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Aug 08, 2019, 06:57 PM
Jer. 29:11
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Other Parts


The horizontal stabilizer and elevator are each made of two layers of 1/4 in. foam. After laminating the parts, sand the outlines square. Then bevel both top and bottom of the stabilizer and the elevator, and round the leading edge of the stabilizer and trailing edge of the elevator. I used 3D printed tools [1 and attached] for these tasks but a sanding block works too.

[1] Foam Airplane Bevel Cutting Tool on Thingiverse

The optional wing-tip tanks are each made from four layers of 1/4 in. foam. The inner two laminations have cutouts for the wing tips. Make one left and one right tank. After gluing, sand the tanks to shape. I rounded the edges with a 3D printed sanding tool.

Note: Don't glue the tanks to the wing tips until after the wing is glued to the fuselage. Later when the ailerons are added, they'll need to be shortened so they don't interfere with the tanks.
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Aug 13, 2019, 05:50 PM
Jer. 29:11
jeffsch's Avatar
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Fuselage and Wing


The next step is to glue the wing to the fuselage. Here's where attention paid to lining up the fuselage laminations pays off. Trial fit the wing into the fuselage. It should be a snug fit. With the fuselage sides vertical, each wing tip should be the same distance from the table. On the second prototype, I needed to open up the wing slot in the fuselage, so I used the nacelles to hold the wing level while the glue set up.

You can hinge the ailerons before gluing the wing to the fuselage. Or after. Either way works.

The ESCs likely need extensions to reach from the battery bay in the fuselage to the motors in the nacelles. I chose to extend the ESC to motor wires -- they needed to be 12 in. Fish a lead through the channel in the wing for these wires; I used a small washer tied to a piece of dental floss. While you're at it, fish a second lead through the same channel. Use one lead to pull the ESC wires from the fuselage, into the channel, and out at the opening for the nacelle.

Before gluing the nacelles to the fuselage, use the other lead to pull the aileron servo extension from the nacelle through the channel in the wing and into the fuselage. And then route the ESC wires through the nacelle to the opening in the motor mount, and connect the motor. If you're comfortable running the motors up on the bench before the nacelles are glued, this is a good time to connect your receiver and a battery, power up the motors and aileron servos, and verify the connections.

When you're happy with everything, tuck the wires into place, and glue the nacelles to the wing.
Aug 17, 2019, 06:40 PM
Jer. 29:11
jeffsch's Avatar
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Final Assembly


The optional wing-tip tanks are easy to add at this point -- you just need to shorten the aileron to clear the tanks.

I recommend hinging the elevator to the horizontal stabilizer before gluing the assembly to the fuselage. You may wish to add the control horn for the elevator at this point -- on the prototypes, the control horn goes on the bottom, right side of the elevator. Dry fit the horizontal stabilizer to the fuselage with the regular care to align it properly, and then glue it into place. (I used a few small washers to hold the stabilizer level while the glue cured.)

If you want a rudder, cut out and hinge the rudder to the vertical stabilizer. And add the control horn to the rudder -- goes on the left side. Attaching the vertical stabilizer to the fuselage is a weak point in this design. For both prototypes, I added short lengths of round toothpicks -- half into the vertical stabilizer and half into the top of the fuselage -- and this strengthened the attachment nicely.

All of the pushrods are 0.039 in (1 mm) wire. To reduce flex for the elevator and (optional) rudder pushrods, there are two standoffs that glue into the fuselage sides as marked on the plans. There are some commercially-available pushrod supports that would work well; I chose to 3D print some supports (files attached).
Aug 17, 2019, 06:49 PM
Jer. 29:11
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Kits


Kits include four cut sheets of Model Plane Foam, three hotwire sheets of 1 in foam, and some small 3D printed parts. Kits are for $35. Send me a PM to order.

Kits are shipped in a box 36 in x 12 in x 3 in that weights 1lb 6 oz. USPS Priority Mail 2 Day should be $14.10.

3D printed tools are $2 each: corner sanding tool, KF airfoil tool, round edge sanding tool, and/or bevel cutting tool.
Aug 17, 2019, 06:51 PM
Jer. 29:11
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After reviewing similar models, I upgraded the spar to a 5 mm carbon fiber tube. The CAD file and PDF plans in the first post have not been updated yet. I'll update this post when they are.

