Lessons learned building L1 rockets

David,

This is what I wrote last summer for a discussion group on Yahoo when I built my first HPR Rocket with fiberglass.

Lessons Learned:

The small foam rollers fall apart too easily. I am going to use the regular sized 2" long rollers with the shortest nap available.

When working with resin if you think you can do something in 10 minutes then give yourself 20 or pay the consequences.

Every little piece of anything will just cling to fiberglass cloth and show up in your work after your done. The work area must be kept clean.

I was not able to put two wraps of cloth on at the same time and have good results, the 2nd layer messes up the first layer and time runs out trying to fix everything. From now on I will just let the first layer cure, do a little rough up sanding and then go with the next layer.

If you don't own a Palm Sander or have a new one in your budget then be prepared to beg, borrow or steal one because you will end up with arms like the Governator if you try to hand sand a fiberglass coated tube.

The smaller the overlap, the less sanding. No overlap is ideal but obtaining matching edges by cutting the cloth after laying it down and prior to the resin's kick is possible but difficult.

Couplings wrapped in wax paper or some other method of allowing for the smooth runoff of cloth at each end of the tube must be used to prevent the cloth from pulling up from the tube edge. You cannot just let the cloth hang on it's own or you will have something to fix.

If anyone is new at this like I am then expect the project to take days, not hours. This time includes figuring out what is needed to do the job and then putting it all together. My time included finding (buying) tools, building jigs and stands, clearing the carport and worktables of all my other junk so I'd have room to fill it with all this new junk, doing the job and then cleaning everything up.

All in all, I'm glad that I did the work but I know I need to do several more rockets before I'll be able to do a good job the first time and have it all come out looking well and have a minimum number of mistakes to fix.

Andrew

David, As we use to say in the military "Murphy was an optomist!" Been there done all those or similar at one time or another. And always take the phone off the hook and be sure everyone in the house KNOWS it is supposed to be that way before begining ANY rocket assembly with expoxy and or foam.

Interesting post. I might suggest you also build a L1/L2 bird that uses yellow glue and low mass construction and directly compare the two in cost, time, flight characteristics for review in Sport Rocketry magazine. Your unique perspective of going into this fresh is very helpful.

Jerry

Don't buy any. Go to the thrift store and buy used Rubbermaid storage tubs. Leave the stick in and when the epoxy is dry, the epoxy 'cup' lining will come right out.

Epoxy doen't stick to plastic trashbags. Cut a piece and lay it over before the clamp.

Masking parts you don't want adhisive on doesn't hurt eiter.

That's what a dremel is for.

Yep. Can you imagine what sand will do? Don't take an Aerotech kit to the park, finish the motor mount and drop it in the sand.

Gallons with pumps,...

Nor papertowels,.. but you knew that one,...

And adds unneeded weight.

A 1" chip brush does the same thing. And epoxy will soak through your newspaper no matter how many layers you have down.

Never check with your finger to see if that drip on the table is sweat,... or CA.

Hopefully it's realized that much of it was tongue-in-cheek.

I really don't have any intention of doing a yellow glue low mass bird, for the simple reason that I'd never find it again (my running days are OVER). One of the reasons I got the Patriot was specifically that it almost needs an H to get it off the pad!

David Erbas-White

Employ kids!

Yes, but...

I've found that you don't always get the epoxy completely mixed, no matter how hard you might try. There will always be minor areas, little dribs and drabs, that are not mixed well at the edges, and when you remove the 'cup' of epoxy, there is still some residual non-mixed crud on the side in some areas. This means that you then have to clean out the things, which is pointless when they're a few cents each.

I should add that I'm only mixing about a 1/4 ounce of epoxy at a time, these are the ultra tiny cups. I decided to take the assembly slowly and carefully, and only did one glue joint at a time, and waited until 'set' (but not 'cured') before continuing.

Good idea.

Well, yes. Unless you have the hubris to believe that since you've built so many danged rockets that you're not going to spill any. And, of course, prove yourself wrong...

