Project Update

Hey Guys,

I am still currently working the bottom cowling install to ensure its interface with the lower aft fuselage/hell hole is dialed in. The convergence of bottom cowling and bottom fuselage is slowly in progress and I figure both should be completed shortly.

I’ll then focus on the Hell Hole area to create a functional and usable hatch as well as install the belly RAM air scoop. 

While the fuselage is inverted I’ll also press forward to knock out a number of other things, including bottom strake-to-bottom wing intersection finishing and main gear leg-to-fuselage interface. 

I expect this bird to be inverted for a few more weeks before it gets flipped back upright to close out the strakes with the top skin install.

At that point it will be on to the winglet/rudder install (Chapter 20).  Then engine and top cowling install, finish and prime/paint.


Chapter 23/24 – Bottom cowl flange

I started off today by removing some of the hot glued popsicle sticks securing the bottom cowling’s left side.  I then went ahead and marked and drilled out the first of 2 CAMLOC holes.

I then pulled the peel ply on each side, trimmed the left cowling mounting flange and then installed the Skybolt (CAMLOC) receptacle.

I then re-mounted the bottom cowling, marked and drilled out the bottom CAMLOC hole (top hole in these pics, as situated) and mounted another Skybolt lightweight stainless steel receptacle.

I’ll note that I’m using 2 CAMLOCs on the left side for a couple of different reasons.
First, the left side cowling is noticeably bowed on this side and I’m attempting to straighten out the cowling side by pinning it in place in 2 spots vs only one.
Secondly, the area conducive to mounting CAMLOCs is more hospitable on the this left side than it actually is on the right side…. and that all has to do with the curve at each firewall “corner.”  The curve on the left side actually starts lower (higher in pics) than on the right side, so there’s more room to add another CAMLOC receptacle.

I’ll also note that I mounted these 2 CAMLOCs at the same spacing as the strake-cowling horizontal ones: 3.3 inches apart.

Although I grabbed a shot of the cowling installed and secured on the right side (again, left side when inverted) before, I grabbed another one here with the opposite vertical side wall secured by the 2 CAMLOCs.

Here’s the left vertical side secured by 2 CAMLOCs.  As you can see, the cowling’s bottom edge matches up fairly well the aft fuselage/firewall flange.  What’s a bit more difficult to tell is the gap on each corner that will need to be worked to some degree after all the CAMLOCs are in.

I then aligned the cowling’s bottom edge with the aft fuselage/firewall flange before securing the 2 sides together with hot glued popsicle sticks.

Then, just as I did on both the right and left vertical sides, I laid up 5 plies of BID to create a new mounting lip along the very bottom horizontal edge of the bottom cowling.

I then peel plied the layup and left it to cure overnight.

Tomorrow I plan on installing a CAMLOC –one each– at the very outboard edge of this freshly added flange.  Mike Melvill used 4 CAMLOCs along the bottom edge here, but due to clearance with the RAM air canister (I’ll discuss tomorrow or day after) I will not be installing the middle 2 CAMLOCs on this flange.

Chapter 23/24 – Balancing the egg

I started out today by removing the bottom cowling –after extricating the hot glued popsicle sticks from the surface– and checking out the right side bottom cowling vertical 5-ply BID mounting flange I laid up (under duress!) yesterday.

It looked good so I pulled the peel ply and then immediately marked a line 1.2″ from the edge of the stock 1.6″ cowl lip.

I then trimmed the right side vertical cowling mounting flange and hit the edges with a sanding block.

I then set the cowling back into place and ensured the edges were tight against each other at the aft fuselage/firewall to lower bottom cowling junction.

I then drilled a hole for a single CAMLOC on the sidewall, that will sit a couple of inches below the bottom edge of the armpit air intake scoop.

I then removed the bottom cowling and got to work installing the CAMLOC/Skybolt receptacle.

Here we have a lightweight stainless steel fixed Skybolt (CAMLOC) receptacle installed.

And a shot from the inside of the mounting flange.

I then replaced the bottom cowling and secured it with all the hardware to check the fit and integration of my latest installed CAMLOC . . . all looked good at this point.

