AMW Slightly Bigger Daddy.. slow winter build thread

[Salvage-1]

It arrived over the weekend, gave it a bath and a 'babies first weight' run today, and then fed the raw values into Rocksim.
No epoxy or anything, but I did go with a 1.5lb nose weight. This will most likely come down when I start the build and work out what it will finally look like.
I ordered the donut AV bay too, but that is coming in the second package, and will be here early next week.

Already starting to pick out motors for the beastie, and I think that I will be starting this off with a J1520 then move on to my last Kosdon K700 ( I have some KBA versions, too, for later! )
The AV bay will be needed, coz I don't want to go with a 19 second delay grain :lol:

I ordered two of these, and one is being thrown at a friend.

The challenge has gone out.. I will go with the Black Spy, he will go with the White Spy, and Spy vs Spy on J's and K's

This is going to be insane! Can we push a 4" stubby brick through Mach?? Tune back later to view the wreckage!

 

[Andrew_ASC]

Hahahahaa.... A 4" brick through mach, that's gonna leave one hell of an oblique shock as a mark, literally.

 

[Salvage-1]

Adding rocksim file.
I altered the thickness of the objects to match the actual measured weights, instead of doing a mass over-ride.

https://drive.google.com/open?id=1RrA_vlQ7ucKUIgRuv5Ai5oCU-8zIaIlZ

 

[Big_Red_Daddy]

So glad you started a thread on the build. There were no instructions on this model nor a sim file as I'm told it's a new model. I was going to start a thread on my build. I also created a sim file which I think is very accurate on dimensions and weights for mine but I used the override function. Here is my file: https://www.dropbox.com/s/hf130x481hip7uz/AMW Bigger Daddy from Toby.rkt?dl=0. And here are all of the weights of my components in grams to compare to yours. They are all pretty close. Seems irrelevant if you are also adding 1.5 pounds of nose weight!

AMW Bigger Daddy
Body Tube 360g
Nose Cone 385g
Nose cone aluminum tip 33g
Nose Cone Coupler Bulkhead 34g
Nose Cone Coupler 179g
54mm Motor Mount 108g
Fins (x4) 309g TOTAL
Centering Rings (x2) 25g each
Total dry weight 1458g (3.21 pounds)

I'll follow your thread and may start my own. I don't want to hijack yours. Just trying to throw some comparative info in if it helps.
I'm planning to launch mine on a 38mm H123 with an adapter for my level 1 cert on the first Saturday of February 2018. It sims to 1250 feet which I think is low enough to launch on a single parachute, although I do have a Jolly Logic chute release. On an I motor it sims to around 2500 feet. I would very much like to see yours go mach 1. Please continue to post.

 

[Nytrunner]

Make sure and remember to do something buggery with the nosecone so it only ejects 60% of the time!

 

[Salvage-1]

Here is my file
https://drive.google.com/open?id=1l4H07fLSjrNffj2Bm1aGTwZsaPJcxBq8

The 1.5lb of nose weight was to get it to a stability above 1.25
Stubby rockets like this may be stable at 0.75 due to all the base drag.
I am also going to use the donut AV bay, and put the main (as large as can fit) in the nosecone. Whilst all that won't add up to 1.5lb, I will obviously need some noseweight. The file will be updated when I get the AV Bay, and we will see what things look like.

The only slight problems that i can see with the kit are that the fin slots are far to narrow for the fins, and on the two kits that I bought, there is at least one slot that isn't cut all the way through. Not too much of a problem if you have a file or a dremel.

I also have a 4" to 54mm aluminum ogive tailcone which may or may not be put onto this (probably NOT). It makes the Bigger Daddy look really funky, like some kind on winged artillery round.

 

[Salvage-1]

(snip for length)
I'll follow your thread and may start my own. I don't want to hijack yours. Just trying to throw some comparative info in if it helps.
I'm planning to launch mine on a 38mm H123 with an adapter for my level 1 cert on the first Saturday of February 2018. It sims to 1250 feet which I think is low enough to launch on a single parachute, although I do have a Jolly Logic chute release. On an I motor it sims to around 2500 feet. I would very much like to see yours go mach 1. Please continue to post.

Please feel free to add your data, photos and comments to this thread... double build thread!!

Seeing you do yours for a L1 will be really interesting, whilst I go a little extreme!
I don't really think that this will do 10K and Mach 1, but we will see. The initial guesstimation for final weight should be a little over the actual finish weight, so, it could do it... or it could get dissassembled at 250ft! either way, it will be an interesting flight(s)

Adhesives for my build.
hobby epoxy (5 min) for tacking things in place
rocketpoxy for external fillets
west systems for internal fillets and joints.

for the internal fillets, I have some fiberglass rope that is left over from resealing my fireplace. I am going to soak this in a cup of west systems, and then push it inside along the motor tube-fin joints. If I manage to push this far enough to butt against the foreward bulkhead, then it should provide one really strong fillet.

