Boat Tail Retention????????

[mc2-2]

I have three PML kits awaited the epoxy, isn't that cool.

Problem is all three have boat tails and I have never installed a motor retention system on a rocket with a boat tail. I never had one now I have THREE!!!!!!!!

This is the list, Pit Bull 38mm, Bull Puppy 38mm and the Hydra 38mm. No quik switch motor tubes in any of them, although if I want to use an adapter done to a 29mm, how does that play????

Love to hear your thoughts
IRV

 

[Johnnie]

Hey Irv, I found this when I googled:

https://www.joecool.org/pml_black_brant_construction.htm

Johnnie

 

[skycopp]

I'm currently building the PML Black Brant X and was concerned about motor retention as well. What I did was to get the HAMR-KS motor retention set from Public Missiles. Then I pulled back the motor mount tube thru the boat tail about just less than half an inch, enough space to JBWeld the HAMR-KS onto the end. This caused my forward centering ring to be positioned right where the fins would go thru the wall so I had to notch the fins on the root side. Just a couple of modifications.

I'm at work right now, but if it would help picture what I'm talking about, when I get home I can take a snap shot and post it.

 

[dixontj93060]

In the case of boattails or tailcones, I prefer to use a Slimline retainer or similar snap-ring type retainer that I can hide as much as possible inside the aft end of the rocket. This may require some millling/grinding of the inside of the boattail or tailcone, but you get a nice clean look on the rocket with effective retention.

I thought I had a picture of the aft end of the rocket below to illustrate but I don't. The only thing I could find is the boattail test fit on the fin can. Inside the boattail is the Slimline retainer. The black edge of the retainer is visible on the very bottom of the boattail in the picture.

View attachment Boattailsection.JPG

 

[loopy]

Slimline or Aeropack is your best bet in this case. Low profile retainers that usually only require that you pull the motor tube aft about 1/2".

 

[lessgravity]

On my current build (still very much under construction), I ran two threaded rods down through the centering rings next to the 38mm mount. They are bolted and epoxied to the centering rings for added strength .

 

[SpartaChris]

I definitely recommend an aeropack or something. I wish I had known about them when I built my Bull Pup.

 

[narmember]

On my current build (still very much under construction), I ran two threaded rods down through the centering rings next to the 38mm mount. They are bolted and epoxied to the centering rings for added strength .

I think I would avoid the 2 points, rather use 2 long bolts into Tnuts or coupling nuts in the Kaplow style.

What I did instead was use a slimline. I cut the nose (tail)cone off at the point slightly larger than the od of the slimline. Then I wrapped the motor tube with sandpaper and sanded the id of the hole until the cone tapered to a sharp point and the slimline slides right into the cone. It looks very slick.

[edit]Someone pm me easy upload info and I'll try to get a photo up this weekend.

 

[AKPilot]

I think I would avoid the 2 points, rather use 2 long bolts into Tnuts or coupling nuts in the Kaplow style.

What I did instead was use a slimline. I cut the nose (tail)cone off at the point slightly larger than the od of the slimline. Then I wrapped the motor tube with sandpaper and sanded the id of the hole until the cone tapered to a sharp point and the slimline slides right into the cone. It looks very slick.

Any pictures?

 

[irishwebber01]

I have a 38mm Bullpuppy that I drilled two holes inbetween the mmt tube and the tailcone, i then inserted two allthread rods layered in JBweld. I used two washer nut combos to hold the motor in being careful not to use to big a washer to get in the thrust wash...works great...even on an I357T