One minor issue I have, probably more cosmetic than anything else… although there might be a slight drag penalty, is that my fuselage is a lot more rounded than a stock fuselage, looking at it from either top or bottom.  This means that the sides of the cowling tend to match a traditional straighter-sided fuselage shape vs my rounded fuselage shape.  It reminds me of how hard-boiled eggs are served in those fancy egg holders, the egg obviously a rounded shape sitting atop a squarer shaped object.

Not surprisingly, this creates a small depression, if you will, at the junction of the aft fuselage/firewall to the front lower edge of the bottom cowling.  It’s not horribly obvious or any type of challenge when the cowling sidewall is straight, as it is on my right side cowling.  As a point of note, I will mitigate this offset angle depression as best possible when I micro-finish the fuselage for paint.

But when the cowling has a vertical bow to it, it makes this offset intersection angle even more pronounced…. thus requiring a few extra popsicle sticks and hot glue to help “flatten the curve” and better align the lower left vertical side of the bottom cowling to the aft fuselage/firewall.

After determining that my cowl-to-fuselage junction was acceptable, I then laid up my added 5-ply BID cowling mounting lip from the firewall face, across the inside of the original stock 1.6″ mounting flange, to then overlap onto the inside taped cowling edge a minimum of 1.2″.  At the corner of the firewall and 1.6″ flange I added a nice flox fillet, just as I did on the right side, before laying up the glass.

I then peel plied the layup and left it to cure overnight.


Chapter 23/24 – Better than expected…

Well, I have to admit for all my whining and crying in my last post, that once I pulled the peel ply and removed the cardboard forms and tape I was pleasantly surprised with how well the stock plans aft fuselage/firewall flange aligned with the front edge of the bottom cowling.  Not perfect, but again, way better than I expected.

I guess my oft cited phrase, “It’s better to be lucky than good!” held true in this case.

With nearly all the tape and forms removed, I grabbed this shot from inside the bottom cowling before I removed it.

And these shots once I cleaned up the edges of the stock plans 1.6″ cowl-mounting flange that encompasses the bottom perimeter of the firewall.

I had planned on glassing the added vertical mounting flanges on both sides together, but then decided to dial in the straighter and more aligned right side first (left side when inverted), then after installing a CAMLOC and locking it down, move to the left side.

The left side bottom cowling has just a slight bow in the vertical sidewall that will be easily removed when pinned in place by a CAMLOC fastener, but will need some extra attention while the added vertical lip is glassed.  Note that in the pics above the left vertical flange (on right in pics) is not bowed, and I did not mimic the natural shape of the cowling vertical sidewall.  I would estimate that the max apex of the bow is 0.150″.

Using hot-glued popsicle sticks, I then locked in the alignment of the newly glassed stock fuselage-side flange with the front edge of the bottom cowling on the left vertical wall.

I then wet out my 5 plies of pre-pregged BID and laid it up in the inside corner. I then peel plied the layup.

Besides wanting to dial in the cowling install one step at time to make sure all the fasteners play nicely with each other, another reason that it was good I didn’t glass both vertical flanges at the same time is that a huge storm came through my area, replete with torrential downpours, that not only flooded about a third of my shop –right after I mixed up a big batch of epoxy– but also knocked out the power for over 3 hours.

I ended up laying up these 5 plies of BID by kneeling on 2x4s so as not to get wet and using my phone’s flashlight wedged into the wing root to light up the work area.  Obviously not the best environment for layups, but nothing important got wet and I was able to get ‘er done!

Tomorrow I plan on installing a CAMLOC into this side and then glass the left vertical cowling wall mounting flange.  After the vertical sides are secured into place I’ll then move on to configuring and mounting the bottom horizontal flange.

Chapter 23/24 – Close . . . but?

In the military after an exercise or some significant event we would carry out what we called a “hotwash,” or a review of all actions to see where we could improve and gain efficiencies.

I can tell you that my mental hotwash on today’s 5-ply BID layup to bridge the gap between the aft fuselage/firewall to the front edge of the lower bottom cowling was not overly flattering or pretty . . . with a lot of woulda, shoulda, couldas thrown in there as well.

(sigh) Well, as we know: hindsight is 20/20…

The goal was to get the original plans 5-ply BID cowling lip glassed into place with the glass even in elevation to the front edge of the lower bottom cowling.

