light weight

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bachsta

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i am interested in making a light weight upscale of the big daddy based on 5.5" tube. im thinking about using composites to accomplish this. my goal is to be able to launch it on mid power 29 mm motors or possibly a cluster of 24mm motors bcause i dont have any certification. pml's lightweight caarbon tubes look good but there so expensive is there any other way i can accomplish a large yet light weight design?
 

Stymye

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mabey roll your own paper tubes, cheap and easy
 

bobkrech

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It's quite doable.

You probably can't do it under a pound, but you can definately keep ut under the 1500 gm LMR limit.

Dick Stafford has made large paper rockets, and an 8" diameter paper V2 was featured in Sport Rocketry a few issues ago.

On the kit side, check out the 5.54" LOC Minie-Magg. It weights 40 oz.

Bob Krech
 

GL-P

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Composites are cheap if you know where to look and are willing to spend some time perfecting your techniques for composites.
 

bachsta

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ok i think ill make the nose cone with thefoam and then wrap it in carbon. as for the body tube i think ill make it out of carbon because it just looks a lot cooler. then ill use foam for the fins and a loc 29mm motor mount and ill be set.
 

bachsta

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any sugestions on where to get good carbon or carbon kevlar fabric?
 

powderburner

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Are you sure you really want to build out of composites?
You might be surprised at how strong the structure can be if you roll a BT from poster-board-cardboard (the kind that comes in all colors, about two foot x three foot, for about 49 cents a sheet at W-world). You can turn a very adequate NC from foam block and cover with a thin coat of epoxy and tissue paper.

The thing is, once you start building heavier structure, then it also takes heavier structure to hold it together. You start chasing your tail on a growth spiral until you need an M motor to fly the thing. You really should give a try to light-weight approaches first?
 

bachsta

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well the reason im thinking about using carbon is becasue a. it kinda looks better/cooler and b. to keep light.
as far as the nose cone goes im going to have sandman make me one out of foam and then im going to cover it in one carbon aerosleeve. for the body i also plan on using 1 carbon aerosleeve. for the fins i'll probably use foam board, and for the centering rings ill use foam board. lastly the bt will be a 29mm loc motor mount.
 

r1dermon

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carbon is a lot of $. i'd scrounge around home depot for an hour and see what i find for lightweight materials. unless you want to end up with a 300 dollar investment, and a lot of aggravation. fiberglass is way cheaper than CF, and its still pretty strong. you can get sheets of that at most hobby stores and auto body supply stores. unless you're building a rocket thats going to take off with 70g's and break mach 2, i'd advise not using carbon fiber.
 

bachsta

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the reason i want ot use carbon is because of the its waeight. and so far i think the progect will cost as follows:
$24 for foam nc by sandman
$5 for foamboard for fins and cr's (i have some already)
$80 for carbon fiber aerosleeves
$20-30 for chute (i might already have one i can use)
$10 for laminating epoxy

altogether that turns out to be about $150 which really isnt all that bad for a 6" diameter rocket
 

r1dermon

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you're going to be using a lot more than 10 bucks worth of epoxy. wetting out cloth takes a lot of epoxy. make sure its good stuff too. also, i've never seen foamboard centering rings, tell me you will be strengthening those with carbon fiber or glass....
 

bachsta

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thanks for the correction and i will either couple two rings together for each ring or i will fiberglass them
 

r1dermon

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usually, when people are using foam, they cut out sections of the wood, in your case it would be the centering rings, and then they lay them flat and fill them with expanding foam. then they cut them off with some hot wire, then they wet out some CF and lay it over. this makes for a lot lighter piece of hardware. you might have trouble keeping those centering rings flat when you lay over the CF and flatten it so there are no crinkles or bubbles. also, its a good idea to put the whole thing in a vaccum bag, but if you dont have access then you can just lay something flat over it. i find that fiberglass is easier to work with. and also easier to finish(primer, paint...etc..)

actually, the foamboard you're talking about, is it what i just described? or is it 100% foam in a solid state? because if you do decide to wrap foam in CF with no wood, i'd like to see the proceedure and definately a launch report. will you be documenting your steps?
 

GL-P

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I've done a carbon fiber tube but had bad luck with the release material. Use mylar as an outer wrap when making the mandrel!!!

I'd fibreglass the foamboard centering rings with 6oz cloth on both sides. I have pics of the results. Freakin strong and cheap!!! I didn't use a vacuum technique. I just used some good waxpaper and some heavy books!!!

Composite sleeve supply:

https://www.sollerpaddles.com/composites/carbon fiber sleeves.html

This might be too expensive for CF in the bigger sizes but they do have fibreglass.

Be warned: Their site design is horrible but they are good as I have bought from them before!!!

P.S. You'd be surprised at how much epoxy CF will suck in!!!
 

bachsta

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wow thanks for that sight. i was going to buy from aerosleeves.com but with this sight ill save about $5 per square yard. also how much epoxy would you reocmend i get?
 

rstaff3

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If I were going to the expense to do a CF tube and coat the cone I'd also laminate the foamboard fins and CRs with it. Foamboard rings by themselves will work for a big rocket on Gs and small H's but I have no experience with bigger. If you laminate them you could get by with fewer rings. Foamboard fins by themselves won't hold up well without lamination. I'd bild a fin structure from foamboard (spars and ribs etc.) and then cover them. The SpRocketry paper V2 article is a good guide.