A. If I had the flexible shaft, and B. If I could find out where I put the danged thing in the garage.

Not doing glassing. At the rate I'm going, gallons would last decades. These were just little 4 ounce bottles...

Yes, BUT. The PML recommended motors lists shows that the Patriot can fly on a 'J' if you use 'strengthening techniques'. The biggest one appeared to be using foam. Compared to the overall weight of the rocket, it added very little weight, and if it means I can use it for Level 2, I'll have saved some time/money. And since I'm not going for maximum altitude (rather, 'maximum fun'), the fact that it will not go as high is not a problem for me -- it's a feature.

David Erbas-White

Nope. Just mix the next batch right over it. It mixes right in. And stores forever between batches too.

I mix on plastic resealable lids from containers like Pringles, cheese, etc. A bit of flex and the last batch pops off. After 20 or so uses, I toss them when they get too brittle or grungy.

ALWAYS place glue so the slop gets pushed to a harmless location. This is true for an HPR bird or an Alpha motor mount.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

If doing multiple layers, you really need to do the second layer before the first layer fully cures. Multiple layers of light cloth is better than a single layer of heavy cloth.

And get good abrasive material. I've been recommending the stuff from

ever since someone pointed me to them. Industrial grade stuff at bargain prices.

Bob Kaplow NAR # 18L TRA # "Impeach the TRA BoD" >>> To reply, remove the TRABoD!

A Semroc Scorpion on yellow glue and an Ellis H50 motor is really a high flying Bird.

I think Jerry sells a similar rocket called fire and forget ?

I have flown LOCs Loc IV and new Phantom on J motors with fins not even glued to the motor mount let alone expanding foam.

I'm conviced that we need to start building our HPR rockets like they are competition models, not anvil launching ;-)

I did enjoy your main post by the way David !

Considering I just recently purchased the all four of the Semroc SLS kits this is good to know :)

Still, according to Semroc's website any of the SLS rockets will easily hit 1500' with a E9. The SLS series should be good for the AT 21mm Econojets.

Was going to get that one but decided against. With a name like 'fire and forget' you just KNOW how the maiden flight would go :)

Ted Novak TRA#5512 IEAS#75

Yep.

I fly the jaguar or javelin SLS on Ellis G37 and G35 motors almost every launch for crowd pleasers.

don't forget Ellis has those 24mm F20s two for $21 retail , E12s three for $21 and the G37/G35 for about $15 each.

Quality AT parts used in them as well, but with Bob's Hammer propellent for long, long burns.

OMG....what altitudes are you getting? How are you recovering these rockets? ARE you recovering these rockets?

Starting to think dual deployment via perfectflight might be the way to go.

Ted Novak TRA#5512 IEAS#75

I have had those TTBT Loc IV fins pop off upon a nominal landing after a G motor flight.

It's the landing and transport that kills them, not the launching.

Anvils bounce. ;-)

Also remember that Dave Triano (and anyone that knows about composites) will come and get you if you sand into the cloth - if you do that you're losing the strength you added by 'glassing in the first place. The strength is in the fibres, not the epoxy.

If you look on the ShadowAero website, there's quite a lot of detail about how it *should* be done. Ideally you end up with just the right amount of resin to cloth, and then fill the weave - not sand it flat.

Whether this will cause your rocket to disintegrate in flight is another matter - but even if you're not making a high stress flight the point is still valid.

Mostly, So far mostly. Join the over Mile high club with no certs needed !

the first trick I learned from Jerry. I offer a small kit to the kids who bring my rocket back and annouce it over the PA at the launch just before firing the rocket.

second trick is I fly these at HPR launches that have a large field.

once, kids did'nt see the rocket and lost it.

hours later I found it by searching the field with bonoulars and spotting the parachute.

(I should replace that with a streamer this year)

the one I lost of my four SLS, I lost the shyhook SLS on a G35 to a 17min parachute duration up up and away forever before becoming a small dot that disapeared.