mdelgado

Hey there, I was looking at boats for my kid and me and decided on just building one. Someone gave me a 1.8 cu/inch chainsaw that I will never use and I thought that would be a good power plant. So I was hoping someone could give me a ballpark estimate what the running gear would cost? I'm not concerned with the cost of building the boat or the radio/electronics cost. I just can't figure out what rudder/shaft/prop/couplers and such cost for a boat this size. Which leads to the next question, what size boat would you want for this size engine? I would model the boat off a cigarette or donzi mono hull.

Hydro Junkie

Actually, a chainsaw motor isn't a real good choice for use in a boat. Let me give you a couple of addresses to check out:
http://www.bhhanson.com
http://zippkits.com

mdelgado

Thanks for the links! Seems like no one likes chainsaw engines due to the weight, reverse rotation and air cooling. 60cc must put out a lot of torque......I wonder if running a belt or chain drive to two shafts and making the boat a twin screw would help?

Hydro Junkie

Can't say since I've never seen it done.

expresscraft

the price of a good motor is around 200.00 brand new, even less if you look in the classifieds from a good seller, Keep in mind the price of parts and radio gear, A lot you will be making your self with a low RPM (speed) large cc chain saw motor. with the time and money you will spent on a gear box, and if you make the power in not perfect for the power out you will have a heavy boat that will just boil the water with the props. I would love to say the hull is the foundation of a great boat as a hull manufacture but really its the motor. Of course your chain saw motor will make a great Air boat.

mdelgado

I watched some youtube vids of guys with chainsaw or weedwacker engines. You're right, they have a tough time pushing the heavy boats with undersized props and single drives. In the real world big heavy boats are pushed with large diameter props (which it seems they aren't available for rc) or by running multiple engines. Seems the key is to get more prop in the water. As far as low rpms of these gas engines, I think that can be fixed with gearing. With my chainsaw, it's right hand (clockwise) rotation, so it needs to be rotated and connected to the shaft with a belt of chain. My thinking is, if I'm running a belt drive, why not run the belt to two shafts/drives. You can get camshaft pulleys, belts and bearing blocks at McasterCarr for cheap. Since we're dealing with a belt or chaindrive, you can make the drive pulley and shaft pulleys whatever ratio you'd like to get the desired rpms.
I'm just brainstorming here, so welcome to any ideas or opinions

expresscraft

we made a gear box years ago for a quick draw inline twin, that went one shaft in and 2 out that were counter rotation. I do not remember the ratio, but the problem was not HP it was a 70cc motor that turned 18,000 rpm's but had way to much torque for a deep vee. We tested as a straight drive in our 72" sea hawk and you could see the hull flex. So we made the gear box, with the ratio we used, and the extra weight of the gear box, it just boiled the water. When I talked to Tom from Octura madels he told me he could have told me that from his attempt at the same thing 20 years earlier of course my try at it was in the early 90's. We were still doing a lot of learning and i wish I would have just laid up a thicker hull and tried again with the single drive. Props will not be the big issue with what you have, there are big props today. Your issue for the amount of work it will take just to save you 200.00 will be stepping over a dollar to pick up a Nichole. There use to be guys modifying G62 zenoha's and they never caught on because there power came in torque (tug boat) but not rpm's (speed) even if you spin the right big prop at 8,000 or even 10 you will not get the speed you will with a smaller prop at 18,000. when you submerge the right big prop for your motor those rpm's will drop even more. If you are going to teach your son machining then that is great. But to just built a boat with him and enjoy running it together. Buy a motor that has the parts and all available for it. Build your boat out of door skin available at most big hardware stores. Bruce at Gizmomotors.com has lots of great parts and engines, And joe at zippkits.com has the same and some great wood boat kits.

mdelgado

So you had twin surface drives and it still just boiled the water? Do you think making it a true inboard with the whole prop in the water would make a difference?

I'm not looking to break any land speed records, but make something that gets up on plane and moves out. I do a lot of glass work on boats, so I have the materials to build already and the chainsaw collecting dust...

But if you guys insist it won't work, then I won't waste our time. It's hard to believe it won't work though...

Hydro Junkie

To get the engine into it's best operating range, a fully submerged prop may not work. The drag induced by the water on all the prop blades will slow the drive train down. This will require the engine to burn more fuel and take more wear than a surface drive set up would

Justaddwata

My Feedback: (3)

Around 20 years back I went the chainsaw motor route on a build. Spent a few days grinding off excess moldings from the original saw housing to reduce size and weight. An additional problem is chain saws rotate in the opposite direction to 99% of props and shafts on the market (though there are still options). While I ended up with a boat that did run (an Expresscraft apache as a matter of coincidence - Tom who posted earlier likely did the glass work) I also spent more time and effort making something that was plagued with problems every step of the way. It was one of the many valuable learning tools I have played with over the years - but not one I would encourage anyone to attempt unless they are very skilled with the ability to fabricate custom parts and hardware.

Chainsaws generally do not make more power than most RC motors and typically only rev to 7000 - 10 000rpm. Most Marine motors will run in the 16000 - 18000rpm range and out of the box will weigh a fraction of the weight of a saw motor. While the bigger displacement saw motors do pack plenty of torque - this too is something you most likely will not be able to tap into without an elaborate overdrive setup that only complicates things (and robs power in the process).

