scratch built rocket failed on test flight

As built I would be scared to put an 18mm D 21 and a goodly amount of nose weight into this beautiful Los Angeles class looking submarine rocket. Danger! Danger! Danger! Using Mind Sim it is obvious it is a highly unstable rocket, giving rise to the horrible possibility that no amount of lovely raw power coupled with gobs of stinking, performance robbing nose weight will make it fly consistently. An ugly Typhoon class boomer from the Evil Empire would make a better subject. The RSO will have to say "Hey Boy, you got tractor motors on that there silly submarine rocket!" And we all know tractor (caterpillar) motor submarines exist only in the movies.

You must give in to the power of the Dark Side to fly the silly submarine rockets you love. Give in to your fear, it makes you strong. Some will say canted motors above the CG are unnatural, but such are the ways of the Sith. Once headed on the path of the Dark Side, forever rule your destiny it will! Once you learn to quiet your mind before building, the Perchlorates will tell you how to proceed. The fin cans will disappear and the graceful lines of the freedom loving LA class sub will soar through the air. Ignore the pragmatic dogma of the Jedi and focus on yourself, on what you want to fly. Go beyond pure rocket science and into the realm of the silly odd roc. Only then will you discover the ultimate power needed to rule the Galaxy!

SORRY AGAIN! All that crazy "Dark Side of the Force" talk above is in violation of the twelve step odd roc recovery program I am going through. Odd roc junkie rehab can only be had with a massive cure, including large doses of pure rocket science direct from highly certified Care Bears. I've been to rocket launches from one side of the State to the other, seen lots of weird things. But one thing I know is that there is no mystical "Force" guiding my actions and destiny.

Well, here is where I am at. Added weight to the nose, ran a string test and it flew nose first. Weighed the rocket... 11-12 oz.

Obviously too heavy for the BT20 engine tube used for construction. A quick google search gives me either a D12-3 or better yet E9-4.

Here's my plan: build a motor mount for the "e" engine, and somehow couple it to the existing 18mm engine tube (rather than re design and build a new rocket upscaled to accommodate the larger engine needed, and running the risk of the same issues all over again)

comments/suggestions?

Even if i do an external "fin can" I would still need to couple it to the BT20 (18mm) engine tube, so either way, baring reconstruction, that's where i am.

You could use the AeroTech 18/20 RMS case with a D13 reload.

I had the same issue with my Estes Mercury Redstone. A C6 wouldn't cut it, but the D13 cut it nicely. It's a bit pricey, but this solution works when you need more power.

https://www.aerotechstore.com/index.php?main_page=index&cPath=2_10_19

https://www.rocketreviews.com/aerotech-d13.html

Greg

RobPodlaski said:

Well, here is where I am at. Added weight to the nose, ran a string test and it flew nose first. Weighed the rocket... 11-12 oz.

Obviously too heavy for the BT20 engine tube used for construction. A quick google search gives me either a D12-3 or better yet E9-4.

Here's my plan: build a motor mount for the "e" engine, and somehow couple it to the existing 18mm engine tube (rather than re design and build a new rocket upscaled to accommodate the larger engine needed, and running the risk of the same issues all over again)

comments/suggestions?

Even if i do an external "fin can" I would still need to couple it to the BT20 (18mm) engine tube, so either way, baring reconstruction, that's where i am.

Click to expand...

I would paint her up purdy and put it on the display shelf. Christen her "Shelf Queen" and start in on an entirely new design. Do a search on odd rocs and look through the build threads on silly rockets like this. Read some books, just don't look at the pictures as I do. A Mighty D12 is a much better motor in this case than an a wussy E9. I have explained this to a number of amazed new fliers at the club. When you know the answer you will be ready to start a new submarine rocket design. Just sayin' my two cents worth.

A composite motor is better yet if your are not clustering.

Add your nose weight, remove ALL the the mid-ship weight you installed, and if the black powder 18mm A-C engines are still not enough to lift the weight, look into composite 18mm disposable D's so you do not have to fool with more weight and another engine mount for 24mm (just changing too many variables and more stuff to go wrong).

Find a safe place by yourself to launch it and carry out your field experiment and report back. Hoping the best for ya.

