Reversibly plugging lower opening in 26M daggerboard trunk

[Kittiwake]

I think Ratty of Wind-in-the-Willows fame would approve of the MacGregor 26. After a lifetime in canoes, and extensive camping in Eastern Canada, upon my retirement a few years ago I followed my decades-long plan and picked up a MacGregor (2010 26M). I had targeted the Mac since my college days: it allows one to sleep aboard, has a toilet, is simple and inexpensive (low complication rate), and allows one to poke quietly about interesting highly-indented coastlines. You can sail, and you can motor.
My wife and I now live on the east side of Vancouver Island. It certainly is fun to tootle out and raise the mainsail for a peaceful cruise along the various channels. But what I like even better is to trailer the boat to more isolated locales such as the west coast of the Island or to the region southeast of Queen Charlotte Strait. On such trips I have found it very convenient to leave the mast and rudders at home. Heck I even replaced the (heavy) head door with a nice curtain that also turns the V-berth into a separate room. Of course one does encounter the odd disapproving sailor (although this summer we met a Mac owner from Washington in the Broughton Archipelago and his wife commented to her husband, "see, I told you we should have just left the [mast and] sails at home"). Actually up here the commercial fishermen refer to any sailboats as "stick boats" because even dedicated sailors most often run under bare mast.

Well recently I pulled the daggerboard just for fun, and then started thinking - `gee this weighs 30 lbs dry and, while it is great when sailing, it is not much use on my trips to peaceful isolation`. Have people tried stuffing a bit of foam (or whatever) in the lower end of the trunk to temporarily replace the daggerboard`s role as hole plug?

[c130king]

I don't think there is a need to plug the dagger board "hole" in the bottom of the hull. The water will come up that hole about 12"-24" depending on weight/water ballast. The top of the hole is at the deck isn't it.

The dagger board doesn't "plug" the hole or keep water from coming in...the dagger board does not fit in the slot very snuggly.

But I may be wrong on this...frequently am.

Cheers,
Jim

[Crikey]

KittiWake, It couldn't hurt to plug this channel flush, with a tight fitting block of high density foam that could be pushed back out easily. Personally, as a powerboat, I think it could benefit from the bottom six inches of the daggerboard protruding. Like a skeg.
Doing that would entail far more than simply plugging it.

[Kittiwake]

Hi Jim and Crikey.

Yes Jim you are certainly correct; but I gather that if one motors at significant speed without daggerboard in place, water comes up through the daggerboard trunk over the deck ... and associated with this phenomenon one is increasing the hull resistance to forward motion by having a gap below the waterline. My understanding is that Roger has cleverly arranged that the bottom of the daggerboard is flush with the hull when fully raised (to minimize turbulance) even though the fit is loose.

My concern Crikey is that at high speed there may be a tendency of a simple plug to be torn away ... so I have been toying with the idea of 'gluing' the plug to, say, a stick that extends up the trunk to fasten on the daggerboard pulley support. Of course if this all becomes complex (and heavy) one might just as well leave the daggerboard in place and stop trying to improve on Roger. I must admit that, with my love of poking about in, and anchoring in, shallow bays, I like to have no daggerboard protrusion.

Thanks for your thoughts.
Kittiwake

[arknoah]

I've often wondered about this with 26s. Our 25 has a swing keel so there isn't a hole in the hull where a dagger board slips through. What are the physics of this? I mean, how much water would come in if it was removed?

[parrothead]

My understanding is that Roger has cleverly arranged that the bottom of the daggerboard is flush with the hull when fully raised (to minimize turbulance) even though the fit is loose.

I can't deny that Roger is clever, but if your is like mine, the bottom of the dagger board is higher than the bottom of the hull when the board is full raised. See my suggested fix at http://www.macgregorsailors.com/modt/in ... ?view=1094

[Kittiwake]

Hi arknoah and parrothead.
Good question arknoah! ... indeed that's what worries me: the physics of it may be non-trivial; so that one wonders whether a simple plug in the daggerboard trunk lower opening would be torn out, sucked out, or pushed further in ... or all three depending on the speed. I know I have seen at least one comment on this ... so I searched it and came up with only an owner using a 90 HP OB on a 26M at 20 mph getting water up onto the deck and into the cockpit:
..............................................

"by Stefan » Tue Dec 07, 2010 10:51 am"

"today I was able to do the test run with just two people on board, no ballast and no load, even sails, boom and cushions were taken out to garage for winter storage, although didn't put down the mast yet.
The weather was perfect also.
So, I was able to make 21.7 knots at 6300-6400rpm WOT.
at 5000rpm I was running 16 knots, and at 2000rpm it was 5.5 (if not mistaken)
I like the results.

