How to slot for TTW fins?

I'm using TTW on my 2-inch diameter, tall, thin rocket, and I'm wondering- what's the best way to slot my LOC 54mm tube for TTW construction? Also, would you recommend epoxying inside or using the expanding foam method?

Apogee has a video on it. It works with any paper tubes and hasnt failed me once.

That looks like a really good way to do it. I was lazy and used a radial arm saw. Next time though, I'll probably use a miter saw with a small blade on it.

I slotted mine using a standard XActo knife. I use a piece of metal angle as a straight edge, and draw 3 (or 4) lines along the tube to mark the fin locations. Then I draw some parallel lines to mark the width of the slots. I start the cuts with the straightedge and the knife, then make further cuts a little deeper each time until I have cut through the tube. Once you make the first cut, you have something for the knife to follow. You just have to go slow and be careful.

Exacto knife and aluminum angle stock as bjphoenix does.

I also slip an appropriately sized coupler inside the body tube to prevent flex while cutting. Hey, it works.

I like monkeys.

If you have a Dremel with a saw blade or even the sanding discs, that makes it real easy. Depending on how you've designed your fins, you could go either way. If they are near the bottom, epoxying them in place is one way to go. You might have to use a dowel to apply and smooth the epoxy along the fins. If they are further up the body tube, you could use foam. It really is up to you.

I use bjphoenix's method.

bjphoenix said:

I slotted mine using a standard XActo knife. I use a piece of metal angle as a straight edge, and draw 3 (or 4) lines along the tube to mark the fin locations. Then I draw some parallel lines to mark the width of the slots. I start the cuts with the straightedge and the knife, then make further cuts a little deeper each time until I have cut through the tube. Once you make the first cut, you have something for the knife to follow. You just have to go slow and be careful.

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I use this method as well.

Best regards,
Brian

Here are couple of methods that I use, depending on type of tubing and flavor of pie that week:
Xacto
stacked cutting disks in a dremel
radial saw

qquake2k said:

I use bjphoenix's method.

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I followed qquake2k and slotted mine for the first time last week,just make sure you use a new blade and try not to shave the angle guide.As for what to use to build it with,I used epoxy for my last three or four builds.Adds weight,I just bought some Titebind III and will use that for my next build.

cjp said:

I just bought some Titebind III and will use that for my next build.

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When it comes time to replace the Titebond III, try the Titebond II as it's a bunch less expensive.

The difference between the two is largely the degree of water resistance. TB2 is water-resistant while TB3 is water-proof. Unless you're launching from the middle of a pond, the TB2 is plenty good.

If you build during the winter in an unheated garage, the TB3 will set up at a lower temperature (47 degrees vs 55 degrees for TB2).

As far as strength goes, ANY of the Titebond glues will make a joint that is stronger than the materials you're gluing up.

Titebond Molding & Trim Glue is excellent for making fillets, too. Seems to be available only at Lowe's. Very thick and doesn't flow away from the joint. Apply where you want a fillet and wipe with a dampened finger tip. Voila!

does titebond III grab as fast as II?

SteveF said:

does titebond III grab as fast as II?

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Not in my experience. TB3 is rather slow when applied thickly.

o1d_dude said:

Titebond Molding & Trim Glue is excellent for making fillets, too. Seems to be available only at Lowe's.

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Also, Ace Hardware.

When it comes to filling the fin can between centering rings, what are the pros and cons of using canned expanding foam?

eggplant said:

When it comes to filling the fin can between centering rings, what are the pros and cons of using canned expanding foam?

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Canned foam is air activated. So in the tight bodies of our rockets the other layer gets good and hard, but the middle stays gooey. You have to poke tons of holes to get it to kinda set. Two part is the way to go.


Bryce

SteveF said:

does titebond III grab as fast as II?

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If you're referring to tacking the fins on the body tube before fillets, they're both reasonable as long as you use thin layers of glue over the surfaces to be bonded. Obviously, a thicker layer of glue will take longer to set so a thin layer is favorable. Besides, if you're using this to tack fins on, all you need is a thin layer because anything thicker will just ooze out of the sides of the fins. But personally, I tack on with some CA. Then I fillet with Titebond II/III (whatever I have on hand). Again, I use thin layers. They dry reasonably quickly, and I find that thinly layered fillets are stronger and tend to look neater. Thick fillets can take quite a while to dry, because they can be wet at the base of the fin/body tube even though the fillet looks dry from the surface. This also poses some structural problems since the glue may not even be dry at the places it matters most.

judo said:

Not in my experience. TB3 is rather slow when applied thickly.

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Doesn't that go for any type or brand of glue?