The method to reach this goal was taping up some flexible cardboard pieces and then inlaying them in the gap betwixt firewall and cowling front edge.  Thus, I taped up the cardboard and taped it in place from the inside.

My first mistake was that I didn’t test the final configuration of the form, since I left the aft side un-taped in order to get the peel ply slid into place.  Although once the peel ply was in place and the forms taped up, it all still appeared to be acceptably good for the layup.

The problem is that as the layup of the 5 plies of BID progressed, the tape securing the tape covered cardboard form just was not securing the form as tightly or as closely to the inside of the cowling as I needed.

After the layup I consider ripping it all off and trying another approach. But then as I assessed it I figured that it is fairly close and that I would simply call this yet another iterative process, and this would now be step 1 of how many steps? . . . TBD.

But it is a step in the right the direction.

It’s just not the single step I had hoped for.

Here’s a look at the inside of the cowling and firewall, with the copious amounts of tape and even a clamp employed in spreader mode to help keep the form pressed up tightly against the cowling… but not too tightly to deform the cowlings bottom shape.

So tomorrow will begin the mini-journey, and yet another iterative creative task, to get the firewall cowling flange dialed in so that I can get the subsequent added flange glassed in to allow me to secure the bottom cowling to the aft fuselage/firewall.

Chapter 23 – Bottom cowl bling

I started off today pulling the peel ply from the 5-ply flanges I just laid up for the required mod for the new Melvill CF cowlings.

I’ll reiterate that I’m essentially copying how Mike Melvill installed his new style CF cowlings, first by creating the original stock plans cowling lips, then modifying them to convert them into exposed flanges verses lips that simple secured the front edges of the cowlings, only on the inside of the lips.  The wing interfaces and configurations are essentially the same.

Then, before I popped off the hot-glued popsicle sticks, I determined where my front outboard corner CAMLOC would be located and drilled a 1/8″ pilot hole.  Admittedly I would have preferred it a hair more outboard —by maybe a 1/4-3/8″— but when I laid up the glass on the strake & CS spar for this new flange I errantly went off the firewall side first rather than starting at the wing side.  With a healthy flox fillet created along the junction, I didn’t want to mess all that up by pulling and relocating the glass outboard…. so it is what it is.

Here’s the 1/8″ pilot hole coming through the top corner popsicle stick.

I then installed a cleco in the corner and started removing the hot glued popsicle sticks.

I eventually got all the hot glued sticks removed from both sides.  The reason I didn’t drill a pilot hole on the right side (as situated) is that inboard corner needed to come outboard by about 1/16″ (or so I initially thought… see below).

When I removed the bottom cowling to trim the left cowl edge about 1/16″, I then checked out my freshly glassed flanges.  Here we have them with the top peel ply still on.

I then promptly ripped off the peel ply . . .

And then trimmed up the edges.  I’ll note that I was shooting for a 1.2″ wide flange on each side, but because of mental math deficiencies in calculating the required width of my glass, I ended up with barely an inch on each side… workable, but not optimal.

After resetting the bottom cowling back in place, I then checked the corner alignment again on the left side (right as situated inverted).  My 1/16″ wasn’t enough and I still needed at least another approximate 1/16″ trimmed off to bring that corner outboard in line with the corner of the strake/fuselage intersection.  My closest guestimate is that I shaved about 5/32″ total off the outboard edge of the cowling to get this inboard corner aligned.

I’ll note here, since I don’t show it in the pics, that I’m not trimming the entire edge of the outboard cowling side, but rather just the front 6-8″… enough to allow the front edge of the cowling to sit flat against its mounting flange.  I did this on both sides, to be clear.

Thus, once the outboard corner was good, based on the alignment of the inboard corner, I then drilled a 1/8″ pilot hole and secured the left side cowl front corner with a cleco.

The thick black line you can see in the pic below and in many of the previous pics is the outboard edge of the armpit intake scoop that I had previously quickly mocked up with a 3/4″ foam spacer with the sidewall to find this edge.  Since there is also a required 3/4″ gap between strake bottom and intake scoop —which provides a hair more clearance for a slightly angled screwdriver— I skooched the inboard CAMLOC in a bit so it is basically centered on this line.

With my inboard and outboard front cowl horizontal edge hardpoints located, I then simply split the difference (3.3″ each side) for the middle hardpoint.

