Sunday, February 5, 2017

Ch 9.5: MLG / Fuselage Intersection Fairing


Now that the MLG fairing is done, there needs to be an intersection fairing that makes a smooth transition between the fuselage and the MLG.  The key here is that it has to allow for movement between the two.  With weight on the gear and on landings, the gear strut will flex up so the fairing has to allow that without breaking anything.

I really liked Wayne Hick's solution.  See his instructions here for details.  I will only summarize my attempt at it below.

 For starters, I crafted the fuselage side of the fairing out of left over 3/8" PVC foam.  This will form the curvature to the fuselage.  I used the large end of the Eureka CNC MLG fairing I had trimmed off as the template for the airfoil shape.  In the pic, you can see the before and after shaping the contour.




I glued the top side of the fuselage faring to the fuselage using scrap pieces of 3/8" foam to ensure the necessary clearance between the fairing and the MLG.  Afterward, glue the bottom portion to the underside including the MLG cover.  Don't worry, this will become a permanent part of the cover but it will stoll be removable when done.



Now I used other scrap Last-A-Foam approximately 2" wide to serve as the transition from the fuselage-side fairing to the MLG fairing.

I glued it to the MLG fairing butted up against the fuselage-side fairing.  I used expansion foam to fill in the gaps and began sanding to match the fuselage fairing and gently fair it into the MLG fairing.





Here you can see the both starboard (left pic) and port (right pic) from the nose looking back after being sanded to shape.  I'm not sure how I did it but I seemed to be able to shape them almost identical without the use of any templates.

Not shown (sorry) is the shaping of the back edges curving into the fuselage.  See pics below after glassing.

Once I was happy with the shape, I glassed the bottom of each fairing with 2xBID.  I wrapped the leading edge up past the center point and left an overhang at the back supported with card stock.


Here you can see the back edge after glassing the bottom and some trimming and sanding to blend into the existing MLG fairing.  Once I had it the way I liked it, I used a piece of card stock to form a template so I could get the other side to match.

I removed foam from the aft edge and used micro to fill the wedge where the top glass would meet the back edge.  It worked pretty well.



After all the glassing was done, I used an xacto saw and a Dremel with a small saw to carefully cut along line separating the PVC foam from the white Last-A-Foam.  I used a sharpie to help mark it.







After cutting the fairing loose from the fuselage, I used folded over sand paper to clean up the cut line for a nice look.  I also removed the gear and painted the exposed foam inside the fairing with micro to protect against water intrusion.  I also wanted to ensure water could not get trapped anywhere in the gap so the smooth micro finish helps ensure the water drains out the bottom cut line.



MLG Cover on the bottom with
Intersection Fairing mods
I uncovered a problem after separating the MLG cover on the bottom.  I found that I would need to make a few adjustments to accommodate where the corner screws landed for my cover.  I didn't see that coming.  I couldn't move the fasteners without causing a conflict with getting the gear in and out when needed.  So I made adjustments to the intersection fairing on the bottom.  I think it turned out fine.



Main Gear Fairings & MLG Cover Complete!








Sunday, January 22, 2017

Ch 9.5: Gear Strut Fairings

Pick'in up Some Knots

Top View of Eureka CNC Fairings
Side View of
Eureka CNC Fairings
Although the MLG strut has an airfoil shape to it, it's formed in way that puts it out of alignment with the air stream when it's in cruise.  That creates unnecessary drag which reduces speed and fuel efficiency.  Several builders (Wayne Hicks, Kevin Walsh, and others) have formed fairings over the strut to realign the aerodynamic shape which reduces drag and increases speed. Kevin and Wayne did it slightly different but the result is very similar.  Kevin worked to have his made available through Eureka CNC.  These are what I used.

The fairings come in two long straight pieces that won't bend around the curvature of the strut so you have to cut it into pieces.  I cut it into 8 pieces, larger widths toward the top and thinner widths where the strut curves sharper.  I positioned the top piece about 3/8" gap from the fuselage side and went down to about the top of the brake heat shield.  I'm assuming that some of this will end up being trimmed off when the wheel pants are built and installed.


Test Fitting
Then I tested the fit by taping the pieces on each leg.  I numbered each one to ensure I put them on in the proper order.  Note that the closer to the bottom you get, the foam get's very thin and hard to keep from breaking.

Vacuum Bagging
To the left is my poor man's vacuum bagging technique with a small shop vac.  It worked well enough to keep the pieces all together and aligned while they cured.









