1/2 Scale AQM-37A Jayhawk

[sambatterman]

Greetings Rocketeers!
I'm starting this thread to chronicle my build out and maiden flight of a 1/2 scale AQM-37A Jayhawk. The Jayhawk is a beloved rocket in both the low and high-powered rocketry community. The HPR community especially has fond thoughts of the early HPR days with Eric and Dirk Gates flying their full-scale Jayhawk. Later, people like Sather (@SMR) would bring a 10" Jayhawk to the Mid-West. They have unusual features like a delta wing and winglets and usually a distinctive test orange/black or red paint job. In short, they are sexy rockets.

I am building a 1/2 scale version. So, with the basic specifications:

• Length: 14 ft 0 in (4.27 m)
• Wingspan: 3 ft 4 in (1.00 m)
• Height: 2 ft 2 in (0.66 m)

my model will be 7 ft tall, a wingspan of roughly 20" and a central 6" body tube (full scale diameter is 13" - so pretty close).

Propulsion is based on a 75mm MMT able to take L&M motors (and others with adapters). L2200G is my go-to for shake down, but I would like to try a low M in this rocket as well.

I want to do an accurate boat tail and wire tunnel sub tube that runs longitudinally, which is something the Gates brothers did, but rarely do other modelers follow this feature. In addition, for my own skill improvement, I want to focus on an electronics bay in the wire tunnel for a nose ejection and tether recovery - something that I used on my ALCM Cruise Missile and it worked so well.

So, let's get some reference materials out here:






Come along for the journey!

 

[sambatterman]

Jayhawk material gallery

Typical construction for me: 6" 48" Blue Tube for central body tube, a 28" fiberglass nosecone with ruby red, fiberglass nosecone shoulder, a 16" Blue cube coupler, 1/2” marine plywood with wings, 3/8” Birch for winglets, phenolic 75mm MMT, Aerotech retainer with SC Precision thrust plate (4”), 54mm Blue Tube for wire tunnel.

 

[sambatterman]

MMT Tube build out

The MMT is three 6"x75mm 1/2 plywood center rings on a phenolic tube that's 31" long - that's long enough for any reload on an Aerotech RMS 75/5120. So, I can use a multitude of Ls and M motors. Chief among these: L2200G, L1420, M1500, M1297 and L900DMs. Lots of variety.

Because of the 11" boat tail at the end, it terminates with a 4" 3/8 plywood center ring with a SC Precision 4" thrust plate and 75mm Aertotech Retainer.

 

[sambatterman]

Tang - the drink the astronauts took to the moon

After some careful measurements (measure 4 times, cut once), I cut the 75mm MMT track out of the wing (1/2" Birch Plywood). This left three slots for the center rings and tangs that just barely reached the MMT. The picture below shows a dry, test fitting. Getting this thing centered was nerve wracking. Initially I just tacked the aft and forward sections just enough to hold before I moved to reinforcing the whole MMT.

 

[sambatterman]

Send in the reinforcements!!!

Once the MMT was centered, I laid out fiberglass and used West Systems to wet it out.



Once the epoxy has gone to leather (about 2 hours in), I cut the edges and gave it a nice clean edge.



Completed by adding some angle brackets to specific areas and putting JB Weld on all the joints.
As Alfred E. Newman said, "that ain't going nowhere."

 

[sambatterman]

Beginning the boat tail

While the upper portions up to the recovery hard point will be supported by 1/4" all thread, the boat tail makes that more difficult. I decided to use strakes (narrow flag shaped) plywood to both support the bottom MMT pedestal and also provide the initial support for the boat tail.




And a straight on view. The opposite side is similar, but I left the center strake out as that starts to form the avionics bay supporting the wire tunnel. More on that later.

 

[sambatterman]

Foaming the Boat Tail

Similar to how I handled the boat tail on the Nike Hercules Sustainer, I decided to use small cell expanding foam. This stuff is very forgiving and a little goes a long way. Once cured - and that usually takes a day - just cut it off the shape. If you cut into it too early you will find voids that are not cured and that's just yucky! Protecting the wood and the thrust plate makes for easier clean up later.





On the opposite side, the boat tail is abbreviated because of the wire tunnel that travels longitudinally across the body tube. I'm also using this area as the avionics bay. As I mentioned earlier, I'm giving more focus to the AV bay on this rocket than I have on others.

