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Semrock Hydra VII

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Karl

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Id say the Hydra VII is medium power as it takes 7 C impulse motors , if you dont class it as MPR please move it to the appropriate place.
Right heres the question , does anyone have any tips about building this rocket ? Mine should be here any time soon so I want to get some feedback before building it .
-Karl
 

n3tjm

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replace the twelve small fins between the three fins... I have not painted my bird yet, and I already broke three of them off :mad:. The balsa is way too thin, and the grain is going the wrong direction. I would use 1/32nd birch or plywood....
 

Karl

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I think ill coat my fins in CA to reinforce them , and make realy good epoxy fillets :D
-Karl
 

n3tjm

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I coated mine with CA... made then less fragile... but still easy to damage... Remember, CA is brittle...
 

Karl

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What about if i fiberglassed them ? Sureley that will add strength ( And Weight ) Have you got any pics of the parts to see what quality they are ect ?
-Karl
 

n3tjm

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The quality is fine... just 1/32 balsa is awlful thin... and the grain was going the wrong direction. I will take some pics when I get home from work this evening.
 

Karl

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Thank you , I will PM you my email .
-Karl
 

Mike

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A 7-motor cluster is pretty advanced - make sure your launch set up can handle it and you got plenty of cluster experience.

Sounds good, keep us posted.
 

cydermaster

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I've still not painted my Hydra VII, but I've had no problems with the 12 small fins.

No specific tips to pass on. The instructions are littered with tips, and cover most bases.

BE WARNED: Semroc kitbags are like TARDISes. They arrive neatly packed, you open them & shake the bits out, and then you can NEVER get it all back in!

The instructions look pritty daunting at first, but they are well written. You'll be spending a few days going over them, before you get the glue out! ;)

Takes a few days to build too - not something you can slap together with CYA during a Dad's Army repeat.

The Hydra is definatly my most satisfying build to date, and it is one fandabbydosey-looking rocket. As it starts appearing at launches, over the summer months, its going to turn a few heads & become a popular kit (IMHO).
 

Karl

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Originally posted by cydermaster
I've still not painted my Hydra VII, but I've had no problems with the 12 small fins.

No specific tips to pass on. The instructions are littered with tips, and cover most bases.

BE WARNED: Semroc kitbags are like TARDISes. They arrive neatly packed, you open them & shake the bits out, and then you can NEVER get it all back in!

The instructions look pritty daunting at first, but they are well written. You'll be spending a few days going over them, before you get the glue out! ;)

Takes a few days to build too - not something you can slap together with CYA during a Dad's Army repeat.

The Hydra is definatly my most satisfying build to date, and it is one fandabbydosey-looking rocket. As it starts appearing at launches, over the summer months, its going to turn a few heads & become a popular kit (IMHO).
Cool , I carnt wait to get mine! Ive never had any cluster experience , just alot of LPR staging. Ill spend a while going over the instructions , and working out what goes where.
Are you taking yours to any big launches like EARS or UKRA ? I am going to use a Rail to launch this baby , and i have a home brew launch controler to ignite all the motors ( Even though I will use QuickMatch)
Me and the guy who runs Deepsky (Paul) , and I think another WRS member are having a drag with them at a big launch , would you like to join in ?
Could someone explain to me how the rocket returns on 3 'chutes , and what sizes are they please ?
-Thanks
Karl
 

n3tjm

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Ok, this is really getting me fustrated... Having to fix fins after a flight is one thing... but having to repair fins between coats of primer... :mad:... and these things are CA coated!

Next time, I would laminate them with paper...
 

n3tjm

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I am thinking about just shaving off the 12 little fins, because I know I will be doing a lot of field repairs with this bird :(. Semroc offers Rocksim files of their kits, but I never been able to download one... I want to see if this bird is stable fully loaded without the twelve small fins?
 

Karl

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Thanks for the pics , why are they breaking between priming ??? Primer might be to strong ? Ive tried EMRR but they havent got a review of this bird , so looks like I will right one up.
-Karl
 

n3tjm

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I think I just got a bad batch of balsa... too soft. Just touch the fins and they snap. I am going to try one more time... and if I break any more fins... razor blade time... Oh, and I broke another one after I took those pictures :mad:
 

Karl

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I think all the fins might be the same ,theres been lots of complaints of them being to brittle and weak. I think its best to replace them before you build it with thicker balsa/ply. Could you explain to me how it comes down on 3 'chutes , and what sizes are they?
-Karl
 

n3tjm

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Three 12" chutes. One for the payload section, the other two tied to the shock cord on the booster. I may replace all three chutes with a single larger chute.
 

cydermaster

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It does sound like you've got a dodgy batch of balsa there, Doug. The balsa on my Hydra is tip-top quality. Also you mention the grain is the wrong way - I've had a butchers at mine, and the grain is how it should be (ie. parallell to the leading edge).

BTW: Theres a review of the Hydra on EMRR. It was uploaded today.

As for Hydra Drag Racing - yep, I'm up for that Karl! :D
 

n3tjm

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Sorry, I was not clear on that... mine is the same way, but when using balsa that thin, it is best to have the grain perpindicular to the root edge. That yeilds the best strength overall (put unpratical for most fin designs as it wastes balsa). That will yeild the strongest bond.

I had enough... I cut off all the small fins :(.
 

Karl

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Well due to what every1 has said im not going to use the supplied fins , and make my own from ply or thicker balsa. Are the boosters nosecones easy to cut?
-Karl
 

n3tjm

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The three main fins, and six internal fins are fine... it is the twelve small fins that is the pits... replace those :). You want to keep the tail end as light as possible :)
 

cydermaster

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Originally posted by Karl
Are the boosters nosecones easy to cut?
They're nowhere-near as hard to cut as you'd think they'd be. I was very aprehensive about doing it, until I actually did it. A bit like the washing-up/hoovering in that respect ;) . Make sure you've got a sharp blade, if you use an Exacto-type knife (like I did), and take your time. Minor 'imperfections' get sanded away, when you 'round-out' the insides.
 

