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Building a 7'6" Crackerbox

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Old 01-21-2007, 09:15 AM
  #26
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Default RE: Building a 7'6" Crackerbox

Hello Quicksilver,

I appreciate the concern about the liability of running this big boat for promotional events but where most of our events are done is between a bridge, a causeway and a road. On the bridge side there is no problem, at the causeway, there is about 4' or more of retaining wall ( half with big rocks ) with a landing area and the road side is far enough and still about 4' hill. At that area, I would only see the boat being badly damaged if not totaled if something would happen. All the parking area is on the causeway side. I will definitely contact MAAC ( Model Aeronautics association of Canada ) ( our R/C liability insurance ) for more details. Another location where we are asked every year, is at a big car show ( The Atlantic Nationals car show and Model boat Regatta ). This pond would definitely need more protection from spectators by adding fences.
Quicksilver, you were saying that the outboard motor could maybe be used by removing the bottom part of the engine ( the lower unit ) and you think that could be a possibility? I never taken a outboard apart and see where the shaft could be a attached. I will into that.

Yesterday, I sanded the frame and will start sheeting the bottom this week. I will be sending pics during this and after that is done, I will be able to turn the boat upright. At this point, I will see how much room I will have for the engine.

Thanks for the info.
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Old 01-21-2007, 11:02 AM
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Default RE: Building a 7'6" Crackerbox

ok, you know I'm just making sure, since it would be unfortunate to do all that work and not be able to run it.

Well I've never taken apart an outboard, but a 10hp is what about 125cc. I tried finding someone on the net whos done this but no luck, to be honest I dont know. Guess I'd only suggest this if you have a OB motor that you can experiment with. To me this just seemed the most likely of canidates, however maybe it's really hard to do. I was thinking, well its water cooled, big enough and has a built in transmission, all of which a lot of other motors wouldnt have. However Idont know if you just have to remove the lower unit and attach a drive shaft, reroute the cooling lines and exhaust or if it's far more complicated. maybe check around some boating sites about rebuilding OBs or company sites for diagrams. I'ver got to go to work right now, but I'll try to look into this when I get back tonite.
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Old 01-21-2007, 11:24 AM
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Default RE: Building a 7'6" Crackerbox


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ORIGINAL: 2005ARSENEAU

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
Hi dave, I love your boat! I was wondering a thing or two about the original smaller boat plans that you enlarged. I am thinking about making the small version of this boat in the future, and was just wondering, are the plans free, or did you pay for them? If you don't mind, I would really appreciate it if you could give me a copy of the plans through this thread or PM.

thanks!
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Old 01-21-2007, 11:38 AM
  #29
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Default RE: Building a 7'6" Crackerbox

I dont think it will run good if you were planning on mounting the outboard like a regular engine inside the boat. This is becaus the enginge is built to run good with the pistons laying down. if you mount it in the boat I assume you want it to be like a rc engine with the shaft coming out at the back of the boat. So this means you will have to flip the engine over so thet the pistons are standing up.
It might work but it will probably not run as good as it should. An outboard runs best like in pic 1 and if you mount it in the boat you will have it like pic 2. And this is the problem. hope you understand.
The fuelline is your problem here. You have to do something about the carburetor or else the fuel will most likely end up in the hull instead of in the cylinder.(fuel injected outboard will fix that) And you might want to look over the whole fuelline so that it's not "gravityfed" in some part.

And there are some other things to fix if you take away the lower part of the outbord. most outbords(unless its pretty old) will have the exhaust coming out in the center of the prop. so you will have to rebuild the whole exhauste system.

Find a small car/gocart/motorcycle engine and try to get it watercooled.

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Old 01-21-2007, 08:22 PM
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Default RE: Building a 7'6" Crackerbox

ok, that makes sense didnt think, 2-cycle duh cant change configuration like that. Go cart engine is probably a good idea, think it would be cheap too. Could he water cool the motor by wrapping the head in copper tubing or does it have to be internal. I figure he'll be wondering this as well.
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Old 01-21-2007, 10:19 PM
  #31
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Default RE: Building a 7'6" Crackerbox

I have the solution, a single rotor Kart racing engine thats been worked over and adapted to run a mild nitro mix. I built 1 for my brothers Kart about 3 months ago and its a serous powerhouse.
http://www.nova-racing.com/nova_gb/index.htm
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Old 01-21-2007, 10:23 PM
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Default RE: Building a 7'6" Crackerbox

Do you know how much this hull will weigh? You will not need massive HP if the boat is very light (though it does not look like it will be).
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Old 01-21-2007, 10:34 PM
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Default RE: Building a 7'6" Crackerbox

