54mm min dia Build Thread

[tfish]

I loaded all the parts into the rocket and then was able to cut the parts to length today. It came out to 53.5" long. The case in the photo is 32.5" long. I also weighed it. At this point with the chutes and electronics ready to go..less motor I am just over 36 oz. So after finishing and a couple of other goodies I should still be under the 38oz optimal mass.
Tony

 

[cjl]

Looks very nice (although why don't you leave the fibers longer when you mix them with epoxy? The longer the fibers, the more strength they add). Great work, and it looks incredible.

 

[tfish]

It's harder to get it to lay into the filet nicely. If I make the carbon fibers too long it kinda gets all balled up. It just makes it easier to work with. There still is 2 layers of 5.7 oz cabron over the top of it.
Tony

 

[LoSx]

I am making a similar type of rocket... well design wise at least and was wondering how afraid you are of zippers... since the botttom portion isnt a zipperless design..

 

[Nate]

Hey LoSx, Welcome to the Forum.

Usually when using electronic deployment zippers aren't much of a problem. Provided you don't launch an unstable rocket that ends up in a horizontal flight, the drogue should generally deploy at a pretty low speed, and the main is practically guarenteed to deploy under 90 fps (depending on the rocket and drogue size of course)

Zipperless designs are nice, but I prefer to plan on making a nice flight happen everytime, instead of preparing for a catastrophe.

 

[tfish]

LoSx. You can not get away from potentially getting a zipper. Heck I've had some bad ones in the past! The only thing that stopped it was the fin can! Nate is right in that electronics will help! Come to think of it, the worst zipper I had was a 38mm min dia with a J570 and motor ejection. You can design your rocket to help prevent them. Each break point on a rocket has to have a male (coupler) and female (BT) part. The female end is the one that is going to zipper. If the lighter part of the rocket is the female, then there is less weight/less chance of zippering. If I attach the chute as far away from the female part the better. This allows this part of the rocket to slow down slower. It's the quick deceleration that causes the zipper. I can also place break points..4-6 short folds in the shock cord held with electrical tape done in 3-5 places vering the the number of taped areas. This acts like a shock absorber and slows down this part (female) of the rocket before it gets to the end of the shock cord. I love getting my rockets back that still have one or two break points still in place. That tells me that the BP charge was just right..(that the rocket seperated) and that half of the rocket slowed down so slow that it did not pull out all of the break points.
You can't always have perfect flights. You can design your rockets to aid in the recovery stresses. Electronics help and 'break points' in the recovery harness help. I hope this answered you questions.
Tony

 

[LoSx]

Thanks for the information! The reason I asked was basically that I want to prevent as many ba dthings as possible from happening (trying to create an indestructable rocket) however its never going to happen....

I should have realized under electric deployment it is less force... Ive done them before but I usually went with the traditional zipperless design just because it is good practice...

If something goes wrong then itll be a learning experience..

However I decided to break it off at the fin can and use the motor as a long (14") coupler.... ill have to test if the charge will blow this well or not of course!

The other annoying thing is how exactly to mount the electronics bay so I need no outer screws!

Thanks for the help!

 

[LoSx]

Oh and one last comment.... TFish.. your rocket looks amazing... I cant believe how good it looks and how sturdy it appears (by your choice of build materials and how you built it) and still came out with such a rediculously low weight...

I am trying everything to shave weight on my rocket and its still going to be around 59 oz and 65 1/2" long...

Yours is definately a tiny minimum diameter... suprises me you were able to make it dual deploy!

 

[Nate]

LoSx, You'll constantly be suprised by what the members of this forum can do with a little time, money, and words of encouragement.

As for the Electronics bay mounting; A common method is to have the altimeter mounted in the coupler, with a bulkhead on either side. This way, the charge seperates in the middle for the drogue to deploy, then, the second charge blows the nosecone off, and the main parachute comes out with it. The coupler is epoxied into the upper airframe section, which means no screws!

