hoosierdoc

Hi guys, first time posting here. I've read numerous threads about various boats and am ready to get started. I have a homelite z3300 (assume 33cc?) chainsaw that fires up well. I will be trimming the pastic shell down a bit more before mounting. I don't have calipers but the shaft appears to be 5/16" (that a strange size?)

I am taking others' advice and will use doorskin for the hull then coat with glass and resin. The engine weighs about 8 pounds without fuel. As it is now, it is 8" high, 8.5" long, and 15" wide. The center of gravity is the driveshaft and is 10" in from the handle side. Seems to me that means a minimum 20" wide boat to get the engine inside.

questions:

1) Should I rip the handle down more and make a custom throttle-control mechanism to make it less complex and smaller?

2) How wide/long should this boat end up being? I'm planning a deep-vee hull

3) Is a u-joint and straight-shaft system preferred to a flex-shaft to get power to the horizontal prop shaft?

4) As shown the picture, how do I remove the clutch from the driveshaft? It seems to be very tightly tension-mounted. I can always just leave it if it's too difficult I guess.

5) Is birch a good wood for bulkheads?

6) Does a set-screw really hold a round shaft well enough to push a prop without slippage?

I appreciate any and all comments regarding the boat. If I don't get much assitance I'll just buy a large laundry basket and stick my engine in there like my favorite gas-build on this msg board...

-Brian

martno1fan

first i think youll find a chain saw motor will not work they are the wrong way round that is the starter is in the wrong place i beleive.second the set screw doesnt drive the shaft all the set screws do is connect the prop shaft to the flex cable you file a flat spot on the shaft if the set screws are flat if they are pointed drill a dent in to the steel shaft.third never ever use a universal joint allways use a flex cable for a surface drive boat.chainsaw motors need major surgery to make them usable in a boat have a search and see for yourself.far better to get a weed wacker engine and use the square ended flex cable that comes with it to connect to the engine then you use a ferrule which is either silver soldered to the flex at the prop end or you can use loctite retainer 603 and the ferrule connetcs to the stub shaft via two set screws.this shaft rides in a strut and you need a drive dog with one set screw to spin the prop which would be a prather 275 or 280 or similar sized prop. then you need a prop nut to hold the prop on i hope this helps.

hoosierdoc

thanks for the quick response! How does the starter position affect anything? I will do the standard pull-start, it fired up without much problem today for its first run in two years. It does spin clockwise so I would need a RH prop. Besides the rotation of the engine, why would a chainsaw be difficult to modify? Isn't the main thing having a spinning shaft that you can draw power from? Does there exist a connector that takes a round shaft and gets the square connector for flex shaft?

It's a personal pride thing that I'll be using a chainsaw because of the type of competition.

glennb2006

You will also need a flex cable that is wound the other way to ensure it does not come "unwrapped" in operation. Think you need to get as much plastic off it as you can and then take it from there. It's all do-able, maybe the engine (Behind the clutch) has a tapped hole in the crankshaft end that you can get a collet type fitting to fix to.

Looks fun.

OLD_SLOW and in the WAY

here are some dust covered examples of cut down chainsaw engines that were slated for aircraft conversions the first two of a 81cc stihl the third one is a 62cc homelite and the last is a 35cc stihl . you can do a lot of material removal if you look at it closely.
the starter on a chain saw is on the drive side (wrong side) of a boat conversion. to run the stock starter you would need to get a reverse wound shaft and reverse rotation propellor

hoosierdoc

I'm still not sure why I'm being told the starter is on the wrong side. Why does it matter where the starter is, as long as I can get to it and can get the engine running? I'm planning on leaning over the boat (from my boat) and pulling the starter. Will this not work?

Thanks for the advice on the wrapping of the flex shaft. Hadn't thought of that!

Okkels

The probelm is that your choise of props will be limited because most of these run counter clockwise and so does most flex cables. But the biggest problem is in here.... people in here dont like chainsaws. I got the same answer, look for a weed wacker. Any way i am in the process of doing the same as you. I also have a chainsaw that i want to use and i am in the process of figuring out a way to do it.

hoosierdoc

well good, we can beat the odds together then. The way I'm looking at my hull design, I'll have to drop the shaft down 5 inches to get low in my transom. Is this too much or will a flex shaft get there?

I'm still pondering the u-joints with a straight shaft to get there. With a 22.5 degree angle at each u-joint I would need a 12" shaft to get my 5" drop. Hrm...

Also, anyone have any examples of making your own struts for prop and rudder? The nature of this boat is as improvised as possible.

glennb2006

Or you could work out a way to turn the motor round and get drive off the "other end". Then it will turn the right way for most props.

Just a thought....

