February 2010 Archives

I finished deburring all of the small pieces for the forward fuselage and baggage area.  These just need to be cleaned and primed.  I still have to match drill the new side skin stiffener that replaced the piece with the crack, but I want to match drill it to the skin, so I'll wait until I have the fuselage reassembled.



I deburred all of the aluminum bits of the firewall and countersunk the lower fuselage stiffener.  I also deburred all of the engine mount brackets.  I still need to debur and dimple the stainless steel firewall flange.



I didn't have much time to work on the plane today, but I did manage to debur and dimple the stainless steel firewall flanges.
I got in on the group buy for the Andair fuel pump and filter.  It took about 15 minutes or so to assemble the pump and speed controller to the mounting bracket.  This will get mounted just in front of the spar carrythrough between the seats.  The fuel filter is not pictured because Andair sent me the wrong one.  They've been great until now though, so I'm sure they'll take care of it in short order.



I used my self-etching primer to prime the overlap areas between the aft and center fuselage sections.  Since overspray cleans up easily with solvent, I didn't bother trying to mask off the area precisely.



I also finished deburring, dimpling, and priming the overlap areas on the center section.



Rejoined Center Section

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After deburring and dimpling the remaining holes in the center bottom skin and F-705 bulkhead, I managed to join the center and aft fuselage sections by myself.



I neglected to install 12 bolts in the forward half of F-704, so I wanted to do that now before access got worse.  After inserting the bolt in from the front (so there is still access to buck holes in bottom skin), I used a washer wrench to put the washer on the bolt.  These washer wrenches were expensive ($30 for a set of four covering eight sizes), but when you need them, they're worth every penny.



Getting the nuts on these bolts can be tricky.  I've seen people construct contraptions of wrenches held by vise-grips with tape on the end to keep the nut in the wrench.  This however proved to be the perfect tool.  This is basically an adjustable wrench with a vise-grip type clamp attached.  You can run the adjustment screw down snug against the nut and then clamp it shut and it squeezes the nut tight, allowing you to start threading the bolt and then torque it down.

My dad bought this for me years ago and it's come in handy a number of times for stuff like this.  I have no idea who makes this or where you can buy it though.



Here are some of the bolts installed (the ones where you can just see the heads, not the nuts).  There are twelve bolts total (six each on the left and right).



I made it through deburring and countersinking one of the longerons and part of the second.  It's a lot of holes to get through; probably 200 holes per longeron that need to be deburred on one side and coutersunk on the other.

Primed Fuselage Components

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I put an extra thick coat of primer (still translucent thought) on the forward floor area since this may see extra moisture from people getting in with wet or snowy shoes.  I masked off the area in the front so that the firewall sealant can stick to the bare aluminum.



Here are most of the other components after being primed.  I primed the longerons out in the driveway balanced across two sawhorses.



Here are the longerons and outboard seat ribs installed.  I also got some of the deburring on the forward floor done.



I finished deburring the forward bottom skin and dimpled all of the required holes.  Be sure and skip the two #30 holes on the aft end of the sides since those are riveted with AN470 rivets.



Since I'm building a tail dragger, there are two holes that need to just be filled with AN426AD3-3 rivets.  These are used as the pilot holes for the brake lines on the A models.



The F-684 gussets can be riveted to the side firewall stiffeners now.  The remaining holes are also shared with the lower aux longeron and the side skin, so they're left open for now.  Where possible, I'm trying to put the manufactured heads where they will show in the cabin since I think it looks nicer.



The F-7101 gear webs can be riveted to the F-902 forward bulkheads since access would be difficult later.



I still need to debur the side skins, but I wanted to start assembling the forward fuselage so that I didn't have such a big pile of small parts stacked around and in my way.  Here I've clecoed on the firewall and all aux longerons.  Notice the missing longeron on the near side.  This is the piece that had the crack from a couple of weeks back.  I have the new piece, but I want to put the side skin back on in order to drill it.



I went ahead and riveted the F-902 bulkheads to the lower longerons.  The corresponding holes tying the F-902 to the upper longerons need to be left open until the forward top structure is drilled.



The center floor stiffeners can be riveted to the cover support ribs.  I couldn't reach the aft holes with the squeezer, so I'll have to shoot those.  It's too late to run the gun tonight though, so that will have to wait until later.



I also squeezed the rivets attaching the center floor stiffeners to the F-601-J angles.



