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Building a 7'6" Crackerbox

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Old 01-17-2007, 09:41 PM
  #1
2005ARSENEAU
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Default Building a 7'6" Crackerbox

Hi guys, I am building a huge 7'6" Crackerbox wooden boat from a blown up Dumas plans. It will be fairly light. The issue that I am having is the engine and prop set up I will need. I know that there is some large engine out there like the clone Blata, the converted zenoah G62 and more. What is the biggest prop that can adapt to a 1/4" shaft? If anybody can help, I would appreciate it.

Thanks Dave
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Old 01-17-2007, 09:51 PM
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Default RE: Building a 7'6" Crackerbox

How about a mercury 50HP outboard and seat and a steering wheel.

That thing is huge. Good Luck
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Old 01-17-2007, 10:21 PM
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Default RE: Building a 7'6" Crackerbox

thats gona be a cool boat dont forget the progress pics sorry i can help ya with the question
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Old 01-17-2007, 10:24 PM
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Default RE: Building a 7'6" Crackerbox

Northern Tools has some Honda 4 strike engines, running gear would need to be custom made and maybe the prop can be found at Michigan Wheel.
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Old 01-17-2007, 10:38 PM
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Default RE: Building a 7'6" Crackerbox

Can I just ask one thing? Why? Seems a little oversized, but cool none the less!
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Old 01-18-2007, 12:04 AM
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Default RE: Building a 7'6" Crackerbox

I've got to agree with Yeeharacing and Zelatio that it will be cool, but why make it RC?
Not saying you shouldn't do it, but some of the recent rc " models ", are close to full size boats. I would much sooner drive a boat that large, than need three guys to launch it and play with a radio. But hey, that's what hobbies are for, and all the best with it.
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Old 01-18-2007, 07:44 AM
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Default RE: Building a 7'6" Crackerbox

You asked whats the largest 1/4 in. drive prop? Here's one I did a year ago. 115mm Propshop Stainless. (the prop was not totally finished when pics were taken.)

The smaller four blade is an 80mm just to show a size comparison.[X(]

.





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Old 01-18-2007, 07:45 AM
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Default RE: Building a 7'6" Crackerbox

Hi guys, thanks for the messages. I know, it's a big one. My main purpose for the build is to use it as a promotional tool for our boat club and other events. Our downtown area is surounded by water and has many activities at the water front. I would like to have the most speed from the power plant and as scale looking as I can. I will have a custom trailer made for it for transportation. Any feedback from this build would help!!

Thanks again.
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Old 01-18-2007, 07:52 AM
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Default RE: Building a 7'6" Crackerbox

PHCH, WOW!!! what beautiful props. I think I will need a prop that size. If you could help me choose the right size, pitch, 2-3-4 blades? Do you have a price for the props?

Thanks
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Old 01-18-2007, 08:58 AM
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Default RE: Building a 7'6" Crackerbox

we built a 7ft aluminum jet sled and put a 750cc jetski engine pump package in it. and rode in it...something that big in RC can cause some real liability problems if it gets loose
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Old 01-18-2007, 09:31 AM
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Default RE: Building a 7'6" Crackerbox

What to run it on beats me. Its something for my collection and is currently serving as a display piece in my office at work.
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Old 01-18-2007, 11:21 AM
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Default RE: Building a 7'6" Crackerbox

Hi PHCM, Would you sell that prop? If so, how much?

Thanks
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Old 01-18-2007, 11:38 AM
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Default RE: Building a 7'6" Crackerbox

LOL.
Thats a wonderful compliment (wanting to buy it), but there's too much work and time involved. You should see it now. [x(]

Besides, it's a RARE beast of sorts and makes a good paper weight Doubt you'll find anything larger for model boats than that particular one from Propshop... The number for the beast is 115/22.
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Old 01-18-2007, 09:57 PM
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Default RE: Building a 7'6" Crackerbox

You can forget 1/4" drives and your 115mm RC props. All a little too small for a cracker box that size (basically 1/2 scale).

A Blata 40 or G62 Zenoah are not going to do much with a 115mm prop. And they definately wont move what will likely be a 60+ pound boat. I would strongly consider picking up a 4 or 5 hp outboard motor and adapting it to fit. I started doing this with a 4hp out board (Comes with tank, prop, and most other parts you will need). You can pick up a quality used late model one for around $350 (I recently got a 3,4,and 5hp Mercury so have been shopping the prices well).

You are going to need torque to get that boat moving and I am thinking a Mercury will likely do it best for the $$

If your really after an RC prop - I have a 11013/4 factory stock - I paid $135 for it. I could probably ship it your way for a little less [link=http://groups.msn.com/_Secure/0UQA0Ds8YLvm!hA4FjiZ8388xDBLwGVi5Ig7LefMDmyJpQSDyb RZa*YZFI4XiZ1em7dfOJkBXB2BnAyoKfeYrc9eG2N4XlFguEMA IMsBXdKR3ke1bphq5mzLGpetM1srL/Props%20023.jpg?dc=4675531577083026980]Pic of prop here[/link]
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Old 01-19-2007, 12:09 PM
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Default RE: Building a 7'6" Crackerbox

Hi justaddwata,

With the outboard motor.... wouldn't you have a problem controling the steering with 1/4 scale servos? A outboard motor would be heavy to turn would't it? Unless you set up a set up with pullees and cables. What modification would you do on a outboard?

