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Thread: 12" scratch built cat

  1. #61
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    Quote Originally Posted by NativePaul View Post
    Plastruct L section come in many sizes and works well for stakes.
    I have some 3/16" styrene angle (equal length legs). If I used that it would look like the attached screenshot. Strakes should actually be parallel to the water surface (although as shown, might actually increase lift by deflecting the moving water downward). Any "L"-shaped pieces would probably have to be trimmed to get them parallel, and the question then would be how to do that accurately for for several pieces up to 16" long?
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  2. #62
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    Hmm.. my gut tells me that angles might increase drag. I suspect with that convex shape, not only is there a little more surface area, the deflection (lift) would cause also greater pressure and increase friction. I suspect a little more squirrelly handling too.

    But empirical evidence is always welcome. Give it a try.
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  3. #63
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    Quote Originally Posted by Jesse J View Post
    ........But empirical evidence is always welcome. Give it a try.

    Nah.... I think I'll go with table saw cut strips like I alluded to above. Gotta finish the Casper and the Atlas first.

    Oh, since you thought the motor mount was a nice touch, I added a servo tray as well.


    Hmmm.... Should I make mounts for twin motors??



    EDIT:

    OK, it was easy enough to make twin motor mounts and lips for access hatches in the sponsons.

    Last edited by Dr. Jet; 02-01-2018 at 05:41 PM.
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  4. #64
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    You can halve the height of the styrene L section pretty easily by scoring down one side with a scalpel against a steel ruler, once scored you can snap it off pretty cleanly.

    I would ditch the inner lifting strakes, and just fit the outer spray rails.
    Paul Upton-Taylor, Greased Weasel Racing.

  5. #65
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    Quote Originally Posted by NativePaul View Post
    You can halve the height of the styrene L section pretty easily by scoring down one side with a scalpel against a steel ruler, once scored you can snap it off pretty cleanly.
    That's not nearly accurate and repeatable enough for my preferences, but it could work in a pinch.

    Quote Originally Posted by NativePaul View Post
    I would ditch the inner lifting strakes, and just fit the outer spray rails.
    The spray rails really just reduce spray; they don't do much for speed or handling. My BBY Micro Scat cat has no strakes, no spray rails, and nearly vertical gunwales. It handles like a dream and goes like stink. I may just leave them all off and see what happens. I can always add them later if I get the urge.
    Last edited by Dr. Jet; 02-02-2018 at 03:55 PM.
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  6. #66
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    Quote Originally Posted by Dr. Jet View Post
    I may just leave them all off and see what happens. I can always add them later if I get the urge.
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  7. #67
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    I'm compiling balsa and ply to take to the laser guy for the Atlas Prototype #2. I may have enough 1/16" ply to cut a prototype for this one too.
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  8. #68
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    Well, I have enough ply and balsa to make Atlas Prototype #2 and #3....... AND....... I have enough to cut three prototypes of this 16" cat. I'll be contacting the laser guy in a day or two.
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    Quote Originally Posted by Jesse J View Post

    Gotta wait for me to finish the Atlas and the Casper projects. I may frame one up right away, just to make sure everything fits; but skinning and outfitting will be later.
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  11. #71
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    Well, I sent all the pertinent files to the laser guy. I have enough plywood to cut three of these, and each one has the option of being either a single or a twin or even a triple! (Where would the batteries go??)

