Fiberglass weight for LPR to MPR

[Scotty Dog]

I did a search and just spent time reading and watching youtube vid on glassing BTs.
I still have a few questions
What is a good weight for BT 60-80 tubes for LPR to MPR rockets? I don't need to be able to drive a truck over them.
And how do you fill the weaves and make the BTs smooth? Seems like it could be more work sanding drips and filling the weaves and than filling spirals.
I see using peel ply helps to get a smother finish.
Where would I get peel-ply? Is there different types of peel ply?
In the video it looked like he used thinned epoxy on the peel ply. Was the thinned epoxy just to lube the brush to eases the application of the peel ply?

Thanks TRFers for any info.

 

[solid_fuel]

check out John Coker's videos he has a good one that will answer all your questions. I will look for the link if I find it I will post it, but check them all out, He is great at explaining and showing you everything you thought you needed and things you didn't even know you needed,
link to his main page https://www.jcrocket.com/
epoxy basics video https://www.jcrocket.com/epoxy-basics.shtml
fiberglassing a tube video https://www.jcrocket.com/tube-wrapping.shtml

Sorry I just read your post again where you said you already watched the videos. Doh!

 

[Scotty Dog]

check out John Coker's videos he has a good one that will answer all your questions. I will look for the link if I find it I will post it, but check them all out, He is great at explaining and showing you everything you thought you needed and things you didn't even know you needed,
link to his main page https://www.jcrocket.com/
epoxy basics video https://www.jcrocket.com/epoxy-basics.shtml
fiberglassing a tube video https://www.jcrocket.com/tube-wrapping.shtml

Sorry I just read your post again where you said you already watched the videos. Doh!

I thought I read in one of the posts that 0.5 to 1.5 oz was a good weight for up MPR.? Seems a little lite? I cant find it again. I read a bunch of posts in this forum. OK, I went back and see in the beginning of "tfish38" and he used 2 layers of 5.85 glass. However ,is that for a HPR? Seems a bit much for LPR-MPR (3-Es at most). I have cluser rocket that take 3 Es made out of just paper BTs. Im just really looking to beef it up so it doesn't get dinged up so easy. So , not to contradict my own words. If I can make a 3 E cluster out of just paper tubes,I guess O.5.to 1.5 would work for what I want.

 

[Scotty Dog]

Doing some more research on web I see that the release fabric from West Systems I have is the same as peel ply. Top Roman sent me a bunch of pieces of different weights glass a few years ago. So. I guess the best thing to do is give it a shot. See what weights work for what want.

 

[Nytrunner]

What kind of Es? May not even need the glass.

 

[rharshberger]

I would use 2 wraps of .75oz glass, properly wetted out the weave leaves very little to fill and usually filler primer will do the filling just fine.

 

[Scotty Dog]

What kind of Es? May not even need the glass.

BP Es up to now. With the new single use ones with more power was thinking of a building scratcher with more power. As I said above, Ive made rockets out of paper BTs that cluster 3 Es. Just looking to beef it up a little so it doesn't get beat up so easy and takes bigger motors. And I want to try something different . I never glassed before.

 

[Scotty Dog]

I would use 2 wraps of .75oz glass, properly wetted out the weave leaves very little to fill and usually filler primer will do the filling just fine.

Thanks. I see now after looking at my stash that the lighter glass doesn't have much weave.

 

[Steve Shannon]

Aircraftspruce.com has a lot of supplies for glassing.

 

[rharshberger]

I see now after looking at my stash that the lighter glass doesn't have much weave.

Nope its very smooth and is commonly available in any hobby shop that caters to RC Airplanes, it is a bit tricky to work with as it wants to float on the epoxy, I have been known to take a bit of spray adhesive and spray a thin line down the tube to anchor one edge (along a line drawn the length of the tube, the spray adhesive will require masking to limit the spray to a 1/4" or so wide), or let epoxy get a bit tacky and then apply the one edge and start wetting out from there. Its definitely a technique where practice improves the end results.

 

[Scotty Dog]

I have this to try. Might be a little fast dry IDK. I think it will work just to do some practice on some small sections.

 

[rharshberger]

I have this to try. Might be a little fast dry IDK. I think it will workView attachment 376965 just to do some practice on some small sections.

It will work just fine, the 20 minute Finish-Cure is actually a bit thinner and will wet out better IMO, iirc the 30 minute can be thinned a bit with Denatured Alcohol (would need to test to verify though) and still cure fully.

 

[tfish]

I thought I read in one of the posts that 0.5 to 1.5 oz was a good weight for up MPR.? Seems a little lite? I cant find it again. I read a bunch of posts in this forum. OK, I went back and see in the beginning of "tfish38" and he used 2 layers of 5.85 glass. However ,is that for a HPR? Seems a bit much for LPR-MPR (3-Es at most). I have cluser rocket that take 3 Es made out of just paper BTs. Im just really looking to beef it up so it doesn't get dinged up so easy. So , not to contradict my own words. If I can make a 3 E cluster out of just paper tubes,I guess O.5.to 1.5 would work for what I want.

Yes, two layers of 5.85 oz is to much for what you need. Rich is right a couple or more wraps of .75 oz will work. Your 30 min laminating epoxy will work, You can extend the working time by..using a wide thin (pie plate) container for the epoxy instead of a narrow deep container. Also placing the epoxy bottles and mixed epoxy in an ice bath. This will make the epoxy thicker and harder to work into and through the .75 oz cloth. I use the porous teflon coated peel ply from Aircraft spruce https://www.aircraftspruce.com/catalog/cmpages/vb7025.php?clickkey=5724 ...because it is thicker/stiffer then 'others" Thicker/stiffer = less wrinkles and a rounder finished tube.

I often thin my epoxies when doing layups. I don't buy my epoxies based on laminating epoxies. I buy them based on strength and tig temps. Then thin them to use for laminating. My current "epoxy' is rather thick..I really have to work it...lots of brushing with a 'chip brush" to get it to wet out even 6 oz cloth. But it strength and 350 degree tig temp at room temp cures are very good qualities for what I do.

Just like anything. The more you do the better (hopefully) we get at doing it. try a few practice pieces...paper towel roles / TP roll tubes work well. Try 2 layers on one and 4 layers on another. Once it sets up...which 'feels"... squeeze it, like what you want/need.

I added a touch more denatured alcohol to the epoxy..just before wrapping the peel ply to...get it lubed up...which helps wet out any 'dry spots" i don't see, help work out any air bubbles and wet out the peel ply. looking at the peel ply..you would not think it's porous enough for the epoxy to soak through it It does and you may even get epoxy dripping off the peel ply. Which is OK. The un-needed and un-wanted epoxy will just bleed out of the layup.

Tony (tfish)

 

[Scotty Dog]

I want to Thank everyone for all the information you have provided on the subject of fiberglassing BTs. Looks like today's weather is going to be warm. High 40s to 50. Maybe I'll warm up the porch and try some glassing. Thanks Again.