Stub keel first launch

A forum for discussing boat or trailer repairs or modifications that you have made or are considering.
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Ixneigh
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Re: Stub keel

Post by Ixneigh »

Inquisitor wrote: Fri Nov 06, 2020 8:15 am I don't want to be a curmudgeon...

I like the idea, however... about tide beaching. In sand... might be fine. Then again again any wave action while dug in might be an issue. If something hard under it, it'll either snap off (if your lucky) otherwise... might put one hull of a stress load on your keel. Just something to consider.

Image
The bottoms of these boats are already fairly thick, in part because thick fiberglass was cheaper than installing more internal ballast. The keel will not fall off. It may get ground down or gnawed off by rocks I suppose. The keel is long enough and wide enough to support the full weight of the boat. In the common areas I let the boat dry out it’s grassy mud. On hard sand the boat may lean over a little. I’m pretty picky where I let the boat dry because of rocks, or in the Bahamas, conch. (!)
The keel should not be any deeper than the deepest part of the hull at any rate.

Ix
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Ixneigh
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Re: Stub keel

Post by Ixneigh »

Highlander wrote: Thu Nov 05, 2020 1:55 pm Well interesting project & u got all winter in Florida to do it :D :P

Some guy,s on here have added the glue on chines or splash rails , maybe they can chip in :wink:

I,ve often wondered how a inverted swing up dorsal fin under the aft section of the V Berth in a self contained trunk would work for inproving upwind sailing & sailing in general this would b approx 3ft in front of the D/B trunk approx 18" wide & 24" deep :arrow: :idea:
keep us all posted with pic,s :)
J 8)
The boat already has weather helm to various degrees depending on configuration. Anything forward will add to that. The best ways to improve upwind sailing are all pretty cheap. Right sail up. Keep boat light(ish) take down large dodgers or enclosures and have a good reefing system. Running back stays will help keep sag out of the head stay. Or you can motor up wind 🤩🤩😂😂🙄🤷🏻‍♀️

The place for the 2ndary board would be under the aft berth. The twin skegs I installed sort of do the same thing, a little less elegantly, but a lot easier.

Ix
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Re: Stub keel

Post by Inquisitor »

Ixneigh wrote: Tue Nov 10, 2020 8:00 pm The bottoms of these boats are already fairly thick, in part because thick fiberglass was cheaper than installing more internal ballast. The keel will not fall off. It may get ground down or gnawed off by rocks I suppose. The keel is long enough and wide enough to support the full weight of the boat. In the common areas I let the boat dry out it’s grassy mud. On hard sand the boat may lean over a little. I’m pretty picky where I let the boat dry because of rocks, or in the Bahamas, conch. (!)
The keel should not be any deeper than the deepest part of the hull at any rate.

Ix
I am still re-getting the lay of the land on this forum. I am just getting to the point where I recognize someone's post and know enough about their other writings to judge how I "really" need to interpret their words. There are certain people already, that I know their writings will always be well thought out and something I should heed. JimmyT, Highlander, BOAT... others. I look to these people as experts in one thing or another. We all have varied backgrounds. Being an expert in one field does not necessarily carry over into others. A college degree doesn't give any overall superiority status. At my age, I've learned never to assume I "know it all". It only builds glass houses. I know day laborers that have taught me a thing or two. I sincerely appreciate this forum and its experts for what they are teaching me.

Not having crossed paths with your writings, I took your original post at face value only. At the very least, I should have noted your Admiral status. After Highlander's subtle rebuke, I did note that and since then... some of your other writings. I am sure your design is well thought out and will work.

However... for others that might launch their own design from this thread...

As I feel a need to give back to this forum and if I have any expertise to offer, its analytical design and analysis of composite structures. The caveat to that... my background is with more exotic materials. I have never designed professionally with fiberglass matt and cloth (rovings) using polyester. IOW, I'd take someone's advice that has direct experience with fiberglass and actual knowledge of the Mac hull design.

