Lakeroadster's "Hammerhead Shark"

[lakeroadster]

Design Post 1

So tell me fella's.... will the "hammerhead" nose cone make this rocket unstable?

It's based on a BT-60 body tube and plans are for a 29 MM motor.

 

[dhbarr]

I would suspect it might pitch up and down with some regularity as the head blocks/unblocks airflow to two of the fins. How much it bucks would be speed dependent, maybe?

 

[lakeroadster]

I would suspect it might pitch up and down with some regularity as the head blocks/unblocks airflow to two of the fins. How much it bucks would be speed dependent, maybe?

I'll take a look at making the head a bit "thinner".... and maybe some "eye pods" on the ends..

 

[dhbarr]

I'll take a look at making the head a bit "thinner"....

I should clarify that I don't think it will be dangerous -- might be cool to do on porpoise.

 

[lakeroadster]

I should clarify that I don't think it will be dangerous -- might be cool to do on porpoise.

Let the "pun'in" begin...

 

[SDramstad]

Looks fishy to me....,

 

[Daddyisabar]

Why is this not using canted tractor motors?

Hammer head cruiser from Rogue One?

 

[neil_w]

My mindsim says unstable, but as always could be wrong. Try throwing that into OR, using fins for the nose.

 

[mbeels]

I'll take a look at making the head a bit "thinner".... and maybe some "eye pods" on the ends..

Instead of thinner, I think that rounder would be better for the hammerhead nosecone. A cylinder would be a source of drag, which is somewhat destabilizing, but a thin fin would be much more destabilizing. The cylinder might cause more flow disruption and blanking of the rear fins, though. Actually, your current oval cross section may just be good! Total speculation on my part.

But cool design! I hope to see it built and flown!

 

[mbeels]

Oh, and perhaps if you extended the rear fins to stick out into the airstream farther than the hammerhead nose cone, it would see relatively cleaner air.

 

[Daddyisabar]

For a Hammer Head you can have tractors or even a mid cant like I did on my squid rocket. Easily form the nose cone eye stalks out of plastic epoxy clay. Three motor mid cant with creative hiding of the motors with fins. Flexible tail would be nice for a fishy looking launch. Check out my Crazy train thread on flexible rockets. May your RSO be blessed.

 

[Daddyisabar]

A nice gray wet sand paper wrap for finish. Three segment tail with narrow segment gaps covered with a fire retarded cloth. BT 80 or 2.6 inch tube with three 29 mm. 2 F15 0 plugged and an F15 4 to eject. Depending on drag you can even go with no delay on the F15 0 unplugged with a little help...nudge nudge say no more.

 

[lakeroadster]

Design Post 2

Thanks for the ideas and dialogue fellas. Much appreciated.

Ran an Open Rocket Simulation this morning which resulted in:
A) Adding some nose weight,
B) Thinning down the hammer head and,
C) Increasing the body tube length just enough for (3) 12" dia. chutes.

Looks like it'll be stable.... we'll see.

I'm thinking I'll use (1) chute for the head... and (2) chutes for the rest of the rocket and let them go their separate ways. Don't want the "hammer" beating the rocket to death.

I'm making it capable of using a 29mm motor. But a 24mm will boost it to over 1,000 feet which should be plenty of height.

 

[neil_w]

Something fishy about that D12 flight... 207 ft vs. over 1000 for an E?

Did you set the front fin to "rounded"? It produces the same 3D render but my guess would yield a significantly higher flight. If you already did that, then ignore.

 

[Bill S]

Something fishy about that D12 flight... 207 ft vs. over 1000 for an E?

Did you set the front fin to "rounded"? It produces the same 3D render but my guess would yield a significantly higher flight. If you already did that, then ignore.

Well it is a 14oz rocket, so a low flight isn't surprising.

 

[neil_w]

Low flight? Not surprising. 1/5 the altitude of a E15? Fishy.

 

[lakeroadster]

Something fishy about that D12 flight... 207 ft vs. over 1000 for an E?

Did you set the front fin to "rounded"? It produces the same 3D render but my guess would yield a significantly higher flight. If you already did that, then ignore.

I did set it to rounded. I'm using the non-beta OR so it can perform Rocket Optimization.

As for the D12.. look at the vertical velocity in the graphs below. It peaks at like 1/4 of a second with the D12, compared to just under 2-1/2 seconds for the E15

 

[mbeels]

Low flight? Not surprising. 1/5 the altitude of a E15? Fishy.

I believe it, I think it sounds plausible to me. At relatively low impulse levels, a disproportionate percentage of the motor's energy is lost to gravity and accelerating the rocket. That is exacerbated with the D12 being a lower average thrust motor. I see that in my sims with relatively small motors, and I think it bears out in the real world.

