# Properly bonding composites and what your government doesn't want you to know.

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#### markkoelsch

##### Well-Known Member
Is wet sanding acceptable for fiberglass surface prep for epoxying? It would greatly reduce the amount of airborne dust. I wear a good respirator but don't have a dedicated work shop at home so I'm worried about fiberglass dust in the air. I go outside to cut fiberglass, but having to do so for surface prep would be a PITA (New England winter = sunset at 430pm, snow, and freezing temperatures).
As long as you are using a proper grit, and let it thoroughly dry I think it should work.

#### Performance nut

##### Well-Known Member
Would it be possible to host the pictures elsewhere? I'd like to see more on what the speaking points are.

#### pendrin2020

##### Well-Known Member
I am also eager to see this thread with pics. maybe the author could put together a PDF and post a link to Google drive or something?

#### tfish

##### Well-Known Member
There was a post here on TRF about how to view post with old photobucket photos. I think it was Angie that posted it. You do need to view the post on Google Chrome.

below is a photo from the beginning of this thread to prove it does work.

Flynfrog has not posted since Nov 2017

Tony

#### pendrin2020

##### Well-Known Member
There was a post here on TRF about how to view post with old photobucket photos. I think it was Angie that posted it. You do need to view the post on Google Chrome.

below is a photo from the beginning of this thread to prove it does work.

Flynfrog has not posted since Nov 2017

Tony
Well, I hope he comes back someday. That was a great write-up.

BTW... I did some digging, and most browsers have an add-on that fixes those dead links! Just go to your "extensions" or "add-ons" manager and search for: photobucket embed fix

it'll install in seconds, and all you have to do is refresh the page you were trying to look at. The one in Firefox works great.

#### Performance nut

##### Well-Known Member
There was a post here on TRF about how to view post with old photobucket photos. I think it was Angie that posted it. You do need to view the post on Google Chrome.

below is a photo from the beginning of this thread to prove it does work.

Flynfrog has not posted since Nov 2017

Tony
Thanks for trying. Was trying to see what to look for when I sand the surface. I think I know what he was referring to but just want to confirm. I'm new to composites and I have several candidates waiting for epoxy.

#### flynfrog

##### Well-Known Member
I am also eager to see this thread with pics. maybe the author could put together a PDF and post a link to Google drive or something?
I have been planning to rehost just haven't had time. Since Nov I have moved to a new state, got married, started a new job, and building a house. Just low on time. I would like to host them on the rocketry forum so that they will live as long as the forum does.

#### FlyBy01

##### Well-Known Member
TRF Supporter
I have been planning to rehost just haven't had time. Since Nov I have moved to a new state, got married, started a new job, and building a house. Just low on time. I would like to host them on the rocketry forum so that they will live as long as the forum does.
+1

Sent from my SM-G950U using Rocketry Forum mobile app

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#### Ez2cDave

##### Well-Known Member
TRF Supporter
I am also eager to see this thread with pics. maybe the author could put together a PDF and post a link to Google drive or something?
I have been planning to rehost just haven't had time. Since Nov I have moved to a new state, got married, started a new job, and building a house. Just low on time. I would like to host them on the rocketry forum so that they will live as long as the forum does.
Flynfrog,

I created a PDF file of your fantastic tutorial ! ( Attached Below )

Dave F.

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#### base890

##### Well-Known Member
TRF Supporter
Any particular considerations for bonding fiberglass or birch to A LOC nose cone?

#### beeblebrox

##### 8 C6-0, 12 D11-9, 20 D20-0, 20 E5-0, 3 Cinerocs
Any particular considerations for bonding fiberglass or birch to A LOC nose cone?
Loc nose cones are either polyethylene or polyproplyene both plastics are like mold release to epoxy. It is basically impossible to get a good bond unless you have some structure going thru it like metal screws that will bond to the epoxy... Trying to figure where you would want to bond birch? you talking little fins? like the front of an AQM-37A Jayhawk for example. if so, run a rod all the way thru from one fin to the other.

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#### base890

##### Well-Known Member
TRF Supporter
I’m building an electronics bay inside the nosecone. There will be two wood centering rings if you can call them that on the inside. The shoulder has a fiberglass sheath to anchor to the polypropylene as well.

#### Don Allen

##### Active Member
Well, I hope he comes back someday. That was a great write-up.

BTW... I did some digging, and most browsers have an add-on that fixes those dead links! Just go to your "extensions" or "add-ons" manager and search for: photobucket embed fix

it'll install in seconds, and all you have to do is refresh the page you were trying to look at. The one in Firefox works great.
This fix DOES work! Just installed it and seeing old-link photos just fine now.

#### Paulb06

##### Well-Known Member
I’m building an electronics bay inside the nosecone. There will be two wood centering rings if you can call them that on the inside. The shoulder has a fiberglass sheath to anchor to the polypropylene as well.
My favorite method of doing that is to use small(#2) flathead screws placed an inch or so apart around the centering ring, depending on the diameter of the nosecone....use a flashlight inside to show exactly where the ring is...drill and countersink so the screwhead is below the surface on the outside.....I drill and screw it together dry ...then remove it, clean and prep, then apply the glue and screw it together and when its cured you can prep and fill the countersunk holes around the outside..... you want to use a thick enough plywood for the centering ring so you have plenty to screw into