Both previous posts are good options
Apogee sells the disposable single use 18 mm Ds
https://www.apogeerockets.com/Rocket_Motors/AeroTech_Motors/18mm_Motors_Single_Use
$10 per motor, but shipping and hazmat a bit pricey. There maybe other sources cheaper.
DaddyIsABar has great ideas (and a healthy dose of humor) that i think would be great for your next rocket but may be hard to integrate into this one.
If the above don't sound palatable and you really want to fly THIS rocket, the add on fin can with BIG fins (sorry DaddyIsABar) can bump you up to 24 mm. See my previous post on ExoSkell
Looking forward to your flight report!

Go to valuerockets.com for cheaper single use 18mm D 21 -4's. Use a long (at least 6 foot) rod only in calm conditions. Get the CG up as high as you can without exceeding max liftoff weight. This is even worse than flying fin less so I would have the cg at least 2/3rds up the rocket. With the boat tail it might want to wobble. With the asymmetrical canards it will want to go wild if they are not perfectly straight. If you are going to add a 24mm fin can then do the same, get the biggest, peppiest motor you can and load her up with nose weight and pop it into the air (AT SU E 30-4?, F 24 or 39 reload?). The BIGGER the fin area sticking out beyond the body tube the better, the less nose weight and take off speed needed. I would still have cg high above the tail cone, but your guess is as good as mine. As I ponder this I become too scared for rational thought. Launch in a remote, fireproof and open area. Have only adults in full body armor with riot shields present. Pray. A bunker would be nice, Much easier to get more experience flying lesser rockets and then building a monster like this the right way. You are taking something designed to go under water rather slowly and trying to fly it vertically in the air at high speed. Not the best idea for a novice. With one terrible flight on a C6 putting a bigger motor in it will just accentuate its already bad qualities. Who knows, it might be just fine or it may end up stuck in your bum!

Thanks for input. Plan to try the 18mm D reload and test it. right now my CG is right behind the "coning tower" front fin (actually a little higher, because the nose dips slightly) with the added weight, I sit at 12OZ with a c6-5 in it. will let you know how the test goes, and will also try to video it so if it works we can all go WOOOOO, or diagnose the disaster... Thanks again

Don't forget to take cover!

RobPodlaski said:

Thanks for input. Plan to try the 18mm D reload and test it. right now my CG is right behind the "coning tower" front fin (actually a little higher, because the nose dips slightly) with the added weight, I sit at 12OZ with a c6-5 in it. will let you know how the test goes, and will also try to video it so if it works we can all go WOOOOO, or diagnose the disaster... Thanks again

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The Estes C6-5 lifts 4oz safely - so that is a no-go.

The Aerotech D21-4 is what you need for 12oz.

The best idea (really) is a separate "fin-unit" that plugs into the tail only when flying the model.

Daddyisabar had a good suggestion with his Idea to fly some lesser rockets (plain old Estes kits) maybe 50-100 flights to build some experience

RobPodlaski said:

Thanks for input. Plan to try the 18mm D reload and test it. right now my CG is right behind the "coning tower" front fin (actually a little higher, because the nose dips slightly) with the added weight, I sit at 12OZ with a c6-5 in it. will let you know how the test goes, and will also try to video it so if it works we can all go WOOOOO, or diagnose the disaster... Thanks again

Click to expand...

I think the composite is a tad heavier than the C6 so it won't move the CG back much which is good. Sounds like you have loaded her up with mucho nose weight. Pop it up on a long rod and a nice quick D reload for lots of speed and inertia off the rod. If it decides to go submarine on you with the hot motor it will definitely leave a mark! Or the power and inertia will take over and make it fly straight up like a submarine rocket should. Either way it will be cool. That is the great thing about silly odd rocs.

scsager said:

The Estes C6-5 lifts 4oz safely - so that is a no-go.

The Aerotech D21-4 is what you need for 12oz.

The best idea (really) is a separate "fin-unit" that plugs into the tail only when flying the model.

Daddyisabar had a good suggestion with his Idea to fly some lesser rockets (plain old Estes kits) maybe 50-100 flights to build some experience

Click to expand...

For the record, I am NAR level 1 certified with alot of "kit" building exp. This is my first scratch build attempt, and while I am learning alot more with this build than I have previously (thanks to the help of more experienced scratch builders), I kinda take offense with the suggestion that kit building would give me more experience building or designing a rocket from ground up. Kit models have done all the leg work for you, all you do is glue and fly, for the most part. Building this rocket I have begun to understand and learn more as far as stability, CG/CP, upscaling, string testing, ect. If you read the post I already knew a c6-5 wouldn't work (copied here since you missed it:
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Well, here is where I am at. Added weight to the nose, ran a string test and it flew nose first. Weighed the rocket... 11-12 oz.