I then drilled out the outboard corner pilot holes to install a CAMLOC.

Here we have the CAMLOC receptacles mounted on the flange in the front outboard corner for the bottom cowling.

I’ll digress a bit for a brief philosophical building preference discussion.  I know some builders prefer to cleco everything up before then installing the hardware.  Personally, after experience with the aft nose/avionics cover, I like to actually get the hardware installed one point at a time (here, both sides concurrently) since there are minute shifts that happen when installing the hardware, and I want to catch/gauge/note those as they occur and adjust accordingly.

Moreover, on the front edge of the cowlings I’ll be using primarily fixed CAMLOC/Skybolt receptacles, whereas on the wing junctions I’ll be using all floating receptacles.  Since I failed in taking any hardware pics of the inside of the flange, I’ll note that I am installing the Skybolt lightweight stainless steel fixed receptacles here.

After ensuring my bottom cowling alignment was good, especially that it was still centered on the aircraft centerline (it was) I pressed forward with the next hardware install… moving inboard.

Again, I know that I quite often do things differently than other builders, but at this mid hardpoint location I’m installing a K1000-3 nutplate. I’m doing this at a point close to the center of each forward cowl lip on the advice of Wayne Blackler, who noted that the combined internal engine compartment pressure and external on-rushing air pressure can be enough to overwhelm a CAMLOC and pop it free, or worse out.

To secure the front cowl lip in order to avoid this —especially since one of the big changes Mike Melvill made was to have the front cowl lip rest ON, not under, the strake/fuselage cowling flange— I am simply installing one screw on each front cowl lip, both top and bottom. Obviously this means to remove both top and bottom cowlings I’ll have to contend with a total of 4 screws. Not bad at all for a little bit of insurance in my book.

Again, I then double-checked the fit of the bottom cowling with the screws installed.

I’d be remiss if I didn’t note that the screws I have installed here are NOT the ones that will be installed on the flying airplane… much like the clecos will not be left in place either!  These screws have a hex head and can be either driven by a phillips screwdriver, a hex head screwdriver, or a socket.  I’m not going to mess around with driving countersunk screws in and out repeatedly during the building process when I can TEMPORARILY use these screws/bolts instead. They are simply way easier to use. I know this is a difficult thing for all you OCD types that have to look at this egregiousness, but I’m not going to suffer through a major building PITA to appease the sensitivities of builders/viewers who can’t grasp this concept!  There, rant over.

I then moved inboard to the last hardpoint on the bottom cowling’s front horizontal strake-mounted interface to install yet another CAMLOC each side.

The bottom cowling centerline is still just about dead even with the aircraft centerline, so everything is still tracking good at this point.

Tomorrow I’ll start work on the lower center bottom cowling install by first glassing the original 1.6″ lip off the aft fuselage and around the firewall to intersect with the bottom cowling’s front edge.  After that I’ll then add the modified flange to allow the “U” section of the bottom cowl to be secured to the fuselage/firewall.

Chapter 23 – Fiddle-dee-cowling!

I started off today spending a good hour pulling peel ply, trimming glass and cleaning up the aft lower fuselage skin layup.

I then spent a good hour-plus dialing in the bottom cowling alignment.  With the firewall and surrounding glass now a known constant, I was better able to dial in the alignment of the lower “U” front edge of the bottom cowling.  As my buddy Dave Berenholtz so astutely pointed out, these cowlings are finicky because any adjustment in one area has a ripple effect and can throw off previous alignments.

Such was the case here to a minor extent.  I had to trim a slant on the left front horizontal cowling edge (top of first pic below) about 0.1″ off the front outboard edge, converging to a zero point on the inboard corner.  This was due to pulling the sides of the center “U” section (lower fuselage-interfacing part of bottom cowling) inboard just a bit more to better align the cowling with the firewall edge.

All my fiddling caused the alignment of the aft boat tail to come off-center about 3/16″. So this slight trim shifted primarily the aft center of the cowling to the left (right as situated inverted) near to perfect center.

