Dock question

mogulmamna · 07-20-2017, 07:11 AM

Hi. I'm new to this forum and have a question about dock size and strength. I just purchased a 21' Cobalt (3850 lbs). We have an aluminum frame with wood planks dock that is 6'x30'. It's a seasonal crank up style dock. We are located in Moultonborough bay. While we plan to get a mooring, I am wondering if it will be secure at my dock for the time being. It could be several weeks before the mooring is in place.

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codeman671 · 07-20-2017, 09:22 AM

If it is one of the watermark style crank ups that is more than sufficient. We are staying on six mile this week, with long exposure and have a bigger boat on a crank up dock with pipes instead of posts. No concerns.

mogulmamna · 07-20-2017, 01:14 PM

Thank you. Dock is actually 4' wide,not 6' but hopefully still strong enough.

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LIforrelaxin · 07-20-2017, 05:21 PM

Do you know who built the Articulating Dock?

As stated by Codeman, a watermark dock would be more then strong enough, and so would one done by Center Harbor Dock and Pier. If you know who built it go to them directly. What I would suggest if the boat is going to sit at the dock for a while is to look into Mooring Whips, they help relieve stress on the dock and the boat. You may even find that with the whips you don't need to constantly put the boat out on the mooring....

I myself have a wooden dock with a 18' boat that weighs in at around 2800. With the whips, I leave the boat at the dock all the time. I am only considering a mooring in the next couple of years, because I could extend my season, do to water depth at my dock in the fall.

A neighbor has a 28' cruiser that he leaves on the dock with whips as well, and his boat is probably in the 7K-8K category....

Dave R · 07-21-2017, 06:30 AM

If you doubt the robustness of the dock, it is very easy and cheap to dramatically strengthen it with a pair of cables connected to the corner posts on the diagonal directly under the deck framing and tightened up with turn buckles. 1/4" is plenty strong enough. They can't be loose, but they don't need to be guitar string tight. That said, an extra set of diagonal cables between the deep end posts and some posts near the middle would probably be a good idea considering how skinny and long the dock is. Diagonal leg bracing under water is always a good idea too.

Dave M · 07-25-2017, 10:59 AM

If it has galv pipes with foot bases instead of 4X6 post, that's a trait of Raise-A-Dock, another good dock company. I have one built by them. Another thing to check if the dock has cross pieces under the deck. It stiffens the dock. I have two of them since my dock is 33'X6'. I have a 20' boat tied directly to dock, nothing moves.

Dave M

DickR · 07-25-2017, 01:36 PM

My dock also is 6x30, aluminum frame crankup. The header bar was bolted to a huge pile of boulders at the shore end and the frame hung from it before ice-out a couple of years ago. The crew (Center Harbor Dock & Pier) delivered it by truck and trailer over the ice. They couldn't install the 4x6 legs because of the ice, so the frame was cranked up just a bit to await ice-out. In that position, I crawled out over the frame to the end, expecting some teetering. Boy, that frame barely moved at all. It's quite torsionally rigid.

I do have a pair of 8-ft whips for the boat, more for protection of the boat. I had the welder install a pair of mounting brackets for the whip bases, which bolt through the deck directly to the brackets. On summer weekends, when the boat wakes are unending, the boat pitches up and down vigorously, pulling on the whips, but the dock itself doesn't budge.

Bayview Girl · 06-26-2018, 12:35 AM

Quote:

Originally Posted by DickR

My dock also is 6x30, aluminum frame crankup. The header bar was bolted to a huge pile of boulders at the shore end and the frame hung from it before ice-out a couple of years ago. The crew (Center Harbor Dock & Pier) delivered it by truck and trailer over the ice. They couldn't install the 4x6 legs because of the ice, so the frame was cranked up just a bit to await ice-out. In that position, I crawled out over the frame to the end, expecting some teetering. Boy, that frame barely moved at all. It's quite torsionally rigid.

I do have a pair of 8-ft whips for the boat, more for protection of the boat. I had the welder install a pair of mounting brackets for the whip bases, which bolt through the deck directly to the brackets. On summer weekends, when the boat wakes are unending, the boat pitches up and down vigorously, pulling on the whips, but the dock itself doesn't budge.

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Kayla · 06-26-2018, 04:05 PM

Quote:

Originally Posted by DickR

My dock also is 6x30, aluminum frame crankup. The header bar was bolted to a huge pile of boulders at the shore end and the frame hung from it before ice-out a couple of years ago. The crew (Center Harbor Dock & Pier) delivered it by truck and trailer over the ice. They couldn't install the 4x6 legs because of the ice, so the frame was cranked up just a bit to await ice-out. In that position, I crawled out over the frame to the end, expecting some teetering. Boy, that frame barely moved at all. It's quite torsionally rigid.

I do have a pair of 8-ft whips for the boat, more for protection of the boat. I had the welder install a pair of mounting brackets for the whip bases, which bolt through the deck directly to the brackets. On summer weekends, when the boat wakes are unending, the boat pitches up and down vigorously, pulling on the whips, but the dock itself doesn't budge.

