Wayco's RW Mongoose 54 build

[ozwald]

Yeah, Airfield site. It's funny that you are coming from Cottonwood, my sister just moved there and is planning on coming out Saturday with my mom. We shouldn't be hard to find, AZ flag and a tie-dyed windsock about 20 ft. long.

Now I understand why Mike is adapting his Mongoose down to 38mm. I think the Phoenix metro area is larger than New Jersey, so I kinda understand.
I agree with Watermelonman, it's hard to fly this rocket and keep it in sight. The 2 grain J250 should take it over 6k.

I ran into a problem when I started prepping this rocket, one of the 6-32 pem nuts came loose inside the avbay, so I had to drill out the screw. As I stated before, I'm not happy how they looked, so I redid the whole mess with 4-40 screws and pem nuts. I used black Rocketpoxy to fill the holes in, and re-drilled and countersunk for the smaller screws. It came out a lot better, much easier to work with Rocketpoxy than with carbon fiber. This time I used Rocketpoxy to hold the pem nuts in place. I think the carbon fiber is so thin and brittle, it doesn't hold the pem nuts like fiberglass does.
I also noticed that I had failed to drill vent holes in the payload tube and fincan, so I added 1/8" holes at the top of the payload tube and above the internal retainer on the fincan. After I added the decal, I sprayed it with clear Rustoleum acrylic lacquer. If anybody has checked out my latest build thread, you may have seen these pictures of my Mongoose family:

The rockets in the background are some of the ones we will be flying this weekend with the Superstition Spacemodeling Society. This is my old NAR club that has some issues with HPR flights due to the I-10 freeway nearby. I won't be flying the Mongoose 75 there, or anything over about 8000 ft.
Here is the Mongoose 54 with it's new clearcoat, ready for it's maiden flight:

I will also be trying out the fly away rail guides for the first time. Wish me luck!

Will definitely look you up. Nice job on the finished project. I may want to talk to you and run some things by you concerning my current build and my nosecone GPS setup. I would also like to check out the new fly-aways. I'll buy you a beer

 

[wighty44]

...Here is the Mongoose 54 with it's new clearcoat, ready for it's maiden flight...

Very Nice! I'm glad you mentioned your use of the clear coat as I was planning to do that as well, but another person tried to suggest it wasn't necessary.

Did you clear coat the entire rocket or just the decal area?

BTW, I planned from the beginning to use a fly-away guide - actually bought it before the rocket kit (on sale...)

 

[ksaves2]

Make sure ya get a clean rail with no binding. Stupidhead here failed to do so and the railguides were turned into single use on a 38mm MD project. (Destroyed.) I was surprised as there was just a little paint damage on the cardboard/plywood/glass cloth'd fincan and still got 8500' on a J350. Would'a gone higher no doubt and I really love my EggFinder TRS units. Kurt

 

[BDB]

Here are my motor retention accessories and 38mm motor adapter:

I am planning to do something like this too. I figure that the majority of my flights will be with the 38 mm adapter since I'm on the east coast. But I bought this kit because I wanted the ability to have high performance for the occasional trip (maybe URRF). I was planning to build the adapter out of LOC tubing, since I obviously won't be trying to break any performance records with the 38 mm motors. Is there any reason that I should consider building the adapter out of CF instead?

 

[wighty44]

I am planning to do something like this too. I figure that the majority of my flights will be with the 38 mm adapter... Is there any reason that I should consider building the adapter out of CF instead?

Mine is not CF, it is black FG from Rocketry Warehouse. While CF is weighs less, it's also more expensive, and I'm not sure the CR's are available in CF. The finished weight of mine is 265g.

Note that the 3rd CR (one before the AeroPack 38mm retainer) is used as a thrust plate to transfer the motor thrust to the axial wall of the CF BT.

 

[BLKKROW]

Wayne! That is beautiful! I am interested in the fly away rail guides and your experience.

 

[Wayco]

Very Nice! I'm glad you mentioned your use of the clear coat as I was planning to do that as well, but another person tried to suggest it wasn't necessary.

Did you clear coat the entire rocket or just the decal area?

BTW, I planned from the beginning to use a fly-away guide - actually bought it before the rocket kit (on sale...)

I did the entire rocket. It's not a very good job, so I will probably wet sand it down and add another coat after it's first flight.

Wayne! That is beautiful! I am interested in the fly away rail guides and your experience.