In addition, I had taped up the inside edges of the cowling where it intersects along the wing root to mark the cut line.  To ensure I have some wiggle room when I integrate the top cowling install with this bottom cowling, I kicked the line outboard another 1/8″ on the Trailing Edge side.  It then converges with the original line at each respective front corner, which once the sides of the lower “U” section of the cowling are set will in turn fix these front corners as a constant point as well.

With the cowling having a bit of flex to it, you can see where moving the aft edges outboard just a hair, and then setting them in-between the fixed wing roots, will cause the center of the cowling to bow in the only direction it can: downward (up in this orientation) … giving just a bit more room for the engine flywheel if need be.  While installing the upper cowling I can always trim more of the bottom cowling side edges away if I need to, since it’s always easier to cut away then add back.

I then got into the ‘arts n crafts’ portion of the day by hot gluing popsicle sticks to both the strake surface/original 1.6″ stock cowling flange and the horizontal front edge of the bottom cowling on each side.  This will keep the surfaces of the cowling and original 1.6″ cowling flange acceptably level as I add the new extended flange in place “under” the front cowl lip via laying up a 5-ply flange underneath it.

Which is what I did here.  Apparently my math skills are slipping since I should have had, or preferred rather, another 1/2″ of glass down onto the face of the CS spar.  Still, I have a good 1/2″ with 5 plies of BID, a robust flox fillet as well as 1.6″ of glass-to-glass bonding with the stock flange I created earlier, so I’m confident this will be plenty strong… so no re-cutting 10 plies of BID!

I then peel plied the exterior (internal face) of the layups (the taped edge of the cowling got a ply of peel ply as well) and left these new flanges to cure overnight.

Chapter 24 – Aft fuselage glassed

I started off this morning spending a couple of hours slogging through the sanding and final shaping of the hardshelled aft lower fuselage and hell hole cover.

I then spent about another 45 minutes prepping the remaining glass surfaces of the fuselage for glass.  I also installed red plastic NPT plugs into the fuel drain points to protect the threads from any errant epoxy.

I then spent a couple more hours figuring out the glass configuration and cutting the glass.  My layup schedule is 2 plies of UNI that meet –but don’t overlap– at the centerline, covered by 2 plies of BID.  The BID plies overlap 8″ in the center to create a stronger 2″ edge along the 4″ wide center opening which is where the RAM air scoop will get mounted.

I then laid up the first ply to go on which was the UNI.  The original edge of the UNI cloth is situated along the fuselage sidewall and angles up (as situated… technically down) the further forward it goes.  I point this out to show that there is a slight angled bias to the UNI fibers just for a little extra strength (vs just straight front-to-back). And again, it’s 2 halves of UNI that intersect along the centerline.

This single ply of UNI goes from just aft of the landing brake to the firewall, covering both the exposed Kevlar and all the added foam making up the added aft lower fuselage structure and the hell hole cover.

Here’s a closer shot of the first ply down, the UNI.

I then laid up the 2 overlapping plies of BID.  I laid up the left side (as situated, technically right side) first and have to say it laid down without as much of a fuss as the right side… which just required a bit more machinations to get the gear seam overlap in line.

After the actual layups were complete, I then spent a decent bit of time peel plying all the edges and the seams.  All told from start to finish this layup took over 4 hours.

With the peel ply in place you can see that the plies of BID just covers the added pour foam on the bottom of the fuselage (not the Kevlar), but then covers more of the fuselage sidewall —actually overlapping almost an inch onto the bottom strake at the corner.  Thus, these layups cover the exposed Kevlar, which gets a bit fuzzy when you sand it… not something you want when you go to micro finish the surface for paint.

Tomorrow I’ll pull the peel ply and clean up this layup.  Then I’ll start back work on both the bottom cowling install and the cowling-to-firewall interface.

Chapter 24 – Datsa Hard Shell!!

I started out today making up another form to add some pour foam to the area immediately above the left gear . . .  a bit more aft-oriented towards the firewall.

After the foam cured I started dismantling the form . . .

until the foam was bare.

I didn’t get any intermediate shots, but I then spent the next few hours doing a couple of minor pour foam fill additions to some decent sized divots in the foam surface.

And as you can clearly see, I also spent a good bit of time sanding and dialing in the shape of the aft lower fuselage and hell hole cover.

Moreover, I have to say I’m fairly pleased with how the minor firewall extension on the lower left corner and the subsequent foam fill turned out.

