Keel Bedding Survey

[KWKloeber]

@High Anxiety

The aft-most nut was so loose my thumb turned it

I've previously posted about my same experience re: the fingertight aft nut and keel bedding so many times that my head hurts every time I repost about it.

The washers were set into the original gelcoat, which formed a surprisingly poor seal;

Are you thinking that CTY bolted-up the keel nuts/washers into wet gelcoat?  Doesn't seem logical to me.  What does, is the known issue on C-30s of torquing the nuts so many times that the washers compress the glass and bury themselves in the gelcoat.

Whether or not that underlying bedding is still intact is the (hopefully less than) $64,000 question.

hemming and hawing over whether to drop the keel. 

IIWMB my hem/haw would not be whether to drop the keel -- rather, my first step would be to decide WHEN to determine if I EVEN NEED TO drop the keel.  That is, answer that question right now — OR just go sailing now and answer it in fall '24 / spring '25. 
Nothing is going to change before then and the keel will not fall off if you put off finding that out.

Like engines, plumbing, electrical, and other systems: one should not play Whack-a-Mole and willy-nilly replace/fix before one troubleshoots, Troubleshoots, TROUBLESHOOTs.
(Then play "more-informed" Whack-a-Mole.)

possible damage from and difficulty with separating it, and I'm placing a lot of trust in the yard to do everything right

Removing the keel is also a costly job that could lead to more costly jobs on a 34 year old boat. 

Removing the keel is lightyears distant from being rocket science.
If I did it with no previous experience in dismembering the appendage, (IMO only) any other idiot like me **should** also be able to.
It's nasty, laborious (but not "difficult") work. 
Reattaching it takes brain power (unfortunately I learned that the hard way.)

That said I'm unsure whether I would trust the yard with anything.  Someone who blocks jack stands with 2x4s has (IMO only) questionable knowledge/conscientiousness and at worst doesn't care about their customers' yachts.  Gimmeabreak -- don't they have lumber yards in ME?

check torque often.

See above for (IMO) the danger of too-often and too-tighting of the keel nuts.
Keel nuts that are 40 ft-lbs shy do not cause the Catalina smile.

Previous info about my "no aft smile" and the loose aft nut (in no particular order):

https://groups.io/g/Catalina30/search?d=0&ev=0&p=recentpostdate%2Fsticky%2C%2C%2522keel%2522+AND+carbide%2C20%2C2%2C0%2C0&ct=1&startdate=&enddate=

https://www.sailnet.com/posts/2051801875/
https://www.sailnet.com/posts/319785/

https://c34.org/search_gcse/?q=%22kwkloeber%22%20%22keel%22%20joint%20OR%20bedding%20OR%20carbide

https://c34.org/bbs/index.php?msg=97345
https://c34.org/bbs/index.php?msg=82156
https://c34.org/bbs/index.php?msg=81134
https://c34.org/bbs/index.php?msg=74413
https://c34.org/bbs/index.php?msg=71726
https://c34.org/bbs/index.php?msg=67529

My saga about reattaching the keel:
https://c34.org/bbs/index.php?msg=67822

[girmann]

Previous info about my "no aft smile" and the loose aft nut (in no particular order):

I think that the only way you will really know the answer to this question is if you have a mechanical engineering friend. Knowing that type, turn it into some kind of bet and offer them a case of their favorite beverage so they do a "Finite element analysis" of the keel/hull joint blocked in the front or blocked fore and aft.

Logic dictates that the bolt isn't stretching, but the piece of keel that sticks out forward of the forward most keel bolt can bend. I'm not saying it does bend, I'm saying it "could". FEA (finite element analysis) would tell you exactly how much force you would need to create a "smile"

Mark
Mola Mola

[KWKloeber]

Mark

Just for context 'fer others I think you are referring to
https://c34.org/bbs/index.php/topic,11903.msg97457.html#msg97457

not
https://c34.org/bbs/index.php/topic,11903.msg97563.html#msg97563
(which links pertain to deterioration aft, not a fwd smile (which I did not have,) and my prior experience rebedding the keel joint material.)

-ken

Previous info about my "no aft smile" and the loose aft nut (in no particular order):

I think that the only way you will really know the answer to this question is if you have a mechanical engineering friend. Knowing that type, turn it into some kind of bet and offer them a case of their favorite beverage so they do a "Finite element analysis" of the keel/hull joint blocked in the front or blocked fore and aft.

Logic dictates that the bolt isn't stretching, but the piece of keel that sticks out forward of the forward most keel bolt can bend. I'm not saying it does bend, I'm saying it "could". FEA (finite element analysis) would tell you exactly how much force you would need to create a "smile"

Mark
Mola Mola

[Ron Hill]

Guys : It doesn't take a Mechanical Engineer to have a travel lift operator set the boat down and improperly set the hull so you have a "Catalina Smile" in a second!! All he has to do is set the keel on the ground and let the hull rock back!!   

A thought

 

[KWKloeber]

Ron mon ami, are you saying that you have personally witnessed your smile occurring "in one second"?   All I have heard is that it was always claimed to occur over off-season storage, not "immediately."

I wonder how CTY's would square its explanation of the cause with the smile on my keel being at the aft end?  Too much weight on the nose of the keel perhaps?  More CTY fantasy.

