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Boat Lift Center of Gravity ....
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I am trying to make some adjustments on my lift before we build the roof system this weekend ... Rear beam is about midship of motors ....Front Beam is about 18" ahead of Windshield. It seems the rear is doing more work than the front . I called Formual and they tell me center of Gravity is 8'5" from point where Transom meets the Keel ....Any feed back on where that front beam should be ? Keep in Mind I will not move the bunks but rather move the beam under the bunks to the rear ....I know the rear is going to always bare more weight but I think I can get it closer ....
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Re: Boat Lift Center of Gravity ....
Mike, Post some more details about the boat and I can tell exactly how much weight is where.
* what does boat weigh * location of the rear beam * distance between beams * length of boat |
Re: Boat Lift Center of Gravity ....
CG is easy to determine. When had a tool to measure the tension on the cables but it's pretty easy to get close just by hand. Our lifts were always double cable, meaning the cable runs from the top to a pully on the beam and back to the top. You could squeeze the two parts together, feeling the tension. Just make the front and the back the same. CG of the boat should be the center of the lift. There is probably 5' from the rear beam to the transom and probably 25' of the bow hanging off my boat.
So it doesn't matter if the beams are 10' apart or 20' apart, the CG of the boat must be in the middle of the two beams. |
Re: Boat Lift Center of Gravity ....
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When I did my boat lift I called Hustler and they told be the back of the front seat was center of My 388 Hustler. Wrong!!
I back my in and had to use the exesting poles. my front cables are alot tighter than the rear.Its as far back as I can go.I also made it where the fron is higher than the rear , they look funney nose down. I would do as mr_velocity sound s like a good idear. Rob :drink: |
Re: Boat Lift Center of Gravity ....
311 Formula weighs about 7800 dry ...so I would say 9000 LB
The rear beam is 18" from the Transom The front Beam is 14'6" from rear beam or 16' from transom Boat is 31'1" Transom to bow ... 33'1" with platform .... Formula sez CG is 8'5" from Transom ... Using velocity's "Formula" :rolleyes: from the CG (101") the rear beam is 83" (18" from Transom) the front beam is 91" from CG .... So I need to move front beam rearward 8" ...making each beam 83 inches from CG .. Rear beam would be 18" (existing location..not moved) from transom then 83" to CG ......Then 83" to front beam ( moved 8" to rear) ..... So i am only 8" off ??? Only question in my mind is where should the rear beam be ? I just picked 18" when we set it up .. about mid point of Motors ..... Also the bunks are 20' ...the extend about 4" past transom ..all this moving would not affect the bunks ...Also the front 5' of bunks curve up following the hull ....I tried to make it the same as Eagle trailer Bunks .....
Originally Posted by mneal
Mike, Post some more details about the boat and I can tell exactly how much weight is where.
* what does boat weigh * location of the rear beam * distance between beams * length of boat |
Re: Boat Lift Center of Gravity ....
I work for Wiggins Lift, we build the marina forklifts for dry stack operations, We have been trying to deal with the OEM's for years on getting thier CG info straight and none of them get it right EVER.
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Re: Boat Lift Center of Gravity ....
Bump
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Re: Boat Lift Center of Gravity ....
Placing the rear beams really depends on how massive your bunks are. Since you are using a "boat house" lift you can place the beams anywhere. So I would move the rear beam as close to the transom as you can. The #1 concern when setting up a lift is to suppor the transom as much as possible to avoid hooking the boat. 18" from the transom is the best I have ever seen.
The last 8" probably isn't that big of a deal. |
Re: Boat Lift Center of Gravity ....
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I might slide front beam back about 12" .... I still think that because rear beam is 18" from edge of Transom that it bares more than 1/2 the load ... cpl of pics .....
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Re: Boat Lift Center of Gravity ....
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cpl more
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Re: Boat Lift Center of Gravity ....