You could always show up at a launch.... I'm planning on flying it at both the SSS and TRA/PHX launches this month.

 

[WoShuGui]

I will also be trying out the fly away rail guides for the first time. Wish me luck!

Nice looking Mongoose Wayne. I tried out a 38mm fly away guide last weekend with mixed results.
[video]https://m.youtube.com/watch?v=PaB7dvbU7dI[/video]
From the video, it looked like the guide might have hung up on the rail a bit. Then it looked like it hit a fin as it was releasing. The result was a slightly off vertical flight. My take away is to be sure the three buttons run as smoothly on the rail as possible. The accelerometer data showed there was almost a full G of drag while the rocket was on the rail... as if the rocket was twice as heavy. I am not sure what can be done about hitting the fin or if that was even a factor. Overall it worked okay. I have a 54mm guide to use on my Blackhawk, so I will be watching to see how well your flight goes. Good Luck!

By the way, the shock cord twisting on my38mm flight has me totally convinced that your retainer swivel is the way to go. I will be retrofitting that into the next flight.

 

[BLKKROW]

You could always show up at a launch.... I'm planning on flying it at both the SSS and TRA/PHX launches this month.

I may be at the launch in March, its tough since I work Saturdays but March's launch lands on the same week as Spring Break.

 

[glenbo]

Great build thread Wayco.My Mongoose75 CF just arrived from RW BF sale. For motor retention I am deciding between the stock retention with your modifications sized for a 75mm. rocket or Aeropack 75mm. min. dia motor retainer which I also have using a threaded screw retention rather than plastic rivets. I also have a CTI 6X old style casing. I really like the cosmetic effect of of the rear cone retainer on your 54mm. Can this be done on the CTI 75mm. casing, replacing the stock rear closure with a threaded tapered cone closure if it does exist out there and would the casing still be considered certified?

 

[glenbo]

Looks like such a thing does not exist for a 75mm.casing.

 

[blackjack2564]

I really like the cosmetic effect of of the rear cone retainer on your 54mm. Can this be done on the CTI 75mm. casing, replacing the stock rear closure with a threaded tapered cone closure if it does exist out there and would the casing still be considered certified?

Yes it can, I have one for 75 & 98mm. Wildman has them. They are certified for commercial launch.



https://www.wildmanrocketry.com/ProductDetail.aspx?product=4739

I just friction fit and add one wrap of aluminum tape around motor/airframe joint on exterior. Simple way to do it.
Before anyone asks....yes for Generation 2 hardware also.

 

[glenbo]

Yes it can, I have one for 75 & 98mm. Wildman has them. They are certified for commercial launch.

View attachment 282911

https://www.wildmanrocketry.com/ProductDetail.aspx?product=4739

I just friction fit and add one wrap of aluminum tape around motor/airframe joint on exterior. Simple way to do it.
Before anyone asks....yes for Generation 2 hardware also.

Thanks for that Jim.

 

[wighty44]

My drogue charge of .7 grams of 4f black powder is in what you call the booster. I call it the fincan. The main charge of 1 gram is in the payload....

Conducted some ground separation tests today and was quite surprised that my faithful BP calculator did not give a charge result that worked.

The original calculation showed 0.8g 4FG should have separated my payload section (main chute, 3 2-56 nylon screws). It did not. Increased the amount to 1.3g which worked just fine.

Trying to rationalize why I needed more, it occurred to me that while the main chute & nomex protector 'burrito' fit into the payload tube easily, there was little open space around the 'burrito' for the explosive gasses to act on the NC bulkhead. I suspect the light friction between the inner CF tube wall and the NOMEX wrap required more force than what might normally be needed to separate the NC for the payload tube.

Thoughts...?

 

[blackjack2564]

The original calculation showed 0.8g 4FG should have separated my payload section (main chute, 3 2-56 nylon screws). It did not. Increased the amount to 1.3g which worked just fine.



Thoughts...?

Yes...you used 3 shear pins.....Wayne used 2 as stated in a previous post.
I also use 2 in 54 builds.
3 are not needed in my opinion.
3 in my 75mm only needs 1.25 to get the job done.



Besides everyone builds a bit different, your parts may fit tighter or looser than someone else's. No matter how it ends up, as long as everything functions OK....ya did good!

 

[wighty44]

Yes...you used 3 shear pins.....Wayne used 2 as stated in a previous post. I also use 2 in 54 builds. 3 are not needed in my opinion. 3 in my 75mm only needs 1.25 to get the job done... Besides everyone builds a bit different, your parts may fit tighter or looser than someone else's. No matter how it ends up, as long as everything functions OK....ya did good!