Once I got the shape of the aft lower fuselage and hell hole cover dialed in, I then copied my buddy Dave Berenholtz in hardshelling the foam in this area before glassing it.

I don’t normally employ this technique, but I thought it would be a good way to minimize the surface imperfections in the foam and also I wanted to try it out on something to get at least one experience of hardshelling before I finish this bird.

I’m sure I may get some gasps and some thoughts of “that airplane is doomed to fall out of the sky now!” but for the hardshell I used West epoxy.  I will resume with MGS when it comes to glassing the skin on this area.

My version of hardshelling was a simply 2-step process: I first applied wet micro just as if I was glassing the foam surface, and then I went over that with micro about as thick as peanut butter, maybe just a hair lighter on the consistency.

I then left the micro hardshell to cure overnight.

Chapter 13/23/24 – Firewall re-trim

I started out today by setting the bottom cowling back onto the plane and then figured out its install configuration.  Since the bottom cowling skews to the left slightly, I pushed it from the left inboard about 1/8″ to find the “sweet spot” that provided the best shape for it to be mounted.

This 1/8″ really does make a difference in shape and definitely impacts the interface and shape of both the lower firewall and aft bottom fuselage, and especially influences the shape at the bottom corners of the cowling.  Moreover, it’s just enough movement to get a positive effect on the shape of the cowling while still being within the natural free movement of the cowling… so no excessive force to get the cowling into that configuration.

I then slowly captured this inset position of the bottom cowling around the edge of the firewall by using a magenta Sharpie to mark the latest cowling interface line on the firewall aft face.

I then went through a myriad of iterative cycles of trimming and shaping the firewall while removing and resetting the bottom cowling back into place.

Here are the lower bottom cowling-to-bottom fuselage corners after the firewall was shaped.

And the specific area that needs to be reworked.

The goal here is to get the firewall trimmed to set just a hair inside the cowling’s inside edge… so that when the 2 plies of aft bottom fuselage covering glass is laid up, followed by the 5-ply 1.6″ original plans lip then laid up over the 2 plies around the perimeter of the firewall, that it is very close to matching the exact front edge of the bottom cowling. I’ll then later create the added mounting flange as Mike Melvill did to mod his existing stock cowl mounting lip to accept this new cowling.

After a half-dozen more sanding sessions on the edge of the firewall, and happy with the interfacing elevation of the firewall, I then taped up the front edge of the bottom cowling and made my tick marks about an inch apart… the marks of course being 1.6″ from the aft firewall face.

I then played ‘connect the dots’ and created a solid line 1.6″ from the firewall, the cut line for trimming the front edge of the cowling.  Admittedly, to intersect the existing trim cuts of the horizontal cowling front edges I had to bring this line forward on the sides so that the gap where it converges at the strake/fuselage corner is only about 1.4″ wide.

I then carefully cut along the line to give the bottom cowling front edge a trim.

Here we finally have the entire front edge of the bottom cowling trimmed up and ready for install.

I then set the cowling back into place on the bird to check its fit.  All looked acceptably good at this point.

A shot from the back with the bottom cowling set in its future install position.

With the front edge of the bottom cowling trimmed, and the firewall also trimmed in an acceptable interface alignment with the bottom cowling, it was time to add some more pour foam to the aft lower left fuselage/hell hole area to allow for a straight line between the mid-fuselage area to firewall edge, considering I had just added to the firewall in that bottom corner.

I determined my low points in this area and built a trough around it.

If you look at the far end in this pic you can see the new added edge of the firewall peaking up just at the back wall of the pour foam form trough.

I then mixed up 2 batches of pour foam and poured them into the trough, attempting to be as judicious as possible to get an even spread of foam… I’m looking for a slight added depth of foam here across a wide area, not a deep bit right in one spot.

After a good hour or so of cure, I then pulled the trough form walls off this new round of added pour foam.

Here’s another shot from the side.

It was getting late so I called it for the night.  Tomorrow I’ll shape and level this added pour foam, probably do a few more spot fills (one being below the gear leg above [as situated] along the fuselage sidewall).  I then plan on getting the entire aft lower fuselage and hell hole area shaped and leveled to allow me to hard shell it for glassing within the next 2-3 days.