Monday, March 30, 2015

49-17 Oil Hoses

I knew that this would be a challenge.  Those thick, heavy oil hoses don’t like to be bent or twisted.  It was a challenge getting the two from the oil reservoir down behind and under the engine.  The nipple to the bottom of the engine was just barely able to clear the muffler (and there was still oil in the bottom of the case to dribble on things and make a mess.)  Nonetheless, it’s what I expected at this stage of the game.  As more and more things get assembled, there will be less & less room to make it easy.  (After all, if it was easy, then anyone could play!)


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Oil Hoses


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Oil Cooler with Oil Hoses

By the way, the oil cooler looks distinctly crooked in this picture.  It is.  The Book tells me to attach the cowl (with installed duct assembly) and tighten the hoses with it placed thusly.  Don’t worry, I’ll get it straight before I’m done.



Addendum:  The cowling epoxy work was done on 4/3, and I was able to finish up the last step of this page and tighten up the hoses.  I added thread seal and tightened up all 6 oil hose ends.  The cooler still hangs crooked when on its own, but it fit into the cowl OK.   

49-13 cooling duct fitting

 Another day of trimming & sanding fiberglass.  This actually was spread over 2 days, and took quite a bit of head scratching and thinking to ensure that everything fit together properly before I made cuts.  When you look at the page in The Book you’ll note that it’s quite busy with many diagrams that didn’t make much sense to me until I had the pieces in my hands and could relate them (diagrams) to each other (pieces.)    In the second photo, you’ll note some cardboard taped to the radiator.  The Book is pretty clear that there must be an even 1/4” gap between the radiator face and the interface piece (to make room for the flexible seal to be applied later.)  I remember reading that cardboard is pretty close to 1/8”, so I made a double thick piece and taped it to the radiator, then sanded & fit to have the cowl interface flush with the cardboard itself.  I’ll leave that in place until the wet layup step (page 49-14) is done and everything is cured in place.

That page will be deferred, by the way.  It’s currently below freezing (again!) here in central Ohio and I’m going to wait until the outside temps are at least in the 50’s so I can heat the garage to the 70’s recommended for using epoxy. If I’m really tricky, I’ll do the mixing and wet layups in a cool garage (prolong pot life because it’s the first time i will have worked with epoxy) then turn on the heater when I have everything in place.  That also includes having the cowls installed and tightened down, so I won’t be able to do any engine work for that 24 hours.  I’m sure I’ll find something entertaining to do instead.


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Cooling Duct, Duct Interface & Lower Cowl

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Cooling Duct Assembly in situ 

49-12 oil cooler mounted to duct

Nice photo of the oil cooler assembly mounted in the cooling duct.

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installed oil cooler

38-09 lower cowl close out

There is a slot in the bottom of the lower cowl that extends quite a bit forward of the front gear leg.  The reason this is so long is to allow the cowl to be slid up/back and bizarrely rotated in order to capture the exhaust pipe through its opening.  In order to close that space, there is an aluminum plate that is held in place with nut plates.  I wonder why they didn’t make two slots (one each for the exhaust pipe & leg) with a simple plate for each?  


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front view of close-out plate


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rear view of close out plate

Sunday, March 29, 2015

38-08 oil door installation

Sand, file, countersink, drill, rivet.  You get the idea :0)

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49-07 Overflow hose

Well, this took a bit of doing.  The hose is called out at 3/16”, but there’s no way that it would fit.  I used a 1/4” and added a clamp at each end.


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Sunday, March 22, 2015

38-07 Oil Door trimming

No surprises here.  Trim the fiberglass to make the opening; trim the aluminum to fit.  (Tape to hold in place for photo optional.)


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Tuesday, March 17, 2015

38-06 Upper Cowl fitted

Lots of work, but it was worth it.  It took about 6 hours of work just to do this page today.  (I’m writing this at 2:30 AM, so it’s still “today” for me.)

The upper cowl has 4 edges with hinges.  The upper ones went on first and weren’t too bad to install / remove when they were clecoed together.  After I riveted, I couldn’t get the pin to advance no matter how many times I fiddled and tried to get it slide.  I finally realized that I had inadvertently crimped 2 of the eyelets (during riveting) such that the eyelets were no longer round.  Damn!  It took some serious thinking to figure out a repair.  I didn’t want to drill out and replace the entire hinge as the likely hood that I would not damage the cowl was somewhat better than winning the lottery.  I couldn’t get a drill bit in there because of the close set spacing (1/2” gap) between the eyelets.  I finally came up with taking some of the hinge material (guaranteed to be the correct diameter), bending a ~5/8” 90° “tooth” to slide into an eyelet and then grinding the tooth to be flat on one edge (of the 5/8” length).  That left two sharp edges on what had been a round pin.  The sharp edges were enough for me to shave the inside of the eyelet back to being round and permitting the regular pin to pass.  Viola!  Much better than trying to remove a section of hinge and replace.


