Note that I implemented a longer nose than the "per plans" version. The longer nose has two compartments instead of one - so my hatch will be a different size and shape. Also, rather than use nutplates to secure the nose hatch, I wanted a more convenient way of opening/closing the hatch - so rather than use nutplates, I will use a custom hinge.
I started out by drawing out a shape I thought was reasonable (don't worry, I changed it a hundred times before I committed to the final one!)
I placed plastic wrap over the nose and laid up 3-plies BID over it. The plan was to make the nose hatch using the current nose top as a mold.
After cure, I traced out the final shape of the hatch...
I then built a frame over it using 2x1's (using Liquid Nails instead of Bondo; I find it easier to use since it comes in a calking tube, I don't have to mix it and gives me plenty of time to work with it).
After the Liquid Nails cured, I popped the hatch off the nose...
Placed it upside-down on my workbench and rough trimmed the edges...
I added more braces to make the assembly more rigid...
I also added more supports (using mixing sticks) to the outboard sides and centerline using a hot glue gun...
Ah, perfect! This really helped hold its shape on the workbench!
I then sanded the inside surface dull...
Sanded away all the shiny surfaces...
I then poured liquid foam over the inside surface.. took a few pours to make sure I had at least 0.5" thickness... after it cured, I used the belt sander to even everything out...
Much better... now I have to work on the edges...
In order to fine tune the inside of the hatch, I needed to know exactly where my opening was going to be... so I turned my focus to that...
I drew a cutline 0.7" inward... this will serve as the water-seal all around the nose hatch...
For the forward lip, I used a dremel cutting-wheel for better accuracy...
Taaaa-daaaaa!
Ok, now to mill out all that foam underneath! Taking out the BIG GUNS for this job!!
Slowly but surely, I was able to mill out all the foam...
Now I had to smooth everything out...
Using a sanding drum worked great for the meaty parts...
I had to cut out a notch in the top portion of the F1-3 bulkhead... since the hatch has some thickness to it... I marked it and cut away...
Notice the curve on top of F1-3...
I placed an LED light inside of the compartment and placed the nose hatch in place...
This allowed me to see how close I was getting to the edges all around...
I would then take the hatch back to the bench, and with a dremel wheel sand a bit more foam off the edge...
The inside foam is starting to take shape!
I also made sure to bevel the edges to have a smooth transition for the inside glass...
With the inside surface all prepped, it was time to glass the inside surface of the hatch... I started out by patching the foam voids with dry micro, then painted plain epoxy around all edges for a good glass-to-glass bond...
Slurried the foam surface...
Then 3 plies BID....
After cure, I trimmed up all the edges...
With the inside surface glassed, it was time to remove the 2x1 bracing...
Liquid nails is tougher than bondo, so I use the multi tool to help release it...
It leaves a bunch of blobs, but these are easily sanded off with a palm sander...
That's a nice looking hatch! (never mind the edges... I did a rough trim and will cut it to its final shape later)
Now to finalize the inside of the compartment... I sanded all the surfaces smooth, used a dremel to apply a flox corner around the entire perimeter of the hatch opening...
Made sure to file away any micro for a strong flox bond...
Also prepped all the existing glass for a good glass-to-glass bond that will overlap...
The forward nose compartment floor needed some attention...
So I cut out a floor panel out of 1/4" high density foam...
I poured liquid foam into the existing uneven compartment floor, and placed the nice new clean panel into position. The idea being to weigh it down in place and the expanding liquid foam will fill in all the uneven gaps below it. I now have a perfectly flat even compartment floor! Turned out great!
Here's the aft face of the arch... this surface will remain un-glassed for now until I figure out how I want to close out the canard/elevator torque tubes...
Notice how all mating surfaces are prepped... floxed corners around the entire perimeter... all foam has been sanded smooth... just about ready for glass!
Ok, lets do this! I cut enough BID glass to make sure I had at least 2 plies for each surface... making sure to overlap at least 1" with any section...
I painted plain epoxy inside all flox corners and applied flox all around (I worked the aft nose compartment first... and the forward nose compartment the next day to divide the workload)
I then slurried all foam surfaces... I mixed the slurry on the drier side to help keep it from oozing down the walls...
