Epoxy fillets ...

[DeltaVee]

Hi There Folks....

I obtained one of the Cherokee G kits offered on TRF a while back and at last I got around to building it. Working on the electronics bay and so on, I started drilling holes... today got the ones for the rivets done... a genuine p.i.t.a. to do it cleanly.... frankly, now that I have an altimeter for the e-bay, I'm amazed how many holes I'm going to have to drill... never had to use a drill on a rocket so much. But that's holes not fillets....

The author of the kit recommended doing the fillets using microballoons (the preference was for west systems 410 which is $17 for 2 fl. oz.) I've done epoxy fillets on a couple of estes builder's kits (the Ventris and the Sahara). I didn't think I'd ever crack a fillet on a ttw fin that was made out of epoxy, but the ventris got a hairline crack on the fillet after a hard landing... generally I think I do a reasonable fillet job on most of the kits but with basic low power rockets (my Goblin clone as a case and point), a hard landing causes the tube to peel up or delaminate... At least with a ttw fin, a hard landing will tend to NOT have the tube outer layers peel off!

So this leads me to the following question... for a big MPR-HPR, does adding microballons add any advantage strength-wise as far as the fillet is concerned? I can see how it will make the fillet resistant to running if your rocket isn't level, but what is the thinking in terms of added strength? I've never used this stuff before so I picked up a 2 fl oz container of Top Flite MBs (MUCH less expensive than WS's)... and if it makes these fillets resist fractures on hard landings, I'll be very pleased...

Let me know what y'all think!

 

[David_Stack]

West Systems has a filler application guide posted at https://www.westsystem.com/filler-selection-guide/

Interestingly enough, the filler you referenced as recommended (410) is the worst in comparison when it comes to imparting any strength to the epoxy matrix.

Good Luck with the Cherokee G build.

r/
Dave

 

[AfterBurners]

I usually just use milled fiberglass. I never had any issues.

 

[DES]

Hi There Folks....

I obtained one of the Cherokee G kits offered on TRF a while back and at last I got around to building it. Working on the electronics bay and so on, I started drilling holes... today got the ones for the rivets done... a genuine p.i.t.a. to do it cleanly.... frankly, now that I have an altimeter for the e-bay, I'm amazed how many holes I'm going to have to drill... never had to use a drill on a rocket so much. But that's holes not fillets....

The author of the kit recommended doing the fillets using microballoons (the preference was for west systems 410 which is $17 for 2 fl. oz.) I've done epoxy fillets on a couple of estes builder's kits (the Ventris and the Sahara). I didn't think I'd ever crack a fillet on a ttw fin that was made out of epoxy, but the ventris got a hairline crack on the fillet after a hard landing... generally I think I do a reasonable fillet job on most of the kits but with basic low power rockets (my Goblin clone as a case and point), a hard landing causes the tube to peel up or delaminate... At least with a ttw fin, a hard landing will tend to NOT have the tube outer layers peel off!

So this leads me to the following question... for a big MPR-HPR, does adding microballons add any advantage strength-wise as far as the fillet is concerned? I can see how it will make the fillet resistant to running if your rocket isn't level, but what is the thinking in terms of added strength? I've never used this stuff before so I picked up a 2 fl oz container of Top Flite MBs (MUCH less expensive than WS's)... and if it makes these fillets resist fractures on hard landings, I'll be very pleased...

Let me know what y'all think!

Suggest giving the West Systems GFlex Thickened epoxy gel a try. Pre-thickened, nice consistency, shapes well and doesn't run. The GFlex is somewhat flexible, still quite strong, but about 5X the flex of standard epoxy. So it will not crack on impact or bending.

Microballons are simply a filler and reduce the density of the epoxy, making it thicker, and easier to sand. But they will not improve the fracture resistance.

 

[DeltaVee]

Suggest giving the West Systems GFlex Thickened epoxy gel a try. Pre-thickened, nice consistency, shapes well and doesn't run. The GFlex is somewhat flexible, still quite strong, but about 5X the flex of standard epoxy. So it will not crack on impact or bending.

Microballons are simply a filler and reduce the density of the epoxy, making it thicker, and easier to sand. But they will not improve the fracture resistance.

Just found the spec sheet on this stuff... Looks like it's perfect for the task at hand...

 

[DES]

Just found the spec sheet on this stuff... Looks like it's perfect for the task at hand...

Lots of different ways to apply, but the West Systems black plastic popsicle sticks work really well. Prep and clean the surfaces, then goop on the epoxy, break any air bubbles, then shape the fillet with one or two passes of the curved end. Trim off any excess on the sides with the flat scrapper end. The West Systems manual shows how to do it. I have found it works best to do only one or two fillets at a time, so you can keep them "up" and horizontal. If you gauge the amount of epoxy about right, there will be just a little wet epoxy to scrape off, and very little sanding to blend into the fin once cured. Resist the urge to touch it until it is hard! You will mar it. You can test the cure on the waste left on your mixing board. It does take a few hours. FYI, the GFlex Gel is 1:1, so you can get a good ratio just by laying equal beads of resin and hardener on a plastic lid.