I agree that it probably doesn't take an M.E. -- in order to deduce that the hefty hull/keel stub box-beam section (below) between the nose and the first bolt, will not bend in the short distance in front of the first bolt. 

(M.E.s deal with moving objects, eivil/structural engineers deal with
mechanics/statics/strength of materials and stress/strain/bending under load.)
.

[Ron Hill]

Ken : Maybe I haven't seen it in "a second", but I've seen it start in a few days!! That 5600 Lb. wing keel

stays put when it's on the ground!!

A thought

[High Current]

@High Anxiety

I've previously posted about my same experience re: the fingertight aft nut and keel bedding so many times that my head hurts every time I repost about it.

Well, thanks for doing it one more time.  I found your post quite helpful.  I've read a lot of posts about keels, including a few of yours, but managed to miss the similarity with the aft nut.

Are you thinking that CTY bolted-up the keel nuts/washers into wet gelcoat?  Doesn't seem logical to me.  What does, is the known issue on C-30s of torquing the nuts so many times that the washers compress the glass and bury themselves in the gelcoat.

Maybe it's not gelcoat per se, but whatever brittle white material coats the bottom of the sump partially covered all of the washers, appeared to be original, and cracked free easily when I disturbed it.  Photos below

That said I'm unsure whether I would trust the yard with anything.  Someone who blocks jack stands with 2x4s has (IMO only) questionable knowledge/conscientiousness and at worst doesn't care about their customers' yachts.  Gimmeabreak -- don't they have lumber yards in ME?

No kidding.  I have stories....

If I had time to do the work myself it wouldn't hesitate to DIY, but it's 4 hours away and I have young children who need me to pick them up from school every day.  My main reason to re-bed NOW would be to preserve integrity of the bolts.  BUT if I weren't going through this process I probably wouldn't be worrying about it...

See above for (IMO) the danger of too-often and too-tighting of the keel nuts.
Keel nuts that are 40 ft-lbs shy do not cause the Catalina smile.

Does it crush the solid glass or only the wood core that I don't have?

I used to think similarly but managed to convince myself otherwise.  Loose keel nuts put extra stress / strain on the keel-hull joint that could lead to cracks and water ingress.  On the other hand, I agree that 65 vs. 105 ft-lb is probably enough pre-load either way; at 105 ft-lb = ~10,000 lbf, a single bolt could hold the entire keel if it were in pure, static tension.

Reasons in favor of re-torquing that I can think of:
1)  Lead creep and other factors (see: corroded washer in my previous post) can reduce bolt tension over time
2)  Low bolt tension can lead to uneven loading of the keel and excessive stress/strain in the joint, possibly compromising the joint / bedding
3)  If a keel bolt has been severely corroded, I would rather have it snap off when I try to torque it on the hard than have it silently stop holding my keel.

------

(1) made me wonder:  What's the coefficient of thermal expansion of our hulls?  Does it matter at what temperature one torques the bolt?  Were my bolts loose simply because it was April?

I'm going to assume the keel stub is one inch thick (0.0254 m).

This says CTE of fiberglass is 25E-6 m/m-C: https://www.engineeringtoolbox.com/linear-expansion-coefficients-d_95.html  10 degC @ 1" would be 6.35E-6 m of expansion, or 0.025%.  Stainless is pretty close but let's ignore that for now to get a worst-case.

If I assume some lubrication (because anti-galling), then 105 ft-lb is about 10,000 lb of clamping force ≈ 44kN.  https://www.engineersedge.com/calculators/torque_calc.htm

The washers are 1 7/8" diameter.  Crudely, that amounts to 0.00178 m^2.  44kN / 0.00178 m^2 ≈ 25 MPa of stress.

Finally, looking here, one presumes strain is fairly linear at about 1% per 40 MPa:  https://www.researchgate.net/figure/Stress-strain-cure-for-fiberglass-Figure-6-The-stress-strain-curve-and-tyre-strip-for_fig4_305627338

Assuming I did it all right, 10C change in temperature causes 0.025% change in thickness which causes 1.8 MPa change in stress out of 25MPa total, before you consider that the stud is also contracting.  So no, temperature isn't a huge factor.  But that was fun!

[KWKloeber]

My main reason to re-bed NOW would be to preserve integrity of the bolts.  BUT if I weren't going through this process I probably wouldn't be worrying about it...

Correction,
The Main reason ..... IF I EVEN NEED to rebed is...
I don't understand the foregone conclusion that you need to rebed (i.e., the bolts are compromised)?

Does it crush the solid glass or only the wood core that I don't have?

at 105 ft-lb = ~10,000 lbf
 ≈ 25 MPa of stress.

But the entire section isn't compressed, just the topmost (floated?) layer of resin gets compromised.
 
https://www.boatdesign.net/attachments/fiberglass-strength-tests-pdf.148849/
Shows that the compressive strength of cured fiberglass resin is 55-mPa.

For a nominal 3/4" ID washer the stress @ 10,000#f would be ~30-mPa (if the nut doesn't bend the fender washer.)  Close enough to be possible considering that, naturally, strength depends on resin/hardener quality/characteristics and the quality of application.