I received my heater valve from Plane Innovations.  It's basically a stainless steel version of the aluminum valve that Van's sells.  In case of a fire, the aluminum version would melt in a matter of seconds.  This would keep the fire contained for long enough that I could likely get on the ground.



I also received a half pint of firewall sealant from SealPak.  This is the same CS1900 sealant that Van's sells, but not in a single use container.  Since the firewall will be sealed over several sessions, this will ultimately save me a fair amount of money.



I trimmed back the ends of the replacement skin stiffener (replacing the one that had a crack) and clamped it in place.  I then match drilled in to the skin and clip that attaches it to the firewall stiffener.



I temporarily reinstalled the rudder pedals so that I could mark the new stiffener for the holes that are used to attach the mounting blocks.



After priming the stiffener, I riveted it to the attach clip and riveted both clips to the firewall side stiffeners.



Since I mixed up an entire ounce of primer, I also shot the bottom of the forward seat pans so that I wouldn't waste it.  These will be removed from time to time, so they'll likely get a little scratched.  This should help protect them from corrosion.



Forward Fuselage Prep

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I drilled two 3/4" holes in the left side skin for the grommets that will pass the pitot and AOA tubes in from the wing.



The side support doubler is riveted onto the side skins using the holes adjacent to the spar cutout (with the exception of the bottom-most forward hole since this also joins the forward bottom skin.



I also drilled a couple of #19 holes to mount the quick disconnect fittings that are provided with the SafeAir pitot/static system.  As you can see, I've also installed the grommets for the pitot/AOA lines.



I also installed the grommet for the fuel line in the side skin forward of the spar cutout.



Finally, I installed the forward bottom skin.  I still need to finish the right side skin (seen in the upper left of this picture leaning against the back wall of the garage), but I'll take care of that tomorrow.



Jenn had to work today, so I got started today by finishing the right skin.  My buddy Andre then stopped by and we installed it and started riveting.  We made it through all of the bottom rivets on the left side aft of F-704 as well as all of the rivets on the side skins aft of F-704 (with the exception of the longeron rivets which I can squeeze).



Here you can see that the outboard seat ribs are riveted to the side skin using AN470 rivets since this is inside the wing root and won't be visible when the wings are installed.  If you look carefully, you will notice that the forward two rows of rivets are AN426 instead of AN470.  This is because I inadvertently countersunk these holes in the side doublers, so I had to dimple the skins to match.  I spoke with Ken at Van's, and he confirmed this was a non-issue.



Here you can see how the conical bend looks when riveted.  I'm really happy with how this turned out.  All of the joints are nice and tight, and the rivets turned out great.



We knocked out the double row of rivets attaching the center skins to the tailcone on the left side as well as the rivets holding the bottom skin to the center rib.



More Fuselage Riveting

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I squeezed all of the rivets between F-902 and F-705 along the upper longerons on both sides.



Aft of F-705, there are a few places on each side where there are three rivets close together.  The middle rivets can be set now since they just keep the longerons in place.  The remaining holes are left open for the time being since they also attach the top skins.



A number of rivets along the aft end of the longerons (where the aft deck sits) can also be squeezed now since there are no other parts that attach here.



I also squeezed a number of the AN470 rivets just aft of F-704.  Near the lower right of the picture, you can see one boogered rivet.  There is a nutplate right behind here (on the seat rib flange) and I didn't notice it when I squeezed the rivet.  It didn't do any significant damage, just slight bends to a couple of pieces.



Andre dropped by again tonight and we knocked out all of the riveting on the right side of the plane aft of F-704.  After applying the firewall sealant, I think we only need one good riveting session and we can flip the fuselage. 



More Forward Fuselage Prep

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The hole right below where the forward fuel tank attach bracket needs to be drilled and countersunk for a #10 screw.  I drilled this out to 3/16" and then used the #10 countersink cutter to countersink through the sandwich of the side skin, bottom skin, and lower longeron.



Here you can see that the screw will sit perfectly flush after install.



I removed all of the forward clecos and pried the side and bottom skins away from the firewall in preparation for applying the sealant.  I also scuffed all of the mating surfaces.  The mixing ratio is too precise for me to use the scale I have (only accurate to 1g), so I'm going to need to track down a more accurate scale before I can mix the sealant.



I used a couple of these stubby #40 clecos to keep the side skins spaced away from the firewall.



I also installed the AN3-10A bolts through the rear spar and spacer blocks.  Getting these spacer blocks in was more of a pain than I would have expected.  It was also tough to get a torque wrench on the nuts on the other side.  I ended up having to use a crow-foot wrench on the end of my torque wrench to get them.



