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Boat Lift Design and Safety
|Author||Topic: Boat Lift Design and Safety|
posted 10-27-2009 07:56 AM ET (US)
I just bought a new house which has a single pile lift made by Hi-Tide rated at 5,000lb. I have a 1995 21 Outrage with an F250. This weight comes in under 5,000lb. However, something just does not look right to me about a boat that big hanging off of 2 "L" brackets and one piling.
Do any of you use a 5000lb single pile lift for a similar sized whaler?
The home is on a "tidal creek" but really its close to deep water (got the 21 to the dock at mid-tide Sunday with plenty of water to spare).
I had intended to keep my 15 Sport on the lift until I realized how much water the creek had and that the lift was actually rated for 5000lb.
This is the marketing picture for the lift:
posted 10-27-2009 08:07 AM ET (US)
Since you asked for thoughts, I agree with you. If that were my beautiful Outrage, I would want something more substantial supporting it. Without knowing how conservative the manufacturer rated his lift, I would seek a local professional for advice. Consider that the actual capacity of the lift will deteriorate over time due to use and environmental factors. My own rule of thumb is that I would want to have at least a 2:1 safety factor no matter what the manufacturer states so I could sleep at night.
posted 10-27-2009 08:57 AM ET (US)
I definitely would want something more substantial, but if this one is ok, I dont want to spend 15k on a boat lift.
Here are a few more pictures of my actual set up:
posted 10-27-2009 09:25 AM ET (US)
What does the manufacture of the lift say? My buddy has a 10,000lb lift but its really rated for 20% more.
posted 10-27-2009 09:36 AM ET (US)
Yes you can use that lift, I probably would not. A new/used lift is not $15k. Surf the net and find a nice used one, people are always upgrading(like you). I bought an alum 4 post lift about 6 years old with a 10k capacity for $1100 and it cost about another $1400 to install with electricity and everything. A new 10k lift is about $4-6k so say $7500 max installed. Yes they are rated for more than stated, rain water, etc.
posted 10-27-2009 11:23 AM ET (US)
My neighbor had a 17' Key West on a single pile lift. One day the boat self-launched, made a mess of the lift as well. Owner wasn't sure what happened. My thought is if the boat isn't centered bow-to-stern on the lift, the weight imbalance twists the piling. Also, rainwater draining to the bow would exacerbate the situation. Bob
posted 10-27-2009 03:41 PM ET (US)
I cant get a permit for a 4 pile lift unfortunately, I dont think. Although the guy up the creek in this pics has a Whaler with a 4 pile lift, and he is on skinner water than me.
Just wanted to know if any of you use a single pile lift.
posted 10-27-2009 03:51 PM ET (US)
Use the lift that you have. It is unlikely that it will catastrophically fail all at once. If it is insufficient for you boat, it will likely begin to labor slowly over time. Even if there was a catastrophic failure, what is the worst that could happen on a shallow creek like that. Not like it's going to sink or anything.
posted 10-27-2009 03:55 PM ET (US)
If it were me - I'd try that setup for a while, assuming it's not too sketchy of an install.
Tell ya what - I'll trade houses with ya. That lift will hold my Montauk 17 just fine. You're living my dream... just a few more years I hope to be in that same area.
posted 10-27-2009 04:18 PM ET (US)
I think it would keep me awake at night. Even in their marketing photo, the piling looks to be bending under stress. Pilings bend a little. then they snap.
posted 10-27-2009 04:47 PM ET (US)
I would not trust one pole for that size boat, If you ever had a heavy rain it would pull the pole or bend the frame in nothing flat. Also Dave is correct the pole will go bad with time especially in salt water. You need to have another pole set in and redo the lift for two poles. Or down size your Whaler...Good luck to you
posted 10-27-2009 05:30 PM ET (US)
From an engineerimg viewpoint, I would be hesitamt to use the lift - unless the lift and installation are guaranteed agaimst failure with your load.
That is, the single pipe pole is loaded as a cantilever - and with a 5000 lb boat supported at about 5 feet from the pole gives a significant cantilever load (about 25,000 ft lbs). That bending moment has to be restrained by the mud - which is very strong. And as I recall, the water table in Florida is something like 5 - 10 feet.
A much better concept would be a two or four pole lift - where there would not be the bendimng momemt concern. --- Jerry/Idaho
posted 10-27-2009 06:44 PM ET (US)
Main concern I would have is the wood pole it's attached to. Wood rots, even treated wood. It might rot slower, but still rot.
Any way to replace the wood pole with one of reinforced concrete, then attach to that?
posted 10-27-2009 08:23 PM ET (US)
As a civil/structural engineer I would not disregard the single lift system without further analysis.
I have to assume (ass out of u and me!) that the device was designed for the stated load and then some, I would guess at least 1.5:1 prior to being marketed and sold. This assumption is based on the device being installed within the manufactures' guidelines/common engineering practices.
That being said why not hire a competent person to perform a basic analysis of the system, both now and periodically (every 2 years?). I would imagine this might take a few hours and could potentially save thousands in a new/re-install of another system.
posted 10-27-2009 08:59 PM ET (US)
How about this
No piles, canopy option, solar powered.