To the right...taken after the foam has been micro'd and glassed with 2xBID. Notice the white trailing edge.  I glassed the bottom side first and then removed foam from about a 1/4" or so on the top at the trailing edge, filled the gap with micro, and glassed 2xBID on top.  This gave it a nice solid sharp edge that should be able to survive a minor hit without permanent damage.

The bottom was trimmed off to be level while sitting on the ground.  Next there needs to be a fairing built for the intersection of the MLG fairing and the fuselage side.

Onward, cab


Thursday, July 7, 2016

Ch 9.5: Axles, Wheels, & Brakes

For wheels and brakes, I selected the Matco Mfg. triple puck brakes...WHL W51 LXT.  The LXT is the extra torque version of the standard triple puck brakes.  I purchased the kit including two wheels, two brake/rotor sets, and two axle sets from Aircraft Spruce and seemed to get a little better deal, including free shipping due to the amount, than buying direct from Matco.

Bullseye - Checking
the centerline
I had to move the fuselage to a new location so I re-leveled and re-aligned the fuselage per plans.  In fact I rechecked it multiple times throughout the ordeal.  I was convinced my center-line was accurate, but I was never quite sure the perpendicular line marking the leading edge of the gear strut was accurate. Ensuring it is in fact perpendicular is important because the error grows the farther out from the center-line you get.  I finally decided it was as close as I thought I could get it, and using plumb bobs, the leading edges of the strut seemed to be within .05" tolerance.  I also set up paper on the far wall to project the center-line and axle positions for adjusting the required toe-in.

Checking each side for accurate
axle center and height
Next I located the axle center points based on the plumb bobs at the appropriate FS mark, and using 42" as the distance from the longeron to the axle centers.






Bernie's Template
BID Wrap Curing
I followed the toe-in alignment procedure in the plans but used a laser level to project points on the far wall approximately 18ft away.  I closely followed Bernie Siu's website description to ensure my toe-in calculations were correct.  Bernie mentioned the possible error when using a laser...something I wouldn't have thought of.  After checking, my laser did in fact have a small error.

Next, I used axle templates from Bernie Siu to locate the mounting holes and outline of the leg cutting I would have to do. Then I performed the BID wrap of the gear leg area.


Port Flox Pad
Starboard Flox Pad
Once the toe-in point was located, I used a 1x scrap of wood and a tension clamp to form a nice flat flox pad for mounting the axles.











Backing Plate
Cutting the Strut
Fit Check
I originally drilled the holes before I fab'd the flox pad...I don't recommend doing this.  Since the strut is curved, it's difficult to keep it at the right toe-in location while drilling...I ended up with a hole off angle and had to fill and re-drill it once the flox pads were on.  I.clamped the axle in place when I drilled the holes and inserted the bolts after each hole to help hold the axle straight and help me drill straight...something hard to do with the long bit you have to use.  I then fabricated the backing plate, round vs square, and floxed them in place.




Cut to Shape
Mounting holes drilled
Now that the wheels and brakes are ready to mount, I again turned to Bernie for his heat shield templates.  These were fairly simple to make...a couple of hrs work...and came out nicely I think.  I used some Mother's aluminum polish from your local Auto Zone aircraft supply house to put a high gloss finish on them to reflect radiant heat.  Lastly, they have to be bent per Bernie's template to clear the brake calipers.

Polished but not yet bent to shape
I mounted the axles, tires & wheels, heat shields, and brakes, torqued everything to specs...and Ta Daaa!  After a few other clean up items while it was inverted, she's was now ready to flip back over. A Big thanks to Bernie Siu for his excellent builders log and allowing me the use of his axle and heat shield templates.

Onward to the gear leg fairings,

Port Side - head on
Note the heat shield bends
Ready to roll...once I get it turned over of course.






Tuesday, July 5, 2016

Ch 9.4: Main Gear Cover (2 of 2)

When last we left our MLG Cover...

Now that the gear strut is in place, I can complete the removable cover for the bottom access to the "hell hole" where the main gear is mounted.  Other than the gear mountings themselves, the only thing that will be in this area is brake line connections I think.

Taped off ready
for layups
The cover has been fabricated but it has no way to be mounted.  As mentioned, I followed Wayne Hicks method of fabricating the cover.  This continues into the mounting flange and fasteners for it.  I first taped off the edges of the inside of the cover with packing tape to prevent epoxy from sticking.  Then I bondo'd craft sticks to the cover so it would sit flush over the access hole.

