Hard dodger strength and weight limit ? - SailNet Community
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post #1 of 12 Old 02-06-2016 Thread Starter
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Hard dodger strength and weight limit ?

Hey folks,
I have your typical dodger frame 1" SS .06 wall 2 bows setup, with side supports. I am planning to add a hardtop 0.5" plywood and 2 layers of epoxy. I would like to kneel if not stand on it. I am sure the top will hold it, but will the frame do ?
I am planning to add 2 transversal SS strips, then the load should be spread along the full structure. Would that work ?

Or should I add straight support tubes under the strips? Ugly and maybe overkill ?

Thoughts?
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post #2 of 12 Old 02-06-2016 Thread Starter
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I am not planning to add any side reinforcement. Ideally the side and front would be only lexan panels bolted to the frame, not a full hard enclosure you can see typically.
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post #3 of 12 Old 02-07-2016
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Re: Hard dodger strength and weight limit ?

Having a hard dodger, I completely understand you wanting one! It's one of the most comfortable features of the boat. You are correct to try to figure out what you want it to do prior to installation as it is a feature that will grow on you!

Firstly, depending upon your boat's setup, you may find yourself wanting to stand on the dodger more than you think. Our boom is long and we need to stand on the dodger to properly furl the sail. Having that ability makes the process much easier. People will want to stand on it as well so when you have friends aboard, or other non usual guests, you will find that they will attempt to climb on top automatically, figuring they could.

To make it capable, you really need to have stronger supports than the ss bows found on the typical canvas dodger. The supports on ours are easily 1-1/2" diameter for the aft support and 2" for the forward supports. There is also diagonal braces up forward to support side to side movement. The top itself is made from fiberglass encased plywood, sealed top and bottom. The result is a 200# adult can stand on it with no deflection or movement. What is, perhaps, more critical is how the tubes are secured on the cabin top. The typical hardware supporting canvas bows are nowhere near the strength they need to be to support the fore and aft or side to side pressures of standing or even kneeling on the top. I'm certain that the jaws will bend and break with those forces. Our dodger has a solid foot that is attached through the cabin top with backing plates. The attached photo should give you an idea of our set up.

I was not the owner of the boat when this was installed so I can't provide cost estimates but suffice it to say, we have owned it for at least 12 years without any issues. It's an investment well worth the cost!

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post #4 of 12 Old 02-07-2016
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Re: Hard dodger strength and weight limit ?

Hard dodger is divynicell core with woven then mat then gel. Two layers of safety glass with uv membrane between. Supports three people with no flex. Attached to house on 6" centers and 5200 then glassed over. Think it's as strong as the hull.
Two issues to think about. Ours is high enough it prevents road travel. Between it and a 6.5 keel we are above height for trunking withou permitting.
Whether to tint glass. UV is a good idea. Tints look great but decrease night vision. We went clear.
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post #5 of 12 Old 02-07-2016
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Re: Hard dodger strength and weight limit ?

I think it will depend on how large the dodger frame is. Ours is rather small, with a large radius and no flat runs anywhere.. I think a gymnast could do some routines on our bare frame.. we do have rigid front bow supports and a rigid aft support too, unlike many dodgers, so that helps a lot.

We plan to make a hard top and renew the side curtains/windows this spring too.

Some shots showing the extra support - you'll see how the size and shape also contributes to strength:





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".. there is much you could do at sea with common sense.. and very little you could do without it.."
Capt G E Ericson (from "The Cruel Sea" by Nicholas Monsarrat)
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post #6 of 12 Old 02-07-2016
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Re: Hard dodger strength and weight limit ?

Also think about designing it for

A) Solar panels
B) Rain catching

And also if you enclose the front, ensure that you can open part of it to allow the wind in whilst at anchor to cool the whole area
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post #7 of 12 Old 02-07-2016
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Re: Hard dodger strength and weight limit ?

Thought about panels. But when you watch most sloops/cutters/solents/yawls the top of the dodger is often in partial shadow. Would need two regulators and circuits for relatively small panels. Much expense for little output.

If he truly doing a hard dodger not a soft dodger with a hard top one would think he'd be better off putting in two small hatches on the top. A good dodger blocking all wind, spray and green water makes for a very hot cockpit unless there is some way to get airflow. One of my favorite spots to read at anchor is under the dodger. You are out of the sun, can see your surrounds but with a hatch open in the breeze and cool. Need to make sure hatches don't interfer with main sheet or boom.

Guess it depends where you are but at least in eastern Caribbean and east coast US catching potable fresh water seems hopeful at best.
In tropics may rain hard but usually briefly. First part maybe contaminated by Sahara wind dust and by time boat is washed clean and you're set up rain stops. On east coast rain itself maybe dirty depending where you are. Probably different with pnw liquid sun. Don't know.

If it opens in the front need to be concerned about integrity. Hard to do right and prevent leaks. Especially green water. But is a delightful way to get some wind in. Friend can open bottom of the middle panel of his soft dodger and close top sliding hatch of the companionway/ seahood. Even in a light rain gets excellent ventilation.

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Last edited by outbound; 02-07-2016 at 06:11 PM.
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post #8 of 12 Old 02-07-2016
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Re: Hard dodger strength and weight limit ?

A fabric dodger's frame won't keep it from wobbling side-to-side with that added weight on top. (Haven't read thru all the other posts so that may have already been said)
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post #9 of 12 Old 02-08-2016 Thread Starter
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Thanks guys, lots of interesting ideas and pictures. Food for thoughts ! I like the idea of hatches on top. It might discourage guests to try to step on it
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post #10 of 12 Old 02-08-2016
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Re: Hard dodger strength and weight limit ?

The critical design element of a hard dodger is for that dodger support frame (bows) to be NOT subject to 'buckling failure' ... a quite complicated structural situation in which the long thin support members (support frame) slightly bow (deflect from their unloaded of neutral axis), become 'off center' to the applied load and the whole thing collapses and with load/weight at a paltry few percent of the compressional strength of the (tubing) material.

The easiest way to attempt to prevent 'bucking failure' is to add perpendicular or 'triangular' support (tube) and attached to the 'middle' of the span of the vertical support tubing. OR use 'larger diameter' and larger wall thickness support framing, especially on the vertical sections ---- anything that constrains the middle of the long thin 'span' from deflecting or bowing under load. 'Stiffer' is always better when it comes to the prevention of 'buckling failure'.
An example: spreaders on a mast make it 'stiffer' but also less prone to 'buckling failure'.

;-)
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