Obviously too heavy for the BT20 engine tube used for construction. A quick google search gives me either a D12-3 or better yet E9-4.)

Thanks anyway...... SMH

Daddyisabar said:

I think the composite is a tad heavier than the C6 so it won't move the CG back much which is good. Sounds like you have loaded her up with mucho nose weight. Pop it up on a long rod and a nice quick D reload for lots of speed and inertia off the rod. If it decides to go submarine on you with the hot motor it will definitely leave a mark! Or the power and inertia will take over and make it fly straight up like a submarine rocket should. Either way it will be cool. That is the great thing about silly odd rocs.

Click to expand...

Going to go with the D21-4T, lots of punch on liftoff, and will use this at my club launch with a heads up warning. Was hoping to hold off launching it at the club until I got it right, but with the added composite power, just too risky to try in a field (not to mention I only have the short ESTES launch rods that come with the kits). can only wait and see. Next launch is in June so I have time to wait, and rebuild it with a fin can for a backup. Really want to upgrade this to massive proportions for a possible level 2 attempt, but think that may be pushing it. will wait until I get a buddy to help who knows ROCKSIM or OR better than I do to assist with upgrading this to a 10" diameter, possibly more.

RobPodlaski said:

Going to go with the D21-4T, lots of punch on liftoff, and will use this at my club launch with a heads up warning. Was hoping to hold off launching it at the club until I got it right, but with the added composite power, just too risky to try in a field (not to mention I only have the short ESTES launch rods that come with the kits). can only wait and see. Next launch is in June so I have time to wait, and rebuild it with a fin can for a backup. Really want to upgrade this to massive proportions for a possible level 2 attempt, but think that may be pushing it. will wait until I get a buddy to help who knows ROCKSIM or OR better than I do to assist with upgrading this to a 10" diameter, possibly more.

Click to expand...

Great that you are flying with highly experienced club members and good equipment on a big site. A club helps a lot both in cases where things go right or wrong. Don't be surprised if they want you to get your Level Two and Three with more traditional rockets and then go for the big high power odd rocs. I'm also just a Level One so I tell the guys I really don't know what I am doing when I bring up a silly airplane rocket, Over time they don't believe me anymore but I still say it because if I really knew what I was doing I would not be trying to fly an eight motored, sport scale Avro Lancaster as a model rocket. Just be prepared for the Level Three RSO table/inspection. Don't say things like "I just have to fly the nose of the rocket and the rest will follow behind for show." or "more power and nose weight will cure all." or "there are no such things as small and dangerous rockets" or "no sir I do not have a computer simulation, but it has flown well many times in my imagination." Don't be surprised when you walk way out to the pad that you are the only one out there, and when you look back you see what appears to be the Level 2 and 3 guys making bets. Don't be ashamed when you are out at the away pads and the dudes ask what motors you are flying and everyone says J or K and you have to say D 21. And when you bring your submarine odd roc up to the RSO table and you get some weird looks, the high power guys really are scared of the little odd roc even though they might act macho.

A HI PO LA class submarine as a rocket would be awesome. I can see the crowd at the moment of launch at the first flight::y::eyepop::y::eyepop:uke::shock::duck:op: You are the confident guy eating popcorn!

I think the guy above just misinterpreted that you were going to fly it again on a C6. Since you are now firmly with in the city limits of Scratchville it might not apply, but there actually are a few kits out there that do help to get experience with these sort of things. These kits are often criticized because they don't do everything for you when it comes to nose weight and power choices. The ones that come to mind are the Sunward jet fighter kits and the generally reviled Noris kits from Germany. I am just starting on the Noris Natter right now that I picked up cheep off Ebay. As a kit it is nothing short of a disaster and I see why people hate them so much, but looking back it would have helped if I had built and flown one before scratching out a silly P 40.

Rob:
First one correction: You Should be using the cardboard cut-out and Swing Testing not "String" testing Procedure. Particularly if You do not have access to one of the Mod-Roc simulation programs. Some Odd-Roc configurations do not lend themselves to being simulated though your submarine could certainly be closely approximated.
Both Cardboard Cut-out LCP (Lateral Center of Pressure) and Swing Testing Procedures are Extensively covered in "The Handbook of Model Rocketry by G. Harry Stine. Any Edition will do but IT IS THE PLACE EVERY model rocketeer should start before attempting any Scratch building.