#### base890

##### Well-Known Member
TRF Supporter
My favorite method of doing that is to use small(#2) flathead screws placed an inch or so apart around the centering ring, depending on the diameter of the nosecone....use a flashlight inside to show exactly where the ring is...drill and countersink so the screwhead is below the surface on the outside.....I drill and screw it together dry ...then remove it, clean and prep, then apply the glue and screw it together and when its cured you can prep and fill the countersunk holes around the outside..... you want to use a thick enough plywood for the centering ring so you have plenty to screw into
Thanks Paulb - that sounds perfect! I started to grow concerned about the shock loading forces on the bond with the heavy nosecone plastic and would hate to lose my $$GPS hardware! #### Paulb06 ##### Well-Known Member I Thanks Paulb - that sounds perfect! I started to grow concerned about the shock loading forces on the bond with the heavy nosecone plastic and would hate to lose my$$\$ GPS hardware!
I've used that method to replace the plastic nosecone shoulder/coupler with a phenolic one....it shows no sign of coming loose

#### Rail Dawg

##### Always learning!!!
So we’ve got lacquer thinner, acetone and denatured alcohol available in the rocket barn.

Looking for the best prep solvent for an “R” powered G-12 fiberglass rocket that we’re just starting to build. Read the entire thread twice it’s so chock full of great info.

For the maximum cleaning of the G-12 what’s the consensus on which of the above is the best to use?

Thanks!

Chuck C.

#### Steve Shannon

##### Well-Known Member
TRF Supporter
Any one of those will work just fine. Just make sure you adequately sand the areas to be epoxied and then tack with one of those. I usually use denatured alcohol. Acetone will permanently cloud your cornea if you get any splashed in your eye.

#### Rail Dawg

##### Always learning!!!
Any one of those will work just fine. Just make sure you adequately sand the areas to be epoxied and then tack with one of those. I usually use denatured alcohol. Acetone will permanently cloud your cornea if you get any splashed in your eye.

Ah very good Steve. Appreciate the acetone warning.

Chuck C.

#### Paulb06

##### Well-Known Member
So we’ve got lacquer thinner, acetone and denatured alcohol available in the rocket barn.

Looking for the best prep solvent for an “R” powered G-12 fiberglass rocket that we’re just starting to build. Read the entire thread twice it’s so chock full of great info.

For the maximum cleaning of the G-12 what’s the consensus on which of the above is the best to use?

Thanks!

Chuck C.
Great question Chuck! I've always assumed that a bond with a cured composite is a purely mechanical bond and sanding is necessary to give the new epoxy something to hold onto...but sanding does cut some fibers on FW tubing.... .if the solvent is simply removing any grease then they may be pretty much equal......thanks for the warning on acetone, Steve....I generally use acetone

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#### Steve Shannon

##### Well-Known Member
TRF Supporter
Great question Chuck! I've always assumed that a bond with a cured composite is a purely mechanical bond and sanding is necessary to give the new epoxy something to hold onto...but sanding does cut some fibers on FW tubing.... .if the solvent is simply removing any grease then they may be pretty much equal......thanks for the warning on acetone, Steve....I generally use acetone
Over the years I’ve seen a significant number of epoxy joints that popped which were caused by failure to sand, even though solvent was used. Yes, some fibers are cut in sanding. Those fibers then are able to become part of the epoxy structure being used to join the parts.
Added: between the roughening due to the sanding and the exposure of glass fibers sanding greatly increases the surface area of the joint.

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#### tfish

##### Well-Known Member

additional info. This rocket was built to fly on a 3" motor with 40" inch of propellant. On it's 3rd flight it lost half it's exit cone. That put some undo stress on the rocket.

Here's a screen grab from the video. This was at about 1560 ft/sec

here's a video of the flight..

I agree that roughing up FG like I do...will weaken it..some. But it's in an area that gets heavily re-enforced.

Tony

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#### beeblebrox

##### 8 C6-0, 12 D11-9, 20 D20-0, 20 E5-0, 3 Cinerocs
Wash all Fiberglass parts with Dawn dish soap before anything else, this will degrease everything perfectly. (Note this is recommended by Mach 1 Rocketry too...)

#### OverTheTop

##### Well-Known Member
TRF Supporter
I wash all fiberglass components when they arrive to remove any mold release, as per the instructions in this thread. Just before bonding with epoxy I use MIBK as a final wash for the joint. I have also used acetone and alcohol in the past but I read somewhere that MIBK is better. It is also a bit harder to get.

Don't forget to play safe and use the relevant PPE. I always use safety glasses, gloves and work in a well-ventilated area. This is especially important with the MIBK.

Over the years I’ve seen a significant number of epoxy joints that popped which were caused by failure to sand, even though solvent was used. Yes, some fibers are cut in sanding. Those fibers then are able to become part of the epoxy structure being used to join the parts.
Added: between the roughening due to the sanding and the exposure of glass fibers sanding greatly increases the surface area of the joint.
I like Steve’s comment about cutting fibers, the resulting composite “structure” could be even stronger than the original configuration depending on the extent of capillary action of the epoxy (which suggests that thinner epoxy would be a stronger bond).

additional info. This rocket was built to fly on a 3" motor with 40" inch of propellant. On it's 3rd flight it lost half it's exit cone. That put some undo stress on the rocket.

Here's a screen grab from the video. This was at about 1560 ft/sec

here's a video of the flight..

I agree that roughing up FG like I do...will weaken it..some. But it's in an area that gets heavily re-enforced.

Tony
Tony, generally the “exit cone” refers to the shape of the expanding cone of hot exhaust gas (and I assume this is what you mean), but in this case it looks like it may be an effect of a broken nozzle. Are there “after” photos of the nozzle for this event?

Thanks,
Tom