Sent from my iPhone using Winnipesaukee Forum mobile app

07-20-2017, 07:11 AM	#1
mogulmamna Junior Member Join Date: Jul 2017 Posts: 4 Thanks: 3 Thanked 0 Times in 0 Posts	Dock question Hi. I'm new to this forum and have a question about dock size and strength. I just purchased a 21' Cobalt (3850 lbs). We have an aluminum frame with wood planks dock that is 6'x30'. It's a seasonal crank up style dock. We are located in Moultonborough bay. While we plan to get a mooring, I am wondering if it will be secure at my dock for the time being. It could be several weeks before the mooring is in place. Sent from my iPhone using Winnipesaukee Forum mobile app

07-20-2017, 01:14 PM	#3
mogulmamna Junior Member Join Date: Jul 2017 Posts: 4 Thanks: 3 Thanked 0 Times in 0 Posts	Dock question Thank you. Dock is actually 4' wide,not 6' but hopefully still strong enough. Sent from my iPhone using Winnipesaukee Forum mobile app

07-20-2017, 05:21 PM	#4
LIforrelaxin Senior Member Join Date: May 2006 Location: Texas, Lake Ray Hubbard and NH, Long Island Winnipesaukee Posts: 2,871 Thanks: 1,037 Thanked 892 Times in 524 Posts	Do you know who built the Articulating Dock? As stated by Codeman, a watermark dock would be more then strong enough, and so would one done by Center Harbor Dock and Pier. If you know who built it go to them directly. What I would suggest if the boat is going to sit at the dock for a while is to look into Mooring Whips, they help relieve stress on the dock and the boat. You may even find that with the whips you don't need to constantly put the boat out on the mooring.... I myself have a wooden dock with a 18' boat that weighs in at around 2800. With the whips, I leave the boat at the dock all the time. I am only considering a mooring in the next couple of years, because I could extend my season, do to water depth at my dock in the fall. A neighbor has a 28' cruiser that he leaves on the dock with whips as well, and his boat is probably in the 7K-8K category.... __________________ Life is about how much time you can spend relaxing... I do it on an island that isn't really an island.....

07-25-2017, 10:59 AM	#6
Dave M Senior Member Join Date: Jul 2007 Posts: 395 Thanks: 4 Thanked 26 Times in 24 Posts	Another thing to check If it has galv pipes with foot bases instead of 4X6 post, that's a trait of Raise-A-Dock, another good dock company. I have one built by them. Another thing to check if the dock has cross pieces under the deck. It stiffens the dock. I have two of them since my dock is 33'X6'. I have a 20' boat tied directly to dock, nothing moves. Dave M

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07-20-2017, 09:22 AM	#2
codeman671 Senior Member Join Date: Jan 2005 Posts: 3,491 Thanks: 221 Thanked 810 Times in 486 Posts	If it is one of the watermark style crank ups that is more than sufficient. We are staying on six mile this week, with long exposure and have a bigger boat on a crank up dock with pipes instead of posts. No concerns.

The Following User Says Thank You to LIforrelaxin For This Useful Post:
Bayview Girl (06-26-2018)

07-21-2017, 06:30 AM	#5
Dave R Senior Member Join Date: Jul 2004 Posts: 2,984 Thanks: 246 Thanked 743 Times in 443 Posts	If you doubt the robustness of the dock, it is very easy and cheap to dramatically strengthen it with a pair of cables connected to the corner posts on the diagonal directly under the deck framing and tightened up with turn buckles. 1/4" is plenty strong enough. They can't be loose, but they don't need to be guitar string tight. That said, an extra set of diagonal cables between the deep end posts and some posts near the middle would probably be a good idea considering how skinny and long the dock is. Diagonal leg bracing under water is always a good idea too.

The Following User Says Thank You to Dave R For This Useful Post:
Bayview Girl (06-26-2018)

07-25-2017, 01:36 PM	#7
DickR Senior Member Join Date: Apr 2008 Location: Moultonborough Posts: 750 Thanks: 4 Thanked 259 Times in 171 Posts	My dock also is 6x30, aluminum frame crankup. The header bar was bolted to a huge pile of boulders at the shore end and the frame hung from it before ice-out a couple of years ago. The crew (Center Harbor Dock & Pier) delivered it by truck and trailer over the ice. They couldn't install the 4x6 legs because of the ice, so the frame was cranked up just a bit to await ice-out. In that position, I crawled out over the frame to the end, expecting some teetering. Boy, that frame barely moved at all. It's quite torsionally rigid. I do have a pair of 8-ft whips for the boat, more for protection of the boat. I had the welder install a pair of mounting brackets for the whip bases, which bolt through the deck directly to the brackets. On summer weekends, when the boat wakes are unending, the boat pitches up and down vigorously, pulling on the whips, but the dock itself doesn't budge.

The Following User Says Thank You to DickR For This Useful Post:
Kayla (06-26-2018)