Lessons learned building L1 rockets

Well, I've just finished the construction phase for my level 1 rocket(s). I still have to do the final sanding/painting, but the
'construction' part is done. And I've learned a few valuable lessons that I thought I'd share. BTW, I'm planning on using my PML 1/4 Scale Patriot for my L1, and maybe even eventually for a L2. I built it a bit stronger in order to (hopefully) assure it will survive an L2 attempt. I've got a Black Brant Vb as my 'backup', in case preliminary flights (G-level) with the Patriot don't work out, or something similar. Here are the things I've learned:
1. The 50-pack of epoxy mixing cups is not enough. Get two. 2. When using a clothespin to hold a shock cord in place while drying with epoxy, you will either remove it too early and the shock cord will come loose, or you will wait to long and the clothes will be glued as well. There is no middle ground. 3. When using JB Weld to glue an engine retainer to the back of the motor tube, you should smear the JB Weld around the outside of the tube, using very little on the inside of the retainer. Otherwise, you will get little drops of JB Weld on the inside of the motor mount tube, and you will not discover them until after the JB Weld has fully cured. 4. It's very difficult to file JB Weld from the inside of a motor mount tube. 5. Not removing all the JB Weld from the inside of a motor mount tube can score your brand new Dr. Rocket casing. 6. When trying to get that last little bit of epoxy out of the container, bear in mind that the first part that you poured in has been 'mixing' for a while with the first part that was already in the measuring cup. 7. Trying to find out where you put the mixing stick after you've already added the two parts of epoxy together is not the best way of doing things. 8. Expanding foam REALLY DOES expand about 25 times. Really. 9. Placing the rocket being worked on on top of two expensive oak CD cases is a sure fire invitation to spilling epoxy on them. 10. Placing a rocket out of the way to dry in an area where nobody usually goes is a sure fire way of making sure that someone will suddenly need to go there. 11. Epoxy actually CAN be cleaned off the front of your laptop, if you do it quickly enough, and nobody is there to look and laugh at you. Of course, it will leave a new 'sheen' on it... 12. Leaning a long dowel on an itty-bitty plastic mixing cup will knock over the mixing cup. Even if it's full of epoxy. Especially if it's full of epoxy. Really.
If I think of anything else, I'll add it later, and feel free to add your own 'hints'.
David Erbas-White
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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

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writes:

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 www.sandingcatalog.com 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! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
We must have faith in our democratic system and our Constitution, and in our ability to protect at the same time both the freedom and the security of all Americans.
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writes:

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.
--
Niall Oswald
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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.

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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
http://www.v-serv.com/usr/kits/dreammachine-38.htm
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Jerry Irvine wrote:

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! <G>
David Erbas-White
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Employ kids!

--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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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 ?
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AlMax wrote:

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
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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.
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AlMax wrote:

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
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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.
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Perfection of laziness :)

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Jerry Irvine, Box 1242, Claremont, California 91711 USA
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Yep.
--
Jerry Irvine, Box 1242, Claremont, California 91711 USA
Opinion, the whole thing. <mail to: snipped-for-privacy@gte.net>
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Jerry Irvine wrote:

our level 1 machine was a blue Ralphco crayon with 1/8" plywood fins, 1/8" CRs, Kaplow-style baffle and clips, all glued together with yellow glue. (and 10' elastic shock cord!) it's survived many many flights on everything from F40s to H220s.
I built another similar crayon but used epoxy instead of yellow glue. it's heavier enough that it doesn't fly well on F motors.
yellow glue works great!
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The problem with the late Ralphco crayon banks and similar is that neither yellow glue nor epoxy sticks to the plastic. I've had to use hot-melt, silicone caulk, and even pop-rivets.
    Bob Kaplow    NAR # 18L    TRA # "Impeach the TRA BoD"         >>> To reply, remove the TRABoD! <<< Kaplow Klips & Baffle:    http://nira-rocketry.org/LeadingEdge/Phantom4000.pdf www.encompasserve.org/~kaplow_r/ www.nira-rocketry.org www.nar.org
It had become an universal and almost uncontroverted position in the several States, that the purposes of society do not require a surrender of all our rights to our ordinary governors; that there are certain portions of right not necessary to enable them to carry on an effective government, and which experience has nevertheless proved they will be constantly encroaching on, if submitted to them; that there are also certain fences which experience has proved peculiarly efficacious against wrong, and rarely obstructive of right, which yet the governing powers have ever shown a disposition to weaken and remove. Of the first kind, for instance, is freedom of religion; of the second, trial by jury, habeas corpus laws, free presses. -- Thomas Jefferson
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Bob Kaplow wrote:

Gorilla glue (urethane) works great!!
I don't use the bottom cap because of the gluing problem, also I don't like the looks of it on the rocket.
for the nose cone I cut a plywood disk that just fits inside the lip; Gorilla glue works fine there. Used to use silicone caulk which would last a few flights.
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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.

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Bog Launch wrote:

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... <G>

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
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