The E15 is a full "E" with nearly 40 Ns, while the D12 only has about 17 Ns. The tail of the D12 is around 8 Newtons thrust, and a 14 oz rocket = 4 Newtons. So for the majority of the D12 burn the rocket has 1 g of acceleration. I believe it would reach 20% the altitude of the E15.

 

[neil_w]

Fair enough. I haven't seen that big a difference before, but then again I'm normally not simulating 14 oz rockets like that.

I'd probably be reluctant to fly it on the D12 in that case.

 

[BABAR]

Let’s take @Daddyisabar ‘s tractor idea and step it up a notch.

Tractor motors, eject at Apogee, turn your eye pods into airfoils, bump up the rear side fins a bit.

Poof! You have a boost glider! I bet this isn’t a design @burkefj has mastered yet!

 

[lakeroadster]

Let’s take @Daddyisabar ‘s tractor idea and step it up a notch.

Tractor motors, eject at Apogee, turn your eye pods into airfoils, bump up the rear side fins a bit.

Poof! You have a boost glider! I bet this isn’t a design @burkefj has mastered yet!

While that sounds really cool...... One of my goals on this design is to keep it simple. It's really just a standard rocket... with one motor and with a weird nose cone. A slight break from complexity... kinda-sorta.

 

[burkefj]

I've done an RC flying V-2 but not a shark that's for sure

Let’s take @Daddyisabar ‘s tractor idea and step it up a notch.

Tractor motors, eject at Apogee, turn your eye pods into airfoils, bump up the rear side fins a bit.

Poof! You have a boost glider! I bet this isn’t a design @burkefj has mastered yet!

 

[BABAR]

I've done an RC flying V-2 but not a shark that's for sure

Come on, if you can glide a Klingon Battle Cruise, this ought to be a cinch!

 

[lakeroadster]

Drawing Package, post 1 of 2

Here's the latest construction drawings, as of 2020-02-02. I'll keep updating these as the build progresses. Also see the next post for the remaining drawing sheets.

 

[lakeroadster]

Drawing Package, post 2 of 2

Here's the remaining drawings from the above post:



_____________________________________________________________________
Made a bit of progress on the build today. Nothing to exciting, just cutting body tubes to size and cut balsa fins.

I'm using a full length C-60 coupler tube, as well as the BT-60 body tube. Why? Just to ensure a more robust design.

 

[BABAR]

here's a link to a Catfish Rocket (which if I read it correctly never flew, although it looked fryable.....I mean flyable)
https://www.rocketryforum.com/threads/cosmic-catfish.33256/

Current rocket looks cool.

Any flight reports on your X-Wing and Lifting Rocket? I might have missed the posts.

 

[mbeels]

Very cool design, one of those that looks fast just sitting there. And sharky, as well.

 

[lakeroadster]

here's a link to a Catfish Rocket (which if I read it correctly never flew, although it looked fryable.....I mean flyable)
https://www.rocketryforum.com/threads/cosmic-catfish.33256/

Current rocket looks cool.

Any flight reports on your X-Wing and Lifting Rocket? I might have missed the posts.

Thanks for the link.... neat rocket.

The X-Wing is launch ready... but hasn't. The Lifting Rocket needs copper paint, final assembly and I still need to make the launch fixture. Hoping to have a launchapalooza event this year.

 

[lakeroadster]

Body Tube Perforations

Day Two Of The Hammerhead Shark Build.

I made a template to layout the body perforations for the fins. With a new X-Acto knife blade it was a piece of cake to cut the openings. I used a 1/8" thick fingernail filing board to smooth out the openings and the fins literally just slide into the holes with a good snug fit. Nothing is glued together in the photo's below... everything is just dry fit.

I'm going to purchase a couple 24 mm AeroTek motors before I start gluing any components into the body... just to make sure the motor mount is all sized correctly.

Who is a good vendor to buy AeroTek single use motors from? Probably just a couple F44W-8's?

Based on the way the vertical tail fin is so tall and leaning back behind the motor i'm thinking about papering it for durability. It just seems so flimsy as is made from a single ply of 1/8" balsa. Alternatively I thought about laminating 1/16" balsa pieces to the sides of it. I just know if I don't do something it'll break on the first flight.

I think my idea of a dual deploy chute, one for the hammer head and one for the rocket body should help to keep "the hammer" away from "fragile" components.

Your thoughts on methods of increasing fin strength?

 

[mbeels]

Beautiful, that was quick, and I like your tube marking template.

Who is a good vendor to buy AeroTek single use motors from? Probably just a couple F44W-8's?

The first two that come to mind are Sirius Rocketry and Balsa Machining Service, but there would be many others as well.

Your thoughts on methods of increasing fin strength?

What would 1/16" plywood do to your CG? Another option would be something thinner, like 1/64" ply. I think Mugs914 has had some good results with it. Depending on the final weight of the rocket, maybe papering is sufficient. What kind of landing surface do you expect?