Sealed Firewall

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I started to seal up the firewall last night, but after reading about the mixing ratio (40:1), I realized my digital scale wasn't nearly accurate enough (it was only accurate to 1g).  Tonight after work, I swung by Fry's and picked up this digital scale that is accurate to .1g.  

The A part of this mixture is basically like tar.  You're basically cutting chunks of it out of the can.  The B part is a liquid.  When mixed together, it forms a thick paste that will cure to a flexible state and withstand 400ºF sustained and handle flash temperatures to 2000ºF.

Initially, I started mixing this up in a paper cup, but as you can see, the B part immediately started soaking into the cup.  Rather than guess how much additional B part to add, I tossed this batch and mixed up another one in a plastic cup.  Since I bought a 1/2pt kit, I probably have enough to do two complete firewalls, so this is no big deal.  I'll still have plenty left for the other parts of the firewall that will need sealing.



Here you can see where I've applied the sealant to the firewall flange.  Basically, you just butter on a thin, even coat and then cleco the parts together.



To ensure a good bond, I put a cleco in every hole around the firewall (including the double row along the bottom skin.  I also clecoed in the final two bottom skin stiffeners.  This thing is ready to rivet together.  Andre is planning on stopping by on Sunday.  With any luck, we can finish this up and flip the fuselage.



Flipped the Canoe

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Andre stopped by today to help me finish up the riveting on the forward fuselage.  We didn't get any pictures during the process, but here is the finished result.  The holes along the firewall will wait until they're match drilled to the hinges that are used to attach the cowling.



Some of the holes where the fuel tank brackets attach can't be reached with any of my regular bucking bars, so I taped a hunk of steel to one of my long rivet sets and used the rightmost end to buck the rivets.



Jenn came out and helped Andre and I flip the fuselage.



Jenn took a shot of me checking out the pilot's seat.



Andre and I checkout out how roomy the cockpit is.




Here you can see that I'm using two low saw horses under the front part of the fuselage so that it is nice and stable when climbing in and out.



After Andre took off, I installed the AN3 bolts through the lower engine mounts and lower longerons.  I probably should have done this before riveting on the bottom skin since I couldn't get a torque wrench on these.  I had to calibrate my hand and do these by feel.



Afterward, I leveled the fuselage front to back.  Here is the reading along the longerons between F-704 and F-705.



I also leveled the fuselage side to side at several points along the fuselage to ensure there was no twist.  Here is the reading at F-705.



And at F-704.



And at F-710.  I doubled checked all of the readings with a bubble level and them clamped the aft deck in place.



I needed a ratchet clamp to apply a little side load on the aft vertical bars to remove all of the twist.  After I tripled checked everything was straight, I drilled the aft deck to the longerons.



Goddamnit!  I got my foot caught up in the air hose, pulling my drill and box of rivets to the floor.  After swearing a blue streak for a few minutes, I started trying to sort them and then realized it was going to take several hours.  This is probably only about $10 worth of rivets, so it's just not worth my time.



Misc Fuselage Tasks

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I started tonight by laying out the hole in F-757 for the tip-up latch mechanism.



After drilling and filing for about 15 minutes, I had a nice square hole with radiused corners.  I fit it along with aft canopy deck and match drilled it to the F-705 channel.



After clamping it in place, I then match drilled it to the longeron and laid out and drilled three additional holes in the aft end.  I started working on the left side, but it was making too much noise and keeping our son awake.



I went ahead and torqued down the #10 screws in the tank attach brackets.



I also fit and match drilled the F-709 bulkhead.



Finally, I fit the F-695 gussets that tie the upper longerons and engine mount to the firewall stiffener.  The forward edge of these needs to be filed to be parallel with the firewall when the outside edge is flush with the apex of the longeron.  The forward edge also needs a little bend up to lay flat against the stiffener.



After determining where the aft end of the engine mount is, I laid out 10 holes forward of this point and four holes after.  This resulted in slightly different spacing than called for in the plans.  I had basically 1/2" between the forward 10 holes, but only 13/32" between the aft four.  This ensured adequate edge distance all around.  I also laid out for 5 holes along the front edge.  I then drilled these out to #40.



I then clamped the two gussets together and transferred the holes to the other one.



After clamping the gussets securely in place, I match drilled the longerons, engine mounts, and firewall stiffeners to #40 and then enlarged the holes to #30.



Here are the completed gussets.  I'm going to wait to prime and install these until I have a sufficiently large pile of parts to prime.



