Fitting a through-hull mast on a deck mounted DSII

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Fitting a through-hull mast on a deck mounted DSII

Postby Sailbob » Fri May 31, 2024 4:23 pm

Hello all and happy spring!
I have a 1984 Daysailer II and recently purchased a new mast as the original was badly bent in an accident. A high tree branch got me when backing down a launch ramp resulting in a twisted and bent mast which also pulled up the deck on the bow (I will have to re-epoxy the deck as well). The new mast is a full sized through hull mast which I was going to cut down in an attempt to keep things as they were but before cutting it I thought I should consider cutting a hole in the deck and using the full mast. I'm wondering if anyone has tried this retrofit? I know that there are benefits to the through hull versus deck mounted mast but initially purchased the boat because I was trailering and launching. Now, I have a mooring and so considering the retrofit. Thank you in advance for any information you can impart!
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Re: Fitting a through-hull mast on a deck mounted DSII

Postby RaleighRancher » Sat Jun 01, 2024 8:19 am

All I know is that D&R Marine says the tabernacle is not recommended for boats on a mooring. I don't know the mechanics of that but it suggests your mod might be a good idea.

Also, you may have already seen it, but I started a thread here describing my own experience with "sudden, extreme foredeck separation". I chilled through a lot of articles here before undertaking the repair. Two years later it's all good, though my finishing skills leave much to be desired.
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Re: Fitting a through-hull mast on a deck mounted DSII

Postby GreenLake » Sat Jun 01, 2024 4:31 pm

If retrofitting mast partners (that's what the deck opening is called) plan on some reinforcement (there may already be something to help distribute the load of the mast step on deck, but make sure it's enough). My boat has a bit of a collar that is glassed in, perhaps 1/2" above deck level, perhaps a bit more. If you need to add one, or add to existing reinforcement, make sure to give it a gentle slope and smooth transition around the outer edge to not create hard spots.

On my boat, the thickness works out to where, if the mast is some degrees off vertical, it won't go down, that's how tight the fit is and that's how thick the collar is combined with the deck.

You may need to adjust or create a mast step to receive the bottom of the mast inside the cuddy. The design isn't very particular, anything that can support the weight of the mast plus tension in the rig (say 300# to 500# to be safe) and is strong enough to absorb the peak loads from the hull slamming into a wave. It also needs to keep the mast foot in position, so it can't move forward or sideways, and whatever retains the mast shouldn't be so shallow that the mast foot could jump out if it. Usually, the tension in the rig prevents that, but, again, slamming into waves might make it bounce off anything too shallow.

If there's a support for compression post today, make sure that it's firm (some DSII owners reported issues with the part that's under the cuddy floor not being aligned). Or cut a hole and build directly on the keelson (that's the raised part inside the boat where the keel would be on the outside). You may need to do that if you got a DS1 mast as these are a bit longer (expecting the mast step to be directly on the keelson).

If you make the mast step adjustable in the fore-aft position, you won't need to get the mast rake absolutely correct beforehand. (Mast is generally raked a couple of degrees aft, but getting it dialed in works best with everything in place, that is, after the mast is stepped.)

If you only ever take the mast off at the end of the season or when you need to haul for some other reason, then leave it at that. It'll take two people to step and unstep, and takes a bit of being organized about it, but doable. Key is to control the mast at two points, so it stays vertical while not on the ground.

I trailer, so I'm benefiting from a clever little device some previous owner rigged.

27441545

Simple to make: one disk resting on the mast partners, one hinge, one wooden block and a bit of sheet metal. (And a small strip of aluminum as a guard to prevent trapping the jib sheet). Plywood backing plate below deck, bolts with fender washers.

You stick the mast foot in, tilt up the mast (single-handed if you''re tall), then lower it once it's vertical.

Simple and effective, gets you the benefits of a hinged mast without cutting it.

PS: and the disk is a great place to mount various fairleads. I have one for a spinnaker downhaul (foreguy), a spinnaker halyard and third one for a jib halyard tensioner.
~ green ~ lake ~ ~
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Re: Fitting a through-hull mast on a deck mounted DSII

Postby Sailbob » Fri Jun 14, 2024 9:37 pm

Hi, thanks so much for your replies and information. They were very helpful. I’m still undecided about which way to go and still have a few more questions:

If I cut a hole in the deck, how tight should it be? Should there be room for the mast to move? I’m not planning on creating an adjustable rake mechanism at this point but how do I determine if the compression post mounting is the correct location for the mast foot and will ensure the correct aft rake? Greenlake, you mentioned some others had issues with its location.

The purpose of reinforcing the area around the hole with fiberglass is to withstand movement of the mast? Or to make the deck stronger for bearing body weight during the stepping process?

How do you keep water from running down the mast and into the cuddy? Is there a boot that can be made or bought?

