7.5" - 6" Terrier Sandhawk

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vahpr

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Back in the day, before digital cameras were in widespread use and when "M" flights commanded everyone's attention, I had a blast building and flying a large (for those days) 2-stage rocket.

Inspired by Kevin Mitchell's T/S of similar size, the Terrier-Sandhawk was (and still is) a great rocket to model; naturally stable, good looking, with some cool details. Since then I've used the Terrier (with Nike Smoke nose cone) as a test platform for everything from new propellant formulas to commercial avionics. It's still flying, although somewhat worse for the wear:)

Here's a short compilation of clips of the 3 two-stage flights, sourced from the old renders.

https://www.youtube.com/watch?v=3jGNoh-TfK0&feature=youtu.be

I like making models, so I thought it would be fun to recreate this project with a couple new twists. And with just one motor in the booster it should be less trouble than my recently demised Iris booster. As always I'm sure there are better ways to do some things, I just do it whichever way I'm comfortable.

Jerry

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The original model (7.5"-5.5") was fairly close to 42% scale. I couldn't locate (actual) 5.5" tubing so I'm using widely available 6" for the Sandhawk. I'll need a new transition/interstage and while I'm at it, I'll clean up the Terrier booster.

In researching, I came across an interesting site on the "Hydra-Sandhawk" (https://www.hydrasandhawk.org/) which was a variation and as it happens, the last water-launched sounding rocket. There's a photo there (copied below) which shows a bit of the Sandhawk fin detail, something I'd never seen before. It had a box shape at the root and tapers to the tip as well as leading edge. So the challenge was on. How best to get something close to that profile while remaining as light and stiff as possible?

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The solution I decided on is a carbon-laminated foam core with a combination of plywood hard-points, basswood and balsa for the profile, shaped and vacuum bagged with an additional carbon cloth reinforcement.

A poster-board template helps transfer the fin outline to the Divinycell. The cuts are done with a couple (very handy) crosscut sleds on the tablesaw

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The Divinycell is edged with solid carbon fiber. I saw an excellent trick on a woodworking site to cut perfect miters at any angle, no measuring needed. The pictures explain......

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With the angles verified using (cheap) basswood, I cut the carbon pieces.

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While waiting on some vacuum supplies, I started cutting the basswood leading edges and plywood hard-point strips

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Had to make another sled for the bandsaw, very useful little jig.

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The foam cores are flat, so I'm using a piece of Melamine as a baseboard, waxed with several coats of non-silicone wax and finished with a coat of PVA release film. Although the PVA dries odorless, it's nasty when wet so a respirator is a good idea. The through-bag connector and quick-disconnnect fittings are from ACP Composites.

A word on resins. I've used (relatively inexpensive) Raka marine epoxy with great results however it's not rated for high-temp applications. These fins won't see anything much over Mach 1 but if this were a high-performance rocket I'd use something else. Also, the working time was shorter than I'd remembered, so I'll probably use something else for the final, exterior reinforcement anyway.

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I left them on the vacuum overnight and since they will be further laminated, I used nylon peel ply for a good surface texture for additional gluing. By the way, they popped right off the PVA film very easily.

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A little cleanup and so far so good - nice and light and stiff. Whew, that was a ton of work already :shock:

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I left them on the vacuum overnight and since they will be further laminated, I used nylon peel ply for a good surface texture for additional gluing. By the way, they popped right off the PVA film very easily.

Just as a note: nylon peel ply has release agents on the surface that harm further bonding.

Dacron sailcloth is the cheapest option; it's just a little harder to pull off after curing.
 
That's a good point - although it's never been an issue in the past I plan to clean and scuff the surfaces before adding the profile materials.

Just as a note: nylon peel ply has release agents on the surface that harm further bonding.

Dacron sailcloth is the cheapest option; it's just a little harder to pull off after curing.
 
Nice project. I always acetone and sand after peelply also just to open the surface for a good machanical bond.
 
