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RE: 6' Home built Chain Saw Engine boat!!!! - 5/4/2004 1:43 AM   
lmopar69



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From: Indian Mound, TN, USA
Status: offline 		Well, Skoda, I defenitely agree with you that the drive system is flawed. I use much "harsher" language when I describe it, but thanks for bein polite!

Exactly what is a surface drive? I am not familiar with that. Ive heard it, but never seen it or else saw it and didnt know what it was.

You were pretty close on the output shaft diameter. Its a 1/2" or just a shade less, I cant remember what we machined it down to. Either way, it makes it difficult to get a prop for it.

I put the out put shaft that high on the rear of the boat because I assumed it would sit lower in the water than it does. That and it was just an un-educated guess (like the rest of it has been!).

Which would be easier you think? Putting a surface drive system on it or just moving the output shaft to come out under the boat so as to keep the prop, what ever prop I end up with, under water.

I think this thing would really "scoot" along with the right prop on it.

I just talked to octura. They have a 2 3/4" (70mm) dia. "clockwise" prop with a 3 7/8" pitch. This sounds about right to me, what do you think? Of course, I m just guessing by going off what the one I have now does.

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/4/2004 5:05 PM   
BajaBob-delete


 

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Status: offline 		Surface drive really the prop is positioned so the the prop is half in and half out of the water when the boat is on plane.If you look at keel at transom, the centerline of prop shaft would be approximatly 3/8 above it.The props hub on a standard model prop would just clear the surface of water.A submerged drive type of system places the prop (both blades) below the waterline when boat would be on normal plane.
Either drive would propel a boat,but surface drives are used on to obtain higher speeds by letting prop unload.

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/4/2004 5:09 PM   
skoda450



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From: Valentines, VA, USA
Status: offline 		I checked my Octura catalog last night and found the same prop and figured that it would be the one you need. However there is a problem with the shaft size. That prop is only for a 1/4" diameter drive shaft.
So, there is a decision to be made.
Do you cut down the shaft you have to 1/4" and go with the Octura prop or do you re-build the drive so that it goes under the boat and use the same prop you have submerged under the hull.

If you go with the Octura prop decision and leave the shaft where it is, I am concerned that it will not be in the water far enough. It must be at least 45% in the water. You also, MUST, machine the shaft down to 1/4" accurately so that it is still balanced and rotating on its center axis. Otherwise it will vibrate too much and be unusable. The prop also requires a drive dog which connects it to the shaft and a collate to hold it on the shaft. All 1/4" hardware available from Octura of course.

The problem with the second choice is that it will take some work to reposition the motor to accommodate the new drive angle and to construct the support for the drive shaft hanging under the boat. The boat then will also require twice the water depth (draft) to accommodate all that prop.

Since this is a "lets see what happens and have some fun" kind of project, I would go for the second option and reposition the prop and drive under the boat. It will work much better than it does now and not incur much additional cost to the project. It will just be more work and some more fiberglass.

What kind of drive shaft are you using? Solid shaft or flexible cable? If it is a flexible cable make sure that it is a right hand lay. Your motor turns opposite most motors types. If you use a flexible cable from one a weed whacker it will uncoil under load and that's BAD!! If you are using a straight solid shaft, there is no problem of course. Just point it down enough for the prop to clear the hull and go for it! Keep up the good work and let us know what you decide to do. Quiting is NOT an option!!!

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/6/2004 6:53 AM   
lmopar69



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Status: offline 		It has a solid shaft on it right now. I will probably try to keep it since it seems to spin freely and I think it will work. I will have to get it machined down to 1/4" though to use the Octura prop. They are sending me a catalog so I can see what all they have.

I will probably keep the shaft in the same location for now and see what it does. If it still dosnt work I will move it so it exits under the boat.

And by the way, Quitting has never been an option!!! This thing will work if I have to start over and make an entirely new boat! Of course the wife wouldnt appreciate that! "Here honey, hold this kite string...."

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/6/2004 6:04 PM   
skoda450



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From: Valentines, VA, USA
Status: offline 		Sounds good. The folks at Octura are very helpful when you order parts in making sure you are ordering parts that are compatible with one another. My only issue with them is that they do not accept any credit cards. You must mail them a check and then they will mail you your parts.

