Saturday, June 15, 2024
Home » How To's » RC Kits: The Great Planes Ultra Sport 60 … Building The Turtle Deck

RC Kits: The Great Planes Ultra Sport 60 … Building The Turtle Deck

By Gary A. Ritchie

In this column we will build the turtledeck – the portion of the upper fuselage that lies behind the cockpit. That will set the stage for designing and building a removable battery hatch that contains the canopy.

After the glue dried on the turtledeck formers, the ¼” balsa stringers were positioned in the notches at the upper corners of the former, glued into place with Deluxe Speed Bond and clamped to dry.

Ignore the section in the instruction manual called “Fit Fuel Tank and Fuelproof Tank Compartment” (Page 25, Steps 1 – 6) and be grateful that you will not have to “fuelproof” this electric powered airplane.  Begin at Step 1 of “Install TurtleDeck”. The first sentence contains a typo that can be confusing. The word “pans” should be “parts”. Find the needed formers and then sand them smooth around the edges. Glue them all in place as described in Step 1 and 2. Then glue the ½” square balsa stringers in place on top of the formers and sand the stringers as described in Step 4. I used Deluxe Speed Bond glue here because it dries relatively quickly but offers time to make adjustments (Figure 1).

Before the turtledeck sides were glued in place, 1/8” x 1/8” balsa strips were glued along the tops of the fuselage sides 1/8” in from the edges (white arrow). These served as shelves against which to glue and pin the turtledeck sides.

Following the illustration below Step 5 (Page 26) construct two turtle deck sides and sand them carefully along their bottom edges to assure that they are straight. I added a step here to make it easier to achieve a good joint between the turtle deck sides and the fuselage. This involved cutting several thin strips of 1/8” square scrap balsa and gluing them along the inside edges of the fuselage sides (Figure 2). They are offset in from the fuselage edges by 1/8”, providing a

Each turtledeck side was glued in place along the shelves and fuselage sides using Deluxe Speed Bond glue, and then pinned and taped in place. This photo shows the right side.

shelf against which the turtledeck sides will be glued and pinned. Glue and pin one side in place, against these strips, and tape it down securely with masking tape to dry (Figure 3). After it is fully dried, go ahead and glue the other side in place, and then pin it and tape it down also.

After the glue dried, the turtledeck sides were wetted with water, gently curved inwards by hand, and then glued along the formers and stringers. Then they were securely held in place to dry with masking tape.

Once these joints are fully dry and both sides are glued in place, wet them with water, apply glue to the formers and stringers, pull the sides up tightly and tape them in place. The tape will not stick to the wet balsa, so the tape strips must run most of the way around the fuselage in order to hold tightly (Figure 4). The instructions suggest using thick CA for this step. I would highly recommend slow curing glue such as Deluxe Aliphatic Resin, which will give you more working time, is very strong and sands well.

After the glue was thoroughly dried, the tops of the turtledeck sides were carefully sanded flush with the tops of the formers and stringers.

I let this structure dry overnight then removed the tape and trimmed the sheeting flush with formers F-3A and F-6A (Step 9, Page 26). Then, using my 2” wide sanding block with 80 grit paper, I carefully sanded the top edges of the sheeting until they were flush with the stringers as shown in Step 10 and in my Figure 5. This will bring you to Step 11, Page 27. Before gluing the ½” x 2 3/8” by 26” turtledeck top in place, you may want to bevel its forward edge – it’s easier to do it now than after the top is glued on. Then draw a centerline as shown below Step 11.

The ½” thick turtledeck top was glued in place with Deluxe Aliphatic Resin, then taped and secured with rubber bands to dry.

Finally, liberally apply Deluxe Aliphatic Resin, or another type of slow curing glue, to the tops of the stringers and formers and then glue the turtledeck top to them. Center up it up before the glue dries. Pinning it in place is not practical here because the wood is too thick. So I taped it in place with masking tape and further secured it with rubber bands. I placed them over the tape strips so they wouldn’t dig into the wood and leave marks (Figure 6).

Before sanding the turtledeck top, the fuselage assembly was secured in a Workmate. The surface of the Workmate was covered with several sheets of cloth to protect the fuselage.

Mark the center lines on F-6A and along the top of the turtledeck then fasten it securely in either a vice or a Shop Mate (Figure 7). If you have a small hand razor plane this will speed the sanding process up. Also, if you trust yourself not to get too aggressive, you can also rough it out with a power hand sander (Figure 9). This is what I did and I found that it worked very well. Be sure to wear your respirator because this thing really generates a ton of balsa dust. Then finish it with your block sander and 50 or 80 grit paper.

A hand power sander with #80 grit sandpaper was used to rough sand the turtledeck top. Be sure to use a respirator when sanding balsa.

On the top of Page 27 the HINT suggests sanding the upper turtledeck with a strip of fine sandpaper. This is a good idea. To do this I held the fuselage in my Shop Mate and sanded the aft portion of the fuselage

Final sanding was done with a strip of #320 grit sandpaper while the fuselage was held tightly in the Workmate.

(Figure 9), then turned it around and sanded the forward part. This does a very nice job of smoothing and evening out the turtledeck.

With the turtledeck finished and the battery tray in place, I test fitted the battery in the battery hatch (Figure 10). It fit like a glove.

After the fuselage and turtledeck were finished, the battery was test mounted in the battery hatch.

That does it for this session. Next time we will build the removable hatch cover that will conceal the battery hatch and hold the canopy in place. We will go way off plan for this tricky build. For this you will need to pick up a sheet of 1/8” thick by 4” wide plywood.

Until then, remember to “take your time and enjoy doing a good job”.