Fillet Pulling Tool question

I have a question concerning fillet pulling objects. I know many use PVC to pull their fillets but, last night I took a short length of 1/2" PVC and used it to draw lines on my airframe of my Binder Excel DD and at 1/2" they look like they will be over size. I did a quick calculation using the midrange of the of the 4% and 8% of the fin root and 1/2" PVC has me above the 8% and none of the box or hardware stores have anything smaller. So, I am looking for a smaller alternative around my garage and I spy my large set of chromed deep well sockets. LOTS of sizes to choose from there! I will be using Rocketpoxy for my fillets and I was wondering if anyone has used chromed sockets to pull fillets before and how did it work with the Rocketpoxy. I will be using denatured alcohol to wet what ever I use. I just wanted to see if anyone used anything similar and what were your results?

Having just done this, on a 6" Wildman Darkstar...

PVC works well, but using the tube to mark things I came out further than expected. I think it was just tough to get the marker down to the first contact spot. So instead I used a piece of tape and carefully put it in the joint until it wouldn't go any further. That got me much closer to the joint and about where I wanted to be. I used a 1" coupler as I had it handy.

I tried wet with denatured alcohol and dry. I thought it pulled smoother wet, but the final joint was about the same. The epoxy was a little rougher initially with the dry tool, but self leveled and was about the same after 10 minutes or so.

I see no reason a deep socket won't work fine. The epoxy cleanup was pretty easy on my PVC with a paper towel soaked in denatured alcohol. Some epoxy got inside the coupler, which would be a bigger deal on a socket you intend to use as a socket again. Make sure you clean it out well.

I've used plastic spoons, and small metal tubing before, though not on rockets. So I would think it would work fine. Another option might be copper pipe / tube. That's available around here down to 1/4".

I used Aeropoxy structural with milled fiberglass. I wouldn't think any quality epoxy would be much different and I hear good things about Rocketpoxy. I expect it will work fine. You could always try a test piece with cardboard or similar to make sure if you're concerned about it though.

Plastic spoons work ( disposable type), and I like the cheap plastic toddler spoons for smaller rockets fillets.

I cover the pipe in sharpie, then rub the pipe against the rocket. Leaves marks exactly where it contacts

I've used large popsicle sticks or tounge depressors before.

Sockets would work, but clean up may be fun

I've used PEX/Sharkbite type tubing for pulling smaller fillets. I can usually find smaller 4ft lengths in the hardware stores and it come in various diameters. The PEX tubing is also handy to keep around because it conveniently slides over all-thread when I need to adjust the fit of a sled in an av-bay or nosecone (most of my electronic sleds fit in many rockets and all bays are not the same length):



edit: and it cuts with a utility knife if you don't have a pvc tube cutter around

Look for copper pipe couplers at the hardware store for smaller fillet tools.

The reality is, as long as it's smooth, coated with alcohol, and kept clean, it'll work.

I have used sockets many times. Works well but they always have epoxy residue on them. For my smaller projects I am partial to the handle of and exacto knife.

rharshberger said:

Plastic spoons work ( disposable type), and I like the cheap plastic toddler spoons for smaller rockets fillets.

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+1 I've tried PVC before, but nothing is easier than a plastic spoon. I love how it scoops up the excess epoxy.

You can try a short piece of CTS CPVC instead of NPS PVC. 1/2" PVC od = .84 (NPS size) 1/2 CPVC od = .625 (CTS size) If your looking, the CTS size CPVC is light yellow, rather than grey. Or you can just pick up some 1/2 copper tube.

rharshberger said:

Plastic spoons work ( disposable type), and I like the cheap plastic toddler spoons for smaller rockets fillets.

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Wow, great tip. I can't believe I hadn't ever thought of that.

DavidMcCann said:

I cover the pipe in sharpie, then rub the pipe against the rocket. Leaves marks exactly where it contacts

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I use some "old school tech". I put a piece of carbon paper (yeah you can still buy it) where the fillets are to go and pull the tool going to be used to shape the fillets over the carbon paper. Marks the exact line for taping, quick, easy, no mess, no fuss.
Probably marked fillet lines on 8 rockets or more using the same piece of carbon paper. Bought a package of 10 sheets, can't imagine I will ever need more:wink:

Greg

rms said:

I use some "old school tech". I put a piece of carbon paper (yeah you can still buy it) where the fillets are to go and pull the tool going to be used to shape the fillets over the carbon paper. Marks the exact line for taping, quick, easy, no mess, no fuss.
Probably marked fillet lines on 8 rockets or more using the same piece of carbon paper. Bought a package of 10 sheets, can't imagine I will ever need more:wink:

Greg

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I like this idea! Easy peasy every time.

rstaff3 said:

Wow, great tip. I can't believe I hadn't ever thought of that.

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iirc I got the tip on plastic picnic spoons from CJ in one of his many posts, the plastic toddler spoons work very well for TiteBond TMTG/Q&T fillets too!


