Boat lift - pontoon support

[Pirateover50]

I am planning to modify my boat lift for a pontoon. I purchased an Avalon 22' tri-toon and will take delivery the end of the month. My concern is with supporting the pontoons. I plan to have the pontoons resting on flat bunks, but the bunks wont' be as long as the pontoons. I may have a 4'-5' starboard overhang and am a little worried about damaging the pontoons. I'm not sure how strong, structurally, the pontoons are. I have seen pontoon boats resting on small supports on each end of the pontoon, I assume the strongest points of the pontoons, but that part would be in the overhang. Any opinions?

Thanks!

[dockholiday]

I am a big fan of supporting the entire length of the toon. If for some reason you can't get longer bunks, think the weakest point would be the welds that hold the sections together. Always heard that in steel the welds were actually stronger than the steel, but not sure if that holds true with aluminum since I popped off the end cap on one of my logs last year. It separated perfectly at the weld, like popping a hub cap. So if full support is not possible, I would support as much as I could on either side of the seams.

doc

[lakerunner]

Most toon lifts here use a flat deck on top of the lift. They have treated 2x4's about a foot apart all the way across the lift and the full length . It gives them room to do covers, work on or under deck and no problem when they launch or load.

[BassFrequency]

my lift uses a set of 18' bunks to support the toon.

but not sure if that holds true with aluminum since I popped off the end cap on one of my logs last year. It separated perfectly at the weld

that sounds more like poor penetration of a weld

[wed]

I had a lift built last fall....the contractor insisted on full length suport for the pontoons. Basically they copied my trailer bunks, brought the welder out and he made a drawing from my trailer. He figured that if it would stand the beating of trailering it should work for a lift. The finished product provides suport a little less than the full length of my toon.

The only thing about a flat lift is that all the weight is concentrated on a single line on the pontoon vs two contact lines if it is built like trailer bunks. Two supports cuts the contact load in half. Since a lot of people have flat lifts not be much of an issue. Just somethng to think about.

[smltooner]

My lift supports hold up the deck, not the pontoons.

[Oldboater]

My lift uses 2 each 3" X 8" pieces of treated wood that are at least 18 feet long. There is a rib along the bottom of the pontoons, this sits on the boards. My pontoons overhang the boards by about 4 feet.

Several Pontoons at my building use two 3" X 8" boards which support the outside of the pontoons (one board on the outside of each pontoon). They just laid the boards used for V-Bottom boats over as far as they would go. Two dock consultants did not think much of these modifications.

One guy bolted boards on the two cross support I-Beams as well as laid over the other two boards.

[jimrs]

I used 4ea 2X8's Two on each side and bolted them to the frame. They are 16 feet long and my boat is 22 feet long so that leave me with 6 feet not being supported by the lift. Most of the 6 foot is in the front with a few inches in the back of the toon hanging alone and forgotten. I have experienced no problems with the toons no flat spots or bends nothing. The guy that built mine built my neighbors and he has a 22 foot also the same setup. Again I think we try and make problems when we are not able to use our toons just so we can plan and solve problems in our minds that are not actually there.

[WaltF]

Supporting the length of the toon just makes sense to me.
Hey Doc, if the end popped off, then it was a CRAP weld job. Regardless of metal type, A REAL weld job would have MELTED the two metals together and it would never pop like that...

[HandymanHerb]

Aluminum doesn't melt together, you butter it together, now when making missiles we would mill the part so there would be a big v to fill, then you could mill the weld lines away.

Now with steel you can flat weld and grind the weld line away , you do that on aluminum it will fall apart unless you v the joints.

[dockholiday]

May have been a bad weld job. I would have thought there should have been some tearing involved, but just came off like a bottle cap. Hope the polished toons didn't have anything to do with it. I am sure a certain amount was removed during the polishing. The adjuster didn't even mention it. Still need a gps to locate the standing timber. Heck after that feel like I need sonar to. All the timber left is now at or just below water level.

doc