In hindsight I could have only used 2 shear pins. My first DD build was a 4" FG 6' rocket that used 3 pins. While I know it's never good to only have 1 pin, I guess I didn't consider when fewer pins would be better.

Thanks for the feedback...

 

[crossfire]

I have used only 1 pin for years. Never a problem. Maybe my flights are not extreme enough.

 

[dixontj93060]

I have used only 1 pin for years. Never a problem.

+1.

 

[AfterBurners]

Wayne - I want to thank you for sharing this build thread. I really enjoyed following it. You are very knowledgeable along with the majority of people here at your level. That's what's so great about this forum. I love the build threads and the amount of knowledge that is shared here.

If I wanted to buy the kit I now have detail instructions and techniques on building it. Now I just wish I had a bunch of time, but I know I will soon.

Great job Wayne!! Thanks again!

 

[Wayco]

In keeping with my policy to finish my build threads with results of the first flight, I'm adding this post to warn others about a problem I had. I flew this rocket last month at the SSS launch. Loaded with a J250 that simmed to 6200 ft. I watched the flight with binoculars. What appeared to be a good flight turned bad when we recovered it to find a large hole in the CF tube, just above where the internal retainer was attached. I originally thought that the .7 gram ejection charge may have caused the damage, since the fincan landed in a bush, and did not come in contact with the ground when it landed. After a discussion with Curtis at RW, he expressed concern over the method I used to make the holes in the tube. He suggested that I not use the spring loaded center punch to mark my holes, but clamp the tube in a drill press and use the highest speed to drill the holes. He also had no problem replacing the tube that I broke, and we worked out a deal for a 60" piece so I could accommodate the 54/4000 tube that Scott just shipped to me from LOKI!
Here is a picture of the damage, with the hole on the left being one of three holes I drilled to hold the internal retainer in:

It's quite possible that the damage was caused from drilling and countersinking the holes, or it could have been that some of the thrust generated from the motor was transferred to the screws, causing the CF to de-laminate during the flight. Regardless of the cause, rest assured that this won't be this rockets only flight. We can make it BIGGER, STRONGER, ABLE TO FLY OVER TALL MOUNTAINS!

I also want to thank all those that commented on this thread, sharing info. is what this forum is all about.
Stay tuned.

 

[wighty44]

Just speculating here, but does it seem like the spring-loaded punch may have somehow initiated some degree of de-lamination in the tube so that the internal pressure created by the ejection charge finished the job? Perhaps the stresses introduced during your ground separation testing may have contributed to the failure by propagating any existing de-lamination?

I would have never imagined this type of damage would be possible from such a small ejection charge. :y:

 

[ksaves2]

Thanks for the heads up Wayne. I've used a sharpen awl to twist press a dimple in the tube and then use a smaller drill to make a pilot hole and upsize with a larger diameter bit as required.

I wouldn't think a .7gm charge would blow a side out of a CF rocket. A cardboard tube yeah: [video=youtube;hMvT9BKzbUg]https://www.youtube.com/watch?v=hMvT9BKzbUg[/video]

I've posted that link before and suffice it to say it was a "tired" old rocket that seemed to have a loose fit of which I coated with CA, sanded with progressively finer sandpaper and obviously didn't buff it out enough.
Used the same size charge I used in 8 other successful flights. Believe it or not, due to the my use of a 33", 38mm motor/stuffer tube, the fincan survived the crash and lends itself to a 2nd rebuild after a coupler/new tube fix.
1st rebuild was when it flew as a single motor deploy and grease plugged the ejection charge well. During that death dive, the recovery laundry slide down the tube and pushed off the nosecone a second or so before it hit.
The Covert parachute essentially exploded, the tube zippered a bit and the fincan was knocked sideways and landed flat in some soft dirt. I rebuilt it into the DD rocket that's shown in the video.

It's an art form to get a nominal flight out of larger (4" diameter) cardboard only rockets. Kurt

 

[mpitfield]

I am using 1.3g of BP, .7 was the calculated amount but I added some for margin. My rocket is the 54mm Madcow Tomach, I believe the same CF tubing, supplied from RW, same MD internal retainer with the same retention method, 3 countersunk holes for three 2-56 screws into self clinching nuts. I have 4 flights on mine (I to K, 3000-17,000 AGL, up to Mach 1.89) and about a dozen ground tests, and all is nominal with the tube so far. I did not use a punch, just a drill press and a drill bit and then the same countersink bit that you use as you told me about them.

wighty44 may be on to something with his speculation. Looking at the pics the hole does seem to play a.