 

[sambatterman]

Cutting the Fat

Next Up: Body Tube and Boat Tail Skinning.

Here's a roughed in boat tail...AV/Wire tunnel side first...


Backside that connects rail buttons...

 

[WFWalby]

What brand foam do you use??
W

 

[sambatterman]

What brand foam do you use??
W

I like loctite small cell spray foam, but I’ve used others. Avoid the yellow “good stuff” brand. Everyone has their favorite.

 

[sambatterman]

Smoothing the Foam and First Dry Skinning

Using a long and short serrated knife, I carved the foam back so that it fills the volume but won't impact the skin (blue tube).
Once the foam is dry this is a fast and satisfying process. While not always necessary, I run a 50 grit sanding sheet across the whole thing to smooth it out.


It weighs 8 pounds at this point. I cut the all-thread off and put small 1/4" terminating hubs on the hard recovery point.
I wish I would have masked around the U-bolts so that the JB Weld wouldn't have made a mess, but lesson learned.
No one sees it but me - but, yeah, that's the point.


First dry test fit of the 6" Blue Tube body tube. It was epoxied using the Giant Leap glass sock, which I completely recommend. Then I measured like four times before cutting the tube longitudinally with a Dremel with a cutting wheel. Dremel is a great tool for this. I've used jig saws and Dremel's and the results are always better with Dremel. Notice the 6" coupler at the top. This coupler sits directly against the recovery point disk and allows for easy access to the main chutes and recovery tether. I want to use two 10' Spherachutes to recover this thing, so payload space for recovery is critical. Still have plenty of room for that.



Next up - winglets and glue down of the body tube.

 

[DocSeuss]

As a Jayhawker, and being formerly from Wichita (where Beech came up with these things), I have a huge affinity for the Jayhawk. Plus, it just looks amazing.

This thread is awesome! Your build looks fantastic.

Which paint scheme you going for?

 

[sambatterman]

As a Jayhawker, and being formerly from Wichita (where Beech came up with these things), I have a huge affinity for the Jayhawk. Plus, it just looks amazing.

This thread is awesome! Your build looks fantastic.

Which paint scheme you going for?

Thanks for the kind words. Beechcraft was way ahead of its time when you look at its other products I washed airplanes in the summer between college semesters and I washed hundreds of Beechcraft

I'm vacillating between the typical test range orange and black that is so typical and candy red that the Gates' brothers used.
What is your favorite?

 

[DocSeuss]

Thanks for the kind words. Beechcraft was way ahead of its time when you look at its other products I washed airplanes in the summer between college semesters and I washed hundreds of Beechcraft

I'm vacillating between the typical test range orange and black that is so typical and candy red that the Gates' brothers used.
What is your favorite?

I personally feel like if you're gonna go scale, you gotta go scale, you know? But one could simply argue they're making a scale version of the Gates' brothers Jayhawk. Tough choice.

For my Madcow 2.6 Jayhawk (I emailed 'em about it this spring and they finally got 'em back in stock and I snapped one up the second I saw it), I was gonna go proper scale colors, if I can figure out what the most accurate paint for that is.

 

[sambatterman]

Gluing the Main Body Tube

Used West Systems to wet the entire bottom tube portion and then weighted it down with books (old software programming books for the win )

On the flip side, I used a wood screw temporally at the lowest hard point where the rail button would go. I'm going to have some filling and blending to do on the edges of the tube against the delta wing.

 

[sambatterman]

Dry Fit of the Wire Tunnel

A Jayhawk has a half diameter tube that runs longitudinally on one side of the vehicle. Most modelers have ignored this feature and even some kits are missing this distinctive feature. I decided at the outset of the project to go as scale as possible on this and also to use it practically as an AV bay at the aft end and run the wires to the hardpoint for the tether and then continuing to the nose cone for the initial charge to bring the drogue.

The aft base cap is pretty distinctive - lifting up from the thrust plate and providing a profile of the half tube. The top of the blue tube will be cut to provide a hatch into this space, and it will be the avionic bay for the model. Plenty of space for two MissleWorks altimeters and two nine-volt batteries. That AV bay will be 3D printed.



