Hump Day Happy Hour Mongoose 54

Questions about the HDHH Mongoose 54 from RW.

1. What are folks going to do for a lamination treatment of the fincan for aggressive
motor use.

2. I can determine all the parts except the two 3/4" wide coupler rings. Something to
do with motor retention or shockcord installation?

I've done glass lamination but I'd if used, I'd like something to match the rocket
to avoid painting.

Kurt Savegnago

I'm currently planning on two layers of CF, one 1/2 way up the fins (t-2-t) and the other full, alternating the orientation. I may just go with a single full layer - haven't decided for sure. Properly built, no reinforcement would be necessary for most flights. One layer of CF would cover much of the rest.

The two short coupler rings and the 1/8" CF plate make up the retention. Coupler/plate/coupler. This would be mounted in the booster tube a bit higher than the longest anticipated motor. (planning is necessary) I also purchased an AP MD retainer, but will most likely use what was supplied (if the longest motor isn't longer the the tube...).

For me, the challenging part is the 54mm size and keeping it in perspective and not overbuild. The Loki 4000 case was thought of (with mods to the kit). Had a friend fly a Loki 4000/L MD at Balls with nice results. Decisions - oh bother...

MikeL said:

Had a friend fly a Loki 4000/L MD at Balls with nice results.

Click to expand...

What altitude did he get?

No lamination. It is not needed.

CoyoteNumber2 said:

What altitude did he get?

Click to expand...

27K if I recall, in a MD FG bird.

What case options are available between the AT/CTI 6/6XLs sizes and the Loki 4000? (Non-EX)

MikeL said:

I'm currently planning on two layers of CF, one 1/2 way up the fins (t-2-t) and the other full, alternating the orientation. I may just go with a single full layer - haven't decided for sure. Properly built, no reinforcement would be necessary for most flights. One layer of CF would cover much of the rest.

The two short coupler rings and the 1/8" CF plate make up the retention. Coupler/plate/coupler. This would be mounted in the booster tube a bit higher than the longest anticipated motor. (planning is necessary) I also purchased an AP MD retainer, but will most likely use what was supplied (if the longest motor isn't longer the the tube...).

Click to expand...

Ahhhhhhhh,

I see. I didn't open the bulkhead bags so something like a bulkhead sandwiched between the two couplers with a threaded eyebolt in the
middle to grab the threaded forward closure of the motor.

Oh, forgot to mention, I really appreciate the fin alignment guides really nice. My impression is going with L-1400 type
motors would just require something like Proline 4500 epoxy? Thanks Kurt Savegnago

cwbullet said:

No lamination. It is not needed.

Click to expand...

yea but... but everyone says that... 14 layers of t2t...

I'm doing the same. Wide fillets; no layup.

ksaves2 said:

Ahhhhhhhh,

I see. I didn't open the bulkhead bags so something like a bulkhead sandwiched between the two couplers with a threaded eyebolt in the
middle to grab the threaded forward closure of the motor.

Oh, forgot to mention, I really appreciate the fin alignment guides really nice. My impression is going with L-1400 type
motors would just require something like Proline 4500 epoxy? Thanks Kurt Savegnago

Click to expand...

The Aeropac adapter that screws into the top of the CTI 54mm has 5/16" threads. I cut a different length of allthread for each size of motor and glue a 5/16" nut to the top of the retainer bulkhead:


I only fly CTI motors in my BH 54, best motor yet has been the L935 Imax to 23,231 ft. There might be a LOKI load that could beat this, but the faster you go the more drag it makes.



These shots are from my BH build, but I also did a similar retainer in my Mongoose 75, using both coupler pieces with the CF bulkhead sandwiched in between.
My one beef with RW kits is the lack of instructions, and when I asked for help, several senior members here told me that if I didn't know what I was doing, I shouldn't build it. I started a build thread, but abandoned it and built the rocket my way. It has several flights with great results. Those comments are why you won't find a build thread for RW rockets posted up by me.

Do you epoxy that assembly inside the airframe? Some have mentioned using set screws so the assembly is removable. That would be attractive for being able to replace a worn shockcord. I would think that methodology would be doable as long
as the motor in question would have an aft thrust ring to impart the load to the airframe. Only issue would be whether or not the set screws could take the load of the ejection charge gases.

Yeah, I hate that attitude displayed by some, "If you don't know what to do you shouldn't buy it." Certainly it helps to have some kit building under one's belt. Wildman's instructions give one a basic construction idea but using this place to see some others methods only advances one's knowledge. I've adopted a lot of ideas from here that were a heck of a lot better than my own. Kurt Savegnago

Wayco, thanks for posting these pics!
Can you post more? I would love to see more angles and how you attach it to the BT.
Building a 54 & 75 MD rocket now (my first) and I was just staring to think about motor retention.
Thanks for sharing

When removing the motor, does the all thread ever become unscrewed from the forward coupler and stay in the motor retainer? That would seem like a real pain to get out.