By the way, if you've got pictures of that rocket you're building, start a thread and post pictures, we all go nuts for that kind of thing

 

[tfish]

LoSx, Rocketry is a never ending learning process. Learning from your own mistakes is costly. Learning from others mistakes is priceless! I've learned thing from every one of my..'mistakes' which makes them seem not so costly. One thing that I learned from a couple of other fliers is..that where ever you have an electrical connection (e-match) you have a potential for a failure point. So to fix this potential problem, I connect my e-matches directly to my altimeter. Only one possible failure point! Guess what I've had this point fail! Not from some outrageous G pulling flight but from me placing the wire on top of the little electrical pad thing instead of underneath it. Luckily I had duel electronics which saved it. So now I make it a point to give a little tug on the wire after I screw down the terminals. Other bad things that can happen. Ever wonder what can happen on a 20 G flight? what's that really mean? (I'm not a rocket scientist) but in my mind that means that my rocket and everything in it are going to weigh 20 times there normal weight. So that 9 volt battery weighs what now? Not sure but will your battery holder break or will the battery fall out under this load? Things to think about. Here is the $.05 of masking tape costing $250 story (in a nut shell) My son is the one that came up with the idea of using the motor case as the coupler idea. This idea works great..BUT..the first time we did it ..the fit was a bit loose and we did not want any drag separation so we placed a little piece of masking tape on the motor case to make it a nice snug fit..not to tight because we needed it to separate there at apogee. Guess what. Masking tape placed on motor case (300 degrees?) gets pretty sticky. So sticky that the charge did not separate the rocket. So in comes rocket from umteen thousand feet at mach whatever. That cost was a J570 case, Walston, G-wiz, chutes..etc. We did save the fin can, amazing what they can withstand..So if you need to tighten up the fit when using the motor case as the coupler do not use masking tape! What works is "super glue" smeared inside the BT is good for making a snugger fit..Of course make sure it completely dried for before using. The 'super glue' holds up to the heat really well. How do I get all this stuff in this small of rocket? It's fairly easy. I design the rocket around the motor then around the electronics recovery stuff. The motor is x long. I need 2" for the drougless recovery stuff. I need 6.25" for the electronics bay. I need x size chute and x length shock cord..which will fit into the nose cone and 5" of body tube. So I build it a little bit long as I go then cut the parts down to length once I get close to a finished product. This is my second "high tech" rocket using all these cool things. I had been doing the normal glass over cardboard min dia rocket for awhile now. Now I'm just babbling..sorry
Tony

 

[JGROVER]

This guy knows what he's talking about, take note Very impressive work Tony, I would love to see that thing fly! Cant wait to get back into the hobby and burn some ap with ya.

 

[flyr98]

Tony,
In this pic: https://www.rocketryforum.com/attachment.php?postid=268505

I noticed that you applied Peel Ply to the inside of the tube as well as the outside. Was this easy to remove from the inside of the completed tube? As I understand, Peel Ply comes off in little pieces when used on tubes.

 

[tfish]

Steve,
Miss leading photo. The green tape is holding 2 layers of 2 mil mylar, which is over the motor case. then the carbon fiber. Then two layers of 'brown' peel play. The photo does make it look like you suggest. But it is mylar-carbon-peel ply.
Tony

 

[flyr98]

Alright, I see. Did this fly yet?

 

[tfish]

Steve, Not yet..I did finish it the otherday. It's ready to go. Looking like Mudrock in June at Black rock. I'll post the results.
Tony

 

[flyr98]

Cool, good luck

 

[jraice]

bring life to this thread... how does the peel ply do anything if it isnt squeezed to the airframe with a vacuum bag setup, or shrink tape/tube? What is the theory behind making each tip to tip glass longer then the last (cover 1/2 the fin, then 2/3, then all of the fin)? Is it just because less strength is needed as you go farther up the fin?