I respectively disagree with Highlander's assessment that the Mac's hull is "hull for stout" and you can just do anything, anywhere. MacGregor's design has been optimized... whether it be from analytical design and analysis OR just good old iterative experience... MEANING... he didn't waste material where it was not needed. Yes, the hull will take 11000 lbs (sic) on the trailer... but move that trailer bunk back two feet and I am certain you will get a very bad experience.

Point being... I was in my boat all yesterday scrubbing the bilge. While the reinforcement where the trailer bunk IS hull for stout... probably somewhere between 1/2" and 3/4" thick, the hull underneath the aft bunk is closer to 1/4". It flexes quite easily under my weight. As your design stops at the bunk, I'd guess you're good to go. But... I would not recommend anyone going back to the transom. If they used the same layup schedule mounting a keel in that area as they did forward of the bunk, it would overly stress that weak 1/4" floor. Just saying... bad things will happen.

On a lighter note...
I definitely have added you to my list of tutors. Your experience is far different than mine... and now that I'm retired, I may get to sail in grounds like you have every day. I've never thought about the shallow waters in the Keys nor having too much wind. Maybe, I need to consider that.
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Russ
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Re: Stub keel

Post by Russ »

Inquisitor wrote: Wed Nov 11, 2020 3:42 am I am still re-getting the lay of the land on this forum. I am just getting to the point where I recognize someone's post and know enough about their other writings to judge how I "really" need to interpret their words. There are certain people already, that I know their writings will always be well thought out and something I should heed.
Many members here bring amazing knowledge and skills. I've learned soooo much from them.

Ix has a great youtube channel as well. Check it out.

https://www.youtube.com/user/LastLionMonday/featured
--Russ
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Ixneigh
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Re: Stub keel

Post by Ixneigh »

Image

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Here are some pictures finally. I bonded the keel to the bottom of The boat today. It will be additionally secured with a few passes of fiberglass for now. I like the looks of this. Boy it was a pita to get to this point though. Note the added trailer bunk blocking. That much was needed to get enough space under the very bottom of the boat for the keel. That should also prevent the boat from rocking back on the trailer when pulling her out. (No more Mac bump, no more yanking the winch off because it’s up too tight while pulling out) I’m going to make a fore and aft trailer bunk on each side, attached to the existing transverse supports. I’d like to end up with the boat supported in more places than I started with.

Re hull thickness under aft bunk: the “floor” under the aft bunk is actually the top of the water ballast tank. The bottoms of these boats have to be able to smash through waves at 20 knots ( if your boat is completely empty 😂😂) so it’s substantial, thankfully. You would not be able to flex it by walking on it.
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Re: Stub keel

Post by Inquisitor »

Ixneigh wrote: Thu Nov 19, 2020 4:29 pm
...

Here are some pictures finally. I bonded the keel to the bottom of The boat today. It will be additionally secured with a few passes of fiberglass for now. I like the looks of this. Boy it was a pita to get to this point though. Note the added trailer bunk blocking. That much was needed to get enough space under the very bottom of the boat for the keel. That should also prevent the boat from rocking back on the trailer when pulling her out. (No more Mac bump, no more yanking the winch off because it’s up too tight while pulling out) I’m going to make a fore and aft trailer bunk on each side, attached to the existing transverse supports. I’d like to end up with the boat supported in more places than I started with.

Re hull thickness under aft bunk: the “floor” under the aft bunk is actually the top of the water ballast tank. The bottoms of these boats have to be able to smash through waves at 20 knots ( if your boat is completely empty 😂😂) so it’s substantial, thankfully. You would not be able to flex it by walking on it.
Ix
I think this is way cool! In fact, I'd request more pictures and details... especially, materials used... FG areal weight, resin (polyester, vinylester, epoxy), core, form or whatever you used and going forward what you do to replace the outer gel-coat, barrier, etc. Do you trailer a lot or mainly just to get it to a slip and leave it for the season?

Also... did you do some kind of test to see what your side-slip is with the board up and plan to do the same test with your addition? I'm not asking to challenge you... just... I wonder if there is some way to do such a test without expensive test gear.