Here are three formers that will support the wire tunnel and form the front and aft ends of the AV bay.



Lining everything up you can see the shape the aft end of the wire tunnel will take. I cut out some card stock to figure out the size of the sides of the compartment. They will be made out of 1/8 basswood. Blue tube panels will complete the boat tail, just like I did on the Nike Hercules. There will be some filler work and blending here, but nothing crazy.



Here's the interior of the wire tunnel. There's a PVC tunnel that runs the length and some formers that support it. It should easily hold four wires (two for each charge - nosecone and tether at the hard point).

 

[sambatterman]

Gluing the Wire Tunnel

The wire tunnel, the distinctive spine that runs longitudinally on one side of the Jayhawk, is now glued and pretty well set. I'm still working on closing up the boat tail with "turkey feather" blue tube panels. After that I will fill and sand and then cover the whole thing with a layer of fiberglass that runs over the body tube and is tip-to-tip on the wings. I still have to cut the avionics bay hatch, but the innards are all set - a channel for the wires to go from the altimeters to the tether at the recover hard point and one that extends to the nosecone, where an ejection charge will blow out a drogue to create tension on the tether. You can also see the hole in the AV bay wall for the arming key. Next step is the winglets - cutting them out tomorrow.

In the spirit of Ron Swanson - "you can never have too many clamps."



Sealing the edges and sanding the connections between the tubes will make for a great finish after it's all covered in fiberglass.



The wire tunnel extends past the normal coupler to the upper fuselage and so there is a mini-coupler to help align the two body tubes. The wires from the altimeter in the aft portion run through a channel in the tunnel and have two stops: recovery hard point, a hole right beneath this mini-coupler and to the nose cone for an ejection charge that separates the nose from the vehicle at apogee and pops a drogue. This puts tension on the tether, which releases at 500' for a 10' main chute.



A picture of fitting a "turkey feather" on the boat tail super structure. Notice the hole in the tunnel wall for an AV arming key.

 

[sambatterman]

Winglets

Starting to look like a Jayhawk now. I built the winglets from 3/8" Birch plywood and laminated them with carbon fiber and fiberglass on each side and rounded the edges with a router. The block you see laying on the worktable is a jig I built to accurately line up the 6 screws for attaching the winglet to the wing and ensuring the alignment is precise.


The winglets turned out great and I'm happy with them. Still have some cleanup to do on the leading edge of the wing to smooth out the transition.
This is the bottom of vehicle with the finished boat tail and rail buttons (unistrut).



And the top, with the nearly completed wire tunnel. Still need to do the "nose" of the tunnel. This is a tricky shape. You'll also notice the drill holes for holding the upper body tube to the main chassis of the vehicle. 8 1/4" bolts and t-nuts will do this job. Still need to work on the nose cone, fiberglassing the wire tunnel and wings for a nice finish and the canards and weight in the nose cone. And then the sanding and finishing begins.

 

[sambatterman]

Nosecone and Canards

Epoxied the nosecone coupler in and let that dry. I also marked the nosecone for the areas where the canards will slip through. The nosecone is a beauty, but a little long for scale (28" vs. 24") so I took affordances on the mid-fuselage to make sure it is at scale.



In this photo, you can clearly see the marks for cutting out the area for the canards. I will also handle the nosecone weighting and the recovery hard point when I put the canards in.



Speaking of canards - here's the layup for one side - 3/8" birch plywood laminated with carbon fiber and fiberglass. I'm using the Fiberglast blotter fabric (the pin striped cloth), which gives the surface a nice uniform finish.

 

[sambatterman]

Getting Close

It’s been a few days since I’ve posted, but I was busy working on the Jayhawk. Here are two photos showing full assembly. The wire tunnel on the spine turned out great.

My 1/26 space shuttle orbiter 3d print molds are on the table to the right/behind it.

 

[lakeroadster]

What an awesome bird!

 

[jd2cylman]

Nice.

 

[rfjustin]

Very nice!

 

[tg08]

I'm speechless. Will/when we get a launch video?

 

[NTP2]

Next a 1/1 please.
Ps how is the shuttle coming along?

 

[sambatterman]

Next a 1/1 please.
Ps how is the shuttle coming along?

Printing shuttle molds - 2 months now. I’ll have something to show next week I think