From what I can see in your pics the Octura X470R should work once you reduce the shaft to 1/4". You will also need a 1/4" drive dog and 1/4" collet. Normally I would also recommend that you ballance the prop be for you use it but since you have so much bulk in the drive system it's probably not necessary. The props as manufactured are close to being ballanced but not perfectly. When using them in speed applications ballancing is a requirement.

If the surface drive does not work well, then the same prop will also work if you refit the hull for subsurface drive and will require less draft than your original 5 1/2"er.

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/6/2004 7:46 PM   
lmopar69



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Status: offline 		Cool. After I get their catalog, and check it all out, I may need more advice from you. We'll see.

My new airplane should be here today or tomarrow, so I may just take a few days off from messin with the boat and try to fly. The down side of this is, just like everything else, I dont know how to fly!! And I didnt buy a trainer, no way. So, off to the back yard with my new flying wing I will go to crash it! Later

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/8/2004 6:57 AM   
skoda450



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From: Valentines, VA, USA
Status: offline 		TMT. (Too Many Toys) Enjoy!!

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/8/2004 8:06 AM   
lmopar69



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From: Indian Mound, TN, USA
Status: offline 		LOL You sound like my wife!!

Between the R/C Helicopter, boat, plane, car and 3 trucks, our kites, my 96 Dodge truck, my Dodge Dart Sport, my 70 Challenger, my race car, our 4-wheelers, go kart, models and die cast cars, plus 3 kids and a dog---you could say we stay busy. I think my wife just needs a hobby! Thank God she puts up with all of mine! lol

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/10/2004 4:10 PM   
skoda450



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Status: offline 		Wife, yeah. That's where I got "TMT" from! Let's see, hum... six boats, two airpalnes (neither flying currently) HER car, my two trucks, jet ski, 12' fishing boat, 24'pontoon, three antique Elgin outboards (two running) and there's no end in sight. I have passed this affliction to my sons who both have their own collection started. In fact I am converting a McCulloch 32cc for my son to use in a 80" Giles 202 for some 3D flying. So I guess we have now joined forces. Passing the RC hobby bug to my boys was one of the best things I did as a Dad.

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RE: 6' Home built Chain Saw Engine boat!!!! - 5/10/2004 6:01 PM   
lmopar69



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Status: offline 		That is awesome. I got my 2 year old boy loving it, but my 10 year old and 9 year old just dont get real excited about it yet. They have electric stadium trucks but they very rarely drive them. Im working on it. Tryin to get the wife to fly a plane too. That is not easy. She said no to a heli. Oh well. We will all just have to keep playin and have fun! And you can never have to many toys!! lol No matter what my wife says!

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RE: 6' Home built Chain Saw Engine boat!!!! - 6/13/2004 3:51 AM   
Hurrijeff


 

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From: Pompano, FL, USA
Status: offline 		Hey Imopar69,

Just had to throw my two cents in here Listen you can keep the basic system your using instead of moving the prop under the hull, you'll just have to extend the shaft out behind the back of the boat about 2 1/2 to 3 inches.
Cant tell exactly from the pic but it looks like your prop is within an inch of the transom... your boat just wont get on plane that way... Ya gotta get some bite to get out of the water. Surface piercing works great at speed but the prop needs bite to get the boat going.

I have a 54' Aeromarine Apache , and octura prop and strudder but engine (50cc Tanaka edger motor). 1/4 flex cable drive with handcrafted stainless ends. Hand made v-drive reduction (engine backwards in boat) 1 to 1.25 overdrive. Water cooled cylinder sleve, Blah Blah Blah

Keep us posted !!

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RE: 6' Home built Chain Saw Engine boat!!!! - 7/11/2007 4:20 AM   
motors4fun


 

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Status: offline 		i would try a counter gear system. It would solve your prop direction problem

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RE: 6' Home built Chain Saw Engine boat!!!! - 7/11/2007 5:27 AM   
MrMikeG


 

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Status: offline 		Cut the prop down and make a longer rudder, the rudder should be well below the level of the bottom of the prop

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RE: 6' Home built Chain Saw Engine boat!!!! - 7/11/2007 6:41 AM   
Flabum


 

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Status: offline 		ummmmm thread is over three years old....... think the project was done.

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RE: 6' Home built Chain Saw Engine boat!!!! - 7/11/2007 7:30 AM   
MrMikeG


 

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Status: offline 		Oh My, now I fell like a

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