Floating dock height

[blagrata]

I'm looking for some advice on a floating dock. I need to select some floats and am debating between 12 inch and 16 inch floats. Per my calculations (with weight of dock and height of lumber) the 12 inch floats will put the surface of the dock about 14" to 17" above the waterline with no one on the dock. The 16 inch floats will make it about 18" to 21". The flotation of the dock will be sufficient with either float (and will occupy most of the sq ft of the dock). I have read that the less height.. equals more stability.. and perhaps easier access to a ski boat. The dock won't really be used for hanging out on... so I wouldn't expect it to ever have more that 3-4 people's weight. I have a 2018 Prostar that will be sitting next to the dock (but not living there). The dock is on a small semiprivate lake with minimal wave action. My thought is to go with the 12 inch floats. Any thoughts?... or am I overthinking this?

 

Thanks

[lpskier]

Contact the Dock Doctors https://thedockdoctors.com in Ferrisburgh, Vermont. They are a huge dock building company in New England, and they sell dock building materials like floats and hardware. Ask for sales and then pick his/her mind. You won’t regret the call.

[AkBob]

Everyone ha s an idea I’m sure. I chose 12” floats for my 16x30 dock with a 6x20 connector to shore. My neighbors chose the 16” floats and I think their docks are nervous compared to mine, plus they float too high imo. My dock(s) keep all the wood dry even with a very large live load. I used the floats and hardware sold by these folks...http://scottcomarine.com

 

They can help with the design and I followed their hardware and float recommendations. My dock is currently about 15 yrs old and still rock solid. Good luck on your project!!

 

[Jordan]

I have 16 inches of freeboard, and that puts it at an awkward height where part of my rub rail (1993 Prostar) is above the top edge of the dock and the rest is below. I think 18 inches of free board would be desirable.

If you put a couple of verticle boards approximately 2.5-3 feet long on the side of the dock, then the free board of the dock doesn't matter.

[BraceMaker]

Vertical PVC and particularly 2-3 close together so you can tie the pylon in the middle is perfect as actual dock height vs boat rubrail is always good. Spaced off the dock 4" is about right so it leaves room that you want get pinched by the hull.

 

You want dock floats burdened about 40% in its static condition. If under burdened it will be Herky jerky and over burdened will be too little free and dock will be wet.

 

You want to use post and auger type anchorage at the far end if possible with slip rings to ride up and down as loaded.

 

When we fixed docks at the marina we went from 55 gallon drums to rectangular tubs the 55 gallon drums were somewhat water filled and we replaced with plastic tubs biggest lesson is build torsionally stiff so it doesn't torque when you walk and get the drums at the edges.

 

 

[blagrata]

Thanks for your advice everyone. I think I'll go with the 12 inch floats. They will be about 25% loaded with just the dock. I'm going to spread them under most of the dock to keep it stable. I am going to put the vertical bumpers in as you suggest @Jordan . @AkBob what makes you think your neighbor's dock is nervous? Did you mean something like unstable compared to yours? Thanks for your advice.

[BraceMaker]

See about eliminating some drums if only 25% capacity. OR install some of them higher to let some sink in more. Sort of like using 4 corners to take most of the float with 2x6 blocking above then put drums in the center which dont get as wetted unless heavily loaded.

[Jordan]

Vertical bumpers

 

 

[AkBob]

@blagrata. Docks that have too much floatation feel skittish or nervous to me. You can overcome that by heavy anchors and a large footprint. Less flotation allows the dock to settle in the water a bit and makes it feel less “ herky jerky” as was said earlier. I strongly recommend you use proper galvanized hardware with thru bolts at every juncture. Try not to reinvent the wheel in your design and lean on the pros to help get your material list together. Also, depending on where you live, building on the ice is a great way to build a big heavy dock. Lastly, check out dockproducts.com for vertical bumpers to keep the boat scuff free. Good luck on your project