Oh and to answer your question, OP, I like to cut out the slots by hand with a hobby knife. If I get impatient, I'll hack (carefully) away with a razor saw and clean it up nicely with sandpaper. The razor saw only comes out with the thicker walled body tubes.

jj94 said:

If you're referring to tacking the fins on the body tube before fillets, they're both reasonable as long as you use thin layers of glue over the surfaces to be bonded. Obviously, a thicker layer of glue will take longer to set so a thin layer is favorable. Besides, if you're using this to tack fins on, all you need is a thin layer because anything thicker will just ooze out of the sides of the fins. But personally, I tack on with some CA. Then I fillet with Titebond II/III (whatever I have on hand). Again, I use thin layers. They dry reasonably quickly, and I find that thinly layered fillets are stronger and tend to look neater. Thick fillets can take quite a while to dry, because they can be wet at the base of the fin/body tube even though the fillet looks dry from the surface. This also poses some structural problems since the glue may not even be dry at the places it matters most.



Doesn't that go for any type or brand of glue?

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Yes, but it was noticibly annoying when I was putting together my 4" Photon Probe. I was used to the 1 hour set time of Elmer's Carpenders Wood Glue. I removed my fin jig to apply a second fin and the original one wanted to bend right off. After attending to that I think I glued on the next one after 12 hours and had no further problems.

kelltym88 said:

If you have a Dremel with a saw blade or even the sanding discs, that makes it real easy. Depending on how you've designed your fins, you could go either way. If they are near the bottom, epoxying them in place is one way to go. You might have to use a dowel to apply and smooth the epoxy along the fins. If they are further up the body tube, you could use foam. It really is up to you.

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On several occasions I have tried to slot tubes with my Dremel but the disk or bit always wants to roam and I can never hold it steady enough to make clean, straight cuts with it. It's disappointing since cutting slots was a major motivator for buying the tool in the first place. How does anyone else cut their slots with a Dremel? How do you get it to cut in the precise spot and keep it on the line? Do you use a jig of some sort?

Instead of slashing, gouging and butchering the tube by trying to cut slots freehand with my Dremel, I use the X-Acto knife and aluminum angle method that has previously been described. What I give up in speed and efficiency I gain in precision. Even then the slots that I cut are never as clean as I would like them to be, but covering up my ragged slots are what body putty and thick external fin fillets are for. :wink:

MarkII said:

On several occasions I have tried to slot tubes with my Dremel but the disk or bit always wants to roam and I can never hold it steady enough to make clean, straight cuts with it. It's disappointing since cutting slots was a major motivator for buying the tool in the first place. How does anyone else cut their slots with a Dremel? How do you get it to cut in the precise spot and keep it on the line? Do you use a jig of some sort?

Instead of slashing, gouging and butchering the tube by trying to cut slots freehand with my Dremel, I use the X-Acto knife and aluminum angle method that has previously been described. What I give up in speed and efficiency I gain in precision. Even then the slots that I cut are never as clean as I would like them to be, but covering up my ragged slots are what body putty and thick external fin fillets are for. :wink:

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I just freehand it... maybe I should've been a doctor... seriously though, I've been in the construction trade for over 26 years manufacturing and installing countertops, so maybe just my experience with hand tools helps me to freehand it.

As for the canned foam... I've used it before and think it's great, no issues. But YMMV....

kelltym88 said:

I just freehand it... maybe I should've been a doctor... seriously though, I've been in the construction trade for over 26 years manufacturing and installing countertops, so maybe just my experience with hand tools helps me to freehand it.

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Me to. I encounter no problem at all.

kelltym88 said:

I just freehand it... maybe I should've been a doctor... seriously though, I've been in the construction trade for over 26 years manufacturing and installing countertops, so maybe just my experience with hand tools helps me to freehand it.

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bradycros said:

Me to. I encounter no problem at all.

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Well, I've tried and tried and tried, and I just can't do it. The darn thing cuts too fast! I can't catch it and get it back in line before it has wandered and chewed a few hundredths of an inch of tubing off center, ruining the slot. I will have to come up with some kind of jig to hold everything perfectly rock solid so that the tool absolutely cannot deviate from the line.

Question: do you chuck the bit into the tool itself and hold it while you cut slots or do you use the extension? Also, I'm talking about cutting relatively thin paper tubing with it. Is this what you use your Dremels for? This subject drives me nuts because cutting slots is the job that I bought the tool to do, but I have never been able to successfully execute even a single fin slot with it.

MarkII said:

Well, I've tried and tried and tried, and I just can't do it. The darn thing cuts too fast! I can't catch it and get it back in line before it has wandered and chewed a few hundredths of an inch of tubing off center, ruining the slot. I will have to come up with some kind of jig to hold everything perfectly rock solid so that the tool absolutely cannot deviate from the line.

