PML AGM 256 Pitbull. Please take pity on the BAR and help

[Zoomie]

DELETED. See below.

 

[Zoomie]

AFTER I did this, I reread your post. I have measurements good to +/- 1mm.

That said, I think that my problem here is that I am not familiar enough with OR to understand exactly what needs to be input. I assumed after a mere cursory glance that I could just plug in or plot dimensions. This is what happens when a monkey tries to understand rocketry.

I just measured fin thickness. 2mm or a hair over 1/16th, take your pick.I've seen a number of posts where people were so terrified of these fins that they glassed them at transitions and surface. I have read only one report of a crack and that was caused by a hard surface landing.

This kit is really making my head hurt. I'm trying to learn OR and to use sims with a kit that hasn't been used heavily. I'm really starting to think that I should set this aside for now and look for a more popular model for now. That way I have a ton of public rocket/engine data to use and peruse.

Here's my latest (useless) pic. MM lines don't show but they are there.

 

[K'Tesh]

As it is currently two minutes to midnight here in China, I'll be heading off to bed.

I'll try to pick this up after school tomorrow afternoon.

Basically, 0/0 will be the forward edge of the root, all other points will be calculated relative to that.

 

[Zoomie]

Roger. Thank you.

May you dream of big, bow-legged women.

 

[K'Tesh]

Roger. Thank you.

May you dream of big, bow-legged women.

I have no idea what that means

I decided that since the fins look pretty easy to model, I'd go ahead and work it. you may need to verify my numbers, but I'm sure they're close.

View attachment Public Missiles Ltd. AGM-256 Pit Bull.ork

 

[Zoomie]

K, sincerest thanks. You didn't have to do this. While I am beyond grateful for everyone's experience and assistance here, I do not come here with the expectation that I can lounge while others kill themselves to aid me. Again, thank you !

The comment above was my attempt at humor. Not worthy of explaining.

 

[AlfaBrewer]

I decided that since the fins look pretty easy to model, I'd go ahead and work it. you may need to verify my numbers, but I'm sure they're close.

Thanks for sharing your technique. I'll be using this going forward.

 

[K'Tesh]

K, sincerest thanks. You didn't have to do this. While I am beyond grateful for everyone's experience and assistance here, I do not come here with the expectation that I can lounge while others kill themselves to aid me. Again, thank you !

The comment above was my attempt at humor. Not worthy of explaining.

Not a problem...

And I realized that it was an attempt at humor, but I don't understand the significance of "bow legged". I figured it was something like what Gimli said in LOTR of "little hairy women" in the drinking game, which I'm sure referres to female dwarves.

 

[Exactimator]

Zoomie, while the OR skills will come in handy, if you're looking for the CP on your rocket, you can just contact PML (they're responsive to emails) and they'll tell you where the CP should be.

 

[Zoomie]

Zoomie, while the OR skills will come in handy, if you're looking for the CP on your rocket, you can just contact PML (they're responsive to emails) and they'll tell you where the CP should be.

I was really trying to understand how to select motors based on profiles, etc. I needed accurate info on the rocket to try and have accurate sims. Now Im trying to understand what the sims are telling me.

 

[rcktnut]

I was really trying to understand how to select motors based on profiles, etc. I needed accurate info on the rocket to try and have accurate sims. Now Im trying to understand what the sims are telling me.

I think your racking your brain for naught here as far as worrying about accuracy. You have the kit, build it as instructed with any mods you want, retainer, etc. and then sim it with the information obtained from the completed rocket. The CP on the design, and the components of the kit is a given and that is about it. Sims aren't real world, never will be, your rockets final weight, CG aren't real world until completed. You may have to add weight to get the CG where you need/ want it, and depending on how you build it will determine the final weight. Have fun, build it, then weight it, measure your CG, then sim it with the motors you wish to use.

 

[Steve Shannon]

I think your racking your brain for naught here as far as worrying about accuracy. You have the kit, build it as instructed with any mods you want, retainer, etc. and then sim it with the information obtained from the completed rocket. The CP on the design, and the components of the kit is a given and that is about it. Sims aren't real world, never will be, your rockets final weight, CG aren't real world until completed. You may have to add weight to get the CG where you need/ want it, and depending on how you build it will determine the final weight. Have fun, build it, then weight it, measure your CG, then sim it with the motors you wish to use.

Exactly right and very well said.

 

[KenECoyote]

When I looked at 38mm reloads (Aerotech) on PML's motor guide sheets
( https://publicmissiles.com/images/pmlalti.pdf ), the H's were pushing this thing high enough to bounce of the F1 layer of the atmosphere. I saw nothing but 5000 feet and up. I would want low and relatively slow for L1 cert, based solely on the fact that what goes up higher, lawn-darts better!

What am I missing?

You may have been looking at the BullPuppy 2.1 on the 29mm chart where that smaller version of the 3" BullPuppy goes to 4667' on a 29mm H motor. I made that same mistake a few times when looking up values for my BullPuppy but usually figured it out once the values seemed too high.

I think it would be very cool for an L1 (considered it myself at one point); however I felt it is a bit trickier to build than others given the boat tail and piston system and you should use epoxy along with fillets.

Funny thing is that I just fixed a missing canard on my BullPuppy yesterday - it got treed and that ripped off during recovery. I had it primed and painted black and was going to give it chrome after the maiden, but that tree landing did quite a job on messing up the paint. I was just thinking over the paint again yesterday. So what are your thoughts on paint scheme?