28 Sep: Updated the CAD and PDF plans in the first post to the larger spar.
Last edited by jeffsch; Sep 28, 2019 at 10:53 AM.
Sep 03, 2019, 04:28 PM
Registered User
Just ordered the kit from Jeff. The beautiful thing about this plane is that it can also be civilian. I've sworn off "flying gun platforms" (warbirds), so here is my choice of livery, from the fleet of Air Spray water bombers. Note that "32" has a black rectangle above the tail number. It's supposed to be the same number as on the wing. I love the artist's reconstruction of the "nose art"; it's immaculate! (You should see the highly weathered original.) As Superman might say, "This looks like a job for Callie Graphics!"
Sep 04, 2019, 08:08 AM
Jer. 29:11
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@Jay B. Scott, that looks like a great color scheme!
Sep 04, 2019, 08:38 PM
Registered User
Jeff, what are you using to hinge the control surfaces? I can see that the ailerons are top-hinged, but I don't see any tape sheen. By the way, your paint jobs are immaculate and enviable, as always.
Sep 05, 2019, 08:10 AM
Jer. 29:11
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For both prototypes, the covering is the hinge. On the first prototype ("Stinky"), I used 1/2 oz fiberglass and water-based polycrylic.. The fiberglass goes over both parts, e.g., over both horizontal stabilizer and elevator, on both sides.

On the second prototype ("Alley Oop"), I used laminating film, over both parts and on both sides.
Sep 12, 2019, 10:01 PM
Registered User
Since this will be my first foamy build of this type, I looked at the Kline Fogelman airfoil thread to see what glue they were using, but after the fifth page and no info about glue, I'm just going to ask you, Jeff, what you used. I think you used Gorilla Glue, but I'm not familiar with that glue in that I haven't actually used it. I know you activate it with a little water, and it foams, but I don't want to experiment with a new glue on a kit that doesn't have spare parts. If you can convince me that this glue is easy, I'll try it. Otherwise, I'm probably going to use epoxy.
Sep 13, 2019, 08:50 AM
Jer. 29:11
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Here are some glues I've used to laminate the wing KF step onto the wing itself.

Gorilla Glue White: apply sparingly and spread even with the edge of a gift card (or similar) until there's a thin, even layer of glue on the bottom of the KF step. When laminating, I don't spray either piece with water. Align the KF step with the main wing piece and secure in place with painter's masking tape (typically blue). Clamp with flat weights, e.g., large books, and leave overnight.

Bob Smith Industries Foam Cure glue: apply an even layer of glue on the bottom of the KF step. Align and press the KF step onto the main wing piece and remove once or twice until glue strings form. This takes about 30 seconds. Align the pieces, secure with tape, and clamp. Leave for an hour or more.

3M Super 77 spray glue: spray the bottom of the KF step and the top of the main wing piece. Because the glue is very sticky, you probably want to mask the portion of the main wing piece that is not covered by the KF step. Wait a few (30?) seconds for the glue to tack up. Taking care, you only get one chance, align the pieces and press in place. Clamp and leave for a few minutes.

While very fast, I find the 3M Super 77 to be fairly messy, and I find Foam Cure to be difficult to spread evenly for laminating, so I typically go with Gorilla Glue White.

Happy to cut spare parts for the kit if you need them. Just let me know.
Sep 22, 2019, 12:13 AM
Registered User

Static Power Test Today


I got my second set of extension cables today (the picture shows 6, but you only get 5, so I had to order twice), so I did my static power test with my proposed system. In pic 2 you can see that you have 3 options with this motor: 1--you can use APC 7X5 props on a 2-cell battery, 2--APC 6X4 props on a 3-cell, or 3--APC 7X5 props on a 3-cell. Cobra says the last option should be kept below 80%, but in pic 3 you can see that my amps and watts were below what is in pic 2, so I have no worries about using the 3rd option, as it is my intention to max out the airframe. I believe I can get away with this with enough carbon fiber reinforcement, but of course the proof will be at the flying field.
Sep 22, 2019, 09:23 AM
Jer. 29:11
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@Jay B. Scott, that's a cool setup. Nice to see your careful homework on the power system.
Sep 25, 2019, 07:36 PM
Registered User
Hey anybody with MPF experience: How do you keep your parts from rolling up? All my wing parts are now not flat.
Sep 26, 2019, 08:59 AM
Jer. 29:11
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Thread OP
MPF is fairly easy to shape into curves. The downside is that it can be difficult to keep pieces flat.

In extreme cases, I bake pieces of MPF in the oven at 200 F for 10 minutes, say between two heavy-gauge cookie sheets. In more typical cases, such as laminating the KF step onto a wing, I find that weighting with large, flat, heavy surfaces leaves the pieces flat when the glue cures. And, if it is more like a warp than varied non-flatness, you may be able get flat by applying covering.

Hope that helps.


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