Through The Wall Fin Slots

Question (brought about as as result of the thread on my newest proto types in the Low Power forum):

If your design, or a kit you purchase, calls for Through The Wall (TTW) fin attachements, what do you think about cutting your own fin slots, so long as instructions/patterns are provided?

I know we would all like to have them pre-cut, but, frankly this adds cost. I would be interested in hearing how folks feel about the tradeoff between cost/convienence vrs the complexity (perceived or real) in cutting your own slots.

thanx,
jim

My personal perspective:

I have cut slots in may tubes, from BT50 through 8" Quicktube. I prefer not to, mainly because it just isn't a fun step and I'm basically lazy. However, I haven't been able to tell any difference in the end results between my cuts and the pre-cut varieties. I guess if I had a choice between almost identical kits, I would add this to my list of 'nice to have' features when making my trade-offs. If the kit is unique and I wanted one, cutting my own slots wouldn't matter. Either way, the quality of the materials (nice flat wood for the fins, good quality tubes, clean cones, Kevlar cord as a part of the recovery system, etc) is more important.

My thoughts on the wider market:

If you think the uniqueness of your kits are their main selling point, then I'd say it shouldn't matter much. If you want to compete with Estes' low end kits, then you might find it does make a difference.

The first timer my not be up to the task of cutting fin slots. The first timer or even the second or third timer may have nothing more then an Xacto knife for cutting fin slots (I describe myself here). A very difficult task in my opinion to do well. I guess it would depend on your target audience.

Still... if I liked the rocket enough I might force myself to take up the challenge.

What would the cost differences be between cut your own and factory cut? Are we talking $2 or $20 or more? If only $2 I'm letting you cut them, for $20 I would probably take the savings and cut my own. But then I'm sure everybody would have their own breaking point.

well, it certainly isn't *that* expensive ($20), and, in fact may be in the $2 range (will have to get that quoted), but (for the record), cutting slots isn't very hard, even with just an exacto knife.

Here is a description of how I would instruct one to cut slots, and what the kit would provide:

First, there would be a fin marking guide on peel-n-stick adhesive lable material. This is a medium tack material that stays put, but comes up easily and cleanly when removed.

I would have the modeler cut out the fin marking guide, remove the backing material and stick it to the bottom of the rocket with the edge of the guide even with the edge of the body tube.

Then the modeler would cut out the identified areas on the guide, then remove the guide. In those cases (like with that proto type model we're discussing), where the body tube *happens* to be the same size as a standard motor (24mm in this case), I would instruct the modeler to insert an expended engine casing into the bottom of the body tube to make for easier cutting.

just some random thinking...
*S*

Good ideas all but how do you keep the dang blade straight and true? Patience?

Jim, I agree with you about the difficulty (or lack thereof) of cutting slots with an Exacto knife. I've cut estes thru LOC 5.5" tubing this way. The main TIP is to use a sharp knife. But then, I remember when all fins were cut from templates and this doesn't intimidate me. However, I don't know about the masses (???) of new rocketeers who are used to pre-cut fins, plastic cones, RTF rockets, etc.

Well for $2 or even $5 I'm thinking factory cut. But then again I'm spoiled that way. I'm more interested in the flying than building so anything that can help me get it built faster is a plus to me.

But then again I haven't built or flown anything in over two years so take my suggestions with a grain of salt. When I was building I remember building great rockets in my mind but the implementation always fell way short. I just had no patience for the building part. Then Carl would bring his rockets around and I'd go, yeah that's what I meant to build.

(Hey this is my 1000th post... cool).

Another point on fin slots. The pre cut ones are typically very clean cuts and look soooo pretty. Of course, once you stuff in a fin and lay on a nice filet, they are hidden. When cutting a fillet with a knife, Dremel, Rotozip, or whatever, you need to take your time and have patience. However, you should also realize that you can make and correct minor errors with no detriment. They may not be quire as purty, but if the slot is straight, and you can cover your boo-boos with a fillet, then they are just fine.

Woooohooo...Milo...1000 Posts...U da Man!

Fin slots...I would want em pre-slotted. I do the design and construction...more of the engineering, drawing specs and building. I expect my vendors to slot and cut my materials to my specs.

Carl

One point which I don't think was mentioned is the fact that the modeler would have to cut the tabs when cutting a fin from the balsa stock. Of course, some fins go all the way through the airframe and have no extra tab that glues to the outside of the airframe, but I imagine with the placement of centering rings, tabs will have to be fabricated in some cases. If the fins a relatively small, so will tab fabrication be.