Both types work and give different size fillets, the toddler size were a light bulb moment while I was sitting at my desk eating some pudding with one after my recent gastric bypass surgery and looking at a rocket I needed to do fillets on. Due to the surgery the smaller spoons allow me to eat slower and smaller bites.

rms said:

I use some "old school tech". I put a piece of carbon paper (yeah you can still buy it) where the fillets are to go and pull the tool going to be used to shape the fillets over the carbon paper. Marks the exact line for taping, quick, easy, no mess, no fuss.
Probably marked fillet lines on 8 rockets or more using the same piece of carbon paper. Bought a package of 10 sheets, can't imagine I will ever need more:wink:

Greg

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This is brilliant! I have never been able to get the marker-trick to work. That was always the weakness of the spoon strategy. Now I have a foolproof method!

EDIT: I just ordered carbon paper from Amazon. Can't wait to try this method on my next build.

Thanks for the ideas!
RMS, I was using carbon paper when I tried it and the 1/2" pvc marking just looked way too wide. its only a 4 inch Binder excel and my calculations showed that that radius was way over the 8% suggested limit by quite a bit. I was hoping to shoot for midrange between at about 6%.

MCriscione thanks, I had no idea cpvc was smaller outside diameter, will look at that for other projects.

Rharshberger and BDB, I looked at the plastic spoons we have in the cabinet and the tip seems to be rather too pointed but I guess if I angle them and keep them constant I won't have scallops in the epoxy. But then again it is Rocketpoxy and it will self level before it gets too stiff even waiting the suggested 20 minutes after mixing to lay it in and work it. I could reshape I guess.

farsidius, I am going to keep an eye out for that PEX tubing will definitely come in handy!!

ttabbal, If I end up using a socket it will be on the drive end so that nothing gets up in the barrel of the socket. But as you said if I use them I will definitely have the alcohol standing by for cleaning since I will be using it to wet anyway.

Thanks for the input everyone!

I had no idea you could still buy carbon paper! I'll have to pick some up for weird projects like this.

Ok maybe this is a stupid question but....


Spoon upside down or right side up?

Lowpuller said:

Ok maybe this is a stupid question but....


Spoon upside down or right side up?

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Right side up. The extra rocketpoxy gets scooped.

Angle of the spoon does matter because the spoon tip isn't perfectly round, but holding my hand steady seems to be fine.

Lowpuller said:

Ok maybe this is a stupid question but....


Spoon upside down or right side up?

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Actually, the answer depends on your glue and your technique.

The thinner your glue and the more you put in the fillet, the more you'll want to be a spoon down 'scooper'. Scooping the relatively larger amount of excess epoxy out of the fillet so it doesn't flow back in before you pull the tape. I would scoop RocketPoxy in it's early 'flow' stage.

The thicker your glue and the less that you overfill the fillet, the more you'll want to be a spoon down 'pusher'. Pushing the relatively lesser amount of excess epoxy out of the way and onto the tape, and it won't flow back in before you pull the tape. I would push 4500, and NOT overfill the fillet.

Hint: If you use a spoon or something that isn't 100% round, draw a line down it, and use the line to 'aim' for the fin/body tube joint when pulling each fillet to get a more consistent shape.

Sooner or later, you'll develop routine timing and technique that lets you get fillets that are consistent and need minimal sanding.

I just simply use the "tongue depressor" sticks that are included with ROCKETPOXY kits. I dip the stick in isopropyl alcohol and run the radius end perpendicular across the fillet, the stick centers itself between the fin and frame, the stick radius is 11/16 ( 0.6875) inches, which seems to work great for 2 to 6 inch diameter rockets. This works good, my fillets always look great and never crack, and can simply throw the sticks away and don’t have to clean them like a socket set.

That's a great idea.

rms said:

I use some "old school tech". I put a piece of carbon paper (yeah you can still buy it) where the fillets are to go and pull the tool going to be used to shape the fillets over the carbon paper. Marks the exact line for taping, quick, easy, no mess, no fuss.
Probably marked fillet lines on 8 rockets or more using the same piece of carbon paper. Bought a package of 10 sheets, can't imagine I will ever need more:wink:

Greg

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You can also use wood dowels shortened to an appropriate length which are available at most craft stores in varying diameters. Use the dowel in the same way as you would the pvc.
+1 to carbon copy paper-works great and can be bought at some Walmarts and Office Depot stores.

Fred,
L2, ICBM,Camden
KG4YGP

I use spent motor casings. 18mm BP motors work well for rockets ~ 3" diameter. Dip the motor in denatured alcohol, give a quick shake to remove excess alcohol, run it down the fillet, wipe the casing with a paper towel to remove epoxy, then dip in alcohol again. Repeat as necessary.

For sockets, consider packing it full of playdoh or clay beforehand. Will keep epoxy out, easy to clean up. I use it to form dams and to deal with split fins when pulling my fillets. I like the plastic spoon idea, because I too have been using PVC and similar.