I also painted plain epoxy to the mating glass surfaces below the foam side pillars..
One section at a time, I slowly installed 2-plies BID all around the compartment...
I should note that I also installed 3"x5" trapezoid sections to the armpits of the arch to reinforce the corners...
Here's a better shot of the "armpit" of the arch...
After cure, I trimmed all the overhang...
Now to glass the forward compartment...
Sanded all the foam smooth, prepped the flox corners, etc...
Here is a shot looking forward and up at the F-7.75 bulkhead ... notice how I left a good 0.7" lip all around for a strong glass-to-glass bond... as the lip makes its way around to the sides, it transitions back into a flox corner...
Again, I made sure I had 2-plies BID on all surfaces... including the compartment floor...
After cure, I trimmed everything up... looking great!
It took a bit of thinking.. and this is why deviating from plans is so time consuming... you have to come up with all the details yourself and figure out how to make it work...
I started out by making a hinge out foam to test the dimension/geometry and see if the hatch would clear the opening... I tested 3 different foam hinge geometries before settling on the one I felt confident enough the geometry would work... and finally cut the real hinge out of the expensive 2024-T3 1/8" thick plate.
I also had to come up with a way to bolt the hinge onto the F-7.75 bulkhead. I cut a small plate out of 1/4" birch plywood... and made two brackets out of 1"x1" extruded aluminum...
Installed the t-nuts to the plywood plate...
I then realized I would have a difficult time installed the plate.. how could I keep the plate from sliding down during cure? So I made a small toothpick diameter hole on the centerline of F-7.75...
And drilled the plywood plate to slide a toothpick through it...
Look ma, no hands!!! Taaaa-daaaa!
I prepped the surface for bonding...
Plugged the t-nut threads with plastic wrap to keep flox and epoxy from getting in...
Painted plain epoxy to the F-7.75 bulkhead...
Painted the plywood plate with plain epoxy...
Pancaked flox to the backside of the plate...
And installed it onto F-7.75... using the toothpick as a locating pin...
I then prepregged 5 plies of BID on the bench (approx 6"x5"), and installed the prepreg, using a brush to remove any air bubbles...
After cure, I opened up the t-nut threads and removed the plastic wrap...
Taaaaa-daaaaa! Brackets installed!
I knew the brackets had to be x-distance apart based on the brackets that were installed onto F-7.75... so I drew the hatch centerline... and then measured half x distance from the center line...
I know had the slits marked of where the hinges needed to be installed...
Using the multi tool... I cut the slits...
I then cleaned up the hinges and drilled a bunch of holes for the flox to bite...
I used the dremel to mill out all the foam... all the way down to the glass on the other side for the flox to bond to...
I then installed the hinges to the brackets... and put a bunch of foam blocks to lift the hinges into position...
Notice the 2x1 block at the very top... I cut slits into the 2x1 block to keep the perfect spacing between the two hinges (same spacing I cut the slits into the hatch)...
I played with the foam blocks until I had the hinge height such that it would barely touch the hatch's top skin (in other words, have the hinge fit into the hatch slit.. and go deep into the slit but not touch the glass skin on the other side)...
With everything prepped, it was time to bond the hinges into the slits for good! I mixed up flox and filled the hatch slits..
I then placed the hatch into position, pressing the hatch to force the hinges into the slits. I let it cure overnight and hoped for the best. The next day, I opened the hatch...
Worked great!!! The 2x1 did get stuck to the hinges from a bit of flox that oozed down, but that was easily knocked off...
I uninstalled the hatch from the brackets... took it to the bench and used a dremel to clean off all the excess flox around the hinges... I also prepped the surrounding surfaces to install some glass plies over the hinges...
With everything prepped, I installed flox fillet along the hinge edges.. and filled the holes to give the glass something to bite to...
I then prepregged 2-plies BID at 45 and installed it over the hinge slit... peel plied the edges for a smooth transition...
The next day, I cleaned everything up...
Taaaa-daaaaa! Hinges are installed onto the hatch...
Spent a little bit of time sanding / fine tuning the hatch edges...
And there you have it.. the nose hatch is complete! The step between the hatch and the fuselage will get filled during the finishing phase. Also, I will install a latch mechanism later on...
No comments:
Post a Comment