Looking for advice on towing a dock

O

oldgrowth

New member
It really a dock but I have to move a dock ramp where the dock washed downstream in a storm. This is at South Bend, WA on the Willapa River.

The dock ramp has been sitting submerged at one end for about a year. The other end is hinged on a walkway coming from a building. At low tide I will strap some 55 gallon drums to the submirged end of the ramp and a few more on the upper portion. When the tide comes in I will cut the hinges to let the high end of the ramp drop and tow it about 3/4 miles down river to a boat launch.

I figured I would rig a tow rope in a Y configuration. I will hook each end of the V portion to my stern cleats and the tail to the ramp. I will also attach a float where the tail and V come together to keep it out of the prop. I am not sure how long to make the tow rope but I thought each leg of the V would be 12 feet and the tail about 20 feet. There are some pilings and a log boom I will have to maneuver around to get out into the open water so I may have to shorten the tow rope for this.

I am going to time this so I am towing the ramp down stream just before high tide. I don't want to be towing down stream on an outgoing tide. When I get it to the boat launch I will have a track excavator to pull it in and load it onto the trailer.

The ramp is 8 feet at the widest part and 28 feet long and I am estimating it weighs 3500 pounds

Any body have any advice or something I should be aware of that I am missing. I will be towing with my 16/18 foot C-Dory.

_______
Dave dlt.gif :cigar
 
Dave,
I don't know if you have the water depth, but I prefer to tow "on the hip" when in close quarters. That means along side, about 3/4 of the way aft.

When towing a larger object, the torque of a small outboard prop will push the towing boat side ways before it gets it going forward. This is minimized when along side, and you can also control the steering of the dock by backing and filling when necessary in close quarters.

I have towed a number of boats, and tow them on a line aft when in open water. The danger of any tow, is a fitting breaking--and the tow line acting like a sling slot. I pulled the bow cleat out of a Cal 40 when towing it at 5 knots--after that when towing larger boats (and high resistance tows), I tend to put a bridle around the boat, and the tow. If you look at the real professional tow boats, they have the tow point forward of the rudders or outboards. They have a protection for the crew--and no one is near the tow line.

Another option is the stern rings--if they are adequately backed with either a plate, plywood, or large fender washers. Check the stern cleats to be sure that the thru bolts have fender washers.

A float, and a way for the line to slide thru the aft bridle can also help with control. That is, make a loop between the cleats, then attatch the tow rope with a bowline so it can slide on this loop. Have the dock attatchment equal on both sides.

Joel probably has a good deal of experience towing docks in his business.

Good luck and be safe!
 
I agree with Bob - if you can tow alongside you will have better maneuverability and reduce risk of a line parting/slingshot. Does this thing float fully on it's own? You mentioned having to add drums - make sure this thing will float so you don't risk having it pull you under should something happen.

Have big knife ready to cut lines in either case :shock:

I fairly often tow "canalligators" out of the canals I run for the National Park. Some are quite massive and really drag on the 6 ton/twin engine vessel but dragging them alongside makes it much more doable. Go slow and give yourself as much room to maneuver as possible.
 
I agree with the above. If you side tow, have your stern a few feet aft of the stern of the dock and set up the tow to be slightly "pigeon toed" i.e. wit the bows slightly closer together than the sterns.
 
I would also recommend planning the tow on a slight incoming tide so you can pull "upstream". It is a lot easier to control a climb than to control a fall, especially when significant mass is involved.
 
Thank you gentlemen for your advice.

My first sentence in my original post should have been “It’s not really a dock but I have to move a dock ramp where the dock washed downstream in a storm”

I like the idea of “tow on the hip” but this ramp has cross beams for the deck about every four or six feet and they stick out about 18 inches beyond the walkway.

I am 97% sure I have backing washers on my cleats. My saddle tanks block the bottom of the cleats so I cannot check. The water depth will be 6 feet to maybe 30 feet when I am towing.

I had planned on this project for the 14th of August. The next time I will have favorable tides is the 28th of August. It will also be weather dependent and the later in the year the greater the chances of inclement weather.