G

Okkels

I am just as new as you into this, but i have done some research. I found [link=http://www.rcuniverse.com/forum/m_4718942/mpage_5/key_/tm.htm]this[/link] very nice rudder and strut setup that is homemade. I was also set on a rigid shaft but i think a flex will be easier to work with. If you go for af rigid shaft you also need flexible coupling, between the engine and shaft so you do not tear the boat apart.

martno1fan

scrap it and buy a weedy less hassle and easier to do!!,go to your local lawnmower shop and ask for the broken or returned weedys and you will get a shedfull and should get a few that can be made to work!!.

hoosierdoc

I appreciate the advice to scrap chainsaw and go with a weed eater. However, I will be using a chainsaw for my boat. Besides just being hard-headed, I have irreversibly removed some components from my brother-in-law's saw and will be putting it to use. Gotta make it a martyr now!

martno1fan

by the way if you use solid shafts you dont ever use uni joints on a gas motor,but you use a coupling that has a ball and pin that slides into the hole this allows for a bit of play then you run the boat submerged drive.uni joints wont hold up to the job.

Okkels

Told you. they do not like chainsaws

stevblutu15

if you could clean the motor a bit and take more pics once the plastic is trimmed i think we all may be able to give you a better response. Pics of the starter and position would be nice. Right now atleast i cant see any of the actual motor lol its covered in plastic.

Believe It

if i read correctly on the rc boat drags site... the fastest (i believe) gas boat is a chainsaw powered one, soo........?

MrMikeG

It has nothing to do with weather we like chain saws or not!
Go back through here and Jim's and see how many many many hard headed guys like the 2 of you say the same thing and see how many have EVER put a boat in the water? In the last 5 years that I have been an Admin over on Jim's I have NEVER seen one completed. Even if you can do it why would you want to persue an engine that will cost more and be slower than doing it the easy way??? Some specifics, you need to get the weight down and the size down like Larry has shown you. Hard shafts vibrate if not done properly. Flex shafts are a lot easier! If you want people to help you then you need to listn to what they are telling you. If you don't want to listen then what is the point of asking?
There are guys here that can help you but you need to get rid of the negativity.

gasfreak

My Feedback: (13)

I agree 1000% with what MrMikeG said you will just beat your brains out tring to get that setup to do anything and it will be too heavy and slow even if you did get it going

fastguy

i have a chain saw 62 ccs here is how u can modify yours[link=http://www.modelpowerboat.com/Water_Cool_a_Weedwacker_Engine]how to modify a chain saw [/link] if u want to know what i think that it is too large i recomend that u go to your lawn mower shop and ask for junk engines ask many shops u can get lors of them

Tidnab

My Feedback: (51)

Brian, If you're really set on using that chainsaw engine, maybe these guys www.hyperprod.bizhosting.com/v_drive.html can tell you how to do it and rig up something for you.By the time you spend money to get it to work you could have bought a Zen or Sikk.But I do like your tenacity in sticking to an idea and hopefully you'll do what you intended.

hoosierdoc

who exactly is being negative? I haven't detected any negativity in this thread, and personally I am positive and optimistic, the opposite of negative.

Here's how I see the issue: I have a driveshaft that my engine turns without any problem. There are shafts that will work with my engine. There are props that work with the shaft that will work with my engine. And the green grass grows all around....

more updates coming as I get time.

jacob711

the chainsaw idea is not very good because the output shaft spins the wrong direction and you are not going to be able to couple a flex shaft to it because you will find it hard to find a collet that will fit and the thread on it would have to be left handed other wise it would come loose as soon as you start the engine up and you will have to specialy order a reversed flex shaft and it will be hard to get reversed props and chainsaw engines are very bulky and you cant remove the covers because the forced air cooling on it wont wont

just what i thought anyway

ernest2

brian, chainsaw engines makes very good airboat engines!!! airboats are awesome to drive if you havent tried one yet. airboat is a easier option for you compared to conventional speedboat mainly because of the parts available.
but you can still make it into a speedboat, but i think the easiest is making the engine shaft face forward and then put chain drive on it or belt drive to connect to the shaft and prop.
don't give up!
ernest

martno1fan

Brian i think Mike has it right you say your not negative but what he meant was your been negative towards our helpfull advice.We are all trying to help save you from wasting a lot of time and money.Yes they are powerfull engines yes they will spin a shaft and prop no they wont fit in a boat as they are, everything is in the wrong place.By the time youve modified it to work as was allready said you could have bought a zen or a sikk or five weedy engines.Go to the lawnmower repair shop or similar and ask for a cheap used engine or ask for the junk engines and you may be surprised what they let you have.Now with all the bits they gave you for free build a working engine from all the parts!!!.also check ebay there are bargains to be had i got a weedy engine here for £15 brand new unused 28 cc,thats $28 to you cheap as chips as they say.Put the saw back together and buy a weedy .I like your attitude but dont be a fool listen to the guys who know and have probably tried and failed doing what you intend and are trying to help you out here.Learn from the mistakes they and me have all made.

fastguy

no not negative just stuborn
again it is alot eaiser to use a weed wacker