Fiberglassing Advice Needed

Okay, so I'm going to take that big step from model rocketry into HPR and do some 'glassing.
I've got some 3 and 4 inch rockets to glass and here's my idea.
For each tube: 1 wrap of 4oz. cloth (can I do two layers at once?), peel ply, breather, heat shrink tape. Shrink the tape with a heat gun and let it sit for a day or two. Repeat with 2oz. finsh (like I said, could I do both at once.?)
This means going over fin slots. My idea for that is to cover the inside rear of the tube in the anti-epoxy blue tape, glass over and then cut out with a dremel tool. Sound good?
Anyways, thats my idea. Please let me know if I'm headed down the wrong path or if there is a better way to do it.
Thanks alot guys.
Matt
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You don't NEED to let it sit a day or two between wraps. It is ok to put the second layer (some places claim better to) while the first layer is in the "leather" stage.
I don't even slot my tubes until I finish glassing. If you do, an exacto knife is enough to cut through it (fiberglass, particularly in the leather stage) isn't that strong.
I'm just getting into vacuum bagging. Up to now I've just blotted up the epoxy with a paper towel. Vacuum and/or peel ply is optional. I would avoid it on the first try.
Matt wrote:

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Alex Mericas


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1 wrap of 4oz will hardly make a difference ,Try at least 6 or 7 oz cloth; Or use 3 or 4 wrap of 4oz cloth; if you want to use heat shrink tape , you will have to use couplers or something to keep the tube from crushing under the stresses when you heat up the shrink tape .
JD

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I have the 1st and 3rd video tapes from ShadowAero, and I heartily recommend them. The first covers shrink-wrapping tubes, and the 3rd covers fin and nose cone molding. They cover all the details you need to get started.
http://www.shadowaero.com/VIDEOS.htm
- iz
JDcluster wrote:

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For my 1st L1 H powered rocket attempt, I was thinking of just sanding off the glassine outer wrapper on the BT, and then applying an epoxy finishing resin externally to allow it to soak into the paper BT and harden it up....will this suffice for a H powered model?
shockie B)

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snipped-for-privacy@hotmail.com says...

You expect advice from any of us "evil" HPR guys? Surely you jest.
;-)
Anyway, the paper alone will suffice for H motors. I would think the process you describe would only add needless weight without adding much in the way of strength.
No need to glass unless you want the rocket to hold up better to stresses incurred during recovery and transportation, as that is when they usually get tweaked.
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Kurt Kesler



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says...

off
finishing
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snipped-for-privacy@hotmail.com says...

Change your mind? ;-)
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Kurt Kesler



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Don't waste your time sanding, instead taker a sharp hobby knife & find the seem of the outer most wrap ( glassine )meets the end of the tube; take the hobby knife & carfefuly cut along the seem line NOT TOO deep that it cuts all the way through just the top layer for about 2-3 inches or less; next use the HK to lift up the outer layer ( the shiny layer ) once you get a hold of it peel it slowly untill it's unwrapped the entire tube...
Now you are ready to "Glass" your rocket.
JD
TRA: 4486 L3

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Be careful about the heat shrink tape over a fin slot. I've done that once... once... The shrink tape pulls the slots together giving your tube a hour glass shape where he slots are. What you need to do is put blue tape on the inside of the tube over the fin slots to keep glue from getting inside the tube. The slide a coupler at least the same length as the slots into the tube to keep it from pinching together too much. I've even thought of filling the fin slots with putty after I have done the above. This will keep them from filling with glue. The putty will chip out a lot easier than epoxy. Saving you time.
Geoff

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very good point!
- iz
Geoff Huber wrote:

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Aerocon is a good source for the shrink tape, as well as alot of other goodies
see http://www.aeroconsystems.com/misc/shrink_tape.htm
the epoxy curing gives off enough heat to make the tape shrink
IMO, you don't want to wait so long between layers. If the epoxy is fully cured, you will have a mechanical bond (requiring some roughing up of the underlying layer), but not a chemical one
though I don't see why you can't do all the layers at once
- iz
Matt wrote:

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On 19 Nov 2003 07:46:39 -0800, leppster snipped-for-privacy@yahoo.ca (Matt) wrote:

I'm probably going to repeat what's already been covered, but here goes... :-)
Use two layers of 4oz glass for reinforcement layers, and the 2oz (or lighter) as a 'finish' layer. Stronger that way. Depending on what you mean by 'two layers at once' the answer is yes and no. I use a technique that involves applying the epoxy to the fiberglass, sandwiching it between layers of plastic, and squeegeeing out the excess epoxy. It makes for a good cloth/resin ratio, but it doesn't lend itself too well to cutting two pieces at once. I've found, however, that you can apply the first layer... and by the time you've got the second layer wetted and cut, the first layer has cured enough to give a decent bond

If you're intent on using shrink-tape, then you've GOT to reinforce the tube with removable couplers... or it'll crush under the pressure. When I `glass tubes that have pre-cut slots, I wrap the couplers with waxed paper - waxed side facing out - and wrap enough layers of masking tape to form a 'dam' at the edge of the tube, so that no epoxy can leak in that way. You'll have *some* sanding to do, as there's no way to TOTALLY prevent epoxy from getting under the slots, but it'll be minimal.

Have a look at John Cokers' website (sorry, no URL handy...) for a couple of excellent writeups on fiberglassing techniques.
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Matt wrote:

Do two layers at once; just make sure you get the cloth tight as you go.

Provided you don't deform the tube, that works well. Although why not just wait to cut the fin slots until after the fiberglassing?
A cheap and easy form of shrink tape is sold as "basket wrap" at craft stores. Just be sure to put a thin layer of wax (I use floor wax) on it, or it'll stick to the epoxy. Hit it with a hairdryer after wrapping, and it shrinks down nicely.
-Kevin
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leppster snipped-for-privacy@yahoo.ca (Matt) writes:

IMHO, you're better off with 2 (or 3) layers of 1/2X (or 1/3X) cloth than a single layer of X cloth. FOr this rocket, rather than 1 layer of 4oz and 1 of 2oz, I'd jsut do a triple wrap of the 2oz stuff. Do the middle layer at a 45 degree bias to the other two layers for maximum strength, and of course stagger the seams so yuou don't end up with one high spot.
    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
Save Model Rocketry from the HSA! http://www.space-rockets.com/congress.html
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kaplow snipped-for-privacy@encompasserve.org.TRABoD says...

Why is that? And no, I ain't trolling you either. Just curious.
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Kurt Kesler



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> Why is that? And no, I ain't trolling you either. Just curious.
Well for one the weave doesn't line up so you get more threads per area. The 45 degree thing ads strength in a different direction than the others.
I've been doing 2 wraps of 2oz and it helps with the dings but does nothing for core samples :-( . Also, I had a rough landing on asphalt and while the fiberglass surface was undamaged, the underlying cardboard tube was damaged leaving me with a "squishy" spot on the tube. Perhaps more/stiffer fabric would have helped. PML has a good price on 10yd lots of 6oz fabric. I'll try that next.
Kurt Kesler wrote:

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Alex Mericas


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Alex Mericas wrote: ... > Also, I had a rough landing on asphalt

this delamination happened because the adhesive did not stick to the tube. what kind of surface did the cardboard tube have? did you rough up the tube, with say 150 grit sandpaper before glassing?
you can repair these little squishy spots by drilling two little holes and injecting some more adhesive. be sure to get all the air out of the 2nd hole. close up the holes with masking tape so it won't drain out while it is setting up.
(I wrote adhesive above because I don't know if you are using epoxy or polyester or whatever.)
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This was a LOC tube with the glasine layer peeled. I got plenty good adhesion. I guess I should add that there was no delamination. Two wraps of 2oz fiberglass is not that stiff. The stiffness came from the tube, which was damanged on landing. This was my first attempt at glassing and I was primarily interested in a smooth finish (success) and protection from moderate dings (success). BTW, a litte CA fixed up the squishy part just fine!
Cliff Sojourner wrote:

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Alex Mericas


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