    I've been looking for stingers that are small enough to make a twin and I can't find any off-the-shelf ones that will work. I made the ones for the Micro Scat Cat (see: https://forums.offshoreelectrics.com...-Scat-Cat-Twin), but they are fixed. I would like the ability to adjust the angle on them. I could make something on the lathe and the mill, but it would be cool if I could do something that anybody could build with simple hand tools. I'm going to have to think about that one for a while.
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  12. #72
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    Default Strut Problem for Twin Motor Solved

    Sometimes the best solution is the easiest. I decided to make an option of having a squared-off transom. That solves the tricky "wrapping the sheeting around the corner" with the rounded transom. It also gives enough room to install a pair of the micro struts that Steve sells (https://www.offshoreelectrics.com/pr...prod=ose-80046)

    So stay tuned. I'll frame up one single and one twin, and have one extra "kit" for further experimentation.
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  13. #73
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    I hear ya, that rear end may look nice but it sucks your time away... then you have another compartment to fuss about. And for the bigger ones, would accommodate twin outboards
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  14. #74
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    Default Update on the 16" Laser-Cut Cat....

    I haven't posted in a while because of conflicting projects. I'm building a voltage regulator for the variometer in one of my gliders (I'm running 4S drone LiPos and the vario doesn't like 16V ~ I'm stepping it down to 12V). Additionally, I'm doing a refinish/relic job on a Fender Jaguar for a customer and fitting it out with Jazzmaster pickups (a Jagumaster?? ). Lastly, I was making a power feed for the cross slide and compound on my lathe and when I was parting the rather substantial piece, something moved resulting in the tool digging in and stripping the plastic spindle gears. I now have upgraded steel gears and I'm replacing the spindle ball bearings with tapered roller bearings. That should be a whole lot more stable. Additionally, I've installed a carriage lock and modified the compound rest to lock it as well. The result should be a whole lot more solid machine with less chance of things moving around when doing the admittedly demanding process of parting the work piece.

    The laser guy has the wood and while he thought it would be done today, he asked if some other projects could go in front of it. I gave him the OK, so the laser cutting should be done by this time next week. My voltage regulator and lathe improvements should be done by then and the lacquer on the guitar needs a good three weeks or more to fully cure.

    So stay tuned for another week or so for an update.
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  15. #75
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    While I'm waiting for the laser-cutting, I've been thinking about power options. I have a handful of 450-sized helicopter outrunners in the 3000~4000 rpm/V range, but I found something interesting in my long-neglected parts box. It was the power system that was in my old 17" MHZ Micro Iceberg. It hauled a$$ on a 6-cell 800mah zapped NiCad pack, but due to the narrow scale hull width, it didn't corner for crap. I sold the hull more than a decade ago, but I apparently kept the power system for some reason.... This hull will be an inch shorter and a couple inches wider than the Iceberg. It might be a good fit.

    What is it you ask? Well, it goes to show what an old-timer I really am. It is an Aveox 1005/2Y (3900 rpm/V) with a custom-fitted aluminum water jacket and an Aveox SL-18 ESC with water cooling added. We're talking OLD SCHOOL baby!! Old school or not, these motors were powerhouses and it should be perfect for the 16" cat.

    Stay tuned for top-secret construction details.......

    Now what should I use to power the twin version??
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  16. #76
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    Default A New Dilemma....

    I ordered this strut/rudder assembly for the cat: https://www.offshoreelectrics.com/pr...prod=ose-80972

    It's a nice unit and it fits the transom, but........

    The strut won't go low enough. It needs to go about 1/4" lower. I have two ways I could solve this. The first is to cut the adjusting slot in the strut all the way to the top of the strut blade. That would work, but then I wouldn't have a whole lot of material left to grip the strut blade. The second solution, and the one I think I will do, is to mount the strut 1/4" lower on the transom. This would result in the mounting bracket hanging down in the tunnel by 1/4". I would then make a streamlined wood faring block in the tunnel to go up against the flat surface of the bracket.
    Last edited by Dr. Jet; 02-21-2018 at 12:48 AM.
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  17. #77
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    Plan b sounds like a good option, but maybe some pics would help us think up other options.
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  18. #78
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    Quote Originally Posted by Jesse J View Post
    Plan b sounds like a good option, but maybe some pics would help us think up other options.
    Here's a sketch of my plan. The fairing block (crosshatched) would only be as wide as the bracket on the strut; it would not be the full tunnel width.
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  19. #79
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    I have added blocks like that but concave instead of convex to cats that were too flighty before. IMO cat tunnels need some reflex on the wing section, like WIGs and flying wings, as without it a wing's center of pressure will move forward with increased angle of attack, increasing the angle of attack further, cascading into a blowover.
    Paul Upton-Taylor, Greased Weasel Racing.

