DH 103 Sea Hornet NF Mk21 (oz16869)

About this Plan

DH 103 Sea Hornet NF Mk21. Free flight scale model for rubber power. Wingspan 37 in.

Direct submission to Outerzone.

Quote: "DE HAVILLAND DH-103 SEA HORNET NF MK 21
DRAWN 1 NOV 2022.

This is another twin rubber power model that you don’t see everyday. Plans for this aircraft were made towards the end of WWII but the prototype wasn’t flying till after the war. She was designed to operate in the Pacific so long range and manuverability were top priorities. She came from the heritage of the DeHavilland Mosquito.

CONSTRUCTION:

WING: I drew this plan back in 2022 but didn’t give all the needed information on the plan. It was an early drawing. I’ve learned a lot since then. It shows the main spar dimensions as 3/32” sheet ¾” root to 1/32” at tip. (this should be 3/32” at tip). I would be building this using the cracked rib construction. This uses 1/16” sq for the bottom and top of the ribs. The L.E. and T.E. are pinned down to the building board after wax paper or plastic wrap is used to cover the plans. This keeps the plans being destroyed by the glue sticking to it as the wing is built. Once the bottom of the wing has been constructed, add the main spar over the bottom of the ribs gluing it in place held down by pins. Once the spar has dried add the upper part of the ribs in 1/16”sq strips. I like to use thin super glue to build the wing. I use the plastic tops off the Cringle Potato Chip cans, I squirt a small puddle of glue in the plastic lid and use a tool I’ve made from wire and a 1/8” bamboo skewer(used for shis-ka-bobs. I drill a hole in the bamboo and insert a piece of music wire wire with an “L” bend in the end. Dab this in the puddle and then on to the joint and you won’t be over applying glue this way. Works great!

Once the nose is attached to the L.E. gently bend the stringer over the spar down towards the T.E. and trim at the T.E. and repeat till all the ribs have been constructed. Once all the ribs are complete it’s time to add a rear spar. I use 1/16” x 1/8” strip and slide it into the open ribs and snug it back toward the trailing edge on the 1/16” edge. Once the rear spars has been glued in place using the glue applicator I made I move on to adding trusses not seen on the plan. The trusses are made of 1/32”x1/8” strips starting at the root of the wing passing through one rib to the next rib at the main spar. Gluing the trusses to the spars. Once the trusses have been glued in place you can add the turbulator strips between the main spar and the L.E. I usually use 1/16” sq strips for these turbulator strips. I you want a little more rounded arch at the front use a 1/16”x1/8” strip behind the front 1/16” sq strip. I use the highly technical TLAB technique (That Looks About Right) for the placement of the turbulator strips. Wing is now done except for dihedral, added outside the nacelles.

NACELLES: These nacelles are built like two dime scale fuselages using the box style. Not the T.E. of the nacelle aligns with he T.E. of the wing. Then a hollowed balsa block or tail cone made of 1/8” sheet balsa sanded to shape. The nose block for these nacelles are using a lamination of two 1/16” discs cross grain. I show a round prop block with the prop bushing drilled at a 2 degree angle through the middle of the round block lined with an aluminum or brass tube. This block allows a very snug fit for trimming before fixing with a key once the thrust angle has been set in trimming. Feel free to use a square block if you prefer.

FUSELAGE: Construction uses the box style construction. The plan shows 1/16” sq strips to make the box sides. On second thought I’d recommend 3/32” sq strips toe make the box sides. Make the second side over the first. Once the sides have dried build them over the top vies of the fuselage using foam board templates taped between the sides to hold the trapezoid shaped fuselage sides. Once the templates are in place add the cross members making the box complete. Once cross members are placed and dry, you can remove the templates and add the formers on the top of the box giving the fuselage the rounded shape.

EMPENNAGE: The horizontal stab is made using 3/32” sq and sheet balsa. The vertical stab is built using 3/32”sq and sheet balsa. Build the outline flat on the board, 3/32” sheet L.E. , cap, and
T.E. Once this has dried add the vertical spar 1/16” sheet triangular in shape from the 3/32” top to the 5/16” base. When this is dry add the 1/32”x1/8” ribs over the spar and glued to it and the L.E. and T.E.

I personally hope to build this one in the near future. When I was building RC planes my modeling buddies always said, “Bigger Planes Fly Better”. So build something bigger and tell me if you find this to be true!
Tom Akery/Sky9pilot"

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