Just Jerry

If I ordered one of those I would request a 4th fin and congratulate him on a fine product.

Jerry

QuickBurst

I ordered one yesterday. I am a three fin fan myself.

I plan on surface mounting them and having a min diameter bird with a removable 75x54 motormount.

ddmobley

WOW!!!! Talk about blink, gone!

DAllen

What in the world is that supposed to mean?

heada

There has been a thread or two about how the positive aspects in regard to angle of attack (AOA) with four fins and not three outweigh the negatives of drag and weight of only 3 fins.

Add a 4th fin and it'd be a better rocket.

-Aaron

porthos

Well, if it's like the Intimidator 5, the tube's slotted for the fins. Adding a fourth fin would require a lot of work, or a new booster tube.

QuickBurst

Well he said he would order it that way. This means it would have to come from Performance I suppose.

Any speculation on delivery time?

lalligood

Interesting... Come to think of it, IIRC it seems that most "real" rockets & missiles have 4 fins. (And it would explain why some of my favorite USR kits happen to have 4 fins!) I'd like to read more about this.

However, I'm not having much luck (getting too many results & none appear obviously relevant based on thread title) using this site's search feature to find those threads. Do you have any links handy? Thank you.

heada

Here is the most recent thread that contains the subject.
http://www.rocketryplanet....ms/showthread.php?t=1706

Jerry seems to know the most about this, or rather I have seen him post the most about this on RocketryPlanet but John(denverdoc) and Adrian seem to understand the principals very well too. As a matter of fact, someone mentioned that out of all the real sounding rockets they could think of, only the Aerobee Hi was a 3-fin rocket. All the rest are 4 fin.

-Aaron

ddmobley

And the Black Brant II, IV and VB, Wac Corporal, Aerobee 150 and 300, maybe more.

porthos

The WAC Corporal had three too.

heada

ok, ok...I didn't say *I* could only think on the one, just that *they* could only think of the one.

-Aaron

ddmobley

Good dodge!

porthos

If I remember correctly, I read somewhere that they told Melina the WAC Corporal wouldn't fly with only three fins. Guess he knew more than the military experts, eh?

JRogers

Picked one up at NERRF, can't wait to start work on it, beast will be bullitt proof

QuickBurst

I like 3 fins.
Less weight, less work, .....

Less work.

OK I'm lazy.

One less fin to break off. From what I've seen, I can't think of anything a four fin rocket does better than a three fin rocket.

Note:
There is absolutely no science behind my belief.

porthos

My original L3 design had six fins. When I got to the fiberglassing part, I trashed the idea and bought an Intimidator 5. 3 fins. Less work.

lalligood

That was some great reading! Thank you very much for finding & sharing the link

nh4clo4

The Black Brant II has 3 fins. That was my level 3 project.

Just Jerry

I strongly endorse that link and feel it should be in the FAQ after rereading it.

Jerry

UncleVanya

Moved the fin discussion to here.

ddmobley

Yes, that's the basis of my post, that all of those (the Black Brant II, IV and VB, Wac Corporal, Aerobee 150 and 300) had 3 fins.

What size BBII did you build? The fins give you any grief on landing?

DAllen

Anyone happen to have a RockSim file for this bad-boy? Also, the parts list on Wildman's site does not apparently have any recovery hardware listed on the parts list. Not that this is a big deal but do performance rocketry kits normally come without that stuff?

-DAllen

UncleVanya

Every Performance Rocketry kit I have seen consists of body tubes, centering rings, nose cone, fins, motor tube, couplers, and maybe some bulkheads. No instructions are provided, no eye-bolts, no threaded rod, no parachute, etc.

These are not "ready to assemble" kits like the GLR kit recently reviewed by Darrell - these kits are really just a collection of parts that anyone with experience can turn into a rocket by adding knowledge and some additional parts.

ddmobley

I wonder why some of them are so expensive then, given that they are just a collection of parts.

H_rocket

Probably because they are 100% convolute fiberglass. The finished product is the proverbial S*** Brickhouse.

I actually like the fact that all the recovery stuff is not there. I need another parachute like I need a hole in my head.


Well the hole may not be that bad an idea.

deandome

Wildman offers PR "Completion Kits" that have cords, hardware, chutes, retention, etc. Sometimes, though, they're almost as much $$ as the rocket! And I don't think you can get, say, the kit w/out a chute...it's all or nuttin.

And I think what Mobley is asking is why are some PR kits (the scale ones..like the Arcas) expensive & the others...the Econolines... are cheap? Do they use the same tubes & all?

Whatever...it seems that most people buy the Econolines & that most of their new kits are in that range....'cept for the new carbon Mongooses.

heada

Most of the non-econoline rockets have fincans of some sort. Those fincans are expensive to mold in time, material and master mold-making.

Performance Rocketry kits are great kits as they are simple and nearly indestructible but in no way are they for someone who does not have previous HPR building experience. They truly are just a bag of parts and for some people, that is ideal.

-Aaron

UncleVanya

Since we are talking about these kits:

I have been told that they require a lot of roughing up to get the epoxy to stick to them. Anyone have any words of wisdom?

heada

I have built a Little Dog DD, Mad Dogg DD and I have a 4" Nike Apache waiting to be built. I have used PR tubes for scratch kits before in sizes from 38mm to 6". I always use some 120 grit sandpaper to prep the area before bonding and have never used too much pressure or had a bond come loose.

I would say you have to prep the area no more or less than using Quantum Tube or phenolic from PML but less than LOC paper tubing.

-Aaron

QuickBurst

I have two, both are the Econo Line kits and yes they are nothing but a bag of parts. However for my own preferences they are just what is needed.

All I do is order an extra coupler with the kit, then build it Zipperless and dual deploy. The build scheme works well for me (to each his own ...) .

This one will be a little different because I will be surface mounting the fins.

The attraction (for me) is that the kits are light and virtually indestructable. I have fiberglassed cardboard and phenolic tubing in the past. My own experience tells me that I can not produce a lighter stronger rocket than the PR kits. By the time I buy the tubing, epoxy and tubing I have spent a great deal more time and about the same money.

I have a PR Competetor 4 that I have flown several times, mostly "Ks" and "L's". The last time I flew it I sent it to 11,000 feet at Mach 1.3. No dings or broken parts. Assembly is a breeze and you end up with one hell of a rocket.

I like them.

UncleVanya

I hope that I didn't confuse the issue by implying that this was inappropriate. I'm a primarily scratch builder myself - so a collection of parts is sufficient most of the time for me. I do like instructions and basic info on CP - but really detailed instructions are not a requirement for everyone.

That said, I think there should be some name other than "kit" applied to these to differentiate them from comprehensive kits like PML or LOC.

QuickBurst

No offense taken, at all.

We're cool.

The "Kits" do come with a drawing showing what is intended to go where. No measurements or anything like that. I suppose it's more of a suggested placement guide than anything.

H_rocket

I was robbed! My Gizmo and 1/4 scale Nike Apache came with a newspaper to read (or was that packing), but that was it. I guess they figure if you can't figure where the fins and pointy part go, a 54mm motor mount is probably not your cup of tea...

UncleVanya

Ditto - no pictures with my Gizmo either. But I like you agree that the assembly of the Gizmo is pretty simple if you know something about HPR rockets. But I suspect it would be challenging if you had never built a HPR rocket before.

H_rocket

What's really funny is if you compare a Performance Kit to some of the new Estes (and even Fliskits) designs. these "HIGH POWER" kits are shockingly easy to assemble. I have a Acme Spitfire that I still can't get right.

UncleVanya

Spitfire is still in my build queue. I have read the directions and it does seem like a bit of a challenge.