 

[djkingsley]

Rumor has that a bigger big daddy flew to 19k’ in the desert earlier this year.

 

[Nytrunner]

The 1.5lb of nose weight was to get it to a stability above 1.25
Stubby rockets like this may be stable at 0.75 due to all the base drag.

For long/short rockets I've been noodling over, I've been using an 8-15% Length stability margin from Nasa papers.

Going by your file, that makes a stability margin of between 2.21-4.15". Coincidentally, .75 of your diameter is 3" which is happily in the middle of that range!

 

[Big_Red_Daddy]

Here is my file
I am also going to use the donut AV bay, and put the main (as large as can fit) in the nosecone. Whilst all that won't add up to 1.5lb, I will obviously need some noseweight. The file will be updated when I get the AV Bay, and we will see what things look like.

I'm not sure of the need for the donut AV bay. I have the bulkhead inside the nose cone and the nose cone coupler in next. Is that correct? There's a ton of space. Where does the donut AV bay need come in?

 

[Big_Red_Daddy]

Here is my file
The only slight problems that i can see with the kit are that the fin slots are far to narrow for the fins, and on the two kits that I bought, there is at least one slot that isn't cut all the way through. Not too much of a problem if you have a file or a dremel.

My slots are too narrow for the fins on this, and the two other fiberglass models I got from (AMW 75mm blue baboon and 38mm purple parrot). I'll probably just sand by hand; I'll likely screw it up with power tools.

 

[Big_Red_Daddy]

Please feel free to add your data, photos and comments to this thread... double build thread!!

If you like, I can post here. No need to open another thread.

 

[Big_Red_Daddy]

Rumor has that a bigger big daddy flew to 19k’ in the desert earlier this year.

Must have been way bigger. We will be limited by motor length (around 15") . I think it's possible to get just over mach 1 and just above a mile on something like a K805. J175 should go well above a mile, under mach as well as fit better. K2045-Vmax hits a mile and well over mach 1. Depends on what you are trying to do with it. J175 seems like a good one; margin is 1.06 with no additional weight but that's just my sim. I like short fat rockets with long slow burns.

 

[Big_Red_Daddy]

Rumor has that a bigger big daddy flew to 19k’ in the desert earlier this year.

Dennis, thanks for all of the help so far. I've got a much firmer grasp on building this thing.

 

[Big_Red_Daddy]

for the internal fillets, I have some fiberglass rope that is left over from resealing my fireplace. I am going to soak this in a cup of west systems, and then push it inside along the motor tube-fin joints. If I manage to push this far enough to butt against the foreward bulkhead, then it should provide one really strong fillet.

I think this will work well. Any recommended size? It's pretty cheap at McMaster. We buy stuff from there every week at work.
https://www.mcmaster.com/#catalog/123/3528/=1alhyt7

 

[djkingsley]

I think this will work well. Any recommended size? It's pretty cheap at McMaster. We buy stuff from there every week at work.
https://www.mcmaster.com/#catalog/123/3528/=1alhyt7

I would think that these fiberglass ropes are just going to add weight in the wrong end of the rocket. RocketPoxy internal fillets should be plenty.

 

[farsidius]

I would think that these fiberglass ropes are just going to add weight in the wrong end of the rocket. RocketPoxy internal fillets should be plenty.

While probably true, you haven't seen how this crazy brit flies. The fiberglass rope is a great idea.

 

[crossfire]

Dose the old rule still apply? If the motor is past the CG you shouldn't need a lot of nose weight?

 

[Big_Red_Daddy]

While probably true, you haven't seen how this crazy brit flies. The fiberglass rope is a great idea.

Fiberglass rope is really light. What's a good diameter for it? 1/8"? 1/4"? 3/8"? I think the resin it soaks up is going to weigh a lot more than the rope, relatively, but still not too much overall.

 

[blackjack2564]

I would not worry too much about internal fillets....externals are the ones that count.

 

[LithosphereRocketry]

I would not worry too much about internal fillets....externals are the ones that count.

Why?

I have very little HPR experience (read: none) but I would expect the main failure mode to be shearing at the root, putting most of the stress on the internal fillet to the MMT. This is assuming the fin is weakest in the foldover direction, and it is easily able to "pleat" the tube slightly (in order to rotate in the slot) but not significantly deform it. I would expect the edge of the BT to act as a fulcrum and the failure point to be the root shearing "toward" the direction of the force.

Of course, I could be thinking of this completely wrong. I'd be interested to hear your thoughts.

 

[blackjack2564]

Think minimum diameter rocket, flying on m-n's at speeds approaching M-3.
Fins held on surface of airframe, with nothing but proper glue, and correct fillet size.

Been done many, many,many times. Internal fillets are just gravy, only need to be sized to hold fin in place.

