3-6 the plans call for are too short.
Not only is the overall length of the bolt too short it’s grip length is too short. More than one thread is in the hole, this could allow the bolt too be overtightened crushing the wood.
I also would feel much safer with those bolts safety wired so I ordered up some AN3-7 with drilled heads. With the AN3-7 one thread protrudes through the nut.
With drilled heads I can safety wire the bolts ensuring my aileron will remain attached.
TEAM says rib stitching is not necessary, the fabric manufacturer says it is. To make matters worse both are technically right.
On the Minimax, fabric glue is sufficient to keep the fabric attached to the ribs. But what would happen is there was some sort of failure?
Pirate Pilot over on www.lonesomebuzzards.com posted a link to a video that makes some convincing arguments. The video discusses the cause of a Bushmaster ultralight (C-IAUE) crash that resulted in two deaths. The aileron gap seal broke away from the main structure allowing the fabric to separate from the entire top of the wing. While the Minimax wing has slightly different construction there have been numerous maxes that have had partial separation of the aileron gap seal so it is conceivable that a Minimax could have the same type of catastrophic failure.
I can’t say that rib stitches would keep the fabric attached to the wing if my aileron gap seal were to separate from the wing. However I am sure that without the stitching the glue alone is not strong enough to keep the fabric attached if the gap seal separated.
Rib lacing is not exactly cheap the lacing cord, reinforcement tape and finishing tape set me back around $150. It is time consuming too took me about eight hours to do the left wing, bet the right wing will only take about five hours now that I have some experience.
I have read about some people stitching their wings without reinforcement tape and in my opinion all they did was waste time and materials. OK maybe they added a little strength but using the reinforcement tape increases the strength by orders of magnitude. The lace holds just a 1/4″ piece of fabric on the bottom and since I installed rib caps 1/2″ on the top. A 1/2″ by 1/8″ strip of fabric at each lace is not very strong and could easily allow the fabric to rip around the lacing.
I used three inch spacing for a total of twelve stitches on each rib. Without reinforcing tape that gives a total surface area of just 0.75 square inches of the fabric being mechanically attached to each rib top. The reinforcing tape is extremely strong, it will not rip under the forces imposed on the Minimax. The tape drastically increases the surface area holding the fabric to about 18 square inches on each rib top!
You will need a special needle to stitches around the compression members. I made mine with some music wire a hammer and drill. It’s the curved needle in the picture below. The straight needle purchased and put a small bend on the end to make it more useful.
I used the flat lacing cord because it gives a nicer appearance .
You might have noticed I used a blue chalk line to mark where the laces go. Having them all in nice straight rows looks great, I think it looks nicer than not lacing.
To finish the job I used 2″ finishing tape to cover the stitches and holes.
After applying primer they already look great.
I basically followed the directions in the polyfiber book. To learn how to do the lacing I watched this video.
You won’t regret rib lacing your wings and it very well could save your life.
The lexan is trimmed to fit into the opening, since it is 1/16″ just like the plywood trim around the opening the top surface is flush giving it a great look.
Holes are drilled every 2″ around the perimeter of the lexan then screwed into place.
To prevent the holes in the wood from stripping over time some thin CA is soaked into the holes and allowed to dry before reinstalling the lexan cover.
The lexan is marked and drilled to create an opening for the filler neck. To locate the filler neck position I installed the tank and used a square to locate the center front of the neck. Note that this picture was taken after making the hole and is intended to help show how this step was performed but this step was performed without the lexan in place.
Then the lexan was installed and the center of the filler neck was marked then drilled using a 2 1/2″ hole saw.
The final result looks great.
Because I will need to remove the wings I wanted quick disconnects for the fuel line and some way to drain the fuel.
For the drain I got a 90° 1/8″ NPT to 1/2″ barb brass and a quarter turn drain valve.
Some blocks were glued in place to hold the drain and a piece of plywood is screwed on top to keep it from moving.
A piece of 1/8″ plywood was glued to the root rib to hold the panel mount quick disconnect.
With the disconnect removed the wing was mounted if the fuselage so the hole could be marked and drilled into the fuselage. Once drilled the quick disconnect was reinstalled to test the fit.
The hole is just large enough so I can get my finger into the release tab. The 90° make disconnect will make routing the fuel line’s much easier.
With the drag brace supports in place it’s time to frame in the opening at the top of the wing. I cut a piece of RS-17 to length and notched the side of it where the gussets are located on rib #2 then glued to the side of the rib.
Next I located the rear of the opening and cut the plywood connecting the root and #1 rib. Then removed the front portion of the plywood.
Another RS-17 was cut to fit between the root and #1 rib. At the rear of the opening the RS-17 is notched to make room for a horizontal RS-17.
After checking the fit it was glued into place.
Once the glue was dry rib #1 was cut at the rear of the opening where the notch was made in the RS-17.
Another RS-17 is cut and glued into the notch forming the rear of the opening.
A 1/16″ ply gusset is added to the bottom at ribs #1 and #2 to strengthen the rear opening.
Lastly a piece of RS-3 is glued to the front spar to provide a surface for attaching the lexan cover.
Now it’s time to install the tank floor.