Question: do you chuck the bit into the tool itself and hold it while you cut slots or do you use the extension? Also, I'm talking about cutting relatively thin paper tubing with it. Is this what you use your Dremels for? This subject drives me nuts because cutting slots is the job that I bought the tool to do, but I have never been able to successfully execute even a single fin slot with it.

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I use it after I've glassed a tube.... and I try to start cutting on the inside of the line, and use my hand as a guide as I'm holding it. Then if it needs to be bigger, just kind of sand it closer to the line. I don't use any extensions, I didn't even know there were any. I was able to pick up an actual "blade" type attachment which worked well.

As for using for thin tubing, an exacto knife might be better with a guide as some of the other post have mentioned, but I just freehand those also. For me, the slots do not have to be perfect, I just need to make sure the fins fit. In fact, there's been a couple of times where I messed up on my lines and had to move my fins over an 1/8" of an inch. Instead of trashing the tube, I made my adjustments, and used the cut out pieces of tubing to fill in the gap.

The extension that I was referring to is the 2 or 3 foot long flexible shaft extension. Maybe I'll try using that the next time, because then I won't have to try to hold the actual tool steady with its buzzing motor. I do have saw blades for it, but quite frankly they scare me. I can just see myself dropping that flex shaft while it has a razor sharp saw saw blade spinning on the end at several thousand RPM. :y:

MarkII said:

Instead of slashing, gouging and butchering the tube by trying to cut slots freehand with my Dremel, I use the X-Acto knife and aluminum angle method that has previously been described. What I give up in speed and efficiency I gain in precision. Even then the slots that I cut are never as clean as I would like them to be, but covering up my ragged slots are what body putty and thick external fin fillets are for.

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Cutting fins out of 1/8" plywood with my dremel took a bit of practice and patience [and more than one recharge]. I haven't even attempted fin slots yet, though I'm not sure I would anyway. I've only ever used a hobby knife. And only recently have I started using an angle bracket.

I just cut some slots in LOC tubing. An exacto knife with a new blade and a piece of angle worked great.

If I had to cut slots in a glassed tube, I would use my dremal with the cutting disks and freehand it also. I use the cutting disks for most cutting tasks with the dremal. They go through anything and you can get a tube of 50 for a few dollars. Just wear safety glasses. I've only had one shatter on me, but you definately want some eye protection when that happens.

MarkII said:

The extension that I was referring to is the 2 or 3 foot long flexible shaft extension.

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The flex shaft may work, but I generally avoid it. I find the mass of the dremel in my hand to be a valuable stabilizing factor. It's hard to explain exactly, but I try to vise or block up my work, then use 2 hands on the dremel using my wrist or elbow as a pivot point braced on god knows what, and moving slowly. If you bought it only to slot, you could in theory build some kind of jig/mount for it, attaching under the front screw-off collar.

Handeman said:

I've only had one shatter on me, but you definately want some eye protection when that happens.

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Just for the flying dust alone glasses are a good idea. Above that, I've had a few discs shatter, all the wire wheels toss wires, and last week an EZ lock fiber wheel bound up, destroyed the lock, and bounced off my face. Gloves and Goggles kids.

Dremels are much like gerber/ leatherman multitools. Capable of doing anything, but never the 'right tool' for the job

Oh I've found other uses for my Dremel even though I haven't gotten it to work for cutting slots. Most recently I used it with a spiral bit to cut out a large section of damaged ceiling in one of the rooms in my house.

As far as using it for cutting slots, I guess I should skip that until I have to cut them in much harder material, such as fiberglassed tubes. I was trying to use it to cut them in heavy-walled paper tubes that were equivalent to LOC tubing.

One thing that I get that complicates things when I'm cutting slots in paper tubing is tube "spreading" at the cut. The spiral-wrapped material seems to be under some tension, and making cuts that are parallel to the long axis seem to release the pressure, causing the material to spread in a non-uniform way. When that happens the two sides of the cut are no longer parallel. The uniform-width, straight slot that I cut ends up being shaped like a narrow oval, slightly wider in the center and tapering in width at each end. As long as I keep the fit of the fin tab reasonably close (snug) at each end of the slot, though, the fin seems to stay straight even though it might be a bit loose in the center of the slot. Anyone else see this?

I always cut my slots on one side of the drawn fin line. This is also where I attach surface-mounted fins. It is much easier to line up one side of the fin root along the line than it is to try to center the fin on top of the line. If I get the side of the slot that is along the fin line perfectly straight, then it won't matter so much if the other side is a little bit ragged. Inserting the fin tab so that it is up against this one "good" side of the slot will insure that the fin is straight. I just need to make sure that I put the slot on the same side of the line when I cut out each one.