Some folks like to put masking tape on each edge of the fillet. I've done that, and it works fine, but you have to be careful to get the tape in just the right spot or it will pucker up the edge of the fillet when you pull the tape off. Even if it doesn't, you have a 5-7 mil lip to fill.

 

[blackjack2564]

The West 406 adds strength to fillets. It is added to epoxy holding large cleats on yachts. Cleats are what they tie up to at the dock, why they sell it.

It also makes it like peanut butter for fillet work...great stuff.

 

[G_T]

IIRC, the Cherokee G rocket is a fairly light fairly low power rocket. It may be that using 410 keeps the fillets light, reducing potential need for noseweight, and improving the overall performance of the rocket. 410 is not great for strengh, obviously. But it will thicken the epoxy so it stays in place for a fillet, and the resulting lightweight fillet may be better than no fillet at all. It may be appropriate, depending on the max speed you are going to get it to.

Other additives tend to increase the density of the fillet, rather than decrease it. What is appropriate and what you can get away with all depends on the loads the fins will experience, and what other structural support may be present.

Gerald

 

[dr wogz]

I prefer the West 407 Fairing filler. makes a thick goo, and sands & shapes nicely..

 

[JimJarvis50]

I did a NARCON presentation a few weeks ago on different building techniquest that I use, A video that was the basis of the presentation is posted here. Fillets are discussed starting at 5:20.



Jim

 

[DeltaVee]

I did a NARCON presentation a few weeks ago on different building techniquest that I use, A video that was the basis of the presentation is posted here. Fillets are discussed starting at 5:20.



Jim

Finally got around to watching your video... the phrase "that's the way to do it..." comes to mind!

 

[JimJarvis50]

Finally got around to watching your video... the phrase "that's the way to do it..." comes to mind!

Thanks! One clarification though.....

The method in the video is intended if there will be tip to tip reinforcement added. For that, a round fillet is good. For cases where tip to tip won't be used, I would modify the process to use a smaller dowel at a higher angle to get a little more epoxy into the fillet. But all else the same.

Jim

 

[timster68]

Wow - this was a fantastic tutorial. I Just used it and my fillets look great! Thanks for showing how you did it.

 

[timster68]

Thanks! One clarification though.....

The method in the video is intended if there will be tip to tip reinforcement added. For that, a round fillet is good. For cases where tip to tip won't be used, I would modify the process to use a smaller dowel at a higher angle to get a little more epoxy into the fillet. But all else the same.
No
Jim

Hi Jim,
I will admit I haven’t looked yet, but is there a formula for the additives I will want to use? I purchased the West products you are using and wanted to see if I get mine to look the same.

 

[JimJarvis50]

Hi Jim,
I will admit I haven’t looked yet, but is there a formula for the additives I will want to use? I purchased the West products you are using and wanted to see if I get mine to look the same.

I don't have a formula. I suspect any formula would depend on the epoxy you are using, and remember, I use laminating epoxy. What I do is to add enough of the 404 to partially thicken the epoxy. I find that quite a bit less of the 406 is needed when I do this (and the 404 has some of the 406 in it). Then, I add the 406 until it gets thick enough to form peaks. For a clear epoxy, the mixture gets kind of translucent at that point. It's pretty easy to tell when you're at the right point. If you have a glob of epoxy on a stick, it won't run off or sag.

Jim

 

[timster68]

I don't have a formula. I suspect any formula would depend on the epoxy you are using, and remember, I use laminating epoxy. What I do is to add enough of the 404 to partially thicken the epoxy. I find that quite a bit less of the 406 is needed when I do this (and the 404 has some of the 406 in it). Then, I add the 406 until it gets thick enough to form peaks. For a clear epoxy, the mixture gets kind of translucent at that point. It's pretty easy to tell when you're at the right point. If you have a glob of epoxy on a stick, it won't run off or sag.

Jim

Thanks Jim. I bought the same laminating epoxy you had in the video. I will work on that shorty.

 

[mtnmanak]

Quick note on the "smoothing tool" - I see a lot of people recommend dowels or PVC - I have used both and they work great. However, for the price of a couple sizes of dowels or PVC pieces (and, eventually, you will want a number of different sizes), I have found these Fondant tools to be excellent. Solid steel ends make short work and give you a tailored fillet everytime. The sizes included have worked for me on the smallest LPR tubes all the way up to 8 inch fiberglass tubes.