 

[tfish]

Jraice,
Peel ply works for me. I've tried shrink tape and vacuum bagging and did not have the results I wanted. As I lay up the carbon fiber I only use enough epoxy to get things wet, any more and it's just extra weight. As I lay up the carbon I'm pulling it tight as I go. Once done I then place the peel ply on top of the carbon fiber. I place it on in the same direction (of travel) as the carbon. I then use a brush, squeeze and my hands to work out any extra epoxy. With the peel ply being porous the excess epoxy works it's way through the peel ply. Yes I agree that my tubes may weigh a touch more then those that have been done with shrink tape of vacuum bagging but I do not have any ridges or wrinkles to deal with that I was having with other methods. The tubes that I did are 24.5" long and weigh 150 grams. I did not weigh the carbon before laying them up so I don't know the ratio of glass to epoxy on them. I did lay up three 98mm fiberglass tubes using this method and cane up using less epoxy (weight) then the weight of the fiberglass.
As for the fin's and fin attachment. I started out with .065 G10 and then vacuum bagged 5.7 carbon to each side. I would not do it this way again. The fins are thicker/stronger then they need to be. I would have just used straight .063 G10. And then attach them the same way. This would reduce the final fin thickness by .020" I do the tip to tip glassing in steps. The tips of the fins do not need to be as strong/thick as the root cords do. The reason for the sequence of 1/3 - 2/3 - tip to tip is that it gives it more strength at the cord, where it's needed and there's much less sanding when done in this order. I have been using this method for about 4 years now and have not had a problem. It is extremely durable. I think you were also asking the question on how to maintain the bevels on your fins while doing tip to tip. Use masking tape and mask them off. Once the epoxy is rubbery cut it back to the tape. It mak take and bit of sanding to get them perfect again but it is do able!
As for my 54mm rocket. It's done and ready to go. It's 55.5" long with the boat tail and weighs 8 1/2 pounds ready to go. I have an ARTS for electronics and the motor which is 32.5" long, is a 3000NS L852. I will be test firing the motor this weekend.
Tony

 

[jraice]

That was very helpful.. One thing, I have heard if you do the fins glassing one at a time they dont bond as well and isnt as strong as all layers at once. Instead of using straight G10 fins and then 3 layers of CF, could you put some CF on the fin, then do 2 layers of tip-tip? I just think it would be nice to have them covered with CF and then beveled. How did your tubes turn out? I have been talking to Jon Soller about using sleeves (I said that another tube was made for a similar application using 3 5.7oz layers) and he said one layer would work... but usually two is stronger. I am still talking with him about it but I am thinking about using a layer of heavy (strongest) CF, then cover that with a layer of light, or medium, CF/FG. The heavy CF is like 19oz so it should be very strong, and then the light CF/FG would add a little strength and give it a nicer finish.

Using two medium layers of CF and then the CF/FG would be about 28 oz's of CF plus the CF/FG, verse 19oz's of CF.

 

[KermieD]

You don't have to do them all at once to get the chemical bond as opposed to the physical bond. You just have to put your 2nd layer on before the 1st one is completely cured. You can wait till that 1st layer is set pretty well (sort of on the dry side of tacky to the touch) and that 2nd layer will still get the chemical bond as it cures to the 1st layer.

 

[jraice]

So it is better to attach it to a semi tacky/cured layer then to let the first dry completly and then sand and apply? But I am still assuming the ultimate answer is both at once...

 

[KermieD]

Both at once just seems messy and unnecessarily difficult to me. The answer to the first question would be yes, it's better to do the 2nd layer before the 1st one is completely cured.

From InfoCentral:

4) To elaborate a bit on (2 & 3): Epoxy bonds to surfaces by a mechanical joint--it penetrates porous materials and "locks in" to the nooks and crannies. Non-porous parts must be roughed up in order for the epoxy to have something to "grab on to". However epoxy will bond chemically to itself, even a prior application, provided the prior application has not achieved full cure. This means that if you're bonding with fillers, you don't have to immediately follow the "wet out" step with the "bonding" step. Hours can go by, providing the first application doesn't fully cure.