That Said:
Instead of adding all that nose weight, why not remove all that mass and increase the Aft Fin area with Clear Lexan fins or add on fin unit (removable for display). Most of Us Odd-Roc builders use this trick Often to reduce the overall mass of our creations. You may still need to add a little nose weight to offset the mass of the added Polycarbonate but it shouldn't cause your BT-80 model to require anything larger then a D12

Micromeister said:

Rob:
instead of adding all that nose weight, why not remove all that mass and increase the Aft Fin area with Clear Lexan fins or add on fin unit (removable for display). Most of Us Odd-Roc builders use this trick Often to reduce the overall mass of our creations. You may still need to add a little nose weight to offset the mass of the added Polycarbonate but it shouldn't cause your BT-80 model to require anything larger then a D12

Click to expand...

I think he is going for the absolute best looking submarine rocket possible with no fins. It seems as if there are a growing number of crazy scratch builders who are focused on looks as being the most important factor. They sacrifice everything for beauty that is only paint deep. It is not what is on the inside that counts, only the fleeting beauty on the outside matters in our "sex sells" society. Like Derek Zoolander asks "Is there more to male modeling than just being really really good looking?" These Shallow Hal types only build and hang around the best looking rockets, no add on fin cans allowed, no flame fins, just tons of nose weight and with "Danger" as their middle name. Yes I could put big plastic fins on the back of my new Aggressor Aerospace Unha 3 kit, but it can fly without them. Yes I could have made the tail on the DO 217 and Lancaster bigger for added stability and less nose weight, but good looks were more important. Purdy on the outside but heavy and with big motors loaded on the inside. This leads to more expense for wasted motor power to lift all that nose weight. The subject models have to be pretty too. No ugly Soviet junk. Just the beautiful curvy lines found in an elegant West. Only massive intervention will straighten these guys out. Twelve step deprogramming and lots of Specialized High Intensity Training can help, but after one or two such odd rocs the battle is basically lost. Botox injections will do no good, but powdered Tungsten golf club weight can be helpful in the nose cone. Heavy plastic weld on the front and scrambling to save every gram on the hind end. It is just sad.

For the most part I have to Agree with just about your entire post. Actually Sad too say

That said however: I still Strongly suggest the use of Clear Polycarbonate as an alternative to Huge amounts of Nose Weight which increases the need for higher impulse motors.

The Beauty of the Creation can very easily be preserved with the addition of a removable fin Can or the fact that clear Polycarbonate is dismissed almost immediately by the eye becoming invisible at anything more then a foot or two.

Here https://www.youtube.com/watch?v=Fg3cerIZOvA is what a "swing test" looks like on a rocket that is at least as goofy as Rob's submarine. Finding the center of gravity is as easy as placing the finished rocket horizontally upon an edge and marking the point at which it balances and it need not be perfect...1/4" plus or minus is good enough for the girls I go with.

And for the second time, get and read Harry Stine's Handbook of Model Rocketry, still the best book on the subject ever written.

I twice built a Channel Catfish shaped rocket, but made a concession to reality by adding a third fin to the "tail" and by making the dorsal and pectoral fins removable for flight. I've posted it before so search my posts if you are interested. Good luck with this project.

Yeppers, to us old farts with bad eyes those Polycarb fins just disappear at a foot or two. We love the low and slow performance of the heavily over cased, big clay nozzled, inefficient and cheap black powdered, spewing out tons of rusty goo, so called “Mighty” Estes D12s. But it is the dern Kids these days! They just want to NASTY BLASTY with one of those newfangled 24mm F 44’s.

When was the design of the D12 finalized, in the MING Dynasty?

Today the Kids go and voice activate the HD, on demand wide screen and watch that CGI Iron Man and everything else fly without fins. Whereas all us old farts can remember is running out to the mail box for the TV guide, coming back in to pull the knob at 7:00 PM sharp, clunking the mechanical tuner over to one of three networks, tuning in and moving the antenna, waiting for the tubes to warm up, adjusting the brightness. color and tint, then getting all excited when that Peacock came on in living color. You could still see the old black and white movies with the silver rockets and their big fins spewing sparks out the back. But then on came Gunsmoke in Color and good ole Festus.

