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STRMan
01-11-2008, 01:09 PM
I was browsing the Semroc site last night and found this model. Holy cow! This has got to be one of the coolest rockets I've ever seen. A cluster model that can be flown on 1, 3, or 7 engines? I've got to get me one of these!

Has anyone built and flown this model? I notice that the only power options listed are with C engines. I'm wondering if it would fly with 3 or 7 B's or 7 A's. It looks like the center engine powers the Ejection Charge, and the surrounding engines are used for additional boost. If so, could 5 engines be used instead of the afore mentioned combo's? I'm completely intrigued with this model. It just may be the most versatile cluster model I've ever seen.

http://www.semroc.com/Store/scripts/RocketKits.asp?SKU=KV-29

Pyro Pro
01-11-2008, 05:42 PM
I used to have one (http://www.rocketreviews.com/reviews/kits/sem_hydra_vii.html), it's a very fun kit. As long as there's a motor in the center, and the other motors are symmetrical, the engine combination should work (so that's 1 in the center, 1 + 2 outboards, 1 + 3 outboards, 1 + 4 outboards, or 1 + 6 outboards). According to RockSim, 3 B6-4's should work fine (~450 feet, reaches safe initial velocity in 25"). It also shows that 7 A8-3's would give almost exactly the same flight profile (maybe a hair more altitude). You're given the option to let the outboard tubes vent into the main body tube, or use plugged motor blocks instead to eject the engines. If you don't use the plugged blocks you get an added bit of insurance just in case the central motor does not light, though you have to make sure to put a bit of recovery wadding into the top of the motors to make sure they're not lit by the ejection charges of the others in the event of a misfire.

I will attest that it provides a very impressive flight on 7 C6's :D It's a great kit.

STRMan
01-11-2008, 10:07 PM
I'm sold. I just sent Semroc an email asking when the fins will be available for the old Centuri Stiletto, as this is another rocket I really want to build (again). When I get a response from that question, I'm placing an order for the Hydra VII.

rraeford
01-11-2008, 10:43 PM
Actually, all the parts to build a Centuri Stiletto (except decals) are available from Semroc. I bought them over a year ago. Always was one of my favorites.

Romie

Ltvscout
01-11-2008, 10:45 PM
Actually, all the parts to build a Centuri Stiletto (except decals) are available from Semroc. I bought them over a year ago. Always was one of my favorites.

Romie
I guess the laser cut fins are showing as being out of stock, which is what STRMan was referring to.

rraeford
01-11-2008, 10:52 PM
Oh.

Didn't know that.

Carl@Semroc
01-11-2008, 11:10 PM
They are there now. We have been slow on re-stocking lately. Got to check and see if the Krelvinator has cooled off. :D

STRMan
01-11-2008, 11:54 PM
Thanks for the reply Carl. I also got your email. I'll place an order in the morning as it's almost midnight and I'm turning in. Thanks for the fast response to my question.

Johnnie
01-11-2008, 11:59 PM
I built one of these a few years back (http://www.rocketryforum.com/showthread.php?t=5845&highlight=hydra) It has long since gone bye-bye...but I have a Hydra VII, serial number #009 that I plan to build sometime this year.

You will love the build, good luck.

Johnnie

PaulK
01-12-2008, 01:26 AM
I was browsing the Semroc site last night and found this model. Holy cow! This has got to be one of the coolest rockets I've ever seen. A cluster model that can be flown on 1, 3, or 7 engines? I've got to get me one of these!

Has anyone built and flown this model? I notice that the only power options listed are with C engines. I'm wondering if it would fly with 3 or 7 B's or 7 A's. It looks like the center engine powers the Ejection Charge, and the surrounding engines are used for additional boost. If so, could 5 engines be used instead of the afore mentioned combo's? I'm completely intrigued with this model. It just may be the most versatile cluster model I've ever seen.It IS a great cluster model. I built one 2 years ago, and have launched it a few times on 7 motors. I left the center and 2 outboard tubes open. If you leave any outboard tubes open, make sure to beef up the joint between the engine tubes, half cones, and upper tube. Don't leave all 7 tubes open, that is just too much force on the transition with 7 ejection charges. I used a small amount of epoxy in this area to protect against the ejection charge. I would recommend NOT tying the kevlar cord to the center engine block, mine burned off after 3 or 4 flights. I recently installed a baffle, and tied a long kevlar shock cord between the upper & lower section, with a single nylon chute.

I've launched with these combos, always putting boosters or plugged motors in the 4 plugged tubes.

3xC6-5 - first flight, but not as much fun as 7 motors
4xB6-0 & 3xB6-4 - real nice flight, maybe 700-800'?
4xA10-PT & 3xA8-3 - wouldn't recommend, slow liftoff & very low flight
4xB6-0 & 3xA8-3 - not bad, good for small field, or just using up A8's

More info on my build is here: http://www.rocketryforum.com/showthread.php?t=25439

STRMan
01-12-2008, 09:35 AM
Well, I took the plunge. I just ordered my Hydra VII kit, as well as all the parts necessary to replicate my old Centuri Stiletto. Once I'm done with the three rockets I'm currently building, I'm going to dig in on these two.

