FT Spitfire mods: MiG-3 hatch and foam turtledeck

When I bought this Spitfire speedbuild kit, I knew I wanted to take some ideas from the FT MiG-3 and implement them into it - specifically the foamboard top-loading battery hatch and foamboard turtledeck. Basing these upgrades on parts included in the kit made these changes a bit easier than I'd thought they'd be.

REAR TURTLEDECK

Since the 2 turtledeck formers are designed with cardboard sheeting in mind, the top curvature of these had to be trimmed down the thickness of 1 foamboard sheet. This is more easily done BEFORE gluing these formers in place. I left the tiniest bit of a notch at the base of the curved formers so that the foam from the turtledeck sheet wouldn't end up crushing inward beyond the sides of the plane, and to make them easier to glue in place with proper vertical position.

The foam turtledeck itself was based closely on the included posterboard turtledeck. I traced it out on some scrap foamboard (mind the foamboard grain direction!) and didn't bother making the tabs to go underneath the horizontal stabilizer - I knew that would be more trouble than it's worth.  Remove paper from what will be the inside of the turtledeck sheet, then start curling the foamboard sheet until it almost dry fits over the formers. During the curving process, the bare inside foam of the turtledeck will crunch down a little against the fuselage sides, making a line guiding you on where you'll need to remove the foam from the turtledeck so that it matches up with the sides. ONLY trim off the foam, leave the paper behind it.  It's going to hide seam between the turtledeck and the fuselage sides.

Once you've got a good dry fit without requiring much pressure, it's time to get gluing! I started on the left side, applying glue to the turtledeck where it will meet the fuselage side. You can also put a bead of glue on the bare paper that'll cover the seam and squeegee it out for a smooth cover.  The picture above was taken just before putting glue on the exposed side of the formers and at the top of the side of the fuselage.  Again, you can put a small bead on the bare paper to smooth the joint.

Smooth out the bare paper from the turtledeck side edges over the fuselage sides, trim away any excess foam from where the turtledeck meets the cockpit, and you're done!

BATTERY HATCH

This was a bit of work.  Unfortunately for sharing purposes, a lot of this I made up as I went (without taking many pics or documenting any measurements), closely basing this entire portion on what I learned from the MiG-3 build.  The first step was the top portion between the cockpit and the hatch area - created using the exact same technique as the turtledeck. The speedbuild kit comes with at least 2 formers for the front section of the fuselage ahead of the cockpit. First, trace one of them out (for use in making the battery hatch) and then trim each one down the thickness of 1 sheet of foamboard on the curve.  One of the trimmed formers will go right in the slot on the plans/kit at the cockpit front, the other you'll need to trim the bottom tab off of, and put where you deem necessary.  I chose an inch or so between these two formers.  Then trim a rectangle of foam to wrap over and cover the void between the two formers. Trim off excess foam, but not paper (to smooth the seem between this top and side of the fuselage). Glue in place. Don't worry about the two slots for hatch popsicle sticks for now.

Now you've got to decide where you want access to the power pod/battery bay, and where you want your hook to latch onto. I wish I'd documented where I made these cuts - if there's interest, I'll go back and add them to this article. Again, almost none of this was formal measuring. It's important to not cut too much foam away from the top of the fuselage, sacrificing some structural integrity. You've also got to pick a spot for the latch hook that's got enough foam beef between other structural points (fuselage sides, where the firewall meets the front, where your battery bay is, etc). I do recommend keeping the notches for the power pod intact to some degree for ease of alignment.

Grab some spare foamboard and sketch out the flat piece that will be the base of the battery hatch - bare in mind that it needs to be the width of a power pod (since foamboard will wrap over the top of the hatch to meet at the sides of this base).  Then create a spine for the hatch.  There's a subtle downward slope near the front that closely matches that on the top of the fuselage sides near the front. I really wish I'd taken more pictures of this part. What I did was make a long spine that I could score down the middle, fold in half, have the hatch hook halves meet, then sand the top of the spine to the desired shape.

Before gluing these spine halves, I recommend putting a tongue depressor or something between them, because the foam on this hatch hook will wear out.

NOTE: the space between the bottom of the hatch hook and the base of the spine needs to be the thickness of 2 foamboard sheets. Sorry I don't have dimensions on WHERE to make this hook, but again, I was really just kind of making this up as I went. Full disclosure: I messed up my first attempt at the hatch, got it right on the second one though.

From the front former you traced earlier, come up with the some former halves to help define the shape of the top of the hatch.  I just split the former in half, glued in place, and sanded. A lot.

Much sanding. You may notice a slight dip toward the front of the battery hatch. This is to conform to the way the tops of the fuselage sides slope just toward the front. This was achieved by scoring the top of the base and figuring this slope into the hatch spine.

Get a popsicle stick and snap it in half.  You can cut a small slit with your choice of tool for this to go through the rear of the hatch.  Slide the base into place and the popsicles will jame into the part you made earlier that's between the hatch and the cockpit.  Now, cut slits for them to pass through toward the cockpit. Once things meeting up pretty well, go ahead and glue down these popsicle sticks. Be generous with the glue and apply only to the area of the hatch that will be covered with foamboard sheeting.

Now the fun part: bending a sheet of foam around the top of this hatch.  By now, I'm sure you've got the hang of this process. I did use the posterboard cowling as a starting place (as well as where to place former halves in addition to  where to cut one slit on each side to accommodate the slight angle change).  I really wanted to mimic the broader, flatter, downsloping front of the cowl that the real Spitfire has.  I think it came out OK.

Start by gluing the foamboard sheet to one side of the hatch, then SLOWLY work it over until it closely matches the shapes of the hatch spine and formers without too much pressure. Then glue the sheet to the spine, then around to the other side.  If you have to, do this in front and back halves, since the shapes are a little different. Make sure that on these edges of the hatch, you're holding the things so that the foamboard sheet is bending more than 90 degrees, so it'll keep shape instead of wanting to shallow out at the edge. Again, once the plane tells you where to trim foam out, do so, but KEEP the paper intact to hide your edges. Trim that paper up a bit if need be, and I recommend making a lot of tiny cuts in the front of the top paper hanging off the front of the hatch, then hot glue it and use the table as your friend to curl those little fraying bits to the front of the hatch.

And there you have it! I hope this was helpful. This is my first go at an article like this. I'm posting it at the recommendation of a guy from the Facebook Flite Test Fans page.