ESTES NIGHTHAWK BUILD

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Rktman

Eric
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Nighthawk card image.jpg

I’ve wanted to resurrect this classic ever since I first became a BAR. It was one of the gliders I built when I was a kid and promptly lost on its first flight. Others followed but the Nighthawk was always the coolest-looking, most different, and just darned beautiful...and I never forgot it.

Fast forward to 2015 when I accidentally stumbled on the laser cut sheets for it on eRockets while looking for parts to clone it. I meant to build it as soon as I got it, but I kinda went crazy ordering kits and parts and it was soon buried under the pile.

Anyway, I finally decided to resurrect this beautiful glider and unearthed it from my stack of boxes.

Fair warning: This is going to be a S-L-O-W build. Among other things, hollowing out those pockets for the pod anchor pin and nose weight and sanding in that unusual airfoil can’t be done fast-n-sloppy.
 
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Rktman

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Had to order or scrounge up a few little bits and pieces (not shown) but it’s all here except the decals, which I don’t care to use anyway.
Unboxing.JPG

I’ve decided to omit the “beak” section. It’s fragile and would be the first thing to get damaged in landing anyway.
fuse-nose.JPG
 

Ez2cDave

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Eric,

This is going to be GOOD !

Dave F.
 

Rktman

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Chores and yardwork delayed things, but I finally found some time today to get back to the Nighthawk.

Part of what makes this an LPR Level 5 build is having to hollow out that relief slot for the nose ballast and the pin receiver (which functions as a pylon hook). While the directions say to clamp the 2 pieces of the body (fuselage) together and streamline by sanding the edges round before doing any hollowing out, I elected to do the chiseling first. Much easier when everything is still flat.

I chiseled the outlines inward at an angle first then began removing thin layers of balsa, being careful not to gouge too deeply.

hollow relief-1.JPG


Finished up with shallow cuts using an OOP chisel tip and hobby knife. Took a while but not too bad, since I was cutting with the grain instead of against. (While the instructions say this slot should be 3/32" wide, the lead weight supplied is actually 1/8" thick so I had to deepen each slot enough to fit the weight. Glad I checked).

hollow relief-2.JPG


The pin receiver (dowel hole) was a little more difficult, since I had to hollow out two hemispheres cutting cross-grain. I used the chisel to cut a V-groove along the outline, then cleaned it up using a hobby knife. Final smoothing was sanding with some 400-grit wrapped around the dowel pin.

A thin layer of white glue hardened up the channel as extra insurance against the soft balsa deforming during launches. Sanded again for a snug but smooth sliding release.


hollow relief-3.JPG


Body/fuselage halves joined with yellow TBII and clamped.

fuse-join.JPG
 
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tab28682

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Really enjoying your Nighthawk build. I fondly remember my two Nighthawks built in the very early 1970s. Very reliable flyer and I always thought is was a beautiful design.

I have an upscale Nighthawk on my RC RG/BG bucket list. Either an X1.8 for D12 power or an X2.22 for E power. Will modify the glider so that the wingtips do not supply the up elevator trim for the glider by making the the wingtip joint parallel to the fuselage/center dihedral joint. Elevons on the main wing panels only. Glider fuse likely to be a little plumper than scale to hold the RX and battery.
 

Rktman

Eric
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Really enjoying your Nighthawk build. I fondly remember my two Nighthawks built in the very early 1970s. Very reliable flyer and I always thought is was a beautiful design.

I have an upscale Nighthawk on my RC RG/BG bucket list. Either an X1.8 for D12 power or an X2.22 for E power. Will modify the glider so that the wingtips do not supply the up elevator trim for the glider by making the the wingtip joint parallel to the fuselage/center dihedral joint. Elevons on the main wing panels only. Glider fuse likely to be a little plumper than scale to hold the RX and battery.
That would be outstanding. Looking forward to seeing that build thread and launch pics/video on TRF when you decide to move forward on it!
And I agree, to date it's THE most beautiful glider ever designed IMHO, and I've built well over 30+. "Graceful, poetry in motion," etc. comes to mind when describing it. Someone put a lot of thought into both its aerodynamics and clean minimalist design.
 
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Ez2cDave

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Thanks, this is great Dave! My pattern sheet doesn't show the location of the dowel lock pin within the pylon. This will save a lot of guesswork on my part.
Eric,

You are very welcome, sir !

Dave F.
 

Rktman

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Fuselage body done.

IMG_6045.JPG


For some reason I fail to understand, the Estes instructions that came with the Nighthawk say to join the wings and cut/bend the tip panels down BEFORE creating the airfoils. I can tell you from experience that it’s all but impossible to sand in an airfoil AFTER the wings are assembled. So I’m going off-course here and doing what makes more sense.

Made some airfoil patterns. Very helpful to make sure the unusual airfoils get done accurately.

airfoil pattern.JPG
airfoil pattern-2.JPG


Tape guides.