Iron Man rules dude! And that Gwyneth Paltrow is one hot Cougar!

We can fast forward the VCR tape to the 1980’s and be like Da Mayor, telling Mookie to “DO THE RIGHT THING” Put some fins on that rocket and bring me a cold Miller High Life!

What is a VCR?

All we can do today is sit back and watch the show at the range because they are no longer broadcasting free TV. I say “I don’t see fins on that there rocket, but those Polycarb attachments must have just disappeared to my eyes.” If it doesn’t fly we can give out a good cackle after the crash and tell 'em I told you so! Then it will be time to spit out a bit of that baccy we’ve had between our cheek and gum fer full tobacco pleasure.

Dude, that stuff will kill you!

When was the design of the D12 finalized, in the MING Dynasty?

Careful.....
I clearly remember the excitement of all the new [huge] rockets we could fly with the new Mighty-D.

FredA said:

When was the design of the D12 finalized, in the MING Dynasty?

Careful.....
I clearly remember the excitement of all the new [huge] rockets we could fly with the new Mighty-D.

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Was Milhous still President? Or was it trippy Gerry? I guess I will have to watch that 70's show to find out. All I know is that it says in the old catalog the Mighty D is for experienced flyers only! I can just barely remember those days clearly too, but I can't remember what I had fer lunch yesterday, boy I hope it was mostly puddin'. I recently showed the cool art on the Maxi Brute boxes to a youngster and he wasn't impressed. But it was also about that time the cool LA class attack sub came out. I wonder if one could fly on a D12? NAW, Safer to bulletproof and fly on an F 44.

Nothing wrong with less fin, more nose weight and bigger impulse...so long as it is safe and legal.

FC

Well, I am going to redesign this with the clear fins (like the crayon). not sure how big to make them, or the best way to attach them to the body tube. but it is obvious without them, this cool design wont work safely. After a successful flight, will upgrade this to a 4" main tube, and possibly cluster Estes, or go for an aerotech composite, depending on how the taper works. Open Rocket would help, if I knew the ins and outs of it. I thank everyone for assisting.

Good call. Some longer, thinner ones sticking way out of the back would be the best. Like big clear prop blades or cavitation waves. They need to stick out to avoid the turbulent air around the tail cone and other small fins that would cause it to wobble or cone. Nice clean air one those fins will suck that CP back real nice. Keep the composite motor and add nose weight to taste. Paint her purdy with a nice smooth finish to look marvelous. After the successful flight you will be ready for the odd roc Jedi Knight trials.

Micromeister said:

For the most part I have to Agree with just about your entire post. Actually Sad too say .

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I'm so happy! Micromeister agreed with ALMOST everything I had to say! YIPEEE! :marshmallow::happydeer:

I would try a drag plate approach as a experiment. Cut a circle out of strong cardboard or similar material and cut a hole in the middle to attach it to the base of the sub. Test fly it and see how it does. If it works, then you can use some kind of clear material (small clear plastic plate?) for base drag.
I plan at some point to build a high power Tie Fighter.

https://starwars.wikia.com/wiki/TIE/D_Defender

I built a model with a foam ball and foam board and even with a lead nose it just spun. I then added three dowels going forward to a pringle's can and had a great flight. So the final design will have a tow droid in the front to contain the electronics and recovery system. I still need to find the right size Darth Vader to go along for the ride.

going to go with a 3 lexan fin design. But, after researching lexan, appears to be some concern on attaching them to the existing model. For those who have followed this thread, you know the BT20 body tube goes through the rocket (up to the mid point). At the rear there is not much for a through the wall design. With the 6 fins in the rear, not alot of space to attach the lexan fins there. So I am left with somehow attaching them to the prop shroud. But that is paper, not very sturdy for attaching fins to it. One idea i have is to cut the shape of the prop shroud into the fin, leaving a "TAB" which I can insert into the shroud, attach to the BT20 tube, and hope. But still unsure what to use for adhesive. suggestions?

Wow.

When you get the stability issues under control and really want to challenge yourself... try gap staging scale torpedoes out of the forward tubes.

SMR said:

When you get the stability issues under control and really want to challenge yourself... try gap staging scale torpedoes out of the forward tubes.

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Now THAT would be cool!