You will still be suprized how quickly the weight will build. Are you trying to stay under 3.3lb with motor(s)? Even a 5.5" foam cone will take a bite out of that weight budget.
 

rstaff3

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If I were going to the expense to do a CF tube and coat the cone I'd also laminate the foamboard fins and CRs with it. Foamboard rings by themselves will work for a big rocket on Gs and small H's but I have no experience with bigger. If you laminate them you could get by with fewer rings. Foamboard fins by themselves won't hold up well without lamination. I'd bild a fin structure from foamboard (spars and ribs etc.) and then cover them. The SpRocketry paper V2 article is a good guide.

You will still be suprized how quickly the weight will build. Are you trying to stay under 3.3lb with motor(s)? Even a 5.5" foam cone will take a bite out of that weight budget.
 

rstaff3

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If I were going to the expense to do a CF tube and coat the cone I'd also laminate the foamboard fins and CRs with it. Foamboard rings by themselves will work for a big rocket on Gs and small H's but I have no experience with bigger. If you laminate them you could get by with fewer rings. Foamboard fins by themselves won't hold up well without lamination. I'd bild a fin structure from foamboard (spars and ribs etc.) and then cover them. The SpRocketry paper V2 article is a good guide.

You will still be suprized how quickly the weight will build. Are you trying to stay under 3.3lb with motor(s)? Even a 5.5" foam cone will take a bite out of that weight budget.
 

r1dermon

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you could always lathe a cone out of a block of wood, then wrap that in CF and release it, composite cone action. muhahahaha. or lathe foam to do the same thing. i've always wanted a composite rocket, but the prices are ginormous!!! hawk mountain i believe is the name, they have a rocket that i wanted in 38mm, would break mach on a J350 and can fly on an F50. thats sick. only problem is, its 165 bucks. lol. FULL fiberglass. whatever though. if you pull this off, i demand pictures. lol.
 

bachsta

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im going to drill out a big chung of the foam nc to make it lighter
 

bachsta

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the whole mandrel nc is kinda what im going for like i said im gona take out most of the foam in order to keep it light. and i will most definetly take pictures.
 

r1dermon

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bachsta, why not make a 38mm MMT for this thing and make it your cert bird? surely you'd like to cert at least lvl 1, i'd love to see an upscale big daddy on an I!!! muhahahaha

too bad you're so far away, i'd let you use my hardware to cert on it. im not sure that you'll have the broadest range of motor options with this when its finished. whats the est weight? i mean, if you're tipping 4lbs, then you'll need at LEAST a G80(which 4lbs is definately over the max recommended liftoff weight if we're talking 5:1 ratio here) to lift that honker. you'd need to use a 29mm H or something to get that off the ground with a 29mm mount. plus, on those days where its really clear and no wind, you would'nt have the option of throwing in an I300, which is ALWAYS fun. dont get me wrong, H128s and 238's are fun and all, but they're no I.
 

bachsta

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lol
A. cost: i want to keep the flights as cheap as possible
B. Age: im not 18 yet so i cant certify and therefore i would have to rely on someone else to get the motors for me.
C. for lvl. 1 cert. im thinking about making an even bigger upscale of the big daddy based on 7.5" carbon tubing but that won't be for another couple years (im only 16)

lastly im going to build it as light as possible. i will use 1 carbon sleeve for the tube which will way in at about 8 oz. for the nose cone i will do the same using a foam mandrel and ill leave about 1/2" of the foam in the nose for weight and strength. im estimating that will turn out to be about 12oz. For fins ill probably carbon laminate foam board or basswood (more likely) which will add im guessing about 6 oz. so far thats 2lb 2oz plus the cr motor mount and motor. so im guessin/hoping total weight with motor wont be over 3lbs or 32oz which is a perfect match for aerotech's g-80
 

r1dermon

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bachsta, 29mm H reloads are around 14 bucks, an 38mm H reloads are about 20 bucks, the same as an SU G80. I reloads are about 30 bucks, but its not every day that you let one of those rip. 3 E9's definately would not lift that bird, assuming that its going to be 3.3lbs. pretty much ALL CF birds are HPR birds. you could always get someone to fly the motors for you, in your rocket. YOU'd put the load together, YOU'd get a TON of valuable experience and you'd also get to see how it performs on various motors. then, when you're ready for your cert, it'd just be another routine flight, only with your name on the card. you'd already be a pro at putting reloads together, and the rocket would be a great 38mm HPR rocket for your lvl 1. just a thought.
 

r1dermon

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are you accounting for epoxy? MMT weight? motor weight? etc...G80's are more expensive than an H reload. you COULD go with 3x29mm MMT's, but then the cost per flight would be a lot more than a single 38mm reload.
 

bachsta

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hmm. do you think 1 carbon aerosleeve which is .021" thick would be strong enough for an h?
 

bachsta

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well then i might as well. i know someone in my club who im 99.9% sure would let me use his casing so i might as well. plus im sure flights would be a lot more impressive. it looks like im going to have to follow the advice in my signature:p
 

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