Ok Wayne,

I have some PEM nuts around as I was considering using them on a small project but found out I could simply thread the thick FG couplers I was using on a 38mm project and they hold satisfactorily.

Looking at your ring and bulkhead retainer, I suspect your PEM nuts are secured on the inner side of the ring after drilling the holes through the airframe and ring? That's a sound methodology to me
that I'm going to use!! Thanks. Solves a big problem of replacing worn shockcords and has the potential of being able to remove the attachment point and using a different size all-thread/screws in the future.

I've pretty much given up motor deployment in HPR as the time it takes to do sims and drill delay grains. I find it time consuming although there are those who take satisfaction at pulling off this art. I used to but the time is too much
for me now.

Kurt Savegnago

Wayco said:

I did epoxy the first Aeropac retainer into my first BH, but it was a pain to work with. Since then both the second BH and the Mongoose 75 have removable retainers that are attached with pem nuts and flat head screws.
You can't use motor deploy when using the Aeropac adapter, it screws into the top of the reload where the black powder goes. I use the tailcone retainer on all my CTI motors, it provides a solid thrust ring at the back of the motor. If you intend to fly EX snap ring cases, you will have to be creative with your retention, some don't have anything to screw an allthread into at the top, and if they do, the forward bulkhead spins when you do. Notice the tape in my second pic. above, even the CTI reloads can do this. If your retainer is glued in, that can be a real problem.

Click to expand...

Swissyhawk said:

When removing the motor, does the all thread ever become unscrewed from the forward coupler and stay in the motor retainer? That would seem like a real pain to get out.

Click to expand...

This is why I don't glue the retainer into the fincan. Not so much leaving the allthread in, but if the forward plug in your motor spins, you can't get ANYTHING out. Two things you can do to prevent this, first add a locking nut to the allthread and lock it down on the Aeropac adapter. Second, tape the forward plug to the motor casing. I use the sticky green tape you see in most of my build threads, or the really sticky aluminum tape, cut down to fit.

spyfly said:

Wayco, thanks for posting these pics!
Can you post more? I would love to see more angles and how you attach it to the BT.
Building a 54 & 75 MD rocket now (my first) and I was just staring to think about motor retention.
Thanks for sharing

Click to expand...

You guys are really making me regret not doing a build thread for my MD rockets. I don't have time now to address that, but I can show you how I did the last BH I built for Wildman. This was the project that burnt me out regarding documenting my builds, but I might be getting over that....
Tim (Wildman) had some specific requirements he wanted to document for this project and one of them was using the plastic rivets instead of pem nuts to attach the retainer to the body tube. Since he gave me the kit, I did it his way and changed them out later.
First I built a CTI 6XL motor and attached the Aeropac adapter to the top. Then I added a short piece of 5/16" allthread to it and screwed on the retainer. I laid the assembled motor up against the tube and marked where the retainer was, hooking the rear retainer/thrust ring to the bottom of the tube:



You can see where I marked the tube for drilling the holes in the above picture. I used a CTI 6XL casing for my gauge because unless you are really into EX motors, you can't beat the performance of the L935 for altitude, and these rockets are all about altitude. Here is where my retainer lined up on the fincan with the thrust ring and tape measure up against the bottom of the tube:



I also put an index mark at the back of the rocket and on the retainer to make it easier to match them up after drilling them:


Slide the assembled motor in and drill three holes in line with the fins. My original holes for the rivets were 5/32". The pem nuts I used later where for 6-32 flat head screws, which use a 7/32" hole to seat into. I have documented how to seat pem nuts in several of my builds, so if you need help with that, search for my 3" darkstar or Extreme build threads. Be sure to put a dab of epoxy around the pem nut to prevent it from coming loose. I have a special bit that tapers the holes in the body tube to get the flat head screws to fit flush, and I think it was also covered in an earlier build. If not, I will just take over Kurt's thread and lay it all out here.
You are right Kurt, the pem nuts are attached to the inside of the coupler ring. You can use two rings to sandwich the bulkhead with, but I never bothered. I also made a wrench to hold the u-bolt for adjusting the length of the assembly from a piece of 3/4" pvc pipe. Just cut a slot across the end and fit it over the u-bolt.
I have also built two avbays that hold two altimeters, two batteries and two magnetic switches and fit in a 6" coupler. My first BH had an ematch fail at apogee. It returned ballistically to 700 ft. where the main deployed. The results were repairable, but I decided then that redundant altimeters were mandatory in all my rockets that had room for them.
Here's my disclaimer:
This is just the way I do this, and sometimes I forget to mention a specific point that could trip you up if you try to duplicate this process. If you do have a problem, post up and I will try to help.

