Converting swing board trailer to wing keel trailer? - Page 2 - SailNet Community
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post #11 of 40 Old 03-31-2017 Thread Starter
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Re: Converting swing board trailer to wing keel trailer?

Ugh.....the three axle trailer is simply an old trailer for a mobile home and exhibits numerous problems. The boat that is perched on it sports two large holes in the hull. Perhaps Blackbeard sent a cannon ball through it.

Now for the good news! My understanding of the depth of the fixed keel was possibly off. The past owner estimates the "extension of the shoal keel" to be "be pretty sure the extension did not add more than 1 feet." The current keel is of an upside down T shape that adds 900 pounds. I have a photograph of it but do not know how to post it without using a smartphone tapatalk app that reportedly helps with image posting. I vastly prefer laptops by 1000 to 1.

EDIT: The last owner was kind enough to send a PDF. The shoal draft was 2'6". Adding 18" puts me at ~ 4'. Much easier to accommodate than 5' ... I would think.

Egads.....keels alone are enough to send the mind spinning.
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Last edited by ColoGuy; 03-31-2017 at 03:29 PM.
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post #12 of 40 Old 03-31-2017
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Re: Converting swing board trailer to wing keel trailer?

I wonder if all that extra weight on the keel could cause problems with the rig. When too much wind hits the rig, boats are supposed to heel. It's like a pressure relief valve for your rig.

Did you get a good look at the chain plates and standing rigging when you were at the boat?
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post #13 of 40 Old 03-31-2017 Thread Starter
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Re: Converting swing board trailer to wing keel trailer?

Yes and no....I looked it over good but have a negligible background in sailboat analysis. I'll say this:

Boat was purchased in 1978 and the keel modified in 1980.

The previous owner did say that perhaps a little too much weight was added towards the stern. The boat points slightly while docked.

He anchored off the stern. Felt that was best for him. FWIW, I also preferred to anchor off the stern with my outboard.

I wonder if it is possible that we are getting carried away with engineering details. The boat was successfully used for ~28 years after the modification.

I'd like to get back to the trailer mounting challenge which is still a daunting challenge. More on that in a minute...


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I wonder if all that extra weight on the keel could cause problems with the rig. When too much wind hits the rig, boats are supposed to heel. It's like a pressure relief valve for your rig.

Did you get a good look at the chain plates and standing rigging when you were at the boat?
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post #14 of 40 Old 03-31-2017 Thread Starter
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Re: Converting swing board trailer to wing keel trailer?

Large steel plates are somewhat expensive. Have yet to explore too many options, this is what I have found. In order to get a 48" x 1/2" thick steel plate, I may have to get a 12" width (at least from the supplier that I studied):
Eight 12" x 1/2" x 48" A36 plates costs $950.
Weight: 654 pounds UPS shipping costs $603.

Since I am using eight plates, I see no need for 12" wide plates. We are not supporting a building.
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Re: Converting swing board trailer to wing keel trailer?

The trim could be an issue for a few different reasons. Sailing performance could be altered and anchoring stern to isn't always ideal.

Last edited by Arcb; 04-01-2017 at 07:20 AM.
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post #16 of 40 Old 03-31-2017 Thread Starter
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Re: Converting swing board trailer to wing keel trailer?

I hope you feel well exercised after jumping to so many conclusions. Without an image of the boat and keel, you can't make these assertions in any reasonably scientific way.


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Is there any way you can unload this boat before it costs you any more money?

The trim is going to be a problem. She won't point, the bows going to blow around when maneuvering, the pivot points going to be altered, she's going to be too heavy for her designed sail area, she's not going to heave too and she's going to ship waves into the cockpit when anchored.

I'm not trying to be cute. This boat does not sound like a good boat to learn on.
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Re: Converting swing board trailer to wing keel trailer?

Take an empty water bottle, cap on. Fill your sink with water. Put a fan beside the sink, on. Push the water bottle towards the fan.

Then, get some duct tape and tape a loonie or something to the bottom of the bottle, aft of the centre of floatation and repeat the experiment.

Note any changes in the way your water bottles reacts to the wind from the fan.

Then tell me I don't understand the principles of boat trim.
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Re: Converting swing board trailer to wing keel trailer?

If I remember correctly, many of the S2 models came from the factory with swing keel/shoal keel/fin keel options. And for a time, the factory sold keel conversions for converting swing to shoal/fin.

So dismissing this S2 keel conversion out of hand is jumping to conclusions.

Even if this wasn't an official conversion, consider how much the center of effort, floatation and gravity changes on a swing keel in various states of "swing". Any after market conversion that is placed in the swing keel box area will likely be just fine in comparison.

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post #19 of 40 Old 03-31-2017 Thread Starter
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Re: Converting swing board trailer to wing keel trailer?

It is not a full keel, it stops several feet short of the stern. Wish I could post a picture with my laptop. Then we could make more insightful judgements.

My business name is water plus my name. Not completely new to water movement. Starting to appreciate your effort though.


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Take an empty water bottle, cap on. Fill your sink with water. Put a fan beside the sink, on. Push the water bottle towards the fan.

Then, get some duct tape and tape a loonie or something to the bottom of the bottle, aft of the centre of floatation and repeat the experiment.

Note any changes in the way your water bottles reacts to the wind from the fan.

Then tell me I don't understand the principles of boat trim.
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Re: Converting swing board trailer to wing keel trailer?

The older S2's did come in the swing / shoal / fin keel options. I have a 79 8.0b with the shoal draft and have wished for some larger keel traits when in heavier weather. Not enough to trade off being able to anchor in knee deep water though. The decks on all of them that I have seen are balsa cored but the boat is heavier built and has more big boat amenities than most of that size IMO. All that aside.... Realistically, until you see this thing out of the water and inspect what kind of a job was done, or even see how it might react under sail, its all pretty much just playing armchair quarterback....

As for getting the boat back, I would check on quotes to have it shipped so you can put it on jackstands where you are going to keep it and build the trailer up to fit at your convenience when you can take good measurements. It would be a real kick in the nuts to get all the way there and find out that the pdf and the actual boat aren't built exactly alike. Another option would be to take a few days and an equipment trailer if you have one available, have the boat hauled out at a marina, take a day to build a cradle out of wood and drop it on there to get it back. Unloading once back in Colorado might be the daunting end of that idea though!
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