Looking down (inside) the
cover while layups cure

Then I set the cover in place and bondo'd the craft sticks to the fuselage.  After turning the fuselage right side up, I then laid up BID tapes from the side of the LG bulkheads down and about 1" onto the MLG cover.




Flange cured, trimmed,
with fastener holes
located and drilled.



After cure, I cleaned up the flange and located the holes for the fasteners.  Also, some clearance cuts had to be made to allow the main gear attach tabs to fit down between the flanges.  Everything is a fairly tight fit but works out great.


Installing nut plates
under the flange
I ordered Click-Bond floating nut plates (#CN614CR3P) and Click-Bond adhesive from The Flight Shop to attach them to the underside of the flange.  The rubber installation aid made this very EZ and the nut plates seem to be holding very well.  Using countersink screws make is all nice and clean for airflow.


Clean lines !

Once complete with the install, I went ahead and did some finish work with micro to create a nice clean 1/16" gap between the cover edges and the fuselage.



Onward to the Wheels and Brakes!










Ch 9.6: Landing Brake

The landing brake (LB) helps provide some needed drag during landing approach to make a steeper decent and a better view of the runway for the pilot.  It is a hinged flat board that deploys from the belly just behind the front seats.  The plans call for a mechanical mechanism to deploy it however most builders today convert this to an electric actuator.

Building the Brake
The building of the landing brake started in an earlier chapter when the brake was cut out but then re-glassed back into the fuselage bottom until Ch 9.  So the completion of the brake starts with cutting it lose.

I decided early that I wanted the hinge for the brake to go almost the full width instead of just 10" per the plans.  I'm hoping this will keep it from warping the way several builders have reported.  To do this, all I really had to do is adjust the number of attach points/screws.  I'm also widening the wooden support the actuator connects to to provide a little more crosswise support.  My hinge runs ~22" of the ~24" width of the LB.

Installing the Brake Hinge Support
I used 7 screws to attach the hinge to the fuselage and 8 screws attaching the hinge to the LB.  Other than the added number of screws/slugs to the hinge line, everything else pretty much followed plans.







Preparing the LB Cavity in the Fuselage
After securing the LB-23 hinge support into the fuselage, I routed out the interior of the landing brake cavity using a dremel routing tool to make room for the glass to be added.

I then located where the actuator would come through the bottom and beveled the foam to that area. The cavity was then glassed per plans.  At this point, each slug buried into the foam of the fuselage was drilled and tapped for 10-32 screws and the brake was test fit.  In order for the brake to hide nicely under the fuselage, micro must be used to fill the remaining depression.  I taped off the brake edges and the hinge to ensure release and filled the edges and the surrounding depression with micro. Then I closed the brake flush with the bottom of the fuselage to let cure.  TIP: I would recommend putting some kind of release agent on the tape. I almost epoxied my LB closed :-) .  This process essentially makes a mold of the inside edges and perimeter of the brake in the fuselage bottom so that when it closes it basically disappears nice and neat.  See video at the end.

Glassing the cavity
Routing out the fuselage cavity
Micro curing in the depression
surrounding the landing brake.  The
boards ensure the brake sits flush
with the bottom of the fuselage.

Installation of the Actuator
I'm using a Firgelli actuator, model FA-PO-150-12-4.  It has a 4" stroke, 150lbs of static force, and a feedback potentiometer in case you want to wire it up to an electronic indicator.  I made glass brackets however I only ended up using the larger one and attached the actuator to the back of the seat.

The brackets were made similar to Wayne Hicks brackets, with 8 ply of BID...4 running along the bottom, 4 running from the bottom and up the side on each side, with another 4 layers forming a U-shape in between the sides.  A picture would be good here, but at any point on the bracket there are 8 layers of BID.  I used a scrap piece of foam to form around which was cut the width of the actuator attachment.  I let it cure, cut it to shape, put adjustment holes in it to allow me to adjust the closure of the LB once installed.

Assessing where to mount the bracket
on the seat back.
Installed Actuator
with homemade
bracket
The fuselage side bracket is mounted in the back of seat on the passengers side close to the center seat support.  I glassed an oversized piece of birch plywood on the back of the seat.

Between the seat and the birch, I embedded two EZ-point locking nuts  vertically where two bolts hold the bracket in place.  The actuator is then attached to the bracket with an AN Pin and castle nut to secure it.  For the LB bracket, I simply used the aluminum brackets, part no. CZLB-18 available from the Cozy Girrls.
Voila !...My first moving part...Onward.
video
video