Glen-L.com

I have the engine on the mockup and it's sitting at 15 degrees with an inch under the flywheel and sump so I have a bit to play with.
I can't seem to find the center of gravity on the plans so I am going with 82" to 84" I hope this is not for the 16 1/2 foot one, to get the center of the engine and gearbox I am just going by the way it hangs on the hoist, tomorrow I will make a mock of a 13" prop and put it on a length of 1" pipe and do some more measuring to find the best place to put it so is there anything I should be looking out for, is 15 degrees too much. Any thoughts would be a great help.
Thanks.

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Malahini, SEAN-NÓS http://www.youtube.com/watch?v=Qd6vkPjEy4U
http://www.youtube.com/watch?v=8uDVzcVpdhc
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A few more.

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Malahini, SEAN-NÓS http://www.youtube.com/watch?v=Qd6vkPjEy4U
http://www.youtube.com/watch?v=8uDVzcVpdhc
crackerbox build http://s753.photobucket.com/albums/xx17 ... =slideshow

on the plans I have for the tornado and rampage they mention the center of gravity for the motor somewhere on the plans. For example the CG of the motor in the tornado is 9" forward of frame 1. For the Rampage it says its aproximately mid way between frame 1 and 2. I'd recheck the plans as I would think its on there somewhre (possibly just a little side note somewhere).

Anyway JMHO, but the motor looks steep to me. If you could lower the mounts at the front end of the motor I think it would be better. Of course I could be wrong about that. I just dont like seeing motors at steep angles as you tend to have windage issues with them.

This is 2 degrees less than it was in the ski boat so it should be able to run ok, I will put the shaft and mock prop on it and see how low I can go with it, I may have to get a new strut if I go much lower, I'll go through the plans again with a magnifying glass.

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Malahini, SEAN-NÓS http://www.youtube.com/watch?v=Qd6vkPjEy4U
http://www.youtube.com/watch?v=8uDVzcVpdhc
crackerbox build http://s753.photobucket.com/albums/xx17 ... =slideshow

The mental gymnastics we have to go thru sometimes

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Dave

My Riviera build - the Midnight Cry Project

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Few things in the world measure up to the thrill and satisfaction of boating in a boat that you built.

WOW that motor must have been really steep in the ski boat. It must have beat its oil into a nice frothy foam everytime it was used. Latte anyone?

Fergal, were you able to find the C/G for the motor on the plans?

No I still can't find it unless I'm missing a page or have sawdust on the brain anyone know where it is.
It does say on the plans to use a strut an with an angle of 14-16 so I should be ok with that.

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Malahini, SEAN-NÓS http://www.youtube.com/watch?v=Qd6vkPjEy4U
http://www.youtube.com/watch?v=8uDVzcVpdhc
crackerbox build http://s753.photobucket.com/albums/xx17 ... =slideshow

well maybe its not there. Now I can say that in the booklets I have about building the tornado and Rampage in the motor section they make referece to a specific page in the plans that detail the motor. That is the page I found the info on. If your booklet does have this referfence and you've looked at the page without finding it then can only assume your plans dont show that detail.

Get yourself a 9 or 10 degree strut if you want that boat to perform at all. You'll need to run an outboard of the transom rudder. With your current set up you'll have a poor performing boat and a motor skying out of the top of the hull. I also think you'll have oiling issues in the pan with that steep angle.

My .02

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As Conan the Barbarian says, " It's not how hard you can hit, it's how hard you can get hit and remain standing".

I don't think I can get down to 9-10 with the flywheel it will be 12-13 at a push, in the 16 foot ski boat it was factory fitted at 17 degrees and it ran fine. I'll keep working away at it and see what happens, keep the thoughts coming " I feel the need the need for speed"

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Malahini, SEAN-NÓS http://www.youtube.com/watch?v=Qd6vkPjEy4U
http://www.youtube.com/watch?v=8uDVzcVpdhc
crackerbox build http://s753.photobucket.com/albums/xx17 ... =slideshow

Fergal,

I just looked over the plan set provided by Glen-L. There is no specific CG stated. When I scaled the print it roughly shows the center of the SBC at 5" forward of frame 3 using the 14 degree strut. Using anything other than that strut that they call for will put the motor approx 10" to 14" too far forward using the 71C trans in the 15 foot version. I am going with the ZF Herth trans with the down angle output to help keep the motor angle lower. I will have to go with a larger pitch prop to get the speed back (25% output reduction). Even with the curved transom you will still be bow heavy (motor too far forward). A lower angle strut is better as lakeracer stated but at this point I don't see where you have that option. As I stated a few years back, the mahogany Cbox that Neil in Canada built with a trans had to be nose heavy. In every video shot of that boat it always would porpose as the speed increased. That may be why he sold the boat after a short time.
It won awards for its beauty but he never talked about the performance and the trim.

Jim

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Starflite restoration:
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Crackerbox build:
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Ferg,

I measured the center of my motor from the transom and it's 76". My boat is 15' long. I am using a outboard rudder to keep the shaft angle as shallow as possible. The shaft angle is 10.5 degrees. My motor is bobtailed, another words backwards. I also have direct drive which takes getting used to, but it's not all that bad.

I just tuned into this thread so I don't know if you are using a outboard rudder or not. I would recommend keeping your motor-trans combo as far aft as possible. A outboard rudder will help with this. In my videos you can see how my boat rides compared to Neil's.

I have skied behind many ski boats (Mastercrafts and Ski Nautiques) that have had a 15 degree shaft angles and seem to work fine. There is a lot of great info on this forum but there are also a few know-it-alls on here who seem to blow a lot of hot air. I think Novass said my bobtail motor wouldn't work, but it seems to work OK.

Moral of my story, keep your motor as far back as possible and take what you hear here as merely suggested opinions, not the way it needs to be. It's your boat and I doubt your going to race competitively.

Keep up the good work.

Fran

WTH!!!??? Fergal, I thought you were in Ireland. I see a red pickup truck next to the ski boat. That looks like middle amurca to me

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2011 MALAHINI - KICKED IN THE HEAD

I wake up with a 16ft woody every morning
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Where did I say this? I quickly went though the threads you posted in and the only negative comment I can find that I said about your build is that "I'd be concerned that a motor installed this way would have aeration/windage issues". Maybe I missed where I said it wouldn't work.

Will it work? Of course. Will it have aeration/windage issues due to the crank always being submerged in oil at the front end of the motor? Very likely unless your running several quarts low in oil capicity. Even if the oil pan has a scaper and windage tray built into it, to control windage, I dont believe that would negate that part of the crank must be submerged at all times in oil. Aeration at a min would be happening if the crank is partially submerged. I don't believe I ever said it wouldnt work. If I did say that I'll appoligize as it obviously works.