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Discussion Starter · #1 · (Edited)
Goal 1: Build as much as possible in Catia.
Goal 2: Build Boat.
Goal 3: Manufacture or Purchase hardware and install all hardware in boat.
Goal 4: Build and install motor in boat
Goal 5: Get it running strong.
Goal 6: Race.

Please call me out if you see anything messed up. Rather fix it sooner than later.

There is quite a decent advantage for the community if I can complete this. All my structure parts will be able to be converted to .stp files and then used in either water jets or CNC machines to get accurate parts. Hopefully it can help drive down the cost of crackers and increase the number out there. Everything I do will be open-source unless I start making them one after another myself.

Here's the work of one beer. I only put the lines in for reference because it's hard to look at a point cloud.
Line Sky Purple Violet Atmosphere


Since I found the coordinate system in the rule-book to be a complete pain. Here is a X,Y,Z Reference for each point. The .zip contains this an .xlsx file.

More progress


I'm going to have to get ahold of some of the plans to make sound decisions on this without re-inventing the wheel. Maybe I'll make my way to a race again and talk to the guys...

Trying to figure out how to work like this, crew station is next. I have to use a modeling method I never had to do before. So this will be a self learning thing for me.



Crew station is giving me major issues. I'll have to think about this. My current plan is to get it to a 1/4'' shell to represent the plywood and then build up from there. Frames and other pieces. I might have to start a bit back and do this totally differently we'll see if I can make it work.

Edited and went with a different route, this will get me places. Time for bed. Hopefully revisit this soon. I may need to square up the crew-station, it doesn't follow the Sheer line like I thought, but it's going to look so smooth if it's not a boxed cutout...



On a side note, these coordinates are making my boat look like crap compared to pictures...
STATION 6 5 4 3
BASE TO KEEL 0-8 1-0 0-15 3-12

Why does station 4 stick back down after curving up?
 

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interesting!

It's an interesting idea to develop a CNC plan for crackerboxes...

Have you looked at a framing plan yet? You will probably be able to "build" frames once you have a 1/4" shell built.

What you are doing isn't unheard of, check out this CNC boat kit...

Cocktail Class Skua Racing power boat

Which was originally published in The Rudder Magazine, August 1939, pg. 38, as one of the first plywood "skimmers".

It's gonna be a lot of work though!

Is that a table of offsets you were working from? Usually those are points-along-a curve, and use a batten strung along them to develop a fair curve. You'll have to develop a curve for them yourself.

It would be really nice to develop as much of it as possible for plywood CNC milling, including frames!

Goodluck!
 

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Crackerboxes!

I don't know how this compares to the most current stuff out there, but here are the lines and offsets from 1951...If that is still class legal, it would be a great place to start!

Offsets are listed in inches & eighths, so for Station 1, distance to keel is 11 inches and 4 eighths, or 11 1/2" from the base line.

Found them here http://vintagehydroplanes.com/technical/HopUp_1951_oct.pdf

I haven't used Catia, I don't know what it is like. I haven't done solid modeling in 14 years, and that was ProEngineer version 20...

But I was thinking more about framing and construction...

I think the best thing to do is develop a CNC plan for stitch and glue construction. Rather than using heavy timber frames, stitch and glue usually relies on egg-crate like framing that is CNC cut from material like 3/4" plywood, and stressed outer panels that are pulled together and "sewn" with zipties or wire, then fiberglassed into place. The zipties or wires are then removed. Motor rails would then be bolted in. That is what Chesapeake Light Craft did with the Cocktail Class racer from the original SKUA skimmer plans I linked above.

Then, people could get the CNC file from you, use a CNC router table, buy 6 sheets of 1/4" exterior fir plywood for the bottom and sides, 4 sheets of 3/4" fir plywood for frames, 4 sheets of 1/4" mahogany ply for the dec), and 2 2x6 12 foot pieces of spruce for motor rails. Then they would mill the parts out, glue, stitch, and 'glass the hulls together. Total cost for a bare hull would be less than $1000, probably around 200 hours to build. Or you could get a mill shop to kick out parts kits all milled up and sell them, ready to construct.

I really think finding a way build hulls in this fashion would make a difference in getting more people involved in Crackerboxes. If a couple guys can buy some plywood and knock out a hull in couple months worth of weekends and evenings, it is much more likely that people would be willing to do it.

What about rigging and hardware? Is everything available to build a competitive boat? Or are custom parts required? My father in-law just took over a machine shop in Denver and is looking for some consistent work...

This is really damn good idea, I hope you can pursue it!
 

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Discussion Starter · #6 · (Edited)
I used the offsets from the 2012 APBA inboard rules. I'll work on it more this weekend if I get time.

I plan on making the framing/bracing CNCable because at that point it's just turns into cycle start button push and a new piece of stock. The goal is to have the ground work to make this mass producible.

Giving a CNC file out is kind of scary, no machine uses the exact same code unless it is the same brand and model. In addition, they have no clue what tools I'm using or where I put the offsets, how I flipped the parts ect. unless I make detailed setup sheets. I'll offer .stps and they can program their own parts.

I have access to a GR-712, no need to build a CNC machine :)

As far as hardware goes. I have no clue on that situation right now, I'll have to research. I'm not sure what is available, but I can also design many of those parts. I planned on doing the 3D model with as much detail as possible. I probably won't do an engine but all the running gear, seats, dash and drive hardware I wanted to include. The engine will just be a nominal lump with minimal detail where the drive-line attaches and where it mounts.
 

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Good luck. Looking forward to seeing the progress :))THumbsUp

I would try and make it out to our first Lucas Oil race at Irvine Lake the first weekend in may. Talk to Bob and Tom Patterson. They are a great wealth of knowledge and have been building crackers for many decades
 
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