smooth fillets with epoxy

[thaddeus]

what some techniques to get a nice smooth fillet using epoxy? Should I mix it thinner? use a rubber glove finger? the popsicle sticks I'm using are making a mess! I'm currently using a 30 min by Bob Smith Industries. It seems to kick quickly even with accurate mixing. any help?

 

[noise]

what some techniques to get a nice smooth fillet using epoxy? Should I mix it thinner? use a rubber glove finger? the popsicle sticks I'm using are making a mess! I'm currently using a 30 min by Bob Smith Industries. It seems to kick quickly even with accurate mixing. any help?

I put down a structural fillet with a high density filler and then put down another layer with micro-balloon filler and then sand until smooth.

I do use popsicle sticks with a wider end to form the fillets, it works with a little practice. Also mask around your fillets so you don't make a mess on the surrounding areas.

 

[AKPilot]

I've always used the "back of a plastic spoon" method to level out my fillet on MPR stuff and it works like a champ!

 

[Flamboyant]

ooooh. I hate messing up fillets. Mainly because I always mess it up. I've heard that using a syringe works well. Maybe I'll try that.

 

[eastvolt]

I'm new to this as well, and found the following to give perfect fillets everytime.

1. Use masking tape to mask the area you want to fillet.

2. Mix your epoxy

3. Dump some epoxy into the fillet area

4. Smooth with the back of a spoon. (Rita's Water Ice spoons have great narrow shape for this)

5. Remove tape before epoxy dries.

PERFECT!

 

[new2hpr]

Mask the boundaries, then use a short piece of pvc pipe dipped in alcohol to form and smooth. Different size pipe for different fillet radii.

Works very nicely.
Ken

 

[geof]

I'm new to this as well, and found the following to give perfect fillets everytime.

1. Use masking tape to mask the area you want to fillet.

2. Mix your epoxy

3. Dump some epoxy into the fillet area

4. Smooth with the back of a spoon. (Rita's Water Ice spoons have great narrow shape for this)

5. Remove tape before epoxy dries.

PERFECT!

I use exactly this method (maybe a popsicle stick instead of a spoon), but add a final step:

6. Remove tape when epoxy is pliable but not runny (e.g., 11 mins for 15 min epoxy). Dip rubber glove finger in rubbing alcohol and smooth very firmly along fillet.

This last step smooths any ridges left at the tape edge, and is great for the beginning and end of the fin where it is tricky otherwise to get a nice tapering fillet.

G

PS. Then I use diluted Fill-N-Finish over the top with sanding to obtain absolute perfection as necessary.

 

[thaddeus]

thank you all so much! I'll try these ideas, this is my first MPR so I'd rather not mess up an expensive kit! Its a LOC Viper III. I also am looking for paint job suggestions.

 

[LFLekx]

You may also want to consider using an epoxy with a longer working time. I use West System pretty much exclusively, their Slow Hardener gives me about two or three hours before it starts to set up.

 

[thaddeus]

sorry to drag up an old thread, but I just made my first successful epoxy fillet! I'm stoked anyway. thank you for your ideas they worked great. Now if I can just get the other 5 to match I'll be ready to finish this puppy!

 

[jraice]

Yeah my comp had the BEST fillets I have ever had...

I used aeropoxy and west 406 filler (collodial silica I think) and while it may not be the strongest stuff around, it spreads really nice... I found that the surface was a little rough, but it was a good basic shape. I gave that a bit of sanding and shape wise it would have been fine but it still needed to be a lot smoother... Then I used aeropoxy light filler but you could use regular aeropoxy or west mixed with micro balloons... Anyways, after a coat or two of that and some sanding they were SOOOOO smooth it was incredible...

Also some like to use thinner epoxy's but I like to get it real thick so it wont sag and then use a popsicle stick or a spoon to shape them... Gets them super uniform.

 

[Stymye]

I use the front of a plastic spoon it catches the excess instead of spreading it out . I sand the spoon down if I need a smaller radius.
I didn't use tape last time and they came out fine . I keep a vinegar soaked rag handy to wipe anything up . vinegar works very well on West Systems , they even recomend it, The only downside is how you smell afterward.

 

[thaddeus]

well I just got home from work, and it looks great to me! I used the tape and latex glove finger soaked with rubbing alcohol. just waited til the end, about 15 mins. (using cheap 30 min stuff) and It looks as good as any I've done with glue and spit. I don't think they will need any sanding at all. Geez, Its gonna be a shame to paint over them! I'm taping up the next one right now. I got some old syringes from the vet, works like a charm. I'll post some picts when the wife gets home with the camera

 

[jraice]

The real trick is to tape it off... I have found even with freehand (now I always use a spoon but I used to freehand) I can get decent fillets but I am always tempted to smooth the part that is spread off, which ruins the fillet shape and its a cycle that ends in less then perfect fillets. If you tape off the edges you can scrape it to the proper shape, remove the tape and the excess...

