belcher bits bk10: north american nj

Belcher Bits BK10 North American NJ-I /4 July 2014

Belcher Bits BK10: North American NJThe first of 40 North American NJ-1, NAS Pensacola, 1937.

IntroductionNorth American’s NA-16 trainer was

the sire of a long line of military trainers,theAT-6 Texan being the most famous. How-ever, there were many other variations onthe same airframe.

The NJ was procured for the US Navyas a flight and instrument trainer, a total of40 being built. It was similar in construc-tion to the current USAAC trainer, the BT-9 but differed in that it used the larger R-

1340 engine that was eventually standard-ized on North American trainers, althoughuniquely, this variant had two exhaust portsat the bottom of the engine.

The KitThis kit includes a complete

Occidental Harvard Mk II kit, necessaryresin parts to convert the kit to an NJ , a setof EZ Mask canopy masks and a set of de-cals with schemes for two USN NJ-1s.

FuselageEarly NA trainers had what is known

as a short-arm rear fuselage, which was 6”shorter than the later T-6. The difference inlength is all at the after end. The elevatorsare actually in the same location relative tothe wing, but the later long-arm fuselagesmoved the vertical fin back 6 inches. Fur-thermore, these early machines all had thefabric sided fuselages. Just for interest’s sakethere were a couple later variants which hada metal covered short fuselage, but all longfuselages were metal covered.Assemble thekit interior, using Figs Aand B. Interior col-our is interior green with aluminum lacquerrollover structure. Seats would have beenbare metal; the pilots used seat pack para-chutes. Paint the instrument panels and sideconsoles black; the instruments can bepicked out with a white pencil, or by care-ful drybrushing.

Resin Parts Guide

Figure A


Figure C

Glue the resin fuselage halves (PartsA) together with the upper cowling piece(part 15) and forward instrument panel (part12) using Fig. C. Kit part 10 will need a lit-tle trimming to allow the fuselage halves tomate properly. When you glue on part 15 sothe panel lines up , It will protrude beyondthe front of the fuselage a bit, so that mustbe trimmed. There will also be a small gapat the leading edge of the canopy rail. Fillthis gap with small scraps of plastic becausethe canopy will not fit if you glue part 15further back. I would also recommend leav-ing off the tailwheel until the end.

The resin fuselage will require sub-stantial grinding or filing on the bottom tofit well with the centre section. Best to dothis at this stage so you can test fit the cen-tre section easily.

Engine AssemblyI have built several of these kits and

one weakness is the fit of the cowling andthe engine. I find the engine sits too far for-ward, and the attachment of the cowling is abit undefined. I recommend that you sanddown the exhaust stubs on part 19 so thatthe thickness is 0.156” (4mm), and trim thering on the back of part 20 so that it fits topart 19. This will shorten the whole engineassembly enough so that it doesn’t stick outtoo far into the cowling.

Because the NJ used a fixed gear un-

dercarriage, the wheel well stubs on the resinfuselage parts will need to be removed. Re-inforce the area behind these inside the nosewith some cyano glue before gluing on theengine assembly. You can file these thesedown somewhat now but save any filling forafter the attachment of the wing.

Now, glue part 19 to part 20 and thenglue these to the front of the resin fuselagehalves. There will be a step, but fair it inwith some putty. When the cowling goes on,this area will be in the gap between the cowl-ing and the fuselage.

CowlingYou can assemble and paint the en-

gine separately, and glue the cowling on af-ter all other paintinghas been done. The in-terior of the cowling was also probably natu-ral metal, but could have been zinc chro-mate primer. Remove the moulding ringfrom the front cowling and sand the cowl-ing lip to a smooth radius. Open up the twoslots in the bottom of the cowling. There are3 ‘fingers’ moulded inside the cowling andthese are used to support it against part 20when it is installed. Note that the top two

Figure D

Figure E

Figure B


fingers go on either side of the top centercylinder. If all goes well at final assembly,there should be about a 1/16” (1.5mm) gapbehind the cowling.

WingA word on wings. The first trainers

had a nasty tip stall. One early fix was to fitslats on the outer wing leading edges. Thishelped, but the problem still existed. Later,the wings were de-skinned, the structuretwisted down 2 degrees at the tip and newwing skins installed. The problem was onlyever solved with the ‘new’ wing first seenon the AT-6 which had the twist built in andhad a small sweep-forward to the trailingedge.

The NJ like the BT-9s had the old stylewing with a straight trailing edge. However,it did not use the leading edge slats so fileoff the protruberances on the wing leadingedge and sand smooth. For this model, wewill use the resin centre section with resinouter wings.