Also... are you sure about that being the top side of the ballast tank? I thought the tank was forward and only the two runners (stringers) to the transom contained ballast water. I'll have to get the Admiral underneath while I press on the inside.
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Ixneigh
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Re: Stub keel

Post by Ixneigh »

That’s probably fair request. It’s cored with A grade spruce. Covered with Three laminates of midweight biax glass and steel flex brand epoxy. It’s glued to the bottom with epoxy paste glue and will be bonded with a few passes of biax strips as well for now till I see how it works. If I don’t like it I can remove it with not too much difficulty. If it’s good I can add a few more passes of glass.

Re testing, I’ll be able to tell right away if it’s doing much. I frequently sail the boat in shallow water with no board, and am very familiar with her quirks and vices in this environment. One problem is slip of course. But another Vice is hesitancy to come about. I used to club haul the boat in these conditions but my current anchor does not allow that (too heavy). I can’t blame the boat for not tacking with nothing underneath. Oh yea. A jib helps a lot but I often use only the main out of laziness. Especially if it’s already windy and I want to go slow. So by now the boat is all like, FFS pal what exactly do you want out of me? I hope that little bit of something down there will be just enough to help her through tacks, and give a little bit more slip resistance and also ease the stress on the steering while the rudders are in the “dont sail the boat with the rudders like that” position. When the boat heels in deeper water I *think* the effect of the stub keel will be “lost” since it won’t be on the deepest part of the hull any more. That’s my assumption. I’m not counting on it doing much then and the boat doesn’t need much help then anyway.
It shouldn’t impact high speed motoring much. I’ll report on that anyway.
Re Use: I do not trailer much. I live on the boat most of the year. I park it in my yard during the summer months. I’m
Way late this year getting in.

Re back water tank. Yes that’s the tank top. The M has a water ballast tank back there.

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Re: Stub keel

Post by Inquisitor »

I keep several links to the Weather Channel for places I want to sail. I check them every once in a while... like this morning, I wouldn't aim the boat toward anything north of the Keys. I may be more willing to take risk for sailing enjoyment, but warmth is a must have. :D

Would you mind telling us what is driving your decision to add the stub keel? Is it where you want to sail the most, or is it shifting of shoals that you might strike otherwise? How much of the time do you need to raise the board? I'm looking at the charts for the area around you and see a lot of double digit depths.

VBR
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Re: Stub keel

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I'm also wondering... how much an X differs from the M for this. What is the sailing balance for say... 1 foot DB depth vs 1 foot swing keel depth.
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Re: Stub keel

Post by Ixneigh »

The reason for the keel is just the way I use the boat. I sail with the board up, very often. I like sailing in the shallows at night, or have other places that don’t permit the rudders and board to be down, that I like to go. The visibility is usually poor, and the charts are not as accurate in the shallows.

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Re: Stub keel

Post by Ixneigh »

Here are the pictures of the completed project. This was the most difficult mod I’ve done yet because I had to redo the trailer bunks too. It’s five feet long and four inches deep. Hope it works.

Image

Image


Ix
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Re: Stub keel

Post by Neo »

Interesting :) ... please report back after a full test out.
All the best.
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Re: Stub keel

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That looks like it was built like that from the factory. My fiberglass work on my daggerboard looks like monkeys did it.
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Re: Stub keel

Post by Russ »

Looks great Ix, can't wait to hear performance reports. Looks like that will only add a couple of inches to the depth which maintains your shoal draft objective.
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Re: Stub keel

Post by ris »

Ixneigh we put a 6 inch X 42 inch long skeg on the Jill Kristy in Jan 2019. Its in the mod section under 26 X boats. The reason we did it is that the auto pilot would not work without the rudders down. Since we are a motoring Mac we took the rudders off. With the skeg on the boat it tracks straight, it even helps when docking the boat. We did the 6100 mile loop in 2019 and the skeg worked great. We used two 1/2 plywood pieces epoxyed together, then covered in epoxy and then fiberglassed it to the hull. We then put 4 coats bottom paint and 2 ablative coats on the skeg. I was going to make it longer but this length ends just short of the trailer.

Image

Richard
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