Question asked - Does this thing float fully on its own?
Answer – I would say yes but probably most of the ramp would be under water with just the side rails above water assuming it does not roll over when cut from the walkway. It is made out of wood, two creosote 28 foot logs with the rest made out of treated lumber. The end that has been under water much of the time is probably waterlogged and will float lower than the opposite end.

I should have posted photos of the ramp but did not take any. I will do this and post the photos tomorrow evening.


Dave dlt.gif
www.marinautboats.com
 
If you cannot tow on the hip--then it might be a good idea to have a second boat (small aluminum skiff would work) for "steering and maneuvering--that way you don't ding up the C Dory....use the skiff as a "tug" pushing to move the dock--you will only need 4 to 6 hp to do that. (and a second person in that boat).
 
We had to tow the IOWA (BB-6)1 Down the mighty Mississippi from New Orleans to the Gulf with no engines back in the Mid 80's. Took one Fleet tug ahead and three astern pulling up river to keep her slow enough (River was flooding) and maneuver around the bends. That was HAIRY!! :shock:

Let us know how it goes!!

Charlie
 
With a current behind you, I think I would be especially observant of the towed dock to make sure it does not get stuck and cause you to get swamped by the following current.

As Matt suggested have a knife ready and someone there to use it if needed.
 
Here are photos of the dock ramp. Half of it is under water. The thing I am a little concerned about is that it may turn over when cut from the walkway or when it is being towed.

If it does not flip over when it is cut from the walkway and it seems stable, I have thought of building a makeshift mount on the ramp for my 8hp Honda outboard and use it to move the ramp to the boat launch.

The cross beams I indicated it had between 4 and 6 feet apart are really 8 feet apart.

dock-1.jpg

dock-2.jpg

dock-3.jpg



Dave dlt.gif
www.marinautboats.com
 
HOOOO Boy! That's a PROJECT and a half! Be very careful and take lots of pictures. Don't want to see you or anything to do with it on the Evening News!

If it floats upright and seems stable (as you said) Put the Honda on it and play Huck Finn!!:mrgreen:

Just be sure to have a chase boat with you with a good radio...



Charlie
 
Dave, how do you plan on attaching the 55 gal drums? Since they are larger in diameter than the two main beams, I'd be a bit concerned about putting them under the dock/ramp as that will create a higher center of gravity. If it were me, I'd see if I could strap one on either side of both ends just under the cross beams and attached to both the cross beam and the large log. That would put the drums on the outside edges and keep the center of gravity lower (reducing the possibility of a roll over). I don't know whether it's possible to get the drums attached there tightly though. Four 55 gal drums will add about 1800lbs of buoyancy.

Your creosoted lumber probably weighs about 60lbs/cu. ft. (45 from the wood and 15 from the creosote - plus or minus 5lbs - see this link). I'm guessing those logs are about 12" in diameter. pi * r^2 * 28 *2 = 3.14*1*28*2 = 175 cu ft. of wood in those logs alone. 175 cu ft. * 60lb/cu. ft = 10,500 lbs! If the diameter is only 8", those two 28' long creosoted logs would still weigh around 4700lbs.

One cubit foot of water is approximately 7.5 gallons (which weighs 8.3 lbs/gallon). So, the density of water is about 62lbs/cu foot. As a result, depending on how much creosote per unit volume is actually in those logs and how much water is in them, they may be heavier than the water they displace. If so, you may need considerably more buoyancy than you think and the tow may be MUCH heavier than you think. My suggestion is that you do some really careful measurements to get a good estimate of the total cu. ft of wood that is there and then carefully estimate the weight. You might also want to think about a way to more slowly lower the high end of the dock than just cutting the hinges and letting it drop.
 
From a slightly different adventure, but the same message:

"I think we're gonna need a bigger boat."

Joe. :lol: :thup

(No sarcasm intended, just a passing thought, holding some possible humor, but not a definite conclusion.)
 
And in the same vein (humor) as my buddy Joe, as Noah said to the Lord [as translated by Bill Cosby],

What's a cubit?