Quote:
ORIGINAL: joccee

I dont think it will run good if you were planning on mounting the outboard like a regular engine inside the boat. This is becaus the enginge is built to run good with the pistons laying down. if you mount it in the boat I assume you want it to be like a rc engine with the shaft coming out at the back of the boat. So this means you will have to flip the engine over so thet the pistons are standing up.
It might work but it will probably not run as good as it should. An outboard runs best like in pic 1 and if you mount it in the boat you will have it like pic 2. And this is the problem. hope you understand.
The fuelline is your problem here. You have to do something about the carburetor or else the fuel will most likely end up in the hull instead of in the cylinder.(fuel injected outboard will fix that) And you might want to look over the whole fuelline so that it's not "gravityfed" in some part.

And there are some other things to fix if you take away the lower part of the outbord. most outbords(unless its pretty old) will have the exhaust coming out in the center of the prop. so you will have to rebuild the whole exhauste system.

Find a small car/gocart/motorcycle engine and try to get it watercooled.


Actually, OMC (Outboard Marine Corporation, former parent comany odf Evinrude/Johnson) made a sterndrive using v-4 and v-6 outboard motors and arrangde it so the pistoms were facing up. the only real mod they did was to install updraft carburators.





Oh yeah, Detroit Diesel has bee making two stroke diesels for over 60 years wit the cylinders verticle.
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Old 01-21-2007, 10:38 PM
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Default RE: Building a 7'6" Crackerbox


Quote:
ORIGINAL: Quicksilver

ok, that makes sense didnt think, 2-cycle duh cant change configuration like that. Go cart engine is probably a good idea, think it would be cheap too. Could he water cool the motor by wrapping the head in copper tubing or does it have to be internal. I figure he'll be wondering this as well.
you can make a more reliable engine using a 15 - 30 HP outboard, the only thing to consider would be making an intake manifold to keep the carbs horizontal
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Old 01-21-2007, 10:57 PM
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Default RE: Building a 7'6" Crackerbox

ok, so I was wrong about being wrong
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Old 01-22-2007, 02:48 AM
  #36
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Default RE: Building a 7'6" Crackerbox


Quote:
ORIGINAL: Flabum

Quote:
ORIGINAL: joccee

I dont think it will run good if you were planning on mounting the outboard like a regular engine inside the boat. This is becaus the enginge is built to run good with the pistons laying down. if you mount it in the boat I assume you want it to be like a rc engine with the shaft coming out at the back of the boat. So this means you will have to flip the engine over so thet the pistons are standing up.
It might work but it will probably not run as good as it should. An outboard runs best like in pic 1 and if you mount it in the boat you will have it like pic 2. And this is the problem. hope you understand.
The fuelline is your problem here. You have to do something about the carburetor or else the fuel will most likely end up in the hull instead of in the cylinder.(fuel injected outboard will fix that) And you might want to look over the whole fuelline so that it's not "gravityfed" in some part.

And there are some other things to fix if you take away the lower part of the outbord. most outbords(unless its pretty old) will have the exhaust coming out in the center of the prop. so you will have to rebuild the whole exhauste system.

Find a small car/gocart/motorcycle engine and try to get it watercooled.


Actually, OMC (Outboard Marine Corporation, former parent comany odf Evinrude/Johnson) made a sterndrive using v-4 and v-6 outboard motors and arrangde it so the pistoms were facing up. the only real mod they did was to install updraft carburators.





Oh yeah, Detroit Diesel has bee making two stroke diesels for over 60 years wit the cylinders verticle.

well...I did not say that a 2 stroke cant have the cylinders verticle. I just said that if you take an outbord you will have to fix the carburator problem.
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Old 01-22-2007, 05:35 AM
  #37
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Default RE: Building a 7'6" Crackerbox

a water cooled 125cc later model dirt bike engine would be ideal, most outboards do have the exhaust coming out of the crank, so you might have to use a hollow solid shaft to overcome that. a used dirtbike engine or a used jet ski engine would probably be the best bet in my opinion!!
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Old 01-22-2007, 04:15 PM
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Default RE: Building a 7'6" Crackerbox

That would be a great candidate for a 300cc Jetski engine and Jet. Just get a doner jetski (standup model) and cut the jet and mounting out of the jetski and mount to the boat.

I read an article where they cut a hole in a john boat bottom and mounted the jet and engine from a jetski right in.

