Boat lift question

[Mikey]

Looking at a piece of property with a boat lift. 30,000 lb. max weight, so no prob there. How far apart do I set the bunks for a 31 to sit properly. Could probably figure this out myself but hate reinventing the wheel, or is that the 24 degree deep-vee.
Thanks

[CamB25]

My initial guess would be to space the bunks so that they align (approximately) with the stringers.

[Kevin]

Mikey,

I don't know the dimensions on the 31 but I can recommend a couple things based on my 28. With such deep V bottoms you may be limited to how far apart the bunks can be before the keel or V bottom will touch the aluminum lifting arms. The remedy would be to raise the height of the bunks to allow a wider spacing.

I found that with my boat if each bunk was 4-5 inches inside of the lifting strake that there is more hull flex, as the lifting strakes are directly below the stringers. You could tell by looking at the shafts where they come through the fiberglass tubes that the PSS seals installed on. Get the bunks as close to the stringer as possible to cut down on the flexing. When I put the bunks closer to the stringers (1" from the lifting strake) the shafts stayed fairly centered in the glass tubes.

I have not done so yet, but I plan on installing wood blocks on the lifting arms below the keel to assist with weight distribution and ultimately reduce flexing.

Hope this helps.

[spencer]

I think Pete Fallon told me in was 12'8"at the widest point near the bridge area,
do a search on the boat lift on the board and see what comes up
we talked about it earlier

Spencer

[spencer]

sorry misread the question , thought you were asking for the width between the posts,
Marlin has his on a lift send him a pm

[Pete Fallon]

Mikey,
Give me a couple of days and I will get the measurements from a 31 that's on a lift here in Stuart, like Kevin said the closer to the stringers the less hull flex you will have.
Pete Fallon

[Mikey]

Pete,
Thanks.
The folks at Hi Tide Lifts (who built the lift in question) suggest that the bunks ought to start out close to the outboard engine stringer for max support and adjusted from there.
Any other clues that anyone can give will be most appreciated.

[Bruce]

Your gonna have relatively high bunks then and they will be outboard of the shafts. Thats too far in my opinion.

[Kevin]

Bruce,

Is it better to have them inside the shafts?

I have a Hi Tide elevator lift. The reason I had to place bunks outside the shafts is due to the tide/depth of canal. If the bunks were placed close to keel the boat would sit much higher and it would not float at low tide. The lift arms would bottom out in the mud before there is enough water.

Another positive to how I have mine set up is the stranded steel cables do not get submerged in salt water. They would need to be submerged if I was set up the other way. I expect that the lifespan of cables vary depending on the amount of corrosion.

Most of the "big" boats I see on lifts do have the bunks very close to the keel. Some look so unstable set up that way.

[CaptPatrick]

Mikey,

Maybe of help:

http://bertram31.com/specs/index.html" onclick="window.open(this.href);return false;

http://bertram31.com/santiago/images/trailer/" onclick="window.open(this.href);return false;

[Mikey]

Patrick,
Your diagrams, as always, make the solution much easier to see, I think.
Still hoping for more pictures from those who have their stewardship on a lift.

[CaptPatrick]

Mikey,

There's no difference as to bunk placement between a lift and a trailer...

[Bruce]

Pat,
Correct me if I'm wrong but on the trailer the keel is supported, on a boat lift with a straight across beam support the keel is not supported. Thus the boat is only supported pretty far out. Plus the trailer has a dip in the center so the bunks aren't high. Can't do that with the fore and aft I beams thus the bunks have to be really high or the bunk brackets have to be high.

Almost all the boats on lifts I dealt with had the bunks inside shaft width.

I've seen a few where the owner had a custom cradle built, fastened to the fore and aft lift beams so the boat was supported very well. Much higher cost.

Now that I think about it Andre has 16" aluminum angled bunks on the os stringers. Don't know though if he has pads on the beams for the keel.

[Kevin]

[Rawleigh]

Mikey: I think I have factory cradle drawings if you need them.

[Mikey]

Kevin,
That's a clue. Nice work. How long have you had her like that? ANy issues?

Rawleigh,
Love to see those drawings. Going to Baltimore in the a.m. (up the Bay) and back first of the week.

[CaptPatrick]

Cradle Diagram http://bertram31.com/specs/B31CradleDiagram.pdf" onclick="window.open(this.href);return false;

[Russ Pagels]

I have a High tide lift and the 10" bunks are inboard of the shafts. any more out board and the hull would sit on the I beams. If I used a setup like Kevin, I would not be able to launch or recover at low tide. 10 years two boats and no problem....Russ

[Kevin]

A bit over 2 years for me and no issues that I know of. It makes boating easier that's for sure!

[mike ohlstein]

Kevin

Your lifting strakes don't extend all the way to the transom?

[Kevin]

One pair does out of three. I just noticed the other day that the 31' has four pairs. I did not notice if they all run all the way aft.

[Mikey]

Russ,
Sounds like you have what I am buying. Can you take some pix? It would clinch the deal for me.
Thanks

[Pete Fallon]

Mikey
I haven't been able to get over to look at the 31 on the lift here in Stuart, knee is real bad. The set-up that Kevin and Russ P have seems the right way to do the lift. Sorry I couldn't help you going for MRI Friday morning they drained and injected pain killers into it yesterday.
Pete Fallon

[Pete Fallon]

Spencer,
The widest point on a 31 Bertram is just forward of the house deck joint break or in line with the front of your engine box at the bulkhead . It should be 11'4" at that spot.
Pete Fallon

[Mikey]

Pete,
Stay off that knee and let'er heal.Russ sent me pix of his and the only difference is that my lift has two piles per corner. His pix tell me all I need, I hope. Going to give'r a try next week.
Thanks, Russ. This is what our sandbox is all about.
I have a peculiar problem that I want to bring to the Faithful when I get back. It's a Deusey. Not the car!

[JohnCranston]

Mikey,
I have a cradle lift that Reel Cowboy sits on. The bunks are 35" center to center from each other...which is also the measurements of the inboard stringers. The position seems perfect...fuel tank inboard of the inboard stringers, and, the engines outboard of the inboard stringers. Seems like a happy compromise...weight is distributed accordingly. The running gear is not compromised in any way.
Hope this helps.
John.

[Mikey]

John,
Thanks. That's what the pix that Russ sent me look like. I think I will start there and once she's close to out of the water I can tell whether I have it right without over stressing anything.
When she's up and happy, pix will follow.