The bad thing is that at about 20 knots the water starts getting pushed through the daggerboard trunk and messing around the cockpit. I was surprised that it was still possible after I enlarged the daggerboard size (mostly thickness) to match the trunk size. It was so loose at first. "

...............................
We run only a 60 etec; but it certainly pulls off 18-19 mph (with mast! and 2 adults). I guess I wouldn't cry if water only came up the trunk at 19 mph; but being of scottish ancestry I hate to think of wasting fuel due to water turbulence below full speed.

Parrothead that is a clever mod, and appealingly simple (and inexpensive!). My daggerboard is less far up when fully retracted eg. 1 " ... gee I hope that's not just because I am not man enough to hold it suspended while tying it off. Hmm.

Best,
Kittiwake

[seahouse]

A true story...

In the mid to late 70's my father bought a 16' AMF Sunbird sailboat, restructured it (it was brand new) and installed a 35 hp* outboard and a ski bar, among other things. This was our first sailboat, as we had had power boats up until then. Below a certain speed, nothing unusual happened, but when motoring at speed a stream of water, like a fountain, flowed up from an opening in the centreboard trunk.

Q: Would you expect this to be a problem?

Answer- it was not a problem at all, and no remedial action was required, because the stream of water was directed upward and backward, so it exited over the transom and motor and went right back into the water. The cockpit remained dry, as long as you didn't get in the way of that stream!

It was hilarious when people saw this for the first time.

This reaffirms that there is a considerable positive inward pressure in this area of the hull.

- FYI Bri.

* a must-have here for traversing from the fast current of the Niagara river into Lake Erie.

[Divecoz]

Pull The Board All The Way Up.. Add 2 or 3 layers of Gorilla Tape..done... want it off ? Go under with a razor scraper and get an end / edge loose...

[Catigale]

Nice Dive.li bet that would work....

[Russ]

Pull The Board All The Way Up.. Add 2 or 3 layers of Gorilla Tape..done... want it off ? Go under with a razor scraper and get an end / edge loose...

KISS method. Perfect.

Personally, I want to use the dagger under power at times. Like when docking etc. Under slow speeds, I'll even drop it just a few inches to give a little bite in the water.

Oh yea, and bringing up on the trailer without the dagger would be hard with any wind. I have a helper pull it up just before we "hit" the trailer.

[Kittiwake]

Wow seahouse, that is the greatest story! Hilarious it must have been! And moreover it does seem to affirm that the major physics issue involved will be upward pressure at high speed.

Divecoz, that sounds worth a try (the tape trick) ... but do keep in mind that my original idea was to REMOVE the daggerboard entirely for my 10-day adventures into the unknown: with a 60 HP etec there is no reported problem of waterflow up through the trunk WITH the daggerboard in place.

Based on the feedback, I will try a simple 5" (or longer) tight plug of tough, closed-cell 'styrofaom'; but will place a light 66" length of wood (1.5"x1.5" should do) above it braced against the deck pulley (trunk length is 71") to keep it from being pushed upward. I'll let you know next summer whether it falls out.

Thanks all for your input.
Kittiwake

[Kittiwake]

RussMT I am interested to hear of your experience with the daggerboard while motoring. Roger suggests this can be useful too. Seems it should reduce the amount of oversteering one experiences when motoring with rudders pulled up. And anything that reduces side-slip in tight quarters such as windy marinas is worth consideration! I must admit, I tend to forget that I've got the daggerboard down; and I always am single-handed when launching and retrieving (small wife).
Kittiwake

[mastreb]

If your concern is actually water (as opposed to drag) you could plug the top of the centerboard trunk. Much simpler and accessible while the boat is in the water, and not under pressure.

I think Dive is on the right track with tape, but I'm fairly certain that the variable water pressure beating against the tape will stretch it (like a sail blowing out), causing increased beating, until it fails. Water neutralizes tape glues, and as the tape beats and wets it will separate slightly, be neutralized by water in the new gap, repeat, and eventually come off completely.

Combine the closed-cell foam with the tape. The foam keeps the tape in place without moving, which will eliminated the beating and subsequent failure, and the foam keeps the hull shape optimal for lowest drag.

The problem with foam on a stick is that about five minutes in, you'll watch the stick disappear with your foam attached to it out the bottom of the trunk. The foam plug will compress and move inside the trunk as soon as its subjected to significant forces. Remember that there will be many pounds of water pressure pushing up on that foam at all times, and multiplied when the boat is under power. You'll need to withstand likely 1000 lbs. of force on that foam at 15 knots. Your "stick" would have to be about the size of the dagger-board to put even pressure on the foam plug (hint).

Pull the dagger-board up 2" into the trunk and shape a piece of foam to hold against the daggerboard, fit the hull shape, and then tape over the bottom to keep it dry. By using the dagger-board pulled up higher into the trunk, if you decide you need it you can force it down the trunk, thereby pushing out the foam plug and glue, and be out all of $2 in material.

Tape+foam+daggerboard=solved.

[Catigale]

Couldn't you latch the foam into place with a hasp?