I would really encourage you to look into either a weedeater motor or a true RC motor (preferably water cooled). They have so much more potential, upgradability, resale value, and all the work has been done for you. I encourage you to take a look through some build pics I got from a craftsman in Germany which may give you some tips or inspiration for your build. http://imageevent.com/justaddwata/mo...ipsfromgermany Keep us posted on how you proceed and do not hold back with the questions.

expresscraft

I am not saying a chainsaw motor will not work at all. I am saying when you add the gear box ect. then the weight becomes too much, Our gear ratio was also wrong, You can get the motor you have to work, But the foundation of your boat will be bad, it will push the hull and might even plane it some, of course you might spend a lot just finding the correct right had prop (very limited) and you will spend more time fabricating every part you need to make it work. Like I mentioned earlier if you are teaching your son to be a machinist then have fun, but if you are just trying to save some money, even if it's because you do not have much. then it's even more important that you buy once and not twice. even a used 260 stock will be 100 x's better then if you do all the mods you can to what you have now as a foundation of your whole project. Of course if you decide to go that way anyways everyone one here will help answer as much as we can, But I would never want you to pack my parachute LOL. either way just have fun.
There is a guy on Jim's RC boat dock selling 5 brand new 260 Zenoha's for 160.00 each then you will need a carb and a pipe.1 is already sold. so right this minute he has 4 more left.

mdelgado

Thanks for all the advice guys! This was supposed to be one of those projects made up of stuff I have laying around. I didn't want to dump a ton of money into it, just do something different. I had the motor, fiberglass supplies, RC electronics and figured give it a shot. But given what you say, I think running dual prop is key to the success. And getting these shafts RPM's up with a 2:1 gear box. I pieced the 2:1 ratio gearbox together in my head. Using aluminum plate, aluminum timing belt pulleys, belt, and bearing blocks. it was already at $100 from Mccaster-Carr. I'd still need two 1/4" shafts, stinger drives, rudders, props. It was getting a little out of control. Especially when you can go on Craigslist and find something someone got bored with that needs some TLC. Like this http://worcester.craigslist.org/tag/5708566009.html

I'm going to take a step back and rethink this for now. Once again, thanks for all the comments!

expresscraft

I owned a hobby shop for 25 years, I have always serviced what we sold and tried to help as much as I could, When I was selling helicopters I always told my customers it would take 4-6 weeks to learn how to hover and it would cost around 200.00 every time you crashed, this was before simulators ect. But my point was always if I could talk a customer out of buying a helicopter then it was not the right thing for them and certainly was not someone I wanted to show up hours before we opened or stay hours after we closed trying to help. If you make the choice to do boats because you want to enjoy this hobby and have some great times with your son then do it right. that does not mean you need to set any records to have a great time in gas boating. Gas boats got started with weed eater motors and lots of home made boat. But you also could not get motors made for us back then. I do not know were you can have as much hobby time for the price of a model boat, we do not have gravity like airplanes to destroy them. I have had some boats for 8 years, ran them weekly and still sold them and got back some of my money. Like the one you are looking at on graigs list. offer him 200.00 at the most. It is very old school if you keep looking you can do better.

mdelgado

That's great, you must have put a lot of smiles on kids faces over those 25 years. I remember growing up and spending time after hours with our local hobby shop owner, resurrecting my car. Great memories

expresscraft

In the 25 years I had kids smile then later helped them with there kids lol. I always thought of my shop as a bar for people who do not drink, And I always tried to be a great bar tender. Of course a lot of them did drink, But a big pay off for me were the guys that did modeling as a way from recovering from drugs and drinking. I really hope we never lose that aspect of modeling. I do not know how old you are but I do hope you give that some value with the choice you make on modeling,boating or something else. But it will be great time with your son that will go by very fast.

Justaddwata

My Feedback: (3)

Where abouts are you? If you are in Worcester then I am an hour down the road (near the Casinos) and would gladly show you a little more of what to do and what not to do. Probably have some parts that will put you in the right direction. Let me know!! my name is Matt!

Hydro Junkie

Matt, are you referring to the Mohegan Sun? If so, I was there last year. Nice place, considering it's the least smokey casino I've ever been in

Justaddwata

My Feedback: (3)

Yeah - we have Mohegan Sun and Foxwoods about 5 miles apart. One of my bigger complaints is that they are a little smokey. But they are not bad to have in the neighborhood.

Hydro Junkie

Didn't care too much for Foxwoods. It was too much like walking through a hospital to the wife and I. As far as Mohegan Sun, it had so little smoke, when compared to our local Western Washington casinos, that the wife and I didn't notice any smell at all, though we could see some when backlit by upper level lighting. We ate at Bobby Flay's and Margaritaville on two separate trips. Flay's was really good but spendy, Margaritaville was good, if you like burgers

expresscraft

mdelgato, that is a great offer from Matt he has been playing boats for a long time, and would be a very good hour drive to have real help as opposed to just internet help, The forums are very good. but one crew chief is better then 100. might be all good advice but not when its mixed up.