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Building a 7'6" Crackerbox

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Old 01-31-2007, 10:33 PM
  #51
JS440
 
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Default RE: Building a 7'6" Crackerbox

http://cgi.ebay.com/ebaymotors/KAWAS...spagenameZWDVW

that looks like a WAY clean engine. and i wouldnt be surprised if it didnt even go above the $125 starting bid
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Old 03-04-2007, 04:09 PM
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Default RE: Building a 7'6" Crackerbox

Hi guys,

I am still working on the Crackerbox build and I am thinking of using either two Blata clone 40cc or a Rotax 125cc engine for power. Do you think two Blata 40cc would work on the Crackerbox? I never seen a 1/4 scale version with twin engine before but because of the size of this one, it might work better and easier to find props for this set up. I was also looking for the stringers width dimension for a Blata clone mount. I will probably be making my own mounts from some pics I seen on RCU add.

Thanks for any info.....
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Old 03-04-2007, 05:14 PM
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Default RE: Building a 7'6" Crackerbox

i cant answer your question, but toi state about the outboards: their rev limit is somewhere between 5000 and 6000 RPM nothing(i believe) compared to your other options. How about QD?
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Old 03-04-2007, 09:36 PM
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Default RE: Building a 7'6" Crackerbox

My family races go karts, aprillia makes a 100cc reed jet motor. they push about 35hp,, look on e-bay also there are yamaha 100cc 2-strokes that are a bit cheaper but less power.....quite a bit less. do a search for 2-stroke race kart or something like that... the reed jet motors look almost exactly like one of these smaller boat motors......Have a friend that may want to part with one.. if you like i will ask
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Old 03-04-2007, 09:56 PM
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Default RE: Building a 7'6" Crackerbox

Hi sidriddle,

Please do ask your friend and let me know and ask him to send pics of engine.
Also, I will look for these engines on ebay.

Thanks
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Old 03-04-2007, 11:34 PM
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Default RE: Building a 7'6" Crackerbox

I would get something with electric start already built in. Shorten the shaft of an outboard and build it into the bottom would solve both power and steering. How fast do you really want it to go? A Jon boat with a 10 hp goes about 20mph, to kids it is flying. I don't think your cracker is going to bounce too much at any speed under 30 mph.
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Old 03-30-2007, 05:36 PM
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Default RE: Building a 7'6" Crackerbox

Hi Guys,

I met a guy last week that worked with outboard motors. He use to race those small 3-point hydros with a outboard. He had for sale a Everude 15 HP, newly rebuilt and some mod to it. He suggest for my build, this outboard set up into the boat and have a racing light weight foot, attached under the hull with a cut off and balanced shaft. Exactly like I was suggested in one or two of your replies. He also added that the props used with this set up are made of brass and can be trimmed, cupped and twicked to suit. The question is, where in the boat should this motor be? Should it be in the center of the lenght of the hull or more towards the back giving more weight in the rear? We need to know that also the prop will be right under the motor.
I will be able to move the gas tank front or back if I need to balance the boat afterwards.
Any ideas on these issues?

Thanks.
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Old 03-31-2007, 01:55 AM
  #58
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Default RE: Building a 7'6" Crackerbox

i think that a cart engine would probably be best because they put out alot more rpm than outboards and they are lighter and more compact and you should be able to adapt a collet to it pretty easy

check out these ones they rev to over 13,000 rpm and put out more than 28 horsepower and are liquid cooled and have a clutch and electric start

http://www.dpeng.com.au/Rotax.html
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Old 03-31-2007, 05:24 AM
  #59
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Default RE: Building a 7'6" Crackerbox

Hi,

Thanks, I will look into this engine with some local Karting clubs. It looks real good if I can only find the right prop combination. These engines looks real light and if a electric start can be installed, it would make it easy.

Thanks for the info.
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Old 04-01-2007, 12:36 AM
  #60
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Default RE: Building a 7'6" Crackerbox

Here is an 8' boat I build with me (240 lbs) and 40 lbs of required safety gear plus tools and powered with a 15 hp Yamaha. It goes 30 mph on GPS. I would be afraid of this if it was RC. Notice where the water breaks, it is very much on plain.

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Old 04-01-2007, 03:44 AM
  #61
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Default RE: Building a 7'6" Crackerbox

that little boat is sweet i want one
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Old 04-01-2007, 07:55 PM
  #62
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Default RE: Building a 7'6" Crackerbox

Looks like a Minimost. Plans are available here: http://www.svensons.com/boat/
Doug
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Old 04-01-2007, 11:04 PM
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Default RE: Building a 7'6" Crackerbox

It is a Minimost built from plans on that site. They also have a bunch of other plans, all free, that are good to scale down to RC size. Most would be made at 30 - 50% since they are small already.

