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Old 25-09-2008, 13:58   #1
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Question wave runner on a stern arch

I have a steel 44 foot cruiser.
We have a great atolon 60 miles offshore with 10 mile diameter. Too much for running around in our dinghy.
I wish to carry a waverunner in the arch that carries the solar panels and the wind generator. The structure of the arch to the stern is ok to carry the load, but friends tell me the 1200 lb waverunner weight will complicate my crusing experience, and affect the stability of the sailboat. The boat weighs itself 30,000 lbs. Do you think that just adjusting the rigging will be enough? Should I just forget about the idea?
Thank you!
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Old 25-09-2008, 14:11   #2
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Was the arch really designed for 1200 pounds, dangling on a couple lines? That would be a MASSIVE arch. Even large hydraulic cranes would be damaged by that much weight bouncing around. Think about the shock loads. I would imagine that a 30,00 pound boat could easily handle the weight of a waverunner, amidships and tightly secured, but I have my doubts about a 'solar panel and wind generator' arch surviving long if the waverunner got loose. Is there a plan B?
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Old 25-09-2008, 14:12   #3
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Besides all of the issues and problems with carrying this kind of weight on the stern of a boat not designed to do so, with a jet ski on the stern you will be the least popular boat in any anchorage.
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Old 25-09-2008, 14:33   #4
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Besides all of the issues and problems with carrying this kind of weight on the stern of a boat not designed to do so, with a jet ski on the stern you will be the least popular boat in any anchorage.
Yeah, but look at the conversation piece he'll have hanging there!!

Unless that arch is cast steel, I agree with Sandy.

So Chuck, how's day two (or three) of boatless going? There's a very nice Wildcat 35 Cat for sale across the Lagoon from me with twin diesels (picture it as a trawler with sails ). Might be worth a look!!
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Old 25-09-2008, 14:38   #5
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Rick, Not too bad actually, looked at a couple of trawlers this afternoon. No more sticks.
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Old 25-09-2008, 14:42   #6
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I have seen one of the smaller PWCs on davits on the back of a catamaran ( a 9m catalac) it certainly upset the trim.
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Old 25-09-2008, 15:05   #7
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Any standup jetski would weigh less than 350 pounds dry and the high performance custom ones can scratch 225 pounds dry. Aside from standup jetskiis having an actual learning curve, they can be much more fun than any sitdown(couch) jetski. If I were to suggest a standup, it would be any Yamaha Superjet, and for a couch check out the older (93-96) Seadoo XP models which are more like 1.5 person skiis but small and light. For the arch, I'd have an engineer take a look at it to determine if it is even feasible. The weight distribution can be offset forward by stowing the heavier items near the bow. You should also consider the fresh water usage required to flush the engine of any corrosive saltwater and don't forget to convert them to pre-mix if they are 2-strokes.
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Old 25-09-2008, 18:34   #8
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....The weight distribution can be offset forward by stowing the heavier items near the bow.
NO! That does not work. Adding weight to both the bow and the stern of a sailboat (or any boat for that matter) might keep it on a level water line, but you greatly increase the rotational momentum of the boat as it pitches in waves. The result of this is to greatly increase the amount of up and down pitching of the bow in heavy seas.

Weight belongs near the center of a boat, NOT near the ends.
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Old 25-09-2008, 18:55   #9
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NO! That does not work. Adding weight to both the bow and the stern of a sailboat (or any boat for that matter) might keep it on a level water line, but you greatly increase the rotational momentum of the boat as it pitches in waves. The result of this is to greatly increase the amount of up and down pitching of the bow in heavy seas.

Weight belongs near the center of a boat, NOT near the ends.
Actually I had considered that but I did not write it down. Adding that much weight above the waterline will also decrease your righting moment making a blow-over more likely. I am learning these things in fluid mechanics engineering right now actually.
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Old 25-09-2008, 18:57   #10
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Nice data on the technical. Thank you.
I will let you know what I did.
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Old 25-09-2008, 19:09   #11
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Tanziza……Remember when all the experts said it would be foolish to go to sea in a small boat?

If you have a specific destination and purpose to carry a wave runner and a professional davit fabricator can design the structural modifications needed to lift, chock and secure it…then go for it!

Isn’t that the reason you bought your boat for in the first place?

First test is to jury rig a weight to simulate it loaded on the stern and measure the change in trim.


I don’t think it will be a big issue... but if it concerns you..... choosing either a lighter model or off-loading/ redistributing other gear, can be a simple fix. Remember, for other destinations, you can always replace it with your dingy.


Have fun and don't worry about what other cruisers think, just be considerate at anchor and they will come around!
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Old 25-09-2008, 19:42   #12
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Tanziza……Remember when all the experts said it would be foolish to go to sea in a small boat?

If you have a specific destination and purpose to carry a wave runner and a professional davit fabricator can design the structural modifications needed to lift, chock and secure it…then go for it!

Isn’t that the reason you bought your boat for in the first place?

First test is to jury rig a weight to simulate it loaded on the stern and measure the change in trim.


I don’t think it will be a big issue... but if it concerns you..... choosing either a lighter model or off-loading/ redistributing other gear, can be a simple fix. Remember, for other destinations, you can always replace it with your dingy.


Have fun and don't worry about what other cruisers think, just be considerate at anchor and they will come around!
Let's see...

Step 1: Ask for advice.
Step 2: Get Advice.
Step 3: Don't like answer.
Step 4: Ignore advice.

Wouldn't it be more efficient to skip steps 1 through 3?

Pelegic, do you seriously think hanging 1200 lbs off the stern of a 30,000 lb boat wouldn't be a "big issue"? Really?

It doesn't take much knowledge of boat design to know that that would seriously impact seakeeping ability.

Remember, all internet advice is worth less than what you pay for it (even mine!)
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Old 25-09-2008, 22:52   #13
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I tend to side with Pelagic. Why not try it first before you poo-poo the idea?
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Old 25-09-2008, 23:05   #14
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Awe! what's a little bit top heavy going to hurt. Heck it may come in handy.


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Old 26-09-2008, 00:44   #15
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How about just getting a bigger dinghy and outboard motor?
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