12" scratch built cat

[Dr. Jet]

Incompleted 16" Twin

Here's some photos of the partially-completed 16" Twin (Prototype 2).

[Dr. Jet]

Time to Resurrect This Old Thread

The little Cat project hasn't died, it's just had a rearrangement in my priority list.

What's been delaying it is the need for strakes. What has something seemingly so easy been such a huge delay you ask?

Because I want strakes so sharp they will cut your fingers to shreds if you mishandle them, I have been pondering how I could make something that is the length needed (14" or so), and the width and depth as well. The piece would have to have a 100% consistent width and depth throughout its entire length, so that means some sort of machining process that can be repeated. That also means the strake has to be made of a hard material that is easily machinable, rigid, but somewhat flexible, with a smooth ride surface that is 100% flat and does not require any additional finishing.

I wouldn't want to use most woods because I don't think they are hard enough to have the necessary consistency for the machining process. Carbon fiber is too expensive where the strength really isn't needed. The solution? G-10 (a fiberglass laminate product).

Now, how to cut it? A table saw comes close, but because of the tiny dimensions (1/4" high and maybe 3/32" thick) I don't think the consistency would be there and thus the long time to come up with a solution. What to do?

Eureka! I have an idea.... I'm going to mill a slot in a piece of aluminum such that a square strip of G-10 I cut on the table saw will slide in the slot. Along one side face of the slot. I'll install a linear wave spring to keep the G-10 in constant pressure on the other side of the slot. I'll make a bolt-on top with another wave spring to fully capture the G-10 strip I cut on the saw, yet allow it to slide in and out the slot I created. Then I can clamp this aluminum block at the proper deadrise angle to the bit in my milling machine. I can then locate the mill bit such that pushing the G-10 through the slot engages it it the cutter and Voila`!! I have the pre-finished G-10 surface as the ride surface with a REALLY sharp edge that will require little to no fairing in to the hull bottom and have a razor-sharp chine. Best of all, this is REPEATABLE.


Stay Tuned

[kfxguy]

The little Cat project hasn't died, it's just had a rearrangement in my priority list.

What's been delaying it is the need for strakes. What has something seemingly so easy been such a huge delay you ask?

Because I want strakes so sharp they will cut your fingers to shreds if you mishandle them, I have been pondering how I could make something that is the length needed (14" or so), and the width and depth as well. The piece would have to have a 100% consistent width and depth throughout its entire length, so that means some sort of machining process that can be repeated. That also means the strake has to be made of a hard material that is easily machinable, rigid, but somewhat flexible, with a smooth ride surface that is 100% flat and does not require any additional finishing.

I wouldn't want to use most woods because I don't think they are hard enough to have the necessary consistency for the machining process. Carbon fiber is too expensive where the strength really isn't needed. The solution? G-10 (a fiberglass laminate product).

Now, how to cut it? A table saw comes close, but because of the tiny dimensions (1/4" high and maybe 3/32" thick) I don't think the consistency would be there and thus the long time to come up with a solution. What to do?

Eureka! I have an idea.... I'm going to mill a slot in a piece of aluminum such that a square strip of G-10 I cut on the table saw will slide in the slot. Along one side face of the slot. I'll install a linear wave spring to keep the G-10 in constant pressure on the other side of the slot. I'll make a bolt-on top with another wave spring to fully capture the G-10 strip I cut on the saw, yet allow it to slide in and out the slot I created. Then I can clamp this aluminum block at the proper deadrise angle to the bit in my milling machine. I can then locate the mill bit such that pushing the G-10 through the slot engages it it the cutter and Voila`!! I have the pre-finished G-10 surface as the ride surface with a REALLY sharp edge that will require little to no fairing in to the hull bottom and have a razor-sharp chine. Best of all, this is REPEATABLE.


Stay Tuned

I think you are way over thinking it. I used two square strips of carbon fiber.

[Dr. Jet]

I think you are way over thinking it. I used two square strips of carbon fiber.

Maybe, but then I can make dead-accurate strakes of almost any size and deadrise angle for as long as I want.....

[kfxguy]

Maybe, but then I can make dead-accurate strakes of almost any size and deadrise angle for as long as I want.....

I guess what I should have said was it’s not gonna make any difference. Split
ting hairs is my thing for sure but that little detail won’t make a difference. Just trying to save you some trouble. But if you are like me, I look for excuses to use my mill. Lol

[Dr. Jet]

I guess what I should have said was it?s not gonna make any difference.

Only in the appearance.... Maybe in ease of installation.... I want filling and sanding to be almost nonexistent.

........ But if you are like me, I look for excuses to use my mill. Lol

Exactly. I like making chips.... It's a cool mill project that will result in some tooling I can use more than once in the future to make something that looks uber-cool. Yeah, it will take time, but so what? It's time well-spent.

[kfxguy]

Only in the appearance.... Maybe in ease of installation.... I want filling and sanding to be almost nonexistent.




Exactly. I like making chips.... It's a cool mill project that will result in some tooling I can use more than once in the future to make something that looks uber-cool. Yeah, it will take time, but so what? It's time well-spent.

