Protovamp - A Galaxy Class Predator

les said:

WOW!!! That looks great!!! :clap::clap::clap::clap::clap:

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Thanks Les. What a strange build for me this time. Not only was it the 1st tube finned job in 30 some years, but there was little or no construction until the near end. I've never built a rocket quite this way.

neil_w said:

Very cool, very unique. Bravo to you sir.

How long is it?

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Hey! That's nunya busi......uh 40" LONG

Thanks btw Neil. I'll be doing laundry for all the rockets I've posted this month. That's, 5?....Maybe?

Really sweet! I bet alignment of those tubes, especially pre-finished, was a b.....eaut.

BABAR said:

Really sweet! I bet alignment of those tubes, especially pre-finished, was a b.....eaut.

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Not too hard really. I had to babysit each one until the epoxy set. 5 min? Likewise with all the assembly. Kinda like building with Legos. Went real quick.

Awesome! Nice work. Look forward to seeing launch photos/video!

You really outdid yourself this time Gary.
That is just spectacular amazing.
That needs to be sold as a kit!
If Estes only had the design of the month still...

That is a seriously nice rocket. Excellent design and execution.

TangoJuliet said:

Awesome! Nice work. Look forward to seeing launch photos/video!

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Woody's Workshop said:

You really outdid yourself this time Gary.
That is just spectacular amazing.
That needs to be sold as a kit!
If Estes only had the design of the month still...

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RocketFeller said:

That is a seriously nice rocket. Excellent design and execution.

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Guys, you're all too kind. Thanks a bunch. I am a little concerned about where that one launch lug is though. An RSO would prolly frown that there is no forward lug. It bothers me too. So I am trying to decide how I'd make a temporary lug for flying purposes. I know I could tape some kind of standoff rig to the forward airframe, but I'm wondering if there is an alternative to taping it.

Regarding any kitting, There would certainly have to be some modifications done. That lug housing is custom made and so is that nose cone. Someone would have to go to a lot of trouble and expense just to have certain parts manufactured. For me, I just fabricated what I wanted. Not everything on this rocket can be bought off the shelf.

Hope to have some flight vids and pics in a few weeks when the launch dates come to pass.

What about fly away launch lug, like the rail guides, on a stand off?

Woody's Workshop said:

What about fly away launch lug, the rail guides, on a stand off?

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I've only heard about those. Never saw one. I suppose a little research is in order.

If you're that concerned, maybe it's worth permanently adding a forward lug. It doesn't have to be anything obtrusive. Even some properly bent and secured music wire would be enough.

TangoJuliet said:

If you're that concerned, maybe it's worth permanently adding a forward lug. It doesn't have to be anything obtrusive. Even some properly bent and secured music wire would be enough.

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I've never made one of those. And they always sounded like something flimsy. Do they work well?

I haven't done it either, but all you would need is to form a loop of music wire with two legs that could be glued to the BT. Maybe even pass them into the BT with the ends angled 90* so that it can be epoxied on the inside against the BT wall. Does that make sense?

Here's a quick and dirty drawing to explain:

All you're really looking for is a little more guidance ahead of the CG before it leaves the pad and this would provide it.

TangoJuliet said:

I haven't done it either, but all you would need is to form a loop of music wire with two legs that could be glued to the BT. Maybe even pass them into the BT with the ends angled 90* so that it can be epoxied on the inside against the BT wall. Does that make sense?

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It does, and may be an option. I just found something worth trying also. A collar that isn't permanent. Basically it's a 1"tube length of the same size airframe with a slit on one side, that slips over the airframe. Attach a stand-off and piece of lug and you can tighten it with a small piece of tape. Paint the whole thing black instead of the green I used. That was auto paint that was airbrushed and would be a PIA to mix some new just for this. After the flight, I can take it off and chuck it in the range box.

TangoJuliet said:

Here's a quick and dirty drawing to explain:
View attachment 317664
All you're really looking for is a little more guidance ahead of the CG before it leaves the pad and this would provide it.

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That looks pretty doable, but I'll need 1/2 inch of stand-off. Binding on the rod could pose a threat? Maybe?