IMG_6053.JPG

Definitely one of the harder airfoils to get right (and the easiest to get wrong by over-sanding. Don’t ask me how I know…just glad I have a spare set). Still need to do the same to the bottom side trailing edges.

airfoil-topside.JPG
airfoil-LE-top.JPG
 
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Rktman

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Interrupted putting in the airfoils to sand in the wing dihedral along the root edge. I can feel how carving in the airfoils is making the wings not only lighter but more fragile. Better time to have put in the dihedral would've been right after cutting out the wings, when they were more rigid and less susceptible to damage while the wingtips are propped up at an angle.

The paper dihedral guide wasn’t very effective, so made a jig out of scrap balsa.

jig-1.JPG

dihedral.JPG
 
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Ez2cDave

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Interrupted putting in the airfoils to sand in the wing dihedral along the root edge. I can feel how carving in the airfoils is making the wings not only lighter but more fragile. Better time to have put in the dihedral would've been right after cutting out the wings, when they were more rigid and less susceptible to damage while the wingtips are propped up at an angle.
Hi, Eric !

I am guessing that you will be tissuing the Wings?

Dave F.
 

Rktman

Eric
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Hi, Eric !

I am guessing that you will be tissuing the Wings?

Dave F.
Yup, the balsa supplied in the kit is B grain and soft, so I'll have to. (I otherwise normally use C grain from my own balsa stash when doing clones).
 

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Had a bit of a setback while trying to reorganize my workspace by moving kit boxes and supplies. Put my desk lamp up on a pile of boxes to get it out of the way temporarily…and of course it didn’t stay there. It fell over as soon as I turned my back. And of course it landed in the worst spot possible. :facepalm:

damaged.JPG
 
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Rktman

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Put the build aside for a few days to work on other projects and decide what to do. I ended up cutting off the damaged wing and made another from a sheet that closely matched the density/grain of the original. As it turned out, it was kind of a fortunate accident because it gave me some time to turn my attention to another area that’s bothered me for years: sanding in the dihedral angle on a glider’s root edge.

Below is the accepted standard for how it’s usually done with free flight gliders: prop the wingtip up at the correct dihedral height and sand the root edge.

IMG_6083.JPG


The thing is, pressing down to hold it in place so it doesn’t move puts stress on the balsa and often causes some bowing and an inaccurate root edge, since it still manages to move around incrementally. Inefficient, not always 100% accurate, and often requires touching up the sanded area to ensure a clean, tight edge when glued to the other wing.

Yes I could build a “ramp” type sanding jig to rest the wing on, but a much easier and faster hack is to make a jig with the sandpaper set at the correct dihedral angle instead of the wing.:p

So I used a piece of scrap foam and cut out a 1/8” wide slot to hold a 1/8” piece of balsa bent to the correct angle.

angle-former.JPG

sanding jig.JPG


The bottom half is the guide part that’s placed flush up against a straight edge (in this case just a piece of board). Sandpaper is glued to the top part, which is set at the correct dihedral angle to sand into the wing’s root edge. Simple! And all it took was a few minutes of cutting and gluing.

dihedral jig-1.JPG

dihedral jig-2.JPG


Very happy with the result: a clean, absolutely accurate edge after only 4 passes.

IMG_6124.JPG


So this mini build disaster ended up having a bit of a silver lining.
Now if only I could figure out a way to make a permanent dihedral jig with an adjustable sanding angle, so I could have a machinist make one out of metal. Or have it 3D printed.
 
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Ez2cDave

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Had a bit of a setback while trying to reorganize my workspace by moving kit boxes and supplies. Put my desk lamp up on a pile of boxes to get it out of the way temporarily…and of course it didn’t stay there. It fell over as soon as I turned my back. And of course it landed in the worst spot possible.
Eric,

OUCH . . . I feel your pain !

Dave F..

1622148944846.png
 

Rktman

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Second in difficulty only to creating the unique airfoil, cutting in the wingtip plate relief slot turned out to be a bigger PITA than I expected. In other glider builds that allow making both wings out of one continuous sheet of balsa, I’ll create the dihedral by cutting ¾ of the way through and then sanding in a V-notch at the siamesed root edge to allow bending one wing up to the correct total dihedral angle. As long as I stay conservative with the width of the V-notch, it’ll close up nicely and the joint is barely perceptible. Easy.

With the tip plate having to be bent downward A LOT more than I expected (I believe it turned out to be 45°) I had to keep doing partial bends to make sure the notch was wide enough, hoping all the while that the tip plate wouldn’t snap clear off. Glad I dribbled a smidge of water into the cut to soften the balsa first.

Used a hobby knife to slice about ¾ of the way through, then used a micro-chisel blade held at about a 45° angle to chamfer in the edges. Had to fine tune things using a razor saw and some files and emery boards.

tip plate slot-1.JPG

tip plate slot-2.JPG


Turned out fairly well. A glue fillet and balsa dust should minimize the surgery scar.

tip plate final.JPG
 

Ez2cDave

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Eric,

Coming along, nicely, sir !

Dave F.
 

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