Irhydavi: kitbash of Semroc Hydra VII

[geof]

I'm going to start a new thread with a lot of pictures of my latest project.

The Irhydavi is futuristic 3x18mm cluster kitbash of the Semroc Hydra
VII, created for the 2006 EMRR Challenge. The original Semroc kit is
a nifty 7x18mm cluster design built from a large variety of high
quality parts. Based on the kit's parts and instructions, I think
Semroc's kit looks like a great deal at only $23.

A "kitbash" means to invent a new rocket using only the parts in the
original kit. Nothing may be added (except noseweight). The Irhydavi
adheres strictly to this limitation--even in its name--however there are
a number of places where better/easier solutions can be crafted from
some spare parts. Later, EMRR will have a full writeup.

Geof

 

[geof]

Here are all the parts...

 

[geof]

Construction of the ring fin...

 

[geof]

How to make the main fins from the available parts...

 

[geof]

Here's the aft portion of the rocket with the main fins and the ring fin attached. Note that it's a 3x18mm cluster. Not yet attached are the strake fins and the strake extenders.

 

[geof]

There is a transition midway up the body. It is made from the original nose cone of the kit. Now it will be a BT60-BT20 transition. This photo shows how I made an alignment jig from another BT60 and some CRs. I dryfit the BT20 inside this jig and then slid the jig over the big NC, then glued the BT20 to the big NC by dropping glue down the tube. When the glue dried, I removed the BT60 jig and the CRs, and finished gluing.

 

[geof]

I needed one more nose cone than the kit included, so I had to turn one myself. First I stacked a bunch of scrap balsa from the kit, gluing each layer. Then I inserted a hardwood dowel. Then I turned it on a power drill, using sandpaper. It takes a very steady hand and lots of patience. When it got close, I filled in low spots with repeated coats of Kilz, sanding lightly on the drill between coats, until I was satisfied with the final result.

 

[geof]

Okay, now for some shots of the finished rocket. I think the forward main body might benefit from some slight decoration...Any suggestions?

 

[geof]

It needed 2oz noseweight for stability, bringing the whole thing to 7 7/8 oz. With 3xC6-5, wRASP predicts about 850ft.

 

[geof]

It flies great: absolutely straight and stable. It recovers in two parts, gently.

 

[geof]

Cool front view...

 

[geof]

Here's a view of the business end. This also gives a good idea of how all the fins and rings align...

 

[geof]

One last photo. On its third flight, there was some freak accident with the chute for the upper body. Ejection was exactly at apogee, with the rocket horizontal. The aft section recovered perfectly, but something went wrong with the nose chute. It appeared that the nose section came in ballistic with no chute attached. I thought the kevlar had snapped because we saw no flapping or dangling stuff. However, it was hard to see because it was directly into the sun, and I lost sight of it as it got nearer. I focused on the ground, hoping to sight the dust cloud on impact. I found it. The nose section core-sampled the full length of the nose cone. This failure was mystifying because at the impact site, the nose chute was fully deployed, untangled, unmelted, attached, and looked like an absolutely normal recovery. (Any ideas?)

Fortunately, the nose section is easy to repair. I think I will probably lengthen the rocket, to permit a reduction in nose weight and much greater altitude.

Hope you enjoyed viewing this project as much as I did building/flying it!

Geof

 

[PunkRocketScience]

Hey Geof-

Nice build! Sorry to hear about the in-flight failure.

Geez....I gotta get going on mine before it's too late! So many rockets..so little time...

 

[JBeau]

That's an amazing looking bird. Superb paint job, very jealous. Was that all spray painting? Some clever, clever ideas there. You gotta kit that, puppy!

 

[Carl]

WOW!!

You got that rocket out of that bag?

Best kitbash we have seen of the Hydra VII.

 

[Carl]

We could have sent you a nose cone, but that would have spoiled some of the fun.

 

[cjl]

VERY nice

Incredible

Sorry to hear about the failure, and that is very bizarre. I wonder what happened...

 

[sandman]

That is a SUPER build but I gotta say...

I cannot imagine anybody going through THAT much work to make a BT-20 nose cone!

But, you did wind up making all of the parts from what was in the kit bag!

 

[JRThro]

Originally posted by Carl
WOW!!

You got that rocket out of that bag?

That's pretty funny!

 

[nomopbo]

Wow Man. Nice job and cool paint job as well.

 

[snede2112]

Originally posted by geof
Okay, now for some shots of the finished rocket. I think the forward main body might benefit from some slight decoration...Any suggestions?

How about some cockpit windos? Maybe something like those found on a B-29.

 

[geof]

Thanks to everybody for their kind responses.

Regarding the crash, I've already ordered replacement parts. I'm going to stretch the forward body, especially the BT60 part. Withing 5 minutes, Semroc confirmed my order, and first thing next morning it was ready to ship!

JBeau, yes it was all spraypaint except for black brushed on the inside of the ring. Lots of careful masking with scotch tape.

Carl, Thanks! I've gotta say that I'm really impressed with your business. I love the quick reliable turnaround, the free shipping, the large inventory, and the freebie that the shopping cart offered last night. The Hydra VII looks like a real steal at $23 for a high-quality 7x18mm cluster kit with tons of good parts.

Sandman, you know it dude.

Sneede2112, that's an interesting idea...presumably on the BT60nose/transition? I'll check through my spare decals. I had been thinking of some yellow or blue dots ringing the BT60 below the transition, with a red ring stripe above and below the dot ring....something more abstract.

G

 

[snede2112]

Originally posted by geof

Sneede2112, that's an interesting idea...presumably on the BT60nose/transition? I'll check through my spare decals. I had been thinking of some yellow or blue dots ringing the BT60 below the transition, with a red ring stripe above and below the dot ring....something more abstract.

G

OOOh. Artsy.
Yes that is where I was thinking, sort of like Flash Gordon's ship.
I think your idea definitely fits the paint scheme better though.
That is a beautiful bird. I'm sure I speak for everybody when I say that I would love to see some launch photos.

 

[geof]

This rocket flew great. However, on its third flight, the nose section suffered some sort of mysterious parachute failure (see EMRR). A major repair job was needed, and the result is the stretch version of the craft. It's now nearly 6 feet long.

The overall weight and CG are approximately unchanged. With the longer airframe, I used less noseweight. While swing-testing this version, I snapped a fin before getting any conclusive results. Afraid to do any more swinging, I'll take my chances with a full launch, planned for Octoberfest in two weeks.

Photos of the stretch Irhydavi...

 

[geof]

...and another...