Ac-86 build - Page 3 - RC Groups
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May 29, 2013, 11:52 AM
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John Xman's Avatar


I pretty sure market research will show almost no interest is a RC cat this big. Way to difficult to build and transport. If I sell 4 kits a year I will make no money on this (at cost), but that's OK. I am doing this for fun not for the money. I am having a lot of fun designing and building. That's my reward. Sailing this size of RC boat is more of a demonstration than a quiet day at the pond.

I am building molds because the total displacement cannot exceed 15.18 lbs. So it has to be very light. 86" hulls need to weigh less than 2.0 lbs. The only way to hit the weight is carbon molded construction.

John Xman
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Jun 03, 2013, 11:16 PM
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disabled's Avatar

Even if its built only once -

- the experience and the thrill pays for itself - allways!

Just keep on rocking!
Jun 11, 2013, 12:19 PM
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John Xman's Avatar


Very nice tri! What year are the photos?

OK - AC-86 male plug for the hulls are coming along very well.

I have also finished the Wing design (shape) and am in the process of sectioning for the molds. Will be purchasing plywood for the building board this weekend. The airfoils are thicker than I would of thourght but thats what the software is showing gives the highest lift (preasure). See images below;

I start a new job on the 17th so it will become more difficult to put the hours in, but need to finish the male plug this month.

John Xman
Jun 20, 2013, 10:25 PM
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OK to give everyone a sence of scale I plotted out the wing drawing at full size
(12'-0" tall) tapped it to the rail of my loft and put the male plug on the floor below to get a idea on how big this cat will be.

After I got it put together I stood back took a few shots and then said-
"OH S__T!"

John Xman
Jul 06, 2013, 09:36 AM
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AC-86 3D model

July 4th update-
I have started the 3D model for my AC-86. Check out the images!

I am having troubles with the line weights when exporting to a PDF. I will post new images when I finish the center module, foils, rudders and the wing.

Need to talk with a 3D master at my work to find out how to reduce the background AutoCAD file lines in SketchUP.

I really fun to verify how the cross beams intersect the hulls. I put a figure (people) in the file so you can get an idea of the scale of the cat.

I am very pleased with shaping of cross beams. I widened the main forward beam so the centerboard/foil box will penetrate the beam inside the hull. I also moved the rear beam back 1 .

Still working on how the lower part of the center mod will be shaped. I am debating how the forward jib pole will intersect the front of the main beam.

I am getting close to having hull male plug ready for molding. Two more coats of sanding primer then will spray on 4 coats of tooling gel-coat.
Jul 07, 2013, 09:47 AM
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Looking Good!!!

Great project, can't wait to see it sail.
Jul 07, 2013, 10:40 AM
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I hope you make it in to a kit. I love that design bro
Jul 08, 2013, 10:19 PM
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Yes, once I have the Proto-type sailing and foiling I will be offering Kits.

I will have the molds for Hull (2 sides) Front crossbeam (split horz.), rear crossbeam (split horz.), Board/foil box, Center radio Module (2 sides).
That's 10 molds so I will take about 6 months.

To early to have prices or any info on layup design. Will take a couple of hulls to have a final layup design.

First test sails will be done with only rudder servo and my 6' balsa wing mast.
(no center Module)

Eventually I hope to have full plans for the Wing mast but most likely will not have molds for Wing until 2014.

John Xman
Jul 14, 2013, 11:04 AM
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Update on 3D model-

Here are some additional screen shots of my 3D model for the AC-86.

Next week I will complete the 3D with the addition of the jib boom.

Enjoy - John Xman
Jul 14, 2013, 12:56 PM
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This is awesome.

It's a complete level-above and beyond a large degree of some things in the Sailboats forum.
Great stuff.

Good to see Over-the-top builds, as some of the airplane forums have people building huge scale aircraft such as this, and just completely remarkable what they accomplish.
Jul 16, 2013, 12:22 PM
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The lage size of the AC-86 is to make it easier to foil!

Couple more 3D images for everyone----

John Xman
Jul 18, 2013, 10:30 PM
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I didn't know much about cats but I'm loving your build bro!
Jul 22, 2013, 03:37 PM
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OK need some advice from all builders----

I need to come up with a sanding block that will work for the scale of the male plug. My small 8" long by 3" wide clamp style sanding block is not doing the trick for fairing the 86" length. I am down to 320 grit sanding and having a tough time getting out the 1/100" ripples. Need a flexable sanding block about 18" long?

Any advice would be appricated!

John X Man
Jul 22, 2013, 04:28 PM
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Dick L.'s Avatar

I have always used what I used on my big cat - a narrow piece of 3mm (1/8 inch thick) plywood. If you can't find 1/8 stuff, you can use 1/4 inch but buy the Luan, (underlayment for floors) because even though it is thicker, it is still very flexible and will shape itself to the compound contours of a hull. For my foam plugs, I did find 1/8 inch thick "doorskin" and I cut it about 2 inches wide by about a meter (or 36 inches) long. Cut your paper or sanding media slightly wider/longer and I use spray-on glue (for photos) since it will hold the paper, but still allow easy removal for a fresh piece.

Jul 25, 2013, 04:32 PM
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Dick L,
Thanks for the info. I will post a image later of that I came up with.

Finished the 3D model today. File size is huge mainly due to the number of surfaces in the 5 section wing.

Made some suttle mods to the cross beams and foil boxes.


John X

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