All for $6. And, you get a lifetime of smoothing tools for just about any rocket.

https://www.amazon.com/gp/product/B01LZMSGF2/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

 

[timster68]

Quick note on the "smoothing tool" - I see a lot of people recommend dowels or PVC - I have used both and they work great. However, for the price of a couple sizes of dowels or PVC pieces (and, eventually, you will want a number of different sizes), I have found these Fondant tools to be excellent. Solid steel ends make short work and give you a tailored fillet everytime. The sizes included have worked for me on the smallest LPR tubes all the way up to 8 inch fiberglass tubes.

All for $6. And, you get a lifetime of smoothing tools for just about any rocket.

https://www.amazon.com/gp/product/B01LZMSGF2/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Well shucks, I actually had bought some and forgot to use them!

 

[afadeev]

I did a NARCON presentation a few weeks ago on different building techniquest that I use, A video that was the basis of the presentation is posted here. Fillets are discussed starting at 5:20.

Jim,
Did anyone tell you that you look a lot like John Cleese:

 

[JimJarvis50]

Jim,
Did anyone tell you that you look a lot like John Cleese:

That's a new one. I get Phil Jackson from time to time.

Jim

 

[mtnmanak]

That's a new one. I get Phil Jackson from time to time.

Jim

Either way, you are in rarified air... literally - both Cleese and Jackson are over 6'5"!

Thanks for the video at NARCON, great stuff!

I know this is an epoxy thread and don't want to derail it too much, but did you document that wiring diagram with the shunt and resistors in any more detail someplace? Would love to see a picture and description of the resistors used, shunt design, wifi switch, etc. My rocket building skills are okay, but my electrical engineering skills are subpar and would like to learn more. May be worth another thread, unless there already is one.

Thanks!

 

[Tarantula]

Quick note on the "smoothing tool" - I see a lot of people recommend dowels or PVC - I have used both and they work great. However, for the price of a couple sizes of dowels or PVC pieces (and, eventually, you will want a number of different sizes), I have found these Fondant tools to be excellent. Solid steel ends make short work and give you a tailored fillet everytime. The sizes included have worked for me on the smallest LPR tubes all the way up to 8 inch fiberglass tubes.

All for $6. And, you get a lifetime of smoothing tools for just about any rocket.

https://www.amazon.com/gp/product/B01LZMSGF2/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

Here are the Fondant tools in action...

 

[CPUTommy]

Great job on the video and i love the techniques you referred to.

Are you going to produce more informational videos?

Again, real nice presentation. I found it very easy to watch.


Tom

 

[Tarantula]

Tom,

That video was created by @Ian A Dalton from Mach 1 Rocketry and Bad Ass Rocketry.

https://www.badassrocketry.com/
http://www.mach1rocketry.com/
Awesome product lines and super customer service.

 

[GregC]

Here are the Fondant tools in action...

Thanks for posting that video. I always learn something from videos like this. Never heard of Fondant tools before today and this video did a great job showing them in use. Awesome!

 

[GregC]

Well shucks, I actually had bought some and forgot to use them!

Thanks for the amazon link for Fondant tools. I had no ideas something like that existed. A set is on the way to my home. They will be here in a few days. Amazing. Great tip!

 

[Greg Furtman]

Quick note on the "smoothing tool" - I see a lot of people recommend dowels or PVC - I have used both and they work great. However, for the price of a couple sizes of dowels or PVC pieces (and, eventually, you will want a number of different sizes), I have found these Fondant tools to be excellent. Solid steel ends make short work and give you a tailored fillet everytime. The sizes included have worked for me on the smallest LPR tubes all the way up to 8 inch fiberglass tubes.

All for $6. And, you get a lifetime of smoothing tools for just about any rocket.

https://www.amazon.com/gp/product/B01LZMSGF2/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

+1

 

[Jmhepworth]

Thanks for the amazon link for Fondant tools. I had no ideas something like that existed. A set is on the way to my home. They will be here in a few days. Amazing. Great tip!

I bought a set as well. Thanks.

 

[Greg Furtman]

I did a NARCON presentation a few weeks ago on different building techniquest that I use, A video that was the basis of the presentation is posted here. Fillets are discussed starting at 5:20.



Jim

@JimJarvis50 I watched your video & I have a question. What exactly is a z-fold? I've Googled it but didn't find anything useful. Does anyone know of a video that explains how to do a z-fold?

 

[JimJarvis50]

@JimJarvis50 I watched your video & I have a question. What exactly is a z-fold? I've Googled it but didn't find anything useful. Does anyone know of a video that explains how to do a z-fold?

You probably know it by a different name? I've heard it called an S fold and there are probably others. It's just folding a harness back and forth and then taping the bundle to keep the harness organized. I just do it with blue tape to keep things organized, but with stronger tape, it can also serve as a shock absorber upon deployment.

Jim