  20. #80
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    Quote Originally Posted by NativePaul View Post
    I have added blocks like that but concave instead of convex to cats that were too flighty before. IMO cat tunnels need some reflex on the wing section, like WIGs and flying wings, as without it a wing's center of pressure will move forward with increased angle of attack, increasing the angle of attack further, cascading into a blowover.
    Hmmmm....... That's an interesting thought; essentially a trim tab. I like it, and it's easy enough to do.

    Just cut a couple of slits on the bottom sheeting and bend the resulting tab up to rest on the extended transom tab.
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    Last edited by Dr. Jet; 02-21-2018 at 02:36 PM. Reason: Add sketch
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  21. #81
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    Default The Wood Is Cut

    Well, I got the wood from the laser guy. Photos are of it "Dry Assembled" meaning not a drop of glue anywhere. Other than a couple of slots needing adjustments, it's all good. This is the single-motor version with the rounded ends at the transom. Unfortunately, he cut it before I modified the transom for the relocated strut. No problem though, I can just glue on a piece and a doubler to make it work.
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  22. #82
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    Sorry, but I have no tolerance for angles on sponson tips... for me it ruins the lines... makes it easy to build, but not easy on the eyes.

    BUT I am soper excited to follow your build

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  23. #83
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    Quote Originally Posted by Jesse J View Post
    .... makes it easy to build.....
    That was my entire reason for doing it that way......
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    Well, I tacked everything together with thin CA, then added a 1/8" square basswood chine piece and sanded the left sponson out. Lo and behold, the angled bow took on a nice curve instead of the angle. It just worked out that way.
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    I've made a few revisions to the plans and they are at a point I would call complete and ready to archive for future use. I didn't like the angles on the first two bulkheads and modified them to provide a better curve transition for the sponson bottoms and the gunwales. My original plan was to skin it with 1/32" ply, but for ease of construction and proof-of-concept testing, I think I will use 1/16" balsa instead. It will also give some leeway in dealing with the angles on the first two bulkheads that I didn't like. This boat will never see deck-to-deck racing with a bunch of other similar-sized boats, so I can sacrifice some durability for convenience.
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  26. #86
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    I started some sheeting, but ran out of glue. It will be a couple of days before I run out and get some more.....
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  27. #87
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    Just to confirm the twin motor version will work, I dry installed a motor mount and installed the motor through the various openings. Admittedly, everything is TIGHT, but it will work. Using a long ball-end Allen wrench, it is possible to reach the motor mount screws (that's why I put them on a 45° angle). The motor is installed/removed through a deck hatch in the sponson.
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  28. #88
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    Quote Originally Posted by Dr. Jet View Post
    I didn't like the angles on the first two bulkheads and modified them to provide a better curve transition for the sponson bottoms and the gunwales.
    Good, I didn't like them either! Nice work senyor!!
    Last edited by Jesse J; 02-23-2018 at 07:26 AM. Reason: Fixed typo to not imply old fart
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  29. #89
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    Quote Originally Posted by Jesse J View Post
    Nice work senior!!
    Senior, (as in meaning "Old Fart" in English)?? Or Senõr (as in meaning "Mr." in Spanish)???

    I respond to both.......
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  30. #90
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    Quote Originally Posted by Dr. Jet View Post
    Senior, (as in meaning "Old Fart" in English)?? Or Senõr (as in meaning "Mr." in Spanish)???

    I respond to both.......
    I meant to type the latter, but recon autocorrect wanted the former.
    I changed it back in my post..
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