I cant wait to see the Crackerbox running as RC, I think it will be much faster that people think. Weight may need to be added to keep it on the water.
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Old 04-10-2007, 06:54 PM
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Default RE: Building a 7'6" Crackerbox

Hi,
I have done a little more on the boat. I modified the deck openings from the original plans, to accommodate the engine and gas tank. You will notice I had primed the inside of the hull but sanded it down to put epoxy and cloth for more strenght. I think I will go with the modified outboard motor because I will have more choices for props and to modify them if needed. The boat is still light at 32 lbs. I will still keep my eyes open for a rotax 125 engine. If you have any comments about the build, please feel free to do so. I need all the hekp I can. I also started to make the rudder, twin skeg and trim tabs for it.

Thanks.
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Old 04-23-2007, 08:24 PM
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Default RE: Building a 7'6" Crackerbox

Hi,
I am sending more pictures of the build. I will keep you posted.

Thanks.
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Old 04-24-2007, 01:41 PM
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Default RE: Building a 7'6" Crackerbox

More pics...
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Old 04-24-2007, 02:26 PM
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Default RE: Building a 7'6" Crackerbox

It`s looking good, [sm=thumbup.gif] have you got an engine yet, or decided what engine you will use ?
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Old 04-24-2007, 08:11 PM
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Default RE: Building a 7'6" Crackerbox

Hi rickburnout666,

Thank you. I am looking at either a modified outboard 15 HP motor with a shorten shaft that would be installed inside the hull at the rear opening. Only the foot with prop would be under the boat. Or, a Rotax 125 or a gokart engine that would be in the front opening. The only thing I am worried about using the Rotax or other is choosing the right prop. I don't want to buy four or more large prop and find only one that works. I was offered from (justaddwata) a 11013/4 factory stock prop for a good price and if it didn't work out he was taking it back with a refund. I found him very nice to offer this. Either way I choose to go, the set up can be change pretty easy, without to much modification.

If you have any other suggestions, please feel free to do so.

Thanks.
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Old 04-24-2007, 08:40 PM
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Default RE: Building a 7'6" Crackerbox

Myself i would use a gokart engine they can produce plenty of power to get the big boat going at a good speed with the right prop, not sure what Rotax 125 you was on about The Rotax FR125 MAX kart engine pushes 28.5 BHP at 11500 rpm,but that will cost a lot of $s , but my Daughters Aprilia 125 race bike uses a Rotax125 engine, pushing around 38BHP at the back wheel, I dont know the BHP from the crank but i am considering putting her spare engine, minus the gearbox in a boat one day..... year, lol, i have too many projects running at the same time, I never finish one before i start another
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Old 04-27-2007, 04:19 PM
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Default RE: Building a 7'6" Crackerbox

Very interesting build - Now you just need to recruit a couple of two year olds for a "mock" driover and co-driver - strap em in good though- you don't want to lose them !
Ok - Seriously... If that boat is only 32lbs now and lets say 40 - 45 finished - minus 2 two year olds . a 15 horse outboard will be tooo much. I have a 150 lb boat w/ me 160 lbs. and w/ a stock 15 does about 30-35
I don't know why - yes I do - I like the scale look of an inboard -I would try to find any semi current 125 cc water cooled MX motor and fabricate some running hardware.
Good Luck - I wanna ride in that thing !
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Old 05-03-2007, 12:41 AM
  #71
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Default RE: Building a 7'6" Crackerbox

I found this website that shows how to cut a jetski to use the jetski motor, lower hull and drive system... it would make that crackerbox move!!

http://www.glen-l.com/jetski/jetjon-index.html[>:]
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Old 02-17-2008, 05:09 PM
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Default RE: Building a 7'6" Crackerbox

Hi Guys,

Well I have extra time to work on my Crackerbox boat project. I will be concertrating on choosing the engine needed to push this monster. If you read all comments given for fellow boaters, engine size, prop size is a big issue. I don't know by buiding a gear box drive with a mostly commen engine would be a possibility? Again, I am not looking for extremely fast speeds but the faster the better. This boat will be ran in a upcoming events this summer, if I can finish it in time. The outboard engine, installed inboard with the leg cut off, looks to be the way right now.

I will post drawing from my ideas tonight.

Please give me your comments.

Dave
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Old 02-17-2008, 05:27 PM
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Default RE: Building a 7'6" Crackerbox

I have sent the drawings.
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Old 02-17-2008, 09:26 PM
  #74
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Default RE: Building a 7'6" Crackerbox

Here is a few engines to look at there is one i seen that is an inline 4 cyl and it pushed 28hp it was made for rc boats up to 96 inches. Can't find it now. The net is to big and so many web sites to go through.

http://www.fpengines.com/html/58.htm


http://www.4strokeengines.com/large_...win_petrol.asp
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Old 02-17-2008, 09:48 PM
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Default RE: Building a 7'6" Crackerbox

I am trying to post pictures but can't. I will try later....

Thanks
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