 

[tfish]

Jraice, I like doing all the layers at once. I believe it's stronger. I know that if you use the sleeves you can't really do it this way. I have a couple of buddies that have tried the sleeves and are now doing layups like I am. I used 3 layers of 5.7 carbon... "he said one layer would work"... I would not go any thinner then I did....I'm not sure what motors your planning on putting in your rocket, but maybe one layer will work for your aplication. I made a 29mm tube with one layer of 5.7 and it was not very strong, and that was 29mm. I ended up going with 2 layers and it worked out nicely. If you go with thicker carbon fabric, you may have a problem with it conforming to your mandrel and getting it wet out properly. I've seen post about putting a sanding vail of fiberglass over the top of the carbon..if you do a good job to start with then there is very little sandingto be done. Attached is a photo of my finished rocket if you look at the leading edges of the fins you can seee the G10 peeking out. really no need to cover them in carbon.
Note: This is the way I do it and it's been working for me. That is not to say that other methods, shrink tape. vacuum bagging, sleeves are not as good
Tony

 

[jraice]

Let me clarify, he said one layer of a heavier CF would work, but I am thinking two or three layers of aerosleeves 2.5" CF might be best (it is around 11oz though, so 2 is probably more weight then yours was). And I think I may be able to get the epoxy through two layers without to much trouble. How did you get a boattail on a minimum diameter rocket? That looks really nice! I think I might do the fins with a layer of CF, then attach them and do a 1/2 tip to tip and a full tip to tip with 5.7oz CF... I also plan on using the chopped CF in the fillets. Should be pretty strong... I am also now looking into using mylar on the outside (for a smooth surface) and wrapping that in shrink tape. If the tape is heated from the middle to the ends then the epoxy will flow out the ends of the mylar outer layer, and then when cured they will fully constrict leaving a glass smooth surface, with a small (.014") "line" where the mylar overlapped it self on the actual composite layer. Do you think it would be a lot stronger to go with 3 layers tip to tip on bare .063" G10, instead of CFing the fin's, then doing 2 tip-tip layers... I just think it would make the entire assembly a bit easier to do without a large amount of strength taken away...

I read on a site about a tip-tip technique where you apply the fabric and epoxy, then put a peel ply layer, and a breather. These two layers are taped down (just to hold them in place) and a bag filled with small weights (lead weights work well) is placed and rested so it is touching the entire tip-tip assembly. This keeps the fabric pushing tightly on the fin, and also removes excess epoxy. Does it sound reliable? Did you just push it down by hand?

 

[KermieD]

My apologies. I saw somewhere you were mentioning 2 or 3 layers of tip-to-tip at once and thought you meant doing them all simultaneously.

Sorry, but I don't know enough about the relative strengths of sleeves to know whether your proposed method is sturdier or not.

 

[smurf]

Tony,

awesome finish on the rocket. Could you elaborate a little more on what steps you took to go from the scuffed fin can to the gorgeous clear finish??

thanks

 

[tfish]

Jraice,
Let me pose a question to you. Which is stronger? A piece of solid 1/4" wood? A piece of 1/4" plywood with 3 layers? Or a piece of plywood with 16 layers? The more thinner layers you have the stronger it's going to be.

" How did you get a boattail on a minimum diameter rocket?" That is the boat tail/nozzle of the motor.

As for fin attachment...again like the last post...I feel that .063" G10 with 1/3 -2/3 - tip to tip would be plenty strong/thick..the order in which you do them is up to you.