Below, you can see the installed upper and lower cowl.  I’m not happy with the gap forward of the hinge pin, but there’s not much I can do with it.  I might learn some tricks with epoxy & fiberglass in the future.  For now, it won’t prevent me from being airworthy so I’ good with it.

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Cowls, installed 

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Cowls, installed (front view)

When I return to the project, I’ll install the nut plates on the front, sides and bottom and tackle making the oil door.  Those should be fairly straight forward.  Then, back to the cooling system where the cooling duct goes inside the lower cowl.  That will require my first venture with ‘wet’ fiberglass (e.g., laying down fiberglass) vs. just trimming & sanding dry pieces made by somebody else.

38-05 Lower Cowl fitted

I was actually amazed with this bit of progress!  For many months I’ve been worried that Something Bad lurked in shadows.  I had a bit of trouble figuring out how to slide the lower cowl over the front gear leg and the exhaust pipe, but that took only a few minutes of creative twisting & turning before I figured it out.  I kept reassuring myself that other people take the cowl off with engine installed every day.  The trick is to put the gear leg in the slot, lower the cowling to the right and tilted with the open end down and you can slide the exhaust through the appropriate slot and then the rest of the cowl fits nicely.  In the photo below, you can see a red clamp next the battery.  That’s all it takes to keep the cowl in place, just the two clamps.


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lower cowl fit to airframe


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Upper to Lower cowl hinge

 I put a small dot on the cowling where the bolt will be drilled through to secure the upper to lower cowl hinge pin.  Note the black triangle on the lower cowl.  I wasn’t sure if that needed to be trimmed or not, so I left it in place until I was sure.  Yep, it’s gone now.


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close up of the “flag"

38-04 fitting cowl hinges to airframe

The hinges that fit on the cowl needed to be marked for drilling, bent and fit on to the airframe.  In the picture, you can see tiny black dots on the section of hinge that is curving over the battery.  Also note the small bronze colored pins directly above the overflow bottle cap.  Those pins are a pain to insert!  There’s also a small hinge just to the outside of the battery and outside of the oil canister.


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Hinges installed on airframe

38-03 cowling pins

The RV-12 cowling is attached using an ingenious (or devious) implementation of a piano hinge.  Rather than using the hinge to permit rotation about the pin, the hinges are used as fasteners—think "giant zipper.”  They are often placed in curves, so no rotation is even possible, but by removing / inserting the pin it is possible to make a long and strong closure device.  This picture shows the 8 pins that hold the cowl pieces to the airframe and to each other.  The ones with “flags” on the ends were welded at the factory.  the others were bent and shaped by hand.  Almost all of them got trimmed a bit further as the process proceeded.  Also note that the ends are beveled and smoothed so they have the best chance of finding their way through each eyelet.



IMG 4111Locking pins and upper-to-lower cowl hinge

Because the hinges have to follow a curve, the edges of the eyelets are beveled to make it easier for the mating eyelets to fit in-between.  The Book calls for filing the half on the airframe (installed many months ago) and that’s what is pictured.  Later, I ended up filing the mating eyelets on the cowl as well.

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beveled hinge eyelets

38-02 trimming Upper & Lower Cowls

OK, I’m back.  10 consecutive nights in the ER left me with a severe case of RV-12 withdrawal.  I got back to work by tackling the cowling.  As you recall, I had finished up with the oil radiator, but it  is mounted on the air duct that is mounted inside the cowl.  I had deferred the cowling from its schedule slot (chap 38) due to the advice of hanging the engine and letting its weight “settle” for a few weeks before fitting the cowl.  Made sense to me, so that’s what I did.  First picture:  me, getting ready to attack the fiberglass.  I elected to use a reinforced cutting wheel on a dremel to do the major cuts and a 1 cm sanding drum for medium abrasions/shaping and the traditional 80 grit sandpaper on a block for detailed finish sanding (shaping work only—not surface sanding!)


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protective gear!