Thet`re made in Seattle area and a local dealer here (Ontario,Cda) is selling them and I`ve seen them operate.
posted 10-27-2009 09:21 PM ET (US)
The sky isn't falling and neither will your boat. These lifts are fine. Modern pilings with copper sulfate treatment last 20 years in fla. Plenty of margins.
posted 10-27-2009 09:32 PM ET (US)
The great thing about this forum is most of the posts are actually helpful (as opposed to most where everyone has an opinion. My high school baseball coach told me opinions were like something else cause everyone had one and they all stunk).
Some things which are not practical:
- getting the South Carolina Department of Health and Environmental Control to allow a 2 pile, 4 pile, or concrete lift
That being said, thanks a lot for those who were helpful. My brother is actually a PE and used to build bridges. I will have him check it out for me.
posted 10-27-2009 09:37 PM ET (US)
Sunstream lifts are very popular here in Seattle. I live on an island surrounded by a freshwater lake and most people have the Sunstream SunLift. I haven't heard any complaints about them, but a friend lost a boat a few winters ago during a storm. He had not secured his boat to a dock, and with large seas on the lake his boat was taken right of the lift. It went on to hit a neighbors boat that was not on a lift and sunk it. Regardless of which boat lift type you go with make sure your boat is secured in case the lift fails or the boat is swept off of it.
posted 10-27-2009 09:37 PM ET (US)
Also not practical:
purchasing a floating lift or boat dock.
That being said, since I got water and power, plan to buy me a beater house boat, a window unit A/C, and run cable TV down the dock. Can use the 15 Sport as a tug.
posted 10-28-2009 01:28 AM ET (US)
Congrats on new home man, looks like a boaters heaven.
I would say 5k rated lift is not enough. You need at least 25% head room. I cant imagine a similar setup with 4k rating would cost that much more. Geez, I have hand held chain come alongs rated 4 tons. Single boom davits are similar, stronger. 12v Warn winches are rated 8k on a dead pull.
Im sure your Bro will vouch piles in good condition can hold up the world vertically. Rigging aside....
Go for it.
posted 10-28-2009 10:00 AM ET (US)
Hard for me to tell from the photo but does the metal piling go all the way into the bottom (seabed) and only uses the wood piling to stabilize the lift? I would give that lift setup a try,though I think you should stay at around 70% of lift capcity to allow for rain etc.
posted 10-28-2009 12:37 PM ET (US)
Structurally a single piling is interesting, mainly because of the huge cantilever ~25,000 ft-lbs. Yes a healthy piling can handle this, and it looks like yours has the diameter to do so.
However the devil is in the details. What is not shown in your pictures is how the lift bracketing is attached to the piling. There a bracket at the top of the piling (~10' from the sea floor). But what about the bottom, does it attach to the piling or is there a large foot that is on the sea-floor.
Also it looks like the piling is independent of the dock. Which is good and bad: bad because it lacks additional stiffness from the dock, good because if something fails the dock won't go with it.
Also look at the mode of failure of this system. What components will fail. Assuming the lift components (frame, winch, etc) are more than capable with 5,000 lbs. However, the sea floor (soil) and piling may not be. The piling may end up tipping/leaning over, because of weak soil. This will happen slowly, and you can easily react to the problem with no harm to the boat. However a catastrophic failure of the piling at the sea floor will dump the boat. Can you set something up so that if it does happen, the boat will float, and not be damaged.
What you can do to the piling is stiffen it by sliding a 10' or 12' tube over the top. What I have done with a healthy piling is slide a 5/8" think 10" ID steel tube, and then filled the remain void with an epoxy compound. --- This can be done for ~$800.
posted 10-28-2009 01:57 PM ET (US)
I just reread several postings - and noticed that I slipped a cog in my previous post - left out the word NOT - and the statement - "restrained by the mud - which is very strong." should read - restrained by the mud - which is not very strong." And I suspect that everyone caught that one. ----- Jerry/Idaho
posted 10-30-2009 12:47 PM ET (US)
I have a 130 Sport on a Tide Tamer Swinger skiff lift which has an option to accomodate a small boat up to 6' wide and 1,500 lbs.. There is a Boat Hoist USA motor and gear box attached to a L arm cradle that holds the boat. The motor is attached to a worm gear set and a spool that spools a cable on and off to raise and lower the boat. I grease the gears every 6 months and the lift is 3 years old. I probably have raised and lowered the boat 150 times over those 3 years.
Earlier this year the bronze worm gear gave out while I was raising the boat and the L arm cradle and mast dropped straight down. The boat dropped into the water and the cradle continued down until it hit a stop peg at the top of the mast.
Luckly, I was not in the boat at the time since I usually raise and lower the boat while safely standing on the dock. The boat was not damaged, it simply bobbed a couple of times and that was it. The repair of the lift was another story. Ended up having a machine shop make parts for the gearbox to complete the repair since no one I could find would sell anything but the complete motor and gearbox assembly.
If you decide to use this lift, I recommend you inspect the gears and make sure they are lubricated on a regular basis and never raise the boat completely out of the water if you or anyone else is in it.
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