Sheeeeeoooooot, You're right. just one bulkhead should do it as long as the motor has an aft thrust ring to carry the shockcord loads. A Kosdon case would require another strategy but I don't have one those. The good doctor didn't believe in
aft thrust rings as he felt the external groove weakened the aft end of the case. Kurt

ksaves2 said:

Sheeeeeoooooot, You're right. just one bulkhead should do it as long as the motor has an aft thrust ring to carry the shockcord loads. A Kosdon case would require another strategy but I don't have one those. The good doctor didn't believe in
aft thrust rings as he felt the external groove weakened the aft end of the case. Kurt

Click to expand...

Well, he felt right. Burst or shear of the case at this groove is quite rare, however.

patelldp said:

Well, he felt right. Burst or shear of the case at this groove is quite rare, however.

Click to expand...

Yeah, I agree if one is really pushing the envelope. An internal and external groove might change the strength characteristics. Kurt

The kit came with proline 4500 epoxy in two small unmarked containers. Each container had a sticker on it that says mix 100:16, that's all it says. I've not used this epoxy before. Is the black stuff the resin or the hardener? Is it 100 resin to 16 hardener or vice versa?

Resin is in the bigger container (black stuff). It's a 6.25:1 ratio.

Crash-n-Burn said:

yea but... but everyone says that... 14 layers of t2t...

I'm doing the same. Wide fillets; no layup.

Click to expand...

Lamination, layup, tip to tip, all the same?

Yes, it is.

Personally I wouldn't bother with a 54mm kit. Use the Proline to attach the fins to the tube. Then make a personal decision on whether you like Proline or Rocketpoxy better for fillets. IMHO because Rocketpoxy is thicker I feel like it's easier to make nice big fillets with. I think with Proline you need to let it set up for a while before you try shaping it. Either way if you prep the tube and fins properly I don't think you'll have any problems.

watermelonman said:

Lamination, layup, tip to tip, all the same?

Click to expand...

I put my (originally prophecy's) old school Mongoose up on a 54/2550 Kosdon L850S clone. It was the bottom half of the rocket without a payload section and had thick wall tubing and 0.125" fins. Rocket hit 1,431mph and 17,142' and was fine using only the Proline fillets.

None of my MD rockets have any kind of layup on the fins, I use either Proline 4500 or Rocketpoxy and run them out with a piece of one inch PVC. I'm also not a fan of using coarse sandpaper to prepare the surface, especially for carbon fiber. I use 220 grit and "excite the molecules".This process is described in a sticky at the top of the HPR section:
https://www.rocketryforum.com/showt...what-your-government-doesn-t-want-you-to-know

These is the fillets I did for my first Blackhawk 54:


I thought I would give some of you waiting for your kits a little teaser:


I have never seen a nicer kit, and that's saying a lot considering all the rockets I have built. Some of the details might not be noticeable in that first shot, so here are some more:


Not only are the body tubes made from flawless carbon fiber, but the 8" avbay coupler and switchband are also. The only thing that looks a little rough is the finguide:


The nosecone matches up to the payload tube perfectly, and I noticed a special touch that will please the Eggfinder fans, the N/C, coupler and bulkhead are fiberglass.


If you hadn't noticed in the other pics, the avbay lids are also CF, with the stepped edges cut in:


Top quality hardware and a sled are included, and if that isn't enough, all the parts for the internal retainer are made from carbon fiber also:


The fins are all perfectly matched, but will require some work if you want to put a bevel on them:


Here's a close up of how the body tubes match up to the switchband, and a better look at the avbay lids:


Here it is all laid out on an 8 ft. table, ready to build:


Sharon has almost convinced me to change my policy on build threads for RW kits, and I'm curious just how many TRF members have purchased this rocket and if anyone would be interested in my version of this build. If you have this kit, post up, and maybe I will quit blogging all over Kurt's thread and start my own...

Wayco said:

Sharon has almost convinced me to change my policy on build threads for RW kits, and I'm curious just how many TRF members have purchased this rocket and if anyone would be interested in my version of this build. If you have this kit, post up, and maybe I will quit blogging all over Kurt's thread and start my own...

Click to expand...

Hey, yeah, I'd be interested.

Seconded, I'm interested in a Wayco build thread.

Third - Always interested in how others do it.
(No matter the kit or manufacturer.)

Sign me up aswell

I'm curious if anyone is going with a Slimline retainer on theirs. I kind of like the idea of being able to use smaller diameter motors with this light-weight rocket. I understand the extra drag, but I'm not looking for extreme altitudes. Thoughts?

Cheers,
Michael