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Lower Cowl with scribe marks

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Upper Cowl with tape on scribe lines

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trimmed cowls mated together

Friday, March 6, 2015

49-11 oil cooler box

 This is the oil cooler installed in its supporting box.  The blue stuff is tape to keep debris out of the oil passages and the orange is RTV.  Having completed this subassembly, I will have to stop work for 2 weeks to go to work (ugh.)  When I return, it’s time to start the (dry) fiberglass work and sand the cowling and get it assembled / installed.  I will then return to this chapter and sand / install the fiberglass cooling shroud that will serve as the mount point for this cooler.

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Oil Cooler in mounting box

Thursday, March 5, 2015

49-05 Radiator

Yes, the sequence isn’t in order.  I figured “why struggle to reach behind the radiator to install the door & cable that live behind it?”, so I did the control door before installing the radiator itself.    Not hard to install; there are 5 AN3 bolts holding it all together.  The Book says to use some spacing washers QS to maintain a 1/16” gap between the radiator and the supports behind it, but I didn’t need to add any washers.  On the other hand, if you look down on the front gear leg, you’ll see another double-clamp PIA to attach the lower radiator hose.   

The duct tape is there to provide a nice clean line for the RTV sealant around the edges.  It’ll look better when I take it off.


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49-10 Heater Cable Attach

This is the view of the cabin heater door.  The control cable is coming in from the left and is attached to the door with a bearing.  The control wire is wrapped around a (giant) cotter pin.  The Book has you trimming the cable to length and I used the threads on the bearing to fine tune the amount of tension holding the door closed.  I did wipe off more of the wax after I saw this picture.

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Heater Door

49-09 Heater Control routing

What you are seeing is the routing of the control cable under the engine mount, through 3 of the looks-simple-but-is-a-pain-to-attach double cushion clamps and through an ingenious device called a friction comb.  The Book says to string everything up and then completely remove the internal push-pull wire from the spiral sleeve, cut the sleeve to length, then re-instal the push-pull wire.  Wrong.  I didn’t feel good about that instruction and so did a test remove-install after I rigged up the 1st cushion clamp.  No go.  I had to remove the clamp, then I could re-thread the push-pull wire.  I got everything installed and did some careful measuring to pull back the wire before cutting the sleeve.  no problem.


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Heater Control Cable

49-08 Heater Panel Control

This is the first control cable installed into the airplane.  I elected to install this (since it connects to the heater door) before putting on the radiator, which would have made installing the cable more difficult due to restricted access.  Again, I do love the detail that The Book provides, but there is definitely room for significant optimization of steps to eliminate redundant processes and improve accessibility during construction.


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Heater Control Cable

49-06 Oil & Coolant reservoirs

The white plastic bottle in the picture is the coolant reservoir, which holds the overflow of coolant from thermal expansion/contraction out of the radiator system.  The large cylinder in the foreground is the oil tank.  Unlike traditional aircraft engines, the Rotax does not have a sump below the engine. Instead, a hose carries discharged oil to this tank.  The tank removes air from the oil/foam discharge and provides a reservoir as an oil supply to the engine.


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Coolant Reservoir & Oil Tank 

49-04 Heater Door install

The heater door is riveted to the firewall. The green streaks are car wax that is on the fire wall as a release agent for the (orange) RTV.  The RTV is applied as a bead to the inside of the door and acts as a gasket to help keep hot air out of the cockpit in warm weather.  Ironically, it was about -5 °C in my garage when I built this.  (the propane torpedo warms it to about +5 °C).   The door is being held in closed position by some duct tape while the RTV cures.

I found that there was a bit of “spring” to the door from the RTV on the side closest to the hinge.  I ended up shaving down the thickness with an razor blade on a later step.


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49-03 Heater Door assembly

The steel hinge is drilled and one half riveted to the door, and the bracket is ready to be installed.  

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Heater Door & Hinge

Tuesday, March 3, 2015

49-02 Cooling System Prep

Insert stiffening springs in the water hoses and prepare a stainless steel hinge for the heater door assembly.  I’m guessing that the door and associated hardware must be made of steel because they are technically part of the fire wall.  Steel is much more difficult to work with than aluminum.  Glad there’s not too much of it.


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48-07 EGT probes

The EGT probes go into pre-drilled holes in the aft cylinder exhausts.  The pre-drilled holes are  very close fitting and took a fair amount of grunting and struggling to get them installed.  After that, I discovered that 3 of the spade connectors were not well crimped and just came off in my hand.  I used some off-the-shelf connectors and got them put together anyway.

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