A staged model and a clustered model to build... life is good.

Ltvscout
01-12-2008, 10:40 AM
I've launched with these combos, always putting boosters or plugged motors in the 4 plugged tubes.
Let me guess. The launch photo was taken by Dave Seer at the sod farm? Looks like one of his shots.

PaulK
01-13-2008, 12:02 AM
Let me guess. The launch photo was taken by Dave Seer at the sod farm? Looks like one of his shots.Yep. I do appreciate when he is there, he takes great shots. Some day I hope to get one of those going-up photos with all 7 engines.

foose4string
01-13-2008, 01:30 PM
Great lookin' Hydra, Paul!

PaulK
01-14-2008, 07:10 PM
Great lookin' Hydra, Paul!Thanks - just trying to provide STRMan with some motivation. I know sometimes seeing others pics here helps get me going. :) And be sure to post pics of your build STRMan!

foose4string
01-14-2008, 07:39 PM
Thanks - just trying to provide STRMan with some motivation. I know sometimes seeing others pics here helps get me going. :) And be sure to post pics of your build STRMan!

It usually works for me. ;) Was getting inspiration from your Saturn 1b today. Finally made some headway....thanks! :D

STRMan
01-14-2008, 07:53 PM
Thanks - just trying to provide STRMan with some motivation. I know sometimes seeing others pics here helps get me going. :) And be sure to post pics of your build STRMan!

You can count on it! In fact, I'm trying to knock out the kits I have laying around so I can dedicate my time on this one. It looks a bit more complicated than mast of the rockets I've built, so I think I'll take my time with it.


I've got an Estes GBU-24 Paveway III just about ready for primer, and I'll be digging in on an Estes. I'll try to post a picture of the Paveway later tonight.

STRMan
01-15-2008, 09:10 AM
Last night my wife says to me "Oh, by the way, this package came for you today". It says Semroc on it. I ask if there is another, as this is a small box. She says "No, only this on."

I open it up and everything is there. I've now got all the parts to build my Stiletto as well has my Hydra VII kit. I can't believe how compact Semroc can make a rocket kit for a model this size.

Also, I ordered the kit online this weekend. I arrived on Monday. Semroc's reputation for rapid shipping is NOT an exaggeration.

I've got a couple of smaller models to finish assembling, then I'm going to dig into this Hydra kit. More pics to follow as I begin the build

http://i85.photobucket.com/albums/k65/STRMan/Jan15_0006.jpg

http://i85.photobucket.com/albums/k65/STRMan/Jan15_0007.jpg

http://i85.photobucket.com/albums/k65/STRMan/Jan15_0008.jpg

http://i85.photobucket.com/albums/k65/STRMan/Jan15_0009.jpg

Dannycolossus
07-30-2009, 11:07 AM
I ordered the parts for mine yesterday. since i live in NC, fairly close to knightdale, it should get there today.
My uncle grew up in ayden and worked with carl with the original semroc, so i have kind of a special attraction to semroc kits, BUT THIS BIRD IS AWESOME EITHER WAY!!!!!!

jadebox
07-30-2009, 01:05 PM
My Hydra VII is sitting in the corner of my garage that I call the "Island of Misfit Toys" waiting for me to get around to replacing a couple of broken fins (though I bet it would fly just fine without them).

But, before I broke it during transport, I flew it twice on clusters of three C6-5 motors. Both times all three motors lit and the flights were perfect.

Here's a sequence of photos showing one of the flights:

http://www.payloadbay.com/gallery/v/rock/2006-10-07-ROCK-Launch/2006-10-07+ROCK+Launch+541.jpg.html

-- Roger

harsas
07-30-2009, 10:41 PM
My Hydra VII is sitting in the corner of my garage that I call the "Island of Misfit Toys" waiting for me to get around to replacing a couple of broken fins (though I bet it would fly just fine without them).

But, before I broke it during transport, I flew it twice on clusters of three C6-5 motors. Both times all three motors lit and the flights were perfect.

Here's a sequence of photos showing one of the flights:

-- Roger

Three motors? But there are 7 holes.....
:D

jadebox
07-30-2009, 11:20 PM
Three motors? But there are 7 holes.....
:D

I was working my way up to seven.

I'll fix the fins then try it on seven - three C6-7s and four C6-0s. When I built it I plugged four of the motor tubes.

"'Seven at one blow!' said the little man with great pride."

-- Roger

ghrocketman
07-31-2009, 11:28 AM
Stick 7 Aerotech SU 18mm D21's in one of those things. It would equal a G147 !!!
That would get you a full hard-chargin 140 n-sec of total impulse, which is only 21 n-sec from a "baby H".
Now THAT would be a flight, and with the pricing on the "valuerockets.com" website it would not be that outrageously priced either !
Probably would shred the thing though.

Dannycolossus
07-31-2009, 11:14 PM
i finnished my bird this morning. what an awesome rocket!!. i think i'll fly monday, weather permitting