Why the wood on top of the beams? Don't worry the bunks aren't going anywhere. I've lifted 60,000# boats with the same system for bunks. They will not move. If the wood is treated then you will eat the galvanizing off the beam very quickly. Also it will take longer to dry increasing the corrosion problems. If it were mine I would take all the wood off the lift except for the bunks. Even them I would but 2 layers of tar paper under the treated bunks to eliminate any corrosion problems.
You can tell by the tension on the cables if you have the cg correct. Doesn't matter where the beams are if the cg is in the center of the lift then both beams carry the same load. However, with the beams farther apart like you have them you will reduce shock load on the cables. My beams, not by my choice, are closer together on my lift. So I have a lot of bow hanging over the front beam, 41' boat. You can feel the cables stretch and load when you walk to the bow of the boat. Your setup should just about eliminate that problem. CG is CG, doesn't matter where the beams are. With your setup I would be more concerned about single part cables, they are the going to be the point of failure. This is the first 9000# lift I have seen with a single part. Most are 2 part similar to strip's above. |
Re: Boat Lift Center of Gravity ....
Originally Posted by mr_velocity
Why the wood on top of the beams? Don't worry the bunks aren't going anywhere. I've lifted 60,000# boats with the same system for bunks. They will not move. If the wood is treated then you will eat the galvanizing off the beam very quickly. Also it will take longer to dry increasing the corrosion problems. If it were mine I would take all the wood off the lift except for the bunks. Even them I would but 2 layers of tar paper under the treated bunks to eliminate any corrosion problems.
You can tell by the tension on the cables if you have the cg correct. Doesn't matter where the beams are if the cg is in the center of the lift then both beams carry the same load. However, with the beams farther apart like you have them you will reduce shock load on the cables. My beams, not by my choice, are closer together on my lift. So I have a lot of bow hanging over the front beam, 41' boat. You can feel the cables stretch and load when you walk to the bow of the boat. Your setup should just about eliminate that problem. CG is CG, doesn't matter where the beams are. With your setup I would be more concerned about single part cables, they are the going to be the point of failure. This is the first 9000# lift I have seen with a single part. Most are 2 part similar to strip's above. I was wondering the same thing .I bet with the wood it floats :eek: I added 2x12x16 walkways beside the boat. My slip is 14 foot wide and it was hard to reach the boat to do anything to it .I had to add weight to the lift ti get it to sink.I also cut the bunks to match the steps in the bottom of the boat . Really would like the Myco cradle but. this is close . Rob |
Re: Boat Lift Center of Gravity ....
Originally Posted by Strip Poker 388
I was wondering the same thing .I bet with the wood it floats :eek: I added 2x12x16 walkways beside the boat. My slip is 14 foot wide and it was hard to reach the boat to do anything to it .I had to add weight to the lift ti get it to sink.I also cut the bunks to match the steps in the bottom of the boat . Really would like the Myco cradle but. this is close .
Rob |
Re: Boat Lift Center of Gravity ....
No problem Floating ...beams are Steel ...why we put the wood under the bunks ? I have no Clue ... :rolleyes: I think maybe to keep the Keel from Banging the steel ..... we are going to move the front beam 12" towards the rear .... see how it does ...I can always move it back ...been yankin and pullin on those cables all day ....cant really tell much difference . Prob a good idea to remove the wood ....
Single part cables ? you refering to the single cable coming down ? There are two ...one wraped around the pipe down thru a pulley and then back up to a deadman ... There is a single SS cable from the Pulley down to the Beam ... I think The lift is rated 14000 lbs ... Mark Lunmar in louisiana designed the Lift .... http://www.lunmar.com/ |
Re: Boat Lift Center of Gravity ....
Originally Posted by mr_velocity
His lift looks to be galv steel, probably not a problem like our alum lifts. With my massive bunks I have 200# of lead blocks bolted to it, that in addition to the alum catwalk I have. Your catwalks are wood? With the alum I was able to make the walk 20'.
I might need to ck with ya on some cats. Rob |
Re: Boat Lift Center of Gravity ....
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Argh matey walk the plank.
It has some spring on the end so you can dive off of it too :drink: I put the concrete in the pvc. |
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