G10 prepping

[frankenhead]

My first scratch build and first time using G10. I want the strongest bond possible so I thought Id drill a million little shallow holes in the G10 where the fillets will go. Also roughed it up with some 100 grit.

Good idea ? Overkill ?

Not making a mach buster but needs to be able to take the punch from a J.

 

[frankenhead]

...also sanded the glassine and poked holes in the motor tube so the 30 min epoxy soaks in deep.

 

[frankenhead]

fillets will go on G10 to motor tube , G10 to inside airframe and G10 to outside airframe. Bigger hole were drilled to save a little weight and in case I want to do foam around the motor tube.

BTW , Im selling some left over .125" G10 on the ROL if anyone interested

 

[DPatell]

That is surely okay, but a little tedious and overkill. All you really need to do is scuff it up really well. Either use a rasp or low grit sand paper, like 35 or 50 grit should work well. Make sure it's not shiny, and after scuffing wipe it with some acetone to clean the surface to allow for the best bond possible.


You will be fine the way you've done it.

 

[frankenhead]

Originally posted by DPatell
That is surely okay, but a little tedious and overkill. All you really need to do is scuff it up really well. Either use a rasp or low grit sand paper, like 35 or 50 grit should work well. Make sure it's not shiny, and after scuffing wipe it with some acetone to clean the surface to allow for the best bond possible.


You will be fine the way you've done it.

awesome. thx Dan

 

[cjl]

Overkill and tedious, but definitely fine. When I need G10 to stick well, I simply scuff it up with some 50 grit and clean it with rubbing alcohol (make sure the alcohol is completely evaporated before gluing). If it needs to stick REALLY well, I add some glass to the fillet. Either is perfectly adequate. Still, you definitely won't have any issues with that, and it should definitely be fine.

 

[frankenhead]

yeah , overkill and tedious. But I wanna build this sucker STRONG. Dont want the motor to push up through the body. Its my first scratch build and going for L2 on it. I`ll post some more pics soon

 

[astrowolf67]

As others have said, a bit of overkill. I usually scuff all the areas to be bonded with 80 grit, drill two or three larger holes along the middle of the tab as you did, and pour in some foam. My only concern on what you did, was the pin holes on the motor tube. You didn't put them all the way through did you?

 

[cjl]

You said this was 1/8" G10?

Wow - that is overkill. I've flown that on 16lb rockets with K motors before, and I've flown 4lb rockets on J350's with only 1/16" G10 fins. Sounds like you should have no trouble with the L2

 

[frankenhead]

Originally posted by astrowolf67
As others have said, a bit of overkill. I usually scuff all the areas to be bonded with 80 grit, drill two or three larger holes along the middle of the tab as you did, and pour in some foam. My only concern on what you did, was the pin holes on the motor tube. You didn't put them all the way through did you?

no just little stabs it with an awl. maybe went through 1st layer of paper but not all the way through.

 

[frankenhead]

Originally posted by cjl
You said this was 1/8" G10?

Wow - that is overkill. I've flown that on 16lb rockets with K motors before, and I've flown 4lb rockets on J350's with only 1/16" G10 fins. Sounds like you should have no trouble with the L2

.125" a little thick ? Its a little heavier than I thought. The wood fins that came on mi Mini Magg are about .125" so I thought the same thickness would look good. Probably have to and some nose weight when I find out where the CP and CG are. I dont care about heavy. I like the low n slow lift offs.

Your 4lb rocket on a J350 has gotta scream ! The J350 is what Im gonna cert with. Should be awesome since the biggest motor Ive ever used was a I161.

 

[Rock_It]

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[cjl]

Originally posted by frankenhead
.125" a little thick ? Its a little heavier than I thought. The wood fins that came on mi Mini Magg are about .125" so I thought the same thickness would look good. Probably have to and some nose weight when I find out where the CP and CG are. I dont care about heavy. I like the low n slow lift offs.

Your 4lb rocket on a J350 has gotta scream ! The J350 is what Im gonna cert with. Should be awesome since the biggest motor Ive ever used was a I161.

Oh yes, it screams
Here it is on an I284 (great motor, perfect for testing a cert rocket before a J350): https://www.rocketryforum.com/attachment.php?s=&postid=292291

Yeah - 1/16" G10 is fine for most 3" rockets on H-small J motors, and even some 4" rockets that won't approach mach. 1/8" is what I have on a 16lb rocket that flies on K motors (and lands directly on the fins - they're swept back), and it doesn't have a scratch. I've found that in most cases, you can take the thickness of aircraft ply fins and divide it by 2, and have a rough estimate of the thickness of comparable strength G10 fins.

 

[frankenhead]

Originally posted by Rock_It
G10 is a highly compressed high heat rated, and extremely strong material. When you choose it, you choose it because you can use much thinner material yet have more strength than wood, plastic or other materials.

For example, the Talon 3 I have coming has .093" G10 fins. That vehicle weighs 6 pounds, is 6 feet 1 inch long, and can travel at mach speed. That rocket would require 3/16" or even 1/4" ply wood fins and they would have to be glassed on at the root fillets at the very least. 1/8" fins could be used if they were glassed with layers of glass or Carbon Fiber.

With G10, you can cut the cross section down, decrease drag, and have a stronger material. If you go thicker, it can't hurt anything really. It will just increase drag some, and the vehicle will weigh a little more. It ould also add some cost as the thicker material cost more.

I can tell you this, you won't have to worry about breaking a fin!

sounds like strong stuff. hmmmm... I coulda went a lil thinner. Oh well , I definitely dont wanna break a fin. Thats kinda why I choose so thick. That stuff cuts nice with a 4" grinder and a thin fiber cut off wheel for metal.

 

[frankenhead]

Originally posted by cjl
Oh yes, it screams
Here it is on an I284 (great motor, perfect for testing a cert rocket before a J350): https://www.rocketryforum.com/attachment.php?s=&postid=292291

Yeah - 1/16" G10 is fine for most 3" rockets on H-small J motors, and even some 4" rockets that won't approach mach. 1/8" is what I have on a 16lb rocket that flies on K motors (and lands directly on the fins - they're swept back), and it doesn't have a scratch. I've found that in most cases, you can take the thickness of aircraft ply fins and divide it by 2, and have a rough estimate of the thickness of comparable strength G10 fins.

Awesome pic ! I was thinking the same thing . Test with I284. I think they both have 1.8 sec of thrust.
Your 16 lb-er lands on the fins ! Wow strong stuff.

 

[m85476585]

The only problem with preparing G10 like you did is that it eats cutting tools. G10 is the same material uses in PCBs (circuit boards for electronics), and PCB manufacturers have to use tungsten carbide drill bits to last a reasonable amount of time, but those drill bits are so brittle that they can only be used in specialized machines (30,000-100,000rpm with no wobble, according to Wikipedia). A normal drill bit will work (as you have seen), but it will not last long.

I have found that epoxy sticks very well to G10. I usually use 80-grit for the bonding surfaces and 320 to prepare for paint.

 

[astrowolf67]

Originally posted by cjl
Oh yes, it screams
Here it is on an I284 (great motor, perfect for testing a cert rocket before a J350): https://www.rocketryforum.com/attachment.php?s=&postid=292291

Looks like you had the crowds attention in that pic! Very nice lift off shot.

 

[Rock_It]

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