Carl

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Balsa:
Balsa is one of the biggest variables in model rocket kit construction. We use balsa sheets that vary from 8 pounds per cubic foot (pcf) to 14 pcf, with an average of about 10 pcf. Generally, the more dense balsa is harder. Tolerances of the 1/16", 3/32", and 1/8" sheets that we use are +/- .010". We discard balsa that is at the low end of the scale because it is much weaker. The type of grain can affect harness as well. We also discard most of the A-grain balsa because it is significantly weaker and warps too easily, particularly in the 1/16" sheets. Most of the balsa sheets we use are B-grain. Since Balsa is from living trees, it is never perfect. Knots, insect holes, and diseased sections are some of the imperfections we look for and reject when laser-cutting the fins. Man-made imperfections like saw marks, machine handling marks, and areas with improper sanding are other reasons for rejecting balsa sheets.

In any case, we will replace any fins that are not up to our (or the customer's) standards.

Parachutes:
The Hydra VII has three 12" chutes, two for the booster section and one for the payload section.

Augmenter fins:
The 12 augmenter fins provide a significant amount of surface area to move the Center of Pressure rearward. If they are left off, some weight must be added to the nose cone to keep it stable. If they are replaced with heavier material, the nose cone may also need additional weight.
 

Karl

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Hi , I received mine today , and the first thing out of my mouth when i opened the packet is WoW! This is one of the best quality kits ive ever built! And its bigger than I thought it would be.
Theres no need to fill spirals I dont think , as the BT's are so perfectly built! You are right , the fins look at little weak , but I had a idea about that ..........
If you join the payload and the other section of the rocket with the shock-cord and kevlar provided , and increased the size of the 'chute , it would decrease the decent speed and reduce the risk of it getting damaged............BUT (Ohh yes theres allways a but) , when the 'chutes out and its coming down , the payload will be flying all over the place and its going to be banging on the rocket , possibly snapping a few fins off?
-Karl
 

cydermaster

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Originally posted by Karl
the first thing out of my mouth when i opened the packet is WoW! This is one of the best quality kits ive ever built!
All the Semroc kits I've built, to date, are of similar quality. :D

Not a bad idea, having the whole thing come down under one gurt huge 'chute. It would certainly make recovery easier. If you extended the shock cord, and attached the 'chute to the payload end, that might stop any descent damage.

What number Hydra have you got? Mines #61.

Now ... if they would just produce some decal sheets with Great Britain, instead of United States .... ;) - I know, its prohibitivley expensive to do that, but I like to dream! ;)
 

Karl

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lol! Went to the local model shop earlier and got some 12min epoxy , sanding sealer , and the right paints for the rocket , just missing a razor saw now :mad: Ive made the motor tubes , and sanding sealed all the fins ...... gonna leave it at that for a while. But only 2weeks till big EARS , dont know if im gonna have this bird ready :(
The small nosecones look pretty hard to cut !
My Hydra number is : #00118

The only thing this rocket has missed out is , where to put the decals in the instructions.
 

Karl

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Mine is almost finished , all fins epoxy'd to the tubes , small nosecones cut ( Actually not that hard , balsa is realy easy to cut with a new hobby knife) The complete rocket was primed with Plastikote white primer , and then masked off to paint the right colours in the right places. Masking was quite a challenge to get into all those little places.Ive also changed the position of some of the small fins . All that needs doing is the bodytube & nosecone to be painted , decals applied , thrust rings to be inserted. The whole rocket was painted by hand using Humbrol Enamel , a very very still hand , then was coated in NHP 12min epoxy to strengthen the fins & give a nice glossy finish. Ill post some pics when I complete the rocket :)
-Karl
 

WiK

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You coated a rocket in epoxy?!?! Haven't you heard of Clear spray?

On the subject of paint... Have you got a Halfords near you? If so, try their paint. Very good quality.

I'm thinking of buying one of these aswell. :eek: Although I would prefer to have it come down all under one chute. Could someone either tell me how much it weighs, or reccomend a chut size? I only plan on flying this on one C for the time being. Need another launch controller before I attempt clusters.


Cheers,

Phil
 

Karl

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Originally posted by WiK
You coated a rocket in epoxy?!?! Haven't you heard of Clear spray?

On the subject of paint... Have you got a Halfords near you? If so, try their paint. Very good quality.

I'm thinking of buying one of these aswell. :eek: Although I would prefer to have it come down all under one chute. Could someone either tell me how much it weighs, or reccomend a chut size? I only plan on flying this on one C for the time being. Need another launch controller before I attempt clusters.


Cheers,

Phil
Yep I have , and it's worked extremely well! Ive not coated the WHOLE rocket with it , just the motor tubes , rear fins.Im going to use Plastikote Clear finish to complete the rear section of the rocket.
Yep I have a halfords close to me (a 10 minute walk) and I actually have a few of their paints , Yellow Primer , Orange Glow , Copper , but they are quite expensive.
The Hyrdra is supposed to come down on 2 12" 'chutes , and the payload on a single 12" 'chute. What im going to do is , have the rocket coming down on 1 18" ripstpop nylon 'chute , or a Estes 24" 'Chute , the fins should hold quite well with the fillets & coating.
-Karl
 

Karl

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Originally posted by n3tjm
My Hydra VII is now finished.

Notice the mod I made to mine? I added a bolt to the nosecone to compinsate for the loss of fin area.
Thats a hell of a neat paint job! Far much better than the original scheme! Did you get 12 spare small fins with your kit ? I did :confused:
-Karl
 
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