Thanks
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Old 01-19-2007, 12:59 PM
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Default RE: Building a 7'6" Crackerbox


Quote:
ORIGINAL: 2005ARSENEAU

Hi justaddwata,

With the outboard motor.... wouldn't you have a problem controling the steering with 1/4 scale servos? A outboard motor would be heavy to turn would't it? Unless you set up a set up with pullees and cables. What modification would you do on a outboard?

Thanks
The outboard can be run as-is. Just need to hook up the throttle cable to the carb. Any standard 1/4 scale servo will be up to the task of the throttle. For steering, you can run a couple 1/4 servos through a gearbox and create massive torque and still have enough speed. I am also working on a project that will require the futaba "indutrial size servos". You can get everything from www.servocity.com
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Old 01-19-2007, 01:07 PM
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Default RE: Building a 7'6" Crackerbox

Forgot to mention....with a pair of 1/4 scale servos that are running through a gearbox, you can get a combined torque of 4,000oz (not 400) plenty enough torque to steer the wheels of a large 2 passenger go-cart/dune buggy that is converted to RC (don't ask how i know!).
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Old 01-19-2007, 04:02 PM
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Default RE: Building a 7'6" Crackerbox

2005ARSENEAU
hello again as you are having trouble with engines if you can get hold of a cheap 2 stroke 125cc motocross bike/engine take out all the gears as you wont need them, cut off the extra bits of casings you dont need, you will be left with the crank, crank case and flywheel ignition coils, and head and barrel attached much like zenoahs and other rc engines but a bit bigger like your boat , these engines push about 26 bhp at the back wheel not sure about at the crank but i`m sure its more than 5hp, im sure there are people in your club that can do the mounts to fit it and a coupler for the crank , I tune 2 stroke bikes myself and it looks like it would be an easy conversion, My daughters aprilia 125cc is pushing between 35 and 38bhp at the back wheel, maybe next time she stacks it i will try a conversion myself [:@][&:]
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Old 01-20-2007, 02:53 AM
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Default RE: Building a 7'6" Crackerbox

I was thinking more along the lines of laying the powerhead down inside the hull and fabricating a drive to suit. Just not sold on the look of an outboard on a cracker box (though would certainly work fine)
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Old 01-20-2007, 10:18 AM
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Default RE: Building a 7'6" Crackerbox

Hi Guys,

You fellows are giving me good ideas !!!!
Hey, XXXboatworks, I looked at the site you gave me at servocity and I think that is the answer of my steering problem. They have great gearboxes for any applications. I didn't hear about them before.. Thanks.

Hi rickburnout666, I will also look into a bike engine. I will need to look at the weight and size for the room I have for the engine. The outboard engine is not a bad idea from justaddwata, if I could modify it either to have it install at the rear like it should be or having it inside, out -of -sight if I can custom make a drive for it. This would solve the problem finding a prop.

I couldn't do much on the boat lately. Also, I just finished digging myself out of a 35cm of fresh snow. It came down for two days. I am going into my workshop now and I will be sanding down the bulkheads and stringers, preparing for sheeting maybe next week. I will keep you posted and will send pics.

Thanks guys.
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Old 01-20-2007, 10:27 AM
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Default RE: Building a 7'6" Crackerbox

just want to say i love your build and i saw this and made want to build a jersey speed skiff !!!! thats what the east coasters like , well at least me , long time back my dad had a real speed skiff and it was hard to extract me out of that boat , i think i still have ear damage from that boat [8D]
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Old 01-20-2007, 10:47 AM
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Default RE: Building a 7'6" Crackerbox

a stripped down crosser engine should weigh less than 1/2 or a lot less than 1/2 the weight of an out board (depending on outboard)
anyway glad you are getting plenty of ideas
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Old 01-20-2007, 11:59 PM
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Default RE: Building a 7'6" Crackerbox

Excellent job on the build!
I love the idea of using this as a promotional tool!

My main concern would be safety, especially if you get any kind of speed out of it.

You should consider multiple radios and failsafes for redundancy.

Two of everything; transmitters, recievers, batteries, servos, failsafes, switches, etc.

Again, a wonderful idea! Keep it up!


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Old 01-21-2007, 12:12 AM
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Default RE: Building a 7'6" Crackerbox

Found a solution to your power issue... [link]http://www.conleyprecision.com/[/link]
IF you have $5,000
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Old 01-21-2007, 12:42 AM
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Default RE: Building a 7'6" Crackerbox

man that's big. Problem I see with an outboard is weight and appearance. An outboard powerhead however would work like justaddwata suggested. For simplicity, why not just use a boat prop. Mercury makes modified higher pitch props for their outboards. From my experience with small fast boats, I think you need a 10hp motor. Youve got to loose the lower unit though and go with a solid shaft. I don't think a 5hp motor would do the job, well not fast. Definitely need a fail safe. Isnt there a simple device that kills the motor if the signal is lost, remember it on myth busters(rc cop car).

I dont know canadian laws, but I would think here in the states, not only would that boat have to be registered as a motor vehicle, but also insured for liability and in this case, I'm not sure someone would cover it. If I were an insurance agent I wouldnt do it period, not worth the risk. I bring this up, since this is supposed to be a PR event and it will attract a lot of attention, some unwanted as well.
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