 

[glenbo]

Just finished made my retainer as Wayco did for my Mongoose 75. Using three 3/32 Pem nuts & button screws from Missleworks. Was debating whether to countersink the holes but I may not now just in case. (as long as the screws can get enough bite with the curvature of the booster) I just marked using the fin jig & drilled freehand using a high quality bit with masking tape on inner & outer wall to help prevent delaminating of the fibre. Turned out good. At what depth was the countersink done? Was it for the screw to get full bite of the surface or to make the head of the screw flush with the airframe?

 

[Wayco]

Yes, I think Mike may be onto something there. I was not happy with the countersunk holes, I should have used smaller (4-40) flat head screws. I did sink them in to where the screw was flush, which required repetitive drilling. Taking the failure into account, I may not use an internal retainer at all, that would remove the weakness of the holes. With an eyebolt in the forward closure, I could tie the casing directly to the drogue recovery system. With the small size of the area for the drogue, my .7 gram charge would still do the job, without weakening the tube.
Glen, another thing you should be aware of is that the CF tube for the 75 is almost twice the thickness of the tube for the 54, you have a lot more meat to work with.
Lot's of good ideas and perspective here, thanks again to all of you that have contributed to this thread.

 

[ksaves2]

Yes, I think Mike may be onto something there. I was not happy with the countersunk holes, I should have used smaller (4-40) flat head screws. I did sink them in to where the screw was flush, which required repetitive drilling. Taking the failure into account, I may not use an internal retainer at all, that would remove the weakness of the holes. With an eyebolt in the forward closure, I could tie the casing directly to the drogue recovery system. With the small size of the area for the drogue, my .7 gram charge would still do the job, without weakening the tube.
Glen, another thing you should be aware of is that the CF tube for the 75 is almost twice the thickness of the tube for the 54, you have a lot more meat to work with.
Lot's of good ideas and perspective here, thanks again to all of you that have contributed to this thread.

Wayne,

How are you going to do a repair? It would seem a coupler/tube repair would shorten the length of the motor bay or are you simply going to build a new sustainer with fins from scratch?

I would suspect that unless one is shooting for a record, just use and deal with the cosmetics of the flathead or even buttonhead screws without resorting to countersinking and affecting the tube strength.
Perhaps manual scribing a depression with gentle pressure and then drilling a small pilot hole followed by a final size drill bit might help to avoid shock/cracking the tube?

Use two screws instead of three or four? Would that be sufficient without impairing retention?

Kurt

 

[mpitfield]

He also had no problem replacing the tube that I broke, and we worked out a deal for a 60" piece so I could accommodate the 54/4000 tube that Scott just shipped to me from LOKI!

I can't believe I glossed over the most telling comment on this post. I would like to revise my theory. It never ceases to amaze me at what some rocketeers will do just to upgrade their rockets. 54/4000 :jaw: funny thing is I have my eye on that same tube\motor combo and already redesigned my Tomach in OR, 28K @ Mach 2.35...ish. Looking forward to seeing that flight!

 

[ksaves2]

I can't believe I glossed over the most telling comment on this post. I would like to revise my theory. It never ceases to amaze me at what some rocketeers will do just to upgrade their rockets. 54/4000 :jaw: funny thing is I have my eye on that same tube\motor combo and already redesigned my Tomach in OR, 28K @ Mach 2.35...ish. Looking forward to seeing that flight!

Ummmmmmm, Little birdie told me there are further surprises in store with that motor system so hold on to yer hats. Kurt

 

[Loki Research]

Ummmmmmm, Little birdie told me there are further surprises in store with that motor system so hold on to yer hats. Kurt

Johnny Ringo!

Someone tells me you're looking to break mach 3 and 30,000' with a single stage 54mm rocket......

I'm your Huckleberry. :wink:

 

[Wayco]

Yeah, yesterday was a good day. Right after I got tracking data from Scott at LOKI, I got a call from Curtis at RW. Right now I'm trying to decide if I will get a Binder design fincan or just cut the CF fins off the old rocket. Maybe I should get a set of those Space Cowboy fins from Chris Attebery.