Then just sand the tape ridge a bit and you will have great fillets every time.

 

[thaddeus]

Alright, I stayed up late and got 3 more done last night. 2 have some wobble in them. I bought a dowel today for sanding them smooth, going to wrap the sand paper around the dowel to make sure I'm only sanding the epoxy. should work out. Tonight I'll do the remaining two. What I discovered, is to smooth it right away. Not waiting for it to set up. I smoothed it with the alcohol and glove before I removed the tape, to get away the extra, then took off the tape, then smoothed it again. The hard part is making them the same size. I'm lucky because the ViperIII has those deep valleys to hold the epoxy. I'm thinking this was a good first choice for my learning this technique. thanks again, my friends for the tips! thad

 

[rokitflite]

I use my fore finger. No tape, no tools, no solvents.

 

[thaddeus]

really? I love my toxic chemicals but..... I don't want that stuff on my hands

 

[rokitflite]

really? I love my toxic chemicals but..... I don't want that stuff on my hands

Whatever... One of my friends said something like that to me WHILE he smoked a cigarette. Thats just how I do it, and my fillets are flawless and take no time at all.

 

[pencak]

what some techniques to get a nice smooth fillet using epoxy? Should I mix it thinner? use a rubber glove finger? the popsicle sticks I'm using are making a mess! I'm currently using a 30 min by Bob Smith Industries. It seems to kick quickly even with accurate mixing. any help?

First mask it off so you don't make a mess

Notice the plastic spoon on the left. This was used to make the fillets. I used microballons in the mix to thicken it.

Remove the tape before it sets up too much. When the epoxy is in a rubbery state. I used the 30 minute and it worked fine removing the tape at about 45 minutes.

You can see how smooth they came out. You can see the microballons I used.
All you have to do after that is sand it and you're done.

 

[thaddeus]

those look pretty darn good! I guess I'll have invest in better supplies for my next MPR. Does that stuff sand well? I haven't tried sanding down the ones I'm doing yet.

 

[dixontj93060]

I have found the best way to do fillets is to both prep and touch them as little as possible. Also, to get good at the technique I always use the same type of expoxy, 15 minute polyester-base. This gives me a good tradeoff between strength and minimum working time (I hate to waste much time on fillets).

Mix just enough to do the top two fillets at a time. Use a bit of milled fiberglass and about twice the amount of microballoons and get a thick "yogurt" consistency. Drizzle a medium bead along the fin joints stopping about 1/4" to 3/8" from the fore and aft edges of the fin. In about 5 minutes the whole joint will have filled in nicely. If there are slight drips around the edges of the fins dab them off with a paper towel dipped in alcohol. Wait another 3 minutes (just as the epoxy is completing setup) and take your finger (tightly fitting nitrile glove recommended) dipped in alcohol and smooth the fillet.

As long as your "drizzle beads" and your timing for the final smoothing are relatively consistent you will get beautiful fillets every time without sanding.

 

[pencak]

Sands just fine.

 

[thaddeus]

Here's the finished product. I'm very pleased for my first try! Thanx to all your help, ideas and advice.

View attachment viper.JPG

 

[limd21]

My technique is to dab the epoxy into the joint, put on a nitrile glove, wet a finger in rubbing alcohol, (pull the glove tight over that finger if it's a bit loose) and drag it over the epoxy in the joint. Glass smooth and needs no sanding - except perhaps a bit to dull the gloss for primer adhesion. I tried tape joints, but they leave a ridge that needs to be sanded if you want it perfect.

The harder you press your finger into the joint, the smaller the radius fillet you will get. I can get a really tiny radius with my pinky, and a pretty big one using my thumb.

I used to use popsicle sticks and spoons, but I find a the wet-finger technique is faster and cleaner because there is much less chance for excess epoxy to ooze out to the sides.

 

[ctus]

I use exactly this method (maybe a popsicle stick instead of a spoon), but add a final step:

6. Remove tape when epoxy is pliable but not runny (e.g., 11 mins for 15 min epoxy). Dip rubber glove finger in rubbing alcohol and smooth very firmly along fillet.

This last step smooths any ridges left at the tape edge, and is great for the beginning and end of the fin where it is tricky otherwise to get a nice tapering fillet.

G

PS. Then I use diluted Fill-N-Finish over the top with sanding to obtain absolute perfection as necessary.

Exactly the same for me. Fill-N-Finish over the structural fillet and then sand. Makes the fillets perfect, and looks great when painted.

 

[msurocketgurl]

Thanks for y'all advice. I'll definitely use some of y'all's techniques with my next fillets. They usually turn out to be quite the mess :cry:

 

[mrmonteith]

I just put enough epoxy on, lay a piece of clear tape along, and let it cure. For any spots I sand or use my dremel on low speed and clean it up. I would like to try some of the fillers though sometime to make things a bit lighter in weight.

Michael