As for which method to use to layup your body tube....I would suggest laying up some small test pieces to make sure they work for you, before using more of your supplies. I did a bunch of tests(layup and temperature tests) with various materials (fiberglass, carbon fiber, Baltek, cork), methods (shrink tape, vacuum bagging, hand lay ups) and epoxies (West Sytems, Sytem Three, Raka, TCC) before I found what I was looking for.
Tony

 

[tfish]

Smurf,
I did the following. Wet sand with 120 grit...just to find any 'high spots'. I then mixed up some epoxy and used my finger (as a squeeze) to work it into any small pin holes. 220 wet sand. I still had a few pin holes that I hit with 'super glue' (it's much thinner then epoxy and filled the very small pin holes that the epoxy did not).and sanded them smooth (220) while the glue was still wet. Then 3 layers of clear lacquer. I found that if the tubes were to smooth then the lacquer that I used would....(searching for words) sort of sheet off, almost like it had been waxed. Even though the first coat was just a misting coat.
Tony

 

[smurf]

Tony,

Spray laquer?? Any particular brand? I'm impressed with the result - this may just give me an excuse to add a layer of cf to the fincan of my all purpose booster just for the aesthetics.

A couple of other questions....sorry about jumping in so late. You mentioned laying it up with high temp epoxy...what brand did you use? I've found it to be kind of expensive and most of the people that sell it (Cotronics for example) don't really like to deal in small amounts. I'd be interested in your opinion of what you used too.

The case you used as a mandrel looks like a dr. rocket case but when you show the body tubes next to the 54/2560 case they are significantly longer.....What brand did you use or is Dr. Rocket holding out on us??

Thanks

 

[tfish]

Smurf, No problem...I'm a spray can kind of guy..I went to the local 'Auto paint store" and picked up some automotive clear lacquer in a can. I normally use rustoleum brand but have never really licked thier clear. I'll post the actual brand in a few days. Again I did a bunch of testing on the paints that I end up using. Nothing I was trying was working for me. The rocket has it's name painted on it and it was an ordeal to find the right combo of clear and paint that would not react with each other. Even though they are both lacquers The clear over coat was reacting with the lettering. I'm guessing becasue they were different brands or had different solvents in them. I ended up going with the lettering over the clear. The lettering is not going to hold up to well but then again I like that 'just gone mach burned paint look". As for epoxy I don't mean to start an epoxy war. This is what I have found in the unscientific tests that I have done.
"with home made min dia rockets you 'may' need to think about what your using as far as epoxy goes. For two reasons. One is the heat generated by the motor is going directly into the body tube and two is the heat genrated by the flight. I played around with various epoxies and made some test pieces. I then placed a motor case in the oven got it up to 350 degrees and then slid it on the test pieces. Not very scientific..but good enough for me. Here is what I found. West Systems got kinda soft. Sytem Three T-88 no apparent change, Raka Epoxy no apparent change. We all have heard about West Systems. Sytem Three T-88. I get from the local Wood Crafter store. I used to use this all the time and like it. I have gone mach 1.9 with no problems. At this speed, paint (Rustoleum) is just starting to bubble and peel and epoxy failing is not an issue yet. I've used this for fin attachement, building nose cones, laying up body tubes etc... One thing is this epoxy is kinda thick for laying up stuff. I use denatured alcohol to thin it. Some people say this is a no no..but it has been working for me. Raka is a boat building epoxy that Greg Fannin uses. It is a 5:1 ratio epoxy and is thinner then T-88 and easy to work with. Greg has been to just under mach 3 with this stuff. The stuff I'm using now is some high temp epoxy I got on e-bay that I got on e-bay it's good up to 400 degrees, post cure. It's for some sort of commerical application. I got lucky and got a 5 gallon pail. So yes you do need to think about your epoxy choice at some point. Some are better then others. My advsie is to try some System Three and thin it to what you need and if you don't like that try some Raka epoxy.

https://www.systemthree.com/p_t_88.asp
https://www.raka.com/EpoxyPricing.html

The case is a home made EX case that I am trying a few things out on. It's a 9 grain case. The longest I've done yet is a 7 grain case. The motor is 32.5" long and has threaded closure with the aft closure being the boattail/nozzle/thrust ring.
Tony