I recommend doing the wing sepa-rately from the fuselage since it involves glu-ing the outer wing panels to a centre sec-tion, it will be easier to ensure the same di-hedral on both wings. Glue the kit wings(parts 32,33,34 and the flaps 31) togetherand when dry, cut them off flush with theoutside edge of the fairing strip. Glue theouter wing panels (resin part C) to the cen-tre section. I find the best way to do this isto tape the centre section down securely anduse modelling clay to support the outer wingin position. Tack in place with cyanoacrylateglue. Once satisfied both outer wings arecorrect, flow some more cyano in the jointand fill any gaps with putty. Note that theouter wing parts are centred vertically onthe butt edge but the trailing edges are inline. If you want to drop flaps, you are infor a world of work and on your own.

When dry, fit the completed wing tothe fuselage. Some filling will be requiredat the joint between the wing and the fuse-lage along the root.

Tail AreaI recommended doing the wings first,

so that when you come to glue on the tailparts, it will be easy to line everything ei-ther in line or at right angles. The verticalfin (resin part B) is glued in place , liningup the after edge with the end of the fuse-lage. File that surface flat, test fit the rudderand glue it in place .

The port and starboard resin tailplanes

(resin part E) can be glued in place andseams filled. Remember these should be par-allel to the wing centre section.

Landing GearAll the photos I have seen of Navy

NJs showed full spats, unlike many BT-9swhich had the lower section removed. Notethe open sections face outboard.

Cut off the spats (resin parts G) fromtheir base and paint. The Occidental kit pro-vides three tires, one with a diamond treadpattern. Toss it in the spare box, and sandthe line tread patterns off the other two tires… if you can reduce their width slightly, theywill look better. Reduce the thickness of thewheels (part 35) by sanding the back face.The wheels covers (part 36) can be reversedand painted separately from the tire. The fi-nal step is to glue the tire into the spat.

The tail wheel from the kit (part 11)is used but with modification. Cut off themounting pins and the rear section aft of thetailwheel strut. Sand the top flat and glue inposition where indicated on the dawing.

CanopyDepending on the way you like to deal

with canopies, you may want to fit the fixedportions such as the windscreen (part 49)and the rear canopy section (part 53a) priorto painting. The Occidental kit includes op-tional canopy sections for early and laterHarvards; be sure to use the early ones withthe additional canopy frames; kit parts 50a(front), 51a (middle) and 52a (rear).

This kit includes a set of EZ Maskcanopy masks for your convenience. Thisself-adhesive film is pre-cut to fit theOccidental kit canopy, and will definitelysave you time in masking. Mix a smallamount of detergent with water, use a sharpknife to lift the canopy mask section off thebacking and a pair of tweezers to dip it inthe soapy water. Place it where indicated onthe canopy; the soapy water will allow youto move it into position. Once the mask isproperly positioned, press it in place and patit dry. Once all the masks are positioned and

dried, the canopy is ready for painting.

Final StepsFollowing painting, clear wing land-

ing light covers part 48 (starboard) and 48a(port) are glued in place on the port and star-board wings respectively. The Occidental kitdoes not make any attempt to show thelamps; these could be made from small bitsof sprue or railroad lamp lenses.

NJs used a tall antenna mast fitted onthe forward cowling area, just to the portside of the centreline. Fit resin part N afterall other work is completed to avoid break-ing during handling.

On the starboard side just aft of theaccessory section are two small venturi. Toosmall for resin parts, you should make theseup from stretched sprue ends.

Glue the pitch control weights (parts24A) to the kit prop (part 24) hub. The propis natural metal with black on the rear facesof the blades.

References:1. North American Aircraft 1934-1998Vol. 1, by Norm Avery, published byNarkeiwicz / Thompson2. North American NA-16/AT-6/SNJ,Warbird Tech Series Volume 11, by DanHagedorn, published by Specialty Press3. T-6 Texan in Action, by Larry Davis,Squadron/Signal Publications.4. Harvard! by Dave Fletcher and DougMacphail, published by DCF Flying Books.5. The Incredible T-6 Pilot Maker by W.Ohlrich and J. Ethell, published by SpecialtyPress, 1983.6. NorthAmerican’s T-6 by Dan Hagedorn,published by Specialty Pres, 2009

Figure F


North American NJ, s/n 0910, NASPensacola, 1937The first NJ delivered in instrument trainermarkings (red nose, and fuselage bands,wing bands). Overall painted aluminumwith yellow wing tops (wrapped around theleading edge about 6”). Red vertical fin andhorizontal tail. The fuselage band is 30”wide, the wing bands are 24” wide.Roundels top and bottom of wings.Fire extinguisher panel was red with blacklettering.Ref: Warbird Tech, p.23

Decal Guide

North American NJ, s/n 0922, NASPensacola, 1938Overall painted aluminum with yellow wingtops (wrapped around the leading edgeabout 6”). Red vertical fin and horizontaltail. The white fuselage band is 30” wide,no wing bands. Roundels top and bottom ofwings.Fire extinguisher panel was red with blacklettering.Ref: Warbird Tech, p.24

belcher bits bk10: north american nj

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