Strut Q

[Yannis]

As I was wandering around, I saw those 4 + 4 double nuts that attach the 2 struts to the hull. I was from the inside, the deck is removed.
They each took 1/2 to 1 turn, despite that some (...not all, for no reason really) are security nuts.
Someone told me that because of this, I might have to check the shaft alignments.

Is that so? Thanks.

[Navatech]

Loose struts ARE a problem... My first question would be: when did you last tighten the nuts?!... The answer is important because it could indicate a problem...

And yes, if you had to tighten the nuts you should check the shaft alignment... And that's for 2 reasons:

1) The strut nuts may have come loose due to vibration caused by a previously existing miss-alignment...
2) Tightening the strut nuts may have caused the struts to move... That means that even if you previously were aligned correctly you're now miss-aligned...

I would also have the propellors checked... Out of balance propellors might have caused the vibration that caused the nuts to loosen...

[Yannis]

Wow Nav !

I thought I could get away with it.

I last tightened the nuts last spring before i left.
Can you decipher anything from this ?

[Navatech]

I thought I could get away with it.

You still might... Things don't have to be perfect for them to function reasonably well...

I last tightened the nuts last spring before i left.
Can you decipher anything from this ?

Not really but it does bother me that your nuts get loosened in roughly a year's worth of boating... They shouldn't do that...

It might be an alignment issue but you also might have an issue with the hull... Since your boat is hauled out right now I think (it's what I would do if I were you) you should do the following:

1) Take the propellors to a propellor shop and have them checked out (balance, pitch cup etc.)...
2) Have the whole drive train (engine, gear & shaft) realigned... Make sure your engine and gear supports are good...

Then, a year from now, if your nuts are loose again, it's time to redo your strut supports (a.k.a. backing pad)... The problem there is that the hull is stiffened (reinforced) with a "sandwich" of FRP (hull), marine plywood (stiffener a.k.a. backing pad), FRP... It's not impossible that your stiffener (a.k.a. backing pad) is turning into mush... The (phenolic) glue holding the marine plywood together is water proof but the wood plies (layers) are still wood... Given the right (wrong for you) conditions this wood can rot...

If you do have to redo your strut support read the following link:

http://bertram31.com/proj/struts/strut_backing.htm

If your hull is still good (as opposed to the hull in the link) you might be able to get away with just removing the existing pad and putting in a new (larger) pad... Personally, instead of a plywood pad, I would either get a manufactured FRP plate or I would build up an FRP plate myself... If the latter I would look into vacuum techniques...

[Pete Fallon]

Yannis,
I also had the double nut bronze strut bolts on my 1961 31' express, there was also a copper backing plate on the inside of the hull between the strut pad and the bolts. When I had new bronze struts cast at Buck Algonquin in Michigan back in 1994,I redid the backing plates with glassed over plywood. I used Loctite on the nuts and they were tight when I sold the boat in 2014. The reason for having new struts cast was that over the years 9#4) the barrels of each strut were becoming thin, there wasn't that much meat on them to start. In 1993 I wrapped up a lead long line in the starboard wheel at 25 miles an hour and there was a very small crack in the strut barrel that confirmed that I needed to have new struts cast. Back in the mid 90's the new struts cost me $900 a pair plus shipping to Massachusetts $ 80.00 .
I would keep a close watch on those strut nuts and any type of wear around the holes in the plywood backing plates, if you see any elongation around the holes or if you have any water leaks in that area it's time to change out the pads to new FRP or plywood coated backing plates with metal backing for extra support.
Pete Fallon

[Yannis]

Thanks Pete.

There doesnt seem to be either water intrusion or deterioration of the existing plywood.
However, as you're suggesting, I'll be keeping an open eye on the struts and nuts.
One thing though, I was told that proper alignment is done IN the water, not on the hard, since the boat sitting on the metal drums is by definition somehow "twisted". If so, how can you pull the shaft, even for a little while, without risking to keep permanent company to the fish and other marine life?

I also remember that last year my mechanic had pulled the shafts for checking because I had a bent prop fin by a rope. So he pulled the prop to send to the shop and pulled the shafts also while he was at it. In the process he changed the cutlass bearings. How did he do the alignment in the hard? Maybe my alignment needs some revision.

[Carl]

Yannis,

If you have plywood as your backing material...it has been my experience that I can often give a turn or so on the strut nuts even when plywood looks pretty good. Maybe that's the reason its not the best material to use unless its encapsulated.
In my head, I figure the fibers are crushing, humid conditions under the deck deteriorate it a bit, you mentioned bending a prop...could have yanked the strut a bit crushing wood fibers a bit...so a little turn to snug isn't a huge problem...provided the strut is still sealed in place, bolts did not turn breaking seal allowing water to weap in...I'd snug and leave...keep an eye on it...consider replacing pads as an off season project.

Alignment-
If boats on the hard...I'd eyeball the strut...see if angles match the other side, take a look as to how shaft sits in cutless...does it appear to be straight thru and sitting evenly at the 6:Oclock position or do you see gaps on one side with rubber squeezed at the other, that would indicate alignment is out...also the prop should turn fairly easily by hand?
If you really want to verify alignment, you