Estes Saturn V Build - Kit No. 2157
 

I decided to start the new Estes Saturn V build, kit no 2157. It looks like it will be a great build, and of course most of the time will be spent on the painting when I get to that step.

I marked up the main body and third stage tubes as required and built the engine mount and centering rings. I also built the optional cradle for holding the body during assembly.

Now I'm ready to insert the mount into the main BT. It's suppopsed to recess to 3 3/8", and was wondering if anyone has modified this step to decrease the depth. I plan on using Aerotech 24mm RMS motors so I don't have to rely on an Estes D12 to get this thing off the ground and I could add nose weight if necessary. I'd just rather not have the motor recessed the full 3 3/8" into the main BT if I don't have to.

Also does anyone have any glue recommendations for the vac-formed parts. Estes recommends Plastic Weld Cement (Plastruct), Testor's Plastic Cement #3502, Tenax 7R, and Testor's or Tamiya glue pens.

A popular modification is to move the mount back and fly with the F-1 nozzles attached. Additional nose weight, larger fins, clear fins or a combination of these is always necessary to compensate. Too bad there is not a gas with negative mass we can put between the stuffer tube and the outer airframe.


Bill

For vacu-formed wraps I use DAP rubber cement (the stringy, amber stuff that smells like hell). For the fins I SPARINGLY use Tenax 7r.

I'm sure there are other adhesives that work, but this is how I roll.

Remember: always test the adhesive on a piece of scrap material!

Have a fun build! Jeff

If I didn't have to deal with additional fins I might actually consider that... But for this build I may just cheat the mount to between 2 3/4" and 3" instead of 3 3/8". For flight I can compensate with nose weight, and for display I can cut down the spacer ring to make sure the F-1 Nozzles display correctly. The main reason I'd like to do this is to reduce the chance of burning of the inner wall of the rocket by the Aerotech RMS motors...

I still need to do some research and do some thinking though before I go ahead and make the change...

Thanks!

Having never built a Sat V, I thought your measurement on how much the motor mount was to be recessed was a typo, but after reading further, I see that's not the case. 3 3/8" seems like a lot to me. At what point does the Krushnic effect come into play?

I would hopefully always launch this rocket with enough of a stand-off from the blast plate to not allow a vacuum build-up, which I think is what causes the Krushnic effect with recessed motor mounts, although I've never seen it happen and am not all that familiar with it.

What I am really concerned about is just the burning of the inner lining of the main BT from the RMS motor exhaust. If I recess the mount just a little less I think I can reduce the possibility of that inner burning. Actually I see it a lot on one of my TLP kits, where the mount is recessed and the engine exhaust has charred the inside of the BT.

I have a build thread on my Centuri Saturn V here we discussed adhesives there. This model is similar to the current Estes Saturn V.

I noticed this thread on RP, the poster mentions some problems with the third stage reduction wrap not fitting the paper shroud correctly. I have not started building my 2157 yet, but I want to check that out.

ps: I tried flying w/ an F motor, and did get a little scorching on the bottom.

Go ahead and pull the mount back to the bottom and add a little weight to the capsule, plenty of room in there. Just keep the cg at 17.5" from the bottom of the bt and you're good to go.

Randy
www.vernarockets.com

I seem to recall a very general rule of thumb on preventing the Krushnic effect by recessing the motor (i.e., specifically the exit plane of the nozzle) to NO MORE THAN one body diameter. In the case of the Saturn V, that'd be just about 4 inches, so a 3 and 3/8", it would seem by that general rule you'd be ok.

Anyone else confirm this general rule? You don't hear folk talk much about the ol' Krushnic effect anymore.

Earl