Personally, when I can open a kit and dry-fit all of the parts, to include TTW fins with tabs, it truly pleases me to see the precision. Pre-cut slots almost also guarantee perfectly aligned fins. With larger models (3" dia +), it is easier to be sloppy and cover up zig-zags or gaps with filler. If the slots are off a tad on a larger model, the offset of the fins isn't as noticeable. Being off by even a millimeter, marking guides or not, the end result (fin glued slightly off) is much more noticeable. I just can't imagine cutting slots into a .976" dia tube.

This isn't an easy call for me, as I appreciate more time spent in constructing rather than finishing. (Grrr...sanding/sealing, sanding/sealing, to infinity...) I just think on smaller models requiring fin slots, precision is important.

great input folks!

While we're not using TTW mounting at this time, it could come up soon. WIll take these inputs and start getting some numbers from our vendors.

thanx,
jim

If a begining skill level 1 rocket kit had to have the TTW fin slots to be cut by the modeler would it still be ranked as a skill level 1, or would you have to raise the skill level only because of cutting the TTW fin slots?

Quick someone slap ME!


James Pierson Manager
Rocketry Preservation Society
https://groups.msn.com/ROCKETRYPRESERVATIONSOCIETY/_whatsnew.msnw?pgmarket=en-us

If I were the mfgr, it would be raised to a level 2.

Carl

Would the logistics be prohibitive to offer a kit in both pre-cut slots and cut your own slots versions?

My thoughts are this:

Requiring a builder to cut their own fin slots is going to scare off some rocketeers in the earlier stages of their building development. (I'm speaking about myself). Would the uniqueness (or what ever feature) attract a larger amount of experienced rocketeers to buy the kit?

It's obviously a trade off...

Although I personally am getting to a stage where I might try a "cut the slots yourself" kit if it attracted me quite a bit, I would defintiely put "self cut slots" in the "con" category when trying to decide what my next kit might be.

But then again, these are just my thoughts.

bmhiii

well, first of all, i can't imagine offering a rocket that *needed* TTW fins to be skill level 1 or even 2 for that matter, so we would be aiming this kit (no pun intended... ) at experienced modelers.

So, I would figure these to be Skill Level 3. At SL3, I would expect the modeler to be able to cut the fin slots. But, then again, I would expect a SL3 modeler to be able to turn a nose cone, but I don't give him a block of wood and a template either... So, the idea of cutting the slots isn't "against the grain", as it were.

One thing that needs to be understood (some have already inferred this - although we haven't hyped it up on our site yet), we feel that using balsa nose cones, using UNCUT balsa fin stock and providing a pattern, and otherwise doing *some* part fabrication as FEATURES of our kits.

We feel that it is important that the modeler learn the tools and techniques needed to do things such as cut out fins and *possibly* fin slots.

I worked with a rocketeer once who had been in the hobby for 10 years or so and had built quite the fleet up to and including mid-power and many with quite a bit of complexity.

He worked with his son in one of my rocketry camps and cut himself with the xacto knife.... He commented that he didn't realize how sharp "these razor knives are", turns out he had never used one and didn't know how to use it.

Needless to say, i fixed that in a hurry and feel it is important to *teach* with our kits as well as have fun. How else ya gonna scratch build?

ok, ok... nuff preachin ...

Do you want a greater feeling of accomplishment when you're done with a model or do you just want to slap it together and go?

I'm a beginner myself, but I don't feel I would decline a kit just because I had to cut my own slots or fins. Sure pre-cut is nice, but so is a little challenge.

Originally posted by Milo
Good ideas all but how do you keep the dang blade straight and true? Patience?

Click to expand...

On all but the smallest tubes, I find that an architects rule works well. Those are those triangular rulers with different scales on them.... You should be able to pick one up at a good artists supply store for just a few bucks. The shape of the rule makes it almost impossible to NOT cut a nice straight/parallel line.

Nathan

ditto on the architects rule. I also (often) use a length of brass angle section (avail at most any hobby shop). This provides an easy way to inscribe a nice straight line on any tube, and provides a nice metal edge for your knife.

I would be for cutting my own fin slots IF the instructions were clear and included tips on how to cut them well and get a good finish.

Just my two pence

I would have to agree with Mike. I've never had a problem with fabricating my own parts so long as I knew in advance what I was doing and had a technique that would give good results.

I'd say it was more satisfying to learn something new while building a kit than to just assemble it in the same fashion as hundreds of others. So long as you include good, detailed, instructions with your kits I'd say it should make them more interesting in the long run.

Ken

Ken,

that;'s our thinking as well. Also, based on feedback, our instructions and figures go a long way toward making our kit construction a good thing *S*

OK, I'm getting sold on cutting my own slots. After thinking about it for a day, I would look forward to doing some new construction techniques. And as Jim stated, it would let people learn skills needed for scratch building. After all, don't we all want to grow up to be just like Sandman?

bmhiii

When I'm looking for a kit to build, I generally have 3 or 4 kits that I tend to look at. Very rarely does one just leap out at me and scream "take me home!"