Would solve a lot of fabricating issues.....
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Old 01-23-2007, 07:06 PM
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Default RE: Building a 7'6" Crackerbox

2005ARSENEAU, I got your e-mail, thanks for the offer. I did some more research though, and found exactly what I was truly looking for, free printable on-line plans of a 1/4 scale crackerbox. It looks identical to your skeleton picture. For anyone interested, heres the site. Enjoy! http://powerpete.20megsfree.com/photo3.html
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Old 01-23-2007, 08:10 PM
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Default RE: Building a 7'6" Crackerbox

Quote:
ORIGINAL: kritter

That would be a great candidate for a 300cc Jetski engine and Jet. Just get a doner jetski (standup model) and cut the jet and mounting out of the jetski and mount to the boat.

I read an article where they cut a hole in a john boat bottom and mounted the jet and engine from a jetski right in.

Would solve a lot of fabricating issues.....
Normally I'm all for jet drives, however, with the deadrise of a crackerbox, I'd be afraid of cavitation in any kind of chop, I mean its basically a flat bottom, meant to not really be in the water at all right? A jet would have a hard time, but if the intake was really close to the transom it could work, still, might have problems though.
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Old 01-24-2007, 03:04 AM
  #41
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Default RE: Building a 7'6" Crackerbox

i put a graupner minijet on a 1/10 scale vacu cracker, havent actively tested it in the water(on a pond), but in the bath tub, even on sharp turns it doesnt seem to cavitate, well see i guess!! something to consider if it were to cavitate would be to make a small bump right before the jet intake for the water to "stick" to and follow to the impellor. you can also make a small loader grate, examples can be found online!! sorry to get "off topic", just some more suggestions i guess!!
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Old 01-24-2007, 03:30 PM
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Default RE: Building a 7'6" Crackerbox

You could still use a Jetski liquid cooled engine for your powerplant. less modifications to it. The 300cc jetski engine is a single cylendar engine which produce a lot of power for that size boat....cheap too as far as doners go.
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Old 01-24-2007, 06:46 PM
  #43
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Default RE: Building a 7'6" Crackerbox

Hi,

I started to sheet the boat today. I will finish sheeting the bottom and sides tomorrow. I will be able to turn the boat around and see the space I have for the engine. I will post a picture of this also for you to see.
I will be looking around for a engine next. I will be looking for a junked jetski engine and a 10HP engine from Princess auto. They carry all kinds of gas engines for different uses.
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Old 01-24-2007, 08:50 PM
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Default RE: Building a 7'6" Crackerbox

Looking good man can't wait to see this thing running.

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Old 01-25-2007, 03:27 AM
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Default RE: Building a 7'6" Crackerbox

oh man, this is gonna be schweet!!!!
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Old 01-30-2007, 03:21 PM
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Default RE: Building a 7'6" Crackerbox

Hi Guys,

I finished sheeting the bottom and sides. I turned the boat upright to show you guys the room I have for the engine. It weights 29lbs the way it is now. I will be sealing the joints from the inside next then adding epoxy. I have a few leads on a jetski engine set up. I do not know if I could use a jetski engine without the water pump set up and add a shaft to the engine or if I can use the water jet pump to.

I will keep you posted. Keep your ideas coming !!!!

2005ARSENEAU
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Old 01-31-2007, 07:47 PM
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Default RE: Building a 7'6" Crackerbox

what jet ski engine are you planning on using? i'm fairly familiar with a lot of the small displacement kawi engines, i've ridden standups for years
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Old 01-31-2007, 10:15 PM
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Default RE: Building a 7'6" Crackerbox

Hi JS440,

Great!!! You can maybe give me some ideas of what to look for in a jetski set-up.
The room I have where the engine compartment is, is about 19" x 31". I can modify the bulkheads to add bigger if needed. Does a jetski from a kawi engine have room for my boat. I don't know what would be the smallest engine available in a stand up jetski. Could I be able to adapt a shaft collet and a shaft onto the engine's gears? Or do I need to install the water jet pump? If you could give me some ideas of what model and size that would be the ideal set-up for my boat, I can start looking around in a jetski junkyard of some sort. Any help would be appreciated.

Thank you.
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Old 01-31-2007, 10:25 PM
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Default RE: Building a 7'6" Crackerbox

Hi,

I forgot to give a close up shot inside.

Thanks
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Old 01-31-2007, 10:29 PM
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Default RE: Building a 7'6" Crackerbox

the smallest engine you will find will be from a kawasaki JS300 orl a 300SX. it's the same engine, they just had different hulls. it's a 300cc 1 cylinder 2 stroke. you'd probably have to use the jet pump somehow because the drive shaft is about 1 or 1 1/4" and solid. even that engine however, will weight quite a bit, but should be relatively cheap on ebay, craigslist etc
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