What you fat fingered Roger :lol: . Good calculations all, a lot better than I could do this late at night after a brew or two!!

Roger, you're good with the numbers, How many furlongs are there in a fortnight? :mrgreen:

Do be careful Dave, and let us know what happens!

Charlie
 
While I was re-wiring my down riggers, I realized that I did my calculations wrong - I squared the diameter and not the radius! (OOPS!) I was sure that Joe would have caught this by now but I guess I'm lucky today. So my weights for the logs are a factor of 4 off (2 squared). So two 12" diameter 28' logs would be about 2625lbs and 8" diameter logs would weigh about 1175lbs.
 
Roger – always glad to have your input. I just estimated the weight from my life’s experience when I guessed at 3500 lbs for the ramp. I think you got the cu ft wrong for 12” logs. A 12” diameter log one foot long is less than one cu ft. Without doing the calculations, I would guess it to be somewhere between 3/4 & 4/5’s of a cu ft. Using the larger number .8 X 60 is 48 lbs per foot. 28 x 48 is 1344 lbs per log. I don’t think these logs have the same amount of creosote as railroad ties. I don’t remember the diameter but do believe they are over 12” in diameter.

When the dock first broke loose and the ramp dropped into the water, it would float up slightly when the tide came in. When I went out on it and bounced I could feel movement in it. As time went on it quit floating and now the water end is stuck in the mud. Even with a -3 ft tide the water end is still a couple of feet underwater. On the 14th there will be a minus one foot tide so we will not be able to strap barrels on the end. I plan on putting four (two on each side) as far as possible down the ramp towards the water and another one on each side at the other end of the ramp under the second cross beam from the end. The water end should float up and the tide will be a foot higher than the photo so hopefully the barrel does not disintegrate when the ramp is cut loose.

Originally I planned to rig up some pulleys and blocks from the ramp to my track excavator to lower it slowly into the water. I changed my mind about that because I did not want someone cutting the pins under the lines supporting to the ramp. If something went wrong he could be killed very easily.

Timing is critical on this. At low tide (08:15) I have to strap the barrels to the ramp. I will start at 07:00 and finish by 09:15. The tide flats there are mud and you sink in 12+ inches when working on them. High tide is at 14:40 so I want to cut the hinges and have the ramp at the boat launch by 14:45 but at the same time I want the tide to be as high as possible when I drop the ramp. If I cut the hinges at 13:20 there will be a 7 ft tide (one foot higher than in the photo). That will give me a little over an hour to get it to the boat launch.

I still may build an outboard mount on the ramp and use my 8hp Honda to power it to the boat ramp. I won’t know this until the ramp is in the water.

We really wanted to rebuild the dock but the hoops and EIS required made it prohibited so that is why we are removing the ramp.


Dave dlt.gif
www.marinautboats.com
 
It sounds like you guys got it all figured. But, if you want my advice, once you get her free you should bolt one of those 300 hp tillers on it as I think you could get it on step.....LOL.....Now that would be a site....
 
"We really wanted to rebuild the dock but the hoops and EIS required made it prohibited so that is why we are removing the ramp. "
Click to expand...

Dave, If there was already a dock there, why wouldn't it be permissable to replace the missing dock? Seems logical doesn't it?

Good luck. I watched a guy take a 16ft by 8ft dock, with a 1000# concrete block anchor hanging under it, off across Sequim Bay with a 14ft aluminum skiff and about a 15 horse OB on it. Tied at the hip to get out of John Wayne, then switched to a tow behind for the cross bay trip, all in a 10 knot breeze and a 1 ft chop.

Harvey
SleepyC :moon
 
T.R. Bauer":26mcfpj9 said:
It sounds like you guys got it all figured. But, if you want my advice, once you get her free you should bolt one of those 300 hp tillers on it as I think you could get it on step.....LOL.....Now that would be a site....
Click to expand...

Permatrim and Trim Tabs would help!! :mrgreen:

Oh, and we'd like to have video for YouTube!!:thup

Charlie
 
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