I am a big fan of the Qualmann guides - they are incredibly useful.

If I could only get them in Centuri tube sizes...

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Bill Cooke
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Thanks for the feedback Bill. Yeah, that has been part of my hesitation: I build mostly — though not exclusively — vintage Centuri kits, so guides that fit their tubes would be great.

Earl

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Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970

I have 3/32 and 1/8 sets for Estes and metric tube sizes. I also have extras for BT-70 and BT-80.

Finally, I got some 3 and 4 fin 'group build' guides for BT-50 models.

I use these all the time. They work great. They are ESPECIALLY useful in group builds of Alpha (or similar) kits.

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Buzz McD.

Avid rocketeer since 1967.
NAR 13559 / L2

Earl, Bill,

If you dropped David Q. a note and asked, I suspect he could make you a set for Centuri tube sizes.

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Bernard Cawley
NAR 89040 L1 - Life Member
SAM 0061
AMA 42160
KG7AIE

I like the idea of adding guides for Centuri tubes, but my ignorance is showing here. I don't build Centuri rockets much at all, and don't know what fin thicknesses would be needed for the guides.

For example, I found that for the Quest kits, 3/32" was used for most tube sizes, and 1/8" was used on just a few tube sizes. That let me reduce the variations needed for a complete set.

Would it be similar for a set of Centuri fin guides?

Centuri kits are not that much different from Estes, so you would have 1/16”, 3/32” and 1/8” fin thicknesses. 3/32” is the most common for 18 mm Centuri rockets.

I’d start with the 3/32”... as far as tubes, ST-5, ST-7, ST-8, ST-9, ST-10, ST-13, ST-16, ST-20.

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Up next:
Under construction:
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In paint:
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Bill Cooke
NAR #31312
TRA #19705
SAM #0001
Huntsville, AL

My rocket blog
My rocket fleet

I just use an old engine mounted on a board with lines drawn on it. Not ideal but it works. Only bad part is I have to re-draw the lines because I use to as a paint stand too.
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I use the good old double-glue joint detailed in "The Handbook of Model Rocketry". It's everything G. Harry Stine said it was. I use wood glue but white glue works with double glue joints as well.

I have a collection of old foam egg cartons that I cut slits across the egg cups on the bottom with a hobby knife, perpendicular to the long axis of the egg carton. These serve as handy fin holders while doing double glue joints, and they're free! (well, after the omelets have been eaten LOL The valley between the egg cups is also a great tube holder while doing the double-glue joints on the tube.

Once you have your fin lines on the tube (I do the circumference/number of fins routine to make my own marking guides, or you can use a template if you like, and I use some foot long pieces of angle aluminum I have for marking the fin lines on the tubes, or the old doorjamb method LOL simply apply a THIN layer of wood glue to the fin roots and the lines on the tube, and allow it to dry. Once they've dried a couple hours or so, apply a second THIN layer of the same wood or white glue to the fin roots on top of the dried glue from before, line up the fin with the mark, and set it carefully in place. Hold it firmly together for about 20 seconds and the fin will almost instantly LOCK in place, almost like you used instant "superglue" (CA) but with a bond FAR stronger than brittle and shear-prone CA could ever achieve... The fins can all be attached in a matter of about a minute or two at most, and the rocket set aside to dry. I usually set the rear end of the root edge against the tube, then roll the fin forward onto the tube to make sure they're aligned right with the marks. You get a few seconds of "working time" to shift them a bit if you're off from the marks at the leading and trailing edges of the fin with the fin marks on the tube (which will show through the glue somewhat, or should be longer than the fin roots anyway.) I can hold them "vertical" off the tube long enough that they lock in place standing "straight out" from the tube, BUT *IF* one wants to make 100% sure that the fins are EXACTLY perpendicular to the tube face, you could always use an alignment guide like those shown previously. Allow the fins to dry for a couple hours or overnight, then fillet as desired (I use Titebond Moulding and Trim Glue for fillets, best stuff I've found!)

Double glue joints are SO strong that the balsa will shred or shatter or the outer layers of the tube will rip away (delaminate) before the glue joint itself breaks... I've seen it myself when I had a rocket stage horizontally and the upper stage impacted flat to the ground at high velocity-- the fin was partially destroyed (it was papered so it didn't shatter, but about 1/4 of the front fin-tip end simply was ground to dust when the fin struck the ground first at high speed, by then the damage was SO deep into the fin that the tube gave way, and sheared the outer two layers of the tube's spiral paper laminated layers away from the inner layer or two of laminated paper tube wall; I found the fin stuck in the ground a few feet behind the rocket after it came to rest. I simply cut and sanded to shape and papered a new fin, cut away the old damaged fin from the outer layers of the rocket tube wall still stuck to the fillet/fin root, sanded it down smooth, reglued it back onto the tube wall where it came from, did a little smoothing/sanding work to level out the tube, double-glue joint the new fin onto the rocket, filleted with TMTG and smoothed the fillets with a wet finger, allowed to dry overnight, and repainted... good as new!

If you ever try double-glue joints, you'll never build a rocket any other way...

Later! OL J R

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Bill- Couldn’t have said it better.

Bernard- Thanks for the suggestion; I had thought of making the request, but honestly could not attest to the potential popularity of Centuri-based guides.

DavidQ- And thank you for considering a line of Centuri guides.

Earl

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Earl L. Cagle, Jr.
NAR# 29523
TRA# 962
SAM# 73
Owner/Producer
Point 39 Productions

Rocket-Brained Since 1970

David - here's a chart that should give you ODs for Centuri tube guides: http://www.ninfinger.org/rockets/body_tubes.html, though I expect you already have the info.

Interestingly, that chart doesn't have ST-9. It has the same ID as BT-50 but .024 walls (per eRockets data), so it's a touch larger OD than what BMS sells as BT-50H.

ST-8 is the odd one that doesn't really have an Estes tube size that is close by. It's a size that I like to use on scratch builds.

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Bernard Cawley
NAR 89040 L1 - Life Member
SAM 0061
AMA 42160
KG7AIE