Glass rope will work just fine.

 

[tfish]

On my L3 rocket (15(?) years) ago, I Just glued some 3/16" sq spruce strips to form a channel on the motor tube that the fins fit into. Dripped some epoxy down through the fin slot into the channel and then pushed the fin into place. It worked for 45 flights. Something else went wrong to end that rockets life.

I agree with Jim for the most part. Internal glue joints probably add more on basic card board rockets (they're more technical about spreading loads "around") then on fiberglass rockets.

Tony

 

[Salvage-1]

My idea with the glass rope is that I will soak the rope in a cup of thin epoxy and then squeeze most of the epoxy out before pushing it down the gap and then using a square stick to push it down against the motor mount and the fin root.
Lock the fin root where it should be with minimal weight added. 1/2" rope flattens out a little wider.
The madness to my thinking isn't that I am overly concerned about the fin wobbling... but that I don't want that motor mount having any chance of moving, and since the rope will be pushed against the foreward centering ring, it will just help lock everything together as one whole unit, plus I like overbuilding when it won't end up adding that much weight overall.
If you have a good enough external fillet, then any flutter in the fin outside of the tube shouldn't ever have a chance of being transferred inside down to the fin root.

 

[anbhtblr]

Which NASA papers?

Regards, Rich
NAR 59673, L2

 

[Salvage-1]

I'm not sure of the need for the donut AV bay. I have the bulkhead inside the nose cone and the nose cone coupler in next. Is that correct? There's a ton of space. Where does the donut AV bay need come in?

The donut av bay is because I want tracking and dual deploy recovery in this beastie. We fly in some heavy sage scrub and I would like to fly this twice.

 

[Big_Red_Daddy]

The donut av bay is because I want tracking and dual deploy recovery in this beastie. We fly in some heavy sage scrub and I would like to fly this twice.

There's no av bay in this rocket. I though the donut av bay was so a longer motor could pass through an av bay. https://cart.amwprox.com/index.php?..._id=1107&virtuemart_category_id=60&Itemid=482

 

[crossfire]

There's no av bay in this rocket. I though the donut av bay was so a longer motor could pass through an av bay. https://cart.amwprox.com/index.php?..._id=1107&virtuemart_category_id=60&Itemid=482

I would guess the avbay is the nose cone coupler. Not to be glued into nosecone.

 

[Salvage-1]

I would guess the avbay is the nose cone coupler. Not to be glued into nosecone.

The AV bay parts should be arriving this evening. Yes, you utilise the nosecone coupler as part of the AV bay. Mine has a bulkhead and centering ring that will go at the top of the coupler, with a double stepped centering ring at the bottom, and there will be a 54mm tube running the length. The bottom double centering ring will be removable, and then the electronics will go inside the gap between the coupler and 54mm tube. Static port holes will be 1" below the top of the main body tube.
Yes, the top of the motor will go through that 54mm tube.

The connections to the nosecone and body tube will be with shear pins. At apogee, it will blow the bottom off, and come down with a small chute. At 1000 ft, it will blow the nosecone off, which will hold the main.

Will post pics when i get it together.

 

[Salvage-1]

AV bay measurements.
4" g10 bulkhead 40g
4" airframe centering ring 24g
4" coupler centering ring 20.5g (x2)
54mm MMT 12 1/8" long, 176g

alternative part
54mm MMT 8 1/4" long 124g
coupler bulkhead 37g

So... I make a stepped av bay lid by putting an airframe bulkhead and a coupler bulkhead together, then I put a coupler centering ring under that. Put that on top of the coupler and then slide into the nosecone to see how far it will go.



The upper 54mm mmt will click into the upper centering ring when completed.

Stack the other two centering rings (coupler and airframe) together to make a stepped centering ring, and slide onto the 54mm airframe (ext mmt). Slot the 54mm airframe into the coupler, so that it butts centered against the top bulkheads, and then slide the aft stepped centering ring down to 'complete' the donut bay.

Slide 54-1400 case in as far as it will go, (to the top bulkhead) and mark (the pen on 2nd photo)



Slot the bottom centering rings onto the motor case, and measure how long the bottom MMT will be.



Looks like I need a 8 1/4" MMT .


The electronics will go in the space between the top MMT (the one going through the AV BAY) and the coupler. The AV bay will lock together with allthread. Just a normal AV bay, except it has a motor going through the middle.

So... also looks like the 54-1400 will be the longest 54mm case that I can use, and still have a parachute in the rocket.

The idea is that, at apogee, it will blow the nosecone and av bay off as a unit, and will come down 'drogueless' or a small drogue. Then at 1000ft, the nosecone will be blasted off the top of the donut av bay and deploy the main (which was stuffed in the nosecone). Normal head end deployment. As noted earlier, the whole thing will be kept together with shear pins until the black stuff goes boom.