Maybe just add a bit of balsa to the backside of each leg to keep it from wanting to bend backward/aft, but I doubt you'd even need that really. 1/2" isn't much, and it'll only be on what, maybe 18" of the rod before it's clear? And the lower, enclosed, LL would provide the remaining guidance up the rod.

At first, I thought MAYBE, that the really long aft lug would suffice, until after I finished building the rocket. Now I'm certain it just isn't enough. I really really really didn't want some hideous stand-off sticking out of the forward airframe, and I almost considered having a housed lug like what was done on the DOM Starship Excalibur. They called it a "shuttlecraft bay" and it housed the forward lug. But it too would have to stick out too far to be aesthetically pleasing.

Since for the moment, I don't have any music wire on hand, I'll prolly go with the strap on collar to see if it'll suffice. If not, I'll make a point to grab some wire from somewhere. I know that'll be hard to find in this dumpy, bass ackwards town I live in.

Paperclip wire works.

I'd be careful with paperclip wire. It's a bit susceptible to breakage when bending. That's why I recommended music wire.

Ha, I am familiar with this problem. Launch lugs can be a pain in the butt.

Where is the CG, anyway? I'm guessing somewhere around the cannons. Since your existing lug housing (which is beautiful BTW) is centered at the bottom, your front lug could go between the cannons on the bottom, and could probably be made to blend in with the design reasonably well. Based on the discussion above I wonder if you're actually talking about putting the front lug way far forward, but I'm not sure why you would need to.

If you were starting from scratch, you could conceivably have found a location for the front lug in some strategic place in and amongst the cannons, but then the rear lug would have to be somewhere other than where it is now.

neil_w said:

Ha, I am familiar with this problem. Launch lugs can be a pain in the butt.

Where is the CG, anyway? I'm guessing somewhere around the cannons. Since your existing lug housing (which is beautiful BTW) is centered at the bottom, your front lug could go between the cannons on the bottom, and could probably be made to blend in with the design reasonably well. Based on the discussion above I wonder if you're actually talking about putting the front lug way far forward, but I'm not sure why you would need to.

If you were starting from scratch, you could conceivably have found a location for the front lug in some strategic place in and amongst the cannons, but then the rear lug would have to be somewhere other than where it is now.

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I'm sure, that had I thought I was going to need a forward lug, I would have installed it before I painted. And a stand off was out of the question. Hence, the extra long aft lug. The placement you mention wouldn't have been that hard to do either. Now I wish I had done that, but since I didn't, and I'm not screwing up my paint job for that kind of fix, I'll just strap one on for flying. As far as placement of a forward lug is concerned, it really isn't going to matter where it goes. I believe folks put way too much emphasis on lug placement when there are two of them. I say this because I usually eyeball placement and there is no real science or mathematics to it. In most cases, I'll locate 1 lug as far to the bottom as I can and the forward one somewhere above CG. Basically whatever looks OK to me. I figure the strap on can go as far forward as I want it to and it's not going to assist any differently than if it were 6" lower or whatever.

That all changes when you have only 1 launch lug to mount. Then you have to be particular where it goes and how long it should be. And since I detest those centrally located lugs sitting there in the center like a stick out of place, I'll opt for two instead almost always. And conceal them if possible.

CG btw, is center of the spires on the cannons.

Gary Byrum said:

As far as placement of a forward lug is concerned, it really isn't going to matter where it goes. I believe folks put way too much emphasis on lug placement when there are two of them. I say this because I usually eyeball placement and there is no real science or mathematics to it. In most cases, I'll locate 1 lug as far to the bottom as I can and the forward one somewhere above CG. Basically whatever looks OK to me. I figure the strap on can go as far forward as I want it to and it's not going to assist any differently than if it were 6" lower or whatever.

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The only effect I can think of is that the further back on the rocket, the faster the rocket will be going when the front lug goes off the rail. So the main thing I would consider is simply to ensure that it is not positioned too close to the top of the *rail*, otherwise it won't really accomplish very much.

CG btw, is center of the spires on the cannons.

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That is farther forward than I would have guessed based on mindsim. Once you're in front of the cannons, a fly-away lug of some sort is probably a good bet.

