How to Build an RC Jet – Part 3

Dorsal Town

Final shaped dorsal test fit on fuselage

Final shaped dorsal test fit on fuselage

When you build an RC jet like this one, it’s nice to start off small.  Progress comes with small milestones accomplished by small steps at a time.  It really only takes a few hours per week to see notable progress and the key is to just get into the shop and make that progress happen.  Yes, it takes time and will take a while to get done, but that’s half the fun.  So, with that in mind, I started off construction with the dorsal.  Note that I started this build before starting this blog, so in some cases, I’m limited on the pictures that I took.

Sub leading edge glued in place with 'Titebond'

Sub leading edge glued in place

With everything unboxed and setup in my shop, the first item of business was sheeting the dorsal foam core (I plan to make a tutorial video on how to do this when I sheet the wings). Mark’s design incorporates a sub leading edge before sheeting, so that was installed first with some wood glue (I like to use Titebond Premium Wood Glue).  The sheeting was made from contest grade 1/16” balsa (as light as possible) glued edge to edge as necessary to get full coverage over the core.  The grain of the wood runs parallel to the leading edge (important!) which helps with strength as well as makes it easier for the wood to contour over the foam core.  I used Pacer PT-40 Z-Poxy Finishing Resin to adhere the sheeting to the foam.  It was applied to the wood sheeting only (the foam will soak up resin if applied to it since it’s porous), in a light thin coat.  The sheeting was then placed onto the foam core and into the foam cradles.  The cradle was weighted so as to ensure a good bond and that the foam core remains straight.  To ensure it was straight, sight down the leading and trailing edges and place weights as necessary to straighten things out.  Once satisfied, it was left to cure overnight.

Sheeting done, LE and TE sanded to shape

Sheeting done, LE and TE sanded to shape

1/64" ply ribbing on balsa cap

1/64″ ply ribbing on balsa cap

Tip block ready for planning and shaping

Tip block ready for planning and shaping

With the sheeting done, all edges were trimmed and block sanded flush to the foam.  From there, the balsa leading and trailing edge parts were glued on using wood glue and sanded to shape with a sanding block.  On the trailing edges, I like to laminate a 1/64″ ply strip between two pieces of balsa. When glued, the 1/64” ply is placed along the chord line so that once the TE is sanded to shape, it creates a fine, yet sturdy trailing edge.  The same was done for the tip block, but some ribs were added also to get a little space between the blocks.  The tip block was glued on following final shaping of LE and TE and subsequently shaped as well.  In checking my 3-view drawing, I noticed something didn’t quite look right on the supplied tip block, so I cut my own with a modified shape that was more representative of my 3-view reference.  Once all the shapes were final sanded, of course it requires a quick test fit on the fuselage!

Final shaped dorsal

Final shaped dorsal

I have to say, I love getting to this step of shaping the flying components of the airplane.  It’s fun to see it come together and form into what are the primary lifting surfaces for the model.  When I get to the wings, I plan to spend more time discussing how to sheet the cores, shape and sand the LE/TE and tips through videos and step by step tutorials.  Unfortunately, I had already built the dorsal before starting this blog and was limited on pictures for this post.  Next up as we build, we will tackle cutting, shaping and hinging the rudder.

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