I have had preslotted tubes be the deciding factor in which kit I bought. Yes, I can slot the tubes, and yes, I can do so with a reasonable amount of precision, but it honestly adds nothing to the rocket-building "experience" for me and is mainly a PITA (especially when you're doing it in flexible phenolic and all you HAVE is an x-acto knife to do it with).

I have built a few Launch Pad kits and love them. I have notices that the kits usually use a fin stiffiner along the root edge of the fin and no slotted BT. This stiffiner is usually 1/16" balsa about 1/4" tall and runs the length of the fin root. Also the printed pattern for the fin pattern templates from LP and most other kits have wide line patterns and I never know which side of the line I should cut on to be accurate. Fine lines in any template are better or am I just being anal retentive.
Also when cutting fin slot in the past I am always afraid of cutting too wide so I cut small and use a emery board and sand to fit.


James Pierson Manager
Rocketry Preservation Society
https://groups.msn.com/ROCKETRYPRESERVATIONSOCIETY/_whatsnew.msnw?pgmarket=en-us

I agree on fin line thickness. We print our fin patterns with lines 2 pixels wide. We can go any narrower and be assured that our printer will capture the line as they print at 600dpi. When we do scale, we specify to cut down the center of the line.

As for fin slots, i'm still up in the air about it. I am going to look at coming up with some generic instructions for cutting them and will see how they look. may even pass them by this forum.

Originally posted by jflis

As for fin slots, i'm still up in the air about it. I am going to look at coming up with some generic instructions for cutting them and will see how they look. may even pass them by this forum.

Click to expand...

Ah hell. If the kit is cool enough, I'd buy it - slotted or not.

Isn't that the truth?

I just think it is the same reason why someone will go out of their way to scratchbuild a rocket when there is a readily available kit. It all boils down to "how bad you want it". For instance, I'd rather cut up some shipping tube, turn a nosecone, and fabricate rings to avoid paying $50 + for a mid/high power rocket. Likewise, if the low power kit is just so darn cool that I have to have it, slotting the tube would be the gauntlet that would want me to build it even more.

I think the key point here is that the kit should be unique. (ie - Deuce's Wild) It should be so unique, that anyone who has an opinion against slotting a tube, or fabricating any other part of the rocket, would set aside their feelings just to be able to own one.

I got honest with myself reading this thread and figured that my opinion on construction techniques is purely relative to how interested I am in the kit.

If it's 3 fins and a nosecone, you slot the tubes. If it has a twirly worly gizmo feature that is radical in design, send me the paper and I will roll my own body tube.

Jim, present the community with an idea that is unique and I think you will turn heads and opinions. Unslotted tubes on basic design rockets will fall into the hands of some hardcore builders.

Totally agree! If the kits cool, new, different, unique I will roll my own, cut my own slots, and search endelssly of that balsa tree and make my own cone. The recently posted proto 1 & 2 greatly qualify.


James Pierson Manager
Rocketry Preservation Society
https://groups.msn.com/ROCKETRYPRESERVATIONSOCIETY/_whatsnew.msnw?pgmarket=en-us

ya know... it occured to me last night, as I was building another Deuce's Wild! that, for all intents and purposes, I've already answered this question myself and never knew it...

The Deuce has a step that requires the modeler to cut out two *engine tube* slots. These slots are far more difficult than fin slots being clipped ellipses that go right to the end of the tube.

The only comment I ever heard about them is that it was a bit of a tough step and should result in the Deuce being a Skill Level 3 (which it now is, as a result). Other than that, there have been no issues brought to my attention about that, i *guess* because it IS such a cool kit (bar none, our most popular seller)...

so, the reality matches what you folks have been saying. If it's cool enough, the extra work is worth it, if necessary...

interesting that i, frankly, had the answer all along but never saw it....

forest through the trees kinda thing, i guess

I agree with many of the comments these other guys have already made, like do you really need TTW mounting on level 1 or 2 kits, and isn't this (or shouldn't it be) well within the capabilities of the average builder, and, bottom line, I VOTE FOR CHEAP kit prices

I was just about to suggest a metal straightedge when I got to the last posts about the architect scale and the piece of brass angle --- both excellent ideas. My suggestion was that if a builder is afraid to tackle these cuts freehand, maybe you could sell a metal template/cutting guide for a buck or so; it would just have to be taped in position on the outside of the tube and used as an 'idiot proof' way (I like idiot proof stuff) to get it done. You could re-use it on the next kit, and the next, and still keep kit prices a bit lower?

I also vote for unslotted kit components because I often bash a kit and use the tubes for something completely different. In the case of a slotted tube, you may not be able to use it for an alternate application.