It is hard to imagine the CG being where you say it is, unless that NC has added weight.

neil_w said:

The only effect I can think of is that the further back on the rocket, the faster the rocket will be going when the front lug goes off the rail. So the main thing I would consider is simply to ensure that it is not positioned too close to the top of the *rail*, otherwise it won't really accomplish very much.

That is farther forward than I would have guessed based on mindsim. Once you're in front of the cannons, a fly-away lug of some sort is probably a good bet.

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Depends on the length of said rocket too. Longer models would need to be somewhat lower, but on shorter models, not so much.

Your mindsim might have been accurate had the nose been of average weight. It's not, and there's a story about that. I totally screwed up the turn using an undersized block of balsa. I was turning for a BT 60 not considering the overall girth of the nose cone. The average 60 nose cone requires a 2" sq block, where this nose needed a 2.25" sq block. I should have taken pics of this whole catastrophe, but to save face during the build, I didn't. I had to laminate strips of balsa around that girthy section to acquire a 2.25" or better area from which I'd turn down to size. That worked, but not without a lot of doctoring. The overall shape of the cone was incorrect and had a noticeable "dip", or concave area that had to be built up with many layers of putty, sanded and layered again until the desired shape was acquired. THAT, my friend, was a major PIA!!! It prolly weighs 3/4 as much as it would have. So, I'm OK with that too. No additional nose weight required.

Hmmmmm. Your existing lug (and think post 44 pic 4 and post 58 pic 1) is pretty long, seems adequate length to keep the rocket straight. Your CG is not that far forward of the lug, therefore given we must assume the rocket is stable, the CP is behind that so even closer (better) to the forward end of the lug. The lug (if I am picturing it right) also appears pretty strongly built in, like it is bolstered by two strakes, so should hold even with some cross wind given CP isn't that far further forward to cause that much torque. You obviously have a ton more experience than I do, so you are probly right, but again assuming both the lug AND what the lug is attached to (not sure if it is on main BT or on a RING on main BT) are solid, seems like plenty of lug to me.

Another option would be mini rail buttons attached through existing lug, one forward end and one back. Again, still near the rear of the bird, but much stronger and without concern for rod whip. Assumes the tubes and accoutrements wouldn't hang up on the rail, of course.

BABAR said:

The lug (if I am picturing it right) also appears pretty strongly built in, like it is bolstered by two strakes, so should hold even with some cross wind given CP isn't that far further forward to cause that much torque. You obviously have a ton more experience than I do, so you are probly right, but again assuming both the lug AND what the lug is attached to (not sure if it is on main BT or on a RING on main BT) are solid, seems like plenty of lug to me.

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That lug was designed to be a workhorse. It was CA treated, has multiple additions of glue fillets, is housed between two strips of wood with epoxy putty filling the forward and aft gaps on either end, CA on the wood strips, filler putty for a build up sanded smooth, Bondo over all that and sanded smooth and sealed with CA again. I did this anticipating it being the only lug. 98% of the time, I would have never questioned adding another lug to a rocket this long, but I figured beefing up the one lug, should be a safe bet. The BT 80 it's mounted to has four inner braces/ribs attaching it to the 60 airframe. Yes, air will pass through the inside of the BT 80. Custom cut tubes/tube fins and such, usually have a degree of flexibility which is why I treated all of them on the inside with thin CA. It does hold it's position on a 1/4" rod quite well and I prolly could get away with just the one lug. But sure as I'm sitting here, some RSO ain't gonna pass it. Better to have a strap on as a backup rather than wishing I did.

Ahhhh. Now I see. I fly with a small club with a very good RSO. He is all about safety. If there are some questionable cases with smaller rockets he will allow heads up flights either at the beginning of the day when only club members are there or at the end of day again when only club members who will all truly be heads up are present
I imagine at some much more well attended launches this flexibility would be unsafe.

I am sure it is not easy being the RSO

The ones I fly with are pretty lenient and a "heads *** can be any old time of day. I usually have 3-4 rockets getting their maiden launches about every time I go and there's usually no hassle. The one time I had a near no-go was with the Gyro Dragon. Johnny was concerned about the only lug he saw at the bottom of the rocket, until I showed him where the forward one was hiding. I feel pretty certain they might be concerned about the Protovamp like it is, so instead of going through the routine like I have done here, I'll just strap on the hitch hiker and load this bad boy up.