Btw Greenlake I love the hinged mast step mechanism and plate! Is the round plate flush to the deck? It looks proud of the deck in the photos.
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Re: Fitting a through-hull mast on a deck mounted DSII

Postby GreenLake » Fri Jun 14, 2024 11:31 pm

The mast partners should be tight. In fact, mine are so tight, that if I let the mast go just a little bit out of alignment it won't go down any more.

The "disk" is proud of the deck because the partners have a raised "collar" that is part of the deck molding. The purpose (my assumption) is to handle point loads from the mast pushing against the deck. It will, because it bends a bit under tension (or when you pull on sheet or vang). Also, a narrow deck would "saw" through the mast. With the collar it's distributed.

I fitted a very small aluminum strip to close the gap in the front. Keeps the jib sheet out.

There's a North Sails tuning guide for the DaySailer (google) that determines proper mast rake by measuring the distance between transom and mast top. The problem with that is that it sensitively depends on the mast step being at pretty exactly the right height (and ditto the mast top). If you are sure, you could rig your mast temporarily, take the measurement and find out where to put the mast step.

The point of making it adjustable isn't to constantly fiddle with it, but to be able to correct the initial position if your pre-set mast rake doesn't give you a balanced helm (with slight weather helm, and definitely no lee helm).

If you divide it into an upper part that connects to the mast foot and a bottom part that connects to the keelson, then you'd use something as simple as two flat plates (or if you want, two nested U channels) with holes in one and slots in the other so you can fix the mast in the best fore-aft position once you know what that is.

I believe, we are talking about +- 1" if your initial guess at the correct position was correct. And by not committing to a position on build, you can test sail an verify that it's right - or fix it.

Mine has an upside down U channel that slides on the keelson and is fixed with a pair of through bolts. Never had to adjust it, as the previous owner dialed it in perfectly.

I don't consider water coming in a serious issue. If I get rained on, water will collect in the cockpit and mine is open to the front (not like a DSII). So stopping a bit of water at the mast is a non-issue. Keeping a boat on a mooring, you might have reasons to want the cuddy dry (although on a DSII any water would drain out).

Any form of rubber boot might do, but it might have to be removable. Or, you could run a bit of butyl tape in the opening. It stays flexible and isn't as permanent as caulk. It shouldn't be too hard, to pull it out with a wire hook when you are ready to unstep the mast.
~ green ~ lake ~ ~
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Re: Fitting a through-hull mast on a deck mounted DSII

Postby SUNBIRD » Sun Jul 07, 2024 11:34 pm

RaleighRancher wrote:All I know is that D&R Marine says the tabernacle is not recommended for boats on a mooring. I don't know the mechanics of that but it suggests your mod might be a good idea.
.


I keep my Day Sailer on a mooring, and recently (about 3 years ago) added the mast Hinge from D&R, Rudy is not saying that the hinge should not be used if the boat is kept on a mooring! The "warning" just says the contact him before making the modification! The reason for that caution is that several years ago an owner added the hinge to his boat and did not keep the standing rigging properly tuned, is was too loose and I seem to recall that he also did not use cotter pins or split rings through the turnbuckle studs to prevent them from unwinding (that is to prevent the body of the turnbuckle from rotating and unthreading from the studs), well, obviously, the rigging being loose and gradually getting looser as the turnbuckles twisted, the mast was allowed to violently sway side to side as the boat rocked at the mooring. The constant movement and sudden jerks as it was retrained by the rigging stressed the cables and swages, and eventually, part of the rigging failed and the mast toppled over, destroying the mast hinge and probably doing serious damage to the cuddy top.
The boatowner then tried to blame Rudy for his own negligence, and I forget how Rudy was able to solve the problem, but somehow he was able to prove that the fault was not anything that D&R (Rudy) said or did, but purely the actions of the boat's Owner.
SO, To protect himself from that ever happening again, he added that cautionary note to the listing on-line for the mast hinge kit.

If you race, then there are advantages to the one-piece, stepped through the deck (cuddy top) mast, but for general sailing, I really prefer my now hinges mast! It was worth the $100 (I think it has gone up now?) price of the hinge kit, and for extra "insurance", I also replaced my 36 year old standing rigging, as well as the chainplates amd stem fitting. Full cost was around $450 including the hinge, but it is good piece of mind!
Rod Johnson, "SUNBIRD"
1979 DS II, # 10201
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Re: Fitting a through-hull mast on a deck mounted DSII

Postby GreenLake » Mon Jul 08, 2024 9:12 pm

My answer to that is the $15 (estimated) do it yourself hinged sleeve to raise a through-hull mast as if it was hinged. Best of both worlds.

(Where we agree is that stepping a full-length mast without any supportive gear is not for the faint of heart).
~ green ~ lake ~ ~
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