Subscribed. Great to see this project resurrected! I remember following some of those earlier flights on the MDRA and VAHPR sites... Do you remember me emailing you a bunch about those rockets, motor formulas and big bands? Haha, good times.

Since you mentioned it, the Iris booster was awesome. The I540 flight was killer! I'm hoping to do my own "rip off" of that idea by converting my full-scale 4.5 inch HV Arcas to "Boosted Arcas I," with a small 4" booster that uses (2) 38mm motors, either I800s or I540s.
 
Looks awesome Jerry! Subscribed - excited to watch this thing come together.
 
Yea, actually that's 5.38 OD - I was referring to 5.5 ID which fits my Kevlar Sandhawk nose cone but is apparently unavailable.

As far as I know, the only true 5.5" tubing came from the late Darrell Mobley. I know scotglas had a 5.5" BB II nose/tail cone set that was scrapped after his passing.



Braden
 
Good times indeed, very fond memories. Time to make some more:) Cool avatar btw, as jazz musicians in the rocketry community we may be in the minority LOL.

And no such thing as ripping-off, as in music, everything is built on what you've heard/seen before. Boosted Arcas sounds cool, do it!


Subscribed. Great to see this project resurrected! I remember following some of those earlier flights on the MDRA and VAHPR sites... Do you remember me emailing you a bunch about those rockets, motor formulas and big bands? Haha, good times.

Since you mentioned it, the Iris booster was awesome. The I540 flight was killer! I'm hoping to do my own "rip off" of that idea by converting my full-scale 4.5 inch HV Arcas to "Boosted Arcas I," with a small 4" booster that uses (2) 38mm motors, either I800s or I540s.
 
Yea Braden, I think that's where I got it - the nose cone was a one-off from Giant Leap. Still have it, and the remains of the Sandhawk fin can which I've been meaning to make an end table from. It's in pretty great shape actually, the cato sheared off the tubing just above the top CR :)

As far as I know, the only true 5.5" tubing came from the late Darrell Mobley. I know scotglas had a 5.5" BB II nose/tail cone set that was scrapped after his passing.



Braden
 
Thanks for the kind words David, you've taken the rocketry thing all the way and I know many of us feel somehow like proud parents hahahahahaha.

Funny you mention, but I seem to have unearthed functioning (local) copies of the vahpr site when it was FrontPage based and the one prior which was (crude) hand edited html. Long buried on old hard drives but apparently complete with text, photos, videos. In 2000 it was pretty easy just doing html, but web technology advanced far faster than I could keep up - I was always behind. A little like my office right now!


I still browse the old TS construction and flight pages on the Wayback machine when I need inspiration. Thanks for bringing it back, Jerry! I'll be watching the (re)build closely, and I'm looking forward to finally seeing it fly!
 
Inspired by Kevin Mitchell's T/S of similar size, the Terrier-Sandhawk was (and still is) a great rocket to model; naturally stable, good looking, with some cool details.

Jerry[/QUOTE]

Awesome!
Let me know if you need a hand with any part of the project. Can you believe it was 17 years ago that my T.S. first flew!!! The 4 pics are of its maiden flight on a 98mm L952. This was the same weekend that we had our first launch at Higgs Farm (MDRA's home field).

Your fins look great.

Kevin.

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Hey Kevin, from the archives;

https://www.youtube.com/watch?v=LkcRJP83k_k&feature=youtu.be

That flight was the reason I built mine! Whitakers was a good field, the file date says Sept 2000, which could mean the flight was July or Aug that year. I think an M1130-K550 ?

Time sure flies doesn't it?

Jerry O




Awesome!
Let me know if you need a hand with any part of the project. Can you believe it was 17 years ago that my T.S. first flew!!! The 4 pics are of its maiden flight on a 98mm L952. This was the same weekend that we had our first launch at Higgs Farm (MDRA's home field).

Your fins look great.

Kevin.[/QUOTE]
 
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