I finished the left F-757 plate and drilled it to the F-705 channel and longeron.



There were two holes in the aft fuselage that I couldn't dimple earlier because I inadvertently riveted too far up F-711.  The vertical bars prevent getting a squeezer aligned with these holes, so I needed to get creative.  Since the longeron is already dimpled and thick enough not to flex, I could just use the male portion of the die to form the dimple.  Since the vertical bars prevent clamping directly, I used a scrap piece of angle and some clamps to either side to drive the male dimple die flush with the skin.  This worked perfectly, and a rivet sits completely flush in the hole.



I managed to squeeze all of the remaining holes with the exception of the upper two holes in the forward flange of F-711.  I'll have to shoot these, but it's too late to run the rivet gun tonight.



I received confirmation today that my finish kit will ship the week or April 12th.  This gives me about seven weeks before it shows up which should be sufficient to finish up the fuselage kit.



Continued Fuselage Assembly

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Now that all of the rivets along the longerons are set, the F-711D angle could be riveted to the F-711 bulkhead.  I managed to get a squeezer on these. 



I positioned and drilled/reamed the seatbelt anchors just in front of F-708.  I also reamed the 1/4" holes in the front for the bolts that attach the cable.



After drilling the F-728 angle to F-706, I riveted the reinforcing angle in place.  I was able to squeeze one of the rivets that attach F-728 to F-706 at the top.



I was also able to squeeze the upper four rivets that attach the lower end.



I got started tonight by fabricating the spacers that sit under the aft deck.  Here is the one that sits on top of F-710.



And here is the slightly more complex one that sits on top of F-711.  After both were fabricated, I stuck them down with carpet tape, replaced the aft deck, and match drilled them and the bulkhead angles.



Next up, I but out the pieces for the elevator bellcrank and scotchbrited everything smooth.  I then laid out for and drilled the hole used by the autopilot pitch servo pushrod bolt.  Finally, I reamed all the holes for AN3 bolts.



Now that the position of the two ribs holding the elevator bellcrank are fixed, I match drilled and riveted the hole that ties the two angles together.



I then fabricated the two spacers that sit on either side of the elevator bellcrank bearing.  An AN4 bolt runs through these to tie the two ribs together.



Finally, I clecoed on the bulkhead gussets.  I don't want to match drill these to the longerons yet since the bulkheads are pretty flexible at this point and it would be easy to get them in the wrong spot which would throw off the hole alignment with the top skin.



We were busy most of the day at a cub scout event with my son, but I managed to put a couple of hours in this evening.  I got started by fluting all of the bulkheads and making sure their flanges would lie flush with the skins.  I then temporarily attached the rear top skin to mark a few holes that are not predrilled.



The bottom three holes on F-709 on each side are not drilled.  I marked their position through the holes on the skin so that I can determine where to flute.  You can see that this area will need some significant fluting.



I then trimmed and fit the stiffeners and then put on the forward skin.  One final rib is inserted on the top skin between F-706 and F-707 as well as a gusset plate (where the numbers 479 are visible).



Finally, I match drilled the skins to the bulkheads and stiffeners.



Now that the skins were in place, I needed to drill the bulkhead gussets to the longerons.  Instead of peeling back the skins, I just climbed back into the tailcone and drilled the gussets in place.  For the F-706 bulkhead, I clamped a straightedge across the opening to ensure the gussets hold the two sides of the bulkhead perfectly in line with each other.



Finally, I clecoed the baggage floor back in place.



...and then clecoed and clamped the lower back wall of the baggage compartment in place.



Rear Baggage Wall

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I fit and drilled the lower portion of the rear baggage wall.  The top portion needs a radius cut in it.  After measuring for the center, I taped one of my sharpie pens to an old compass and adjusted it to 8.5" and marked the cut.  I then used some tin snips and a vixen file to trim to the line.



After laying out for the holes, I matched drilled it to the F-706 bulkhead.  It's unfortunate that the radius of the baggage wall doesn't match the radius of the bulkhead, but this is what the plans specify.



All of the holes need to be drilled for nutplates.



After deburring and dimpling the bulkhead, I dimpled the nutplates (the bulkhead is only 0.024", so I didn't want to countersink for NAS1097 rivets).  I then installed all of the nutplates that mount directly in the bulkhead.  I'm not installing the ones that also rivet to the baggage floor since I'm not ready to rivet that in yet.



The F-728 rib needs several nutplates where the wall attaches.  Since this is 0.040", I countersunk for NAS1097AD4 rivets.



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