Gotcha. No worries then. :)

[Dr. Jet]

.......... But if you are like me, I look for excuses to use my mill. Lol

And it also gives me an excuse to get something for my milling machine parts bin that is currently missing and just the ticket for precisely establishing the deadrise angle of the strake you are making. A tilting table. This table will more or less permanently bolt to the tooling that holds and moves the G-10 through the spinning mill (bit). Bingo! Perfect strakes. Careful gluing with thin CA might make a joint clean enough to allow the paint to fill it.

The temporary strakes that are currently on the hull are crude by comparison and appear to have been made by some caveman.

[Dr. Jet]

One of the motivating factors behind much of what I do with these minis is that I want to make them available for others to build as well. Before I do that, I want to make sure they are thoroughly tested, work well, and as planned; I want everything as right as I can make it. Hence, the over-thinking and over-engineering of making strakes. It's going to take a long time to tool up to make them as I have so many other irons in the fire, but God willing, I will get it done. The best thing is I can make almost any strake with perfect surfaces and sharp corners.

My eventual goal is to provide laser-cut bones and other "Tedious to create" parts such as perfect strakes in a short kit. I'm still making improvements to the plans based on things I have learned from building the prototypes.

Stay tuned, and don't hesitate to ask questions.

[Dr. Jet]

So I pulled out my tablet of 1/4" grid paper, sharpened my pencil (true!) and started drawing up the tool I'm going to make in order to make strakes. I have all these grandiose plans of intricate machinery, but I have to KISS! I was going to make a power feed, but abandoned that idea (I can still go back if I want). I fire up the old hand-held manual eraser and start simplifying, but issues still arise. What is the maximum length of the workpiece I can accommodate? How will I load that length of work piece into the tool? As it turns out, this is a BIG deal! I could essentially make a bolt that opens a breech, but that adds to overall length and complexity. I need a permanently open breech so the piece will just drop in and push into the cutting tool, but how long can it be??

I diligently research Internet drawings of lead screws, lead screw pillow blocks, lead screw nuts, lead screw nut housings, and I discover all sorts of information. You purchase lead screw assemblies by the overall length, but you have to subtract all the other hardware to get the working length.

I want to be able to make a continuous strake that is at least 12 inches long, so I needed something more accurate than that sharp pencil and a scale. Time to fire up the old AutoCAD program and see exactly what will and will not fit... It didn't take long, but I got all the pieces and sub-assemblies drawn up; then, I began laying them out and found all sorts of ways I could simplify something, move something, or otherwise dial it in.

Finally, I have a plan. A minimal amount of machining required, mostly drilling and tapping holes. A main frame of aluminum with a few Delrin parts where things move. A couple of small parts to make that will keep the work piece from moving around while being cut and that's it.

[Dr. Jet]

Most of the parts I need to build my Strake-Maker tool have arrived. I'll go down to the shop and begin drilling and tapping holes to get the project started as soon as I post this. I think the Strake-Maker may work quite well. I will build one more prototype twin hull with perfect strakes if I like the performance of the single-motor prototype with the Caveman strakes.

Having the ability to make such a precise triangular cross-section piece opens up a whole bunch of possibilities. As should be apparent by now, I like to take an existing design and tweak it to my preferences, usually by shrinking it. I've had my eye on an unusual composite self-righting stepped mono hull that is already a "Mini" at 15" long. Since wood often comes in 12" lengths, I'm considering working up a similar design in wood and making it 300mm (just under 12").

I still have projects in the building queue (the rigger) that are in front of such an undertaking, and I would create another thread around it if I decided to proceed, but I wanted to share some of my current plans.

[Dr. Jet]

As long as I'm doing all this project analysis and queue management, I've been contemplating where this cat build needs to go. I'll be testing the prototype with the caveman strakes soon. Based on that I'll finalize the design. At first, I wanted to do two versions, a single and a twin, but in keeping with the KISS philosophy, I'm going to just do it as a twin. I would need to build one more prototype to confirm that everything was right, but that's a big chunk of building time away from other projects.

Hey JesseJ!!!

Do you want to be a guinea pig and build the prototype twin? I'm sure you'd do a classy job.

[Dr. Jet]

The Strake-Maker is done (well, ALMOST ) and I can cut 12" lengths. Tomorrow, I'll cut some 12 degree strakes and some 42 degree spray rails for the cat and see how it works.......

[Dr. Jet]

Behold!

The 12 degree strake. Hardwood would work in my Strake-Maker tool just as well.

All in all this was a satisfying project. Was it totally necessary? Absolutely not. Will it allow future projects to benefit? Absolutely!

So when Jesse J builds the prototype twin, he will have super-sharp, super accurate stakes for his hull (and I'll revisit the hull on Prototype #1).

[Dr. Jet]

The last post really didn't show the precision of these, and this site rotated the photos due no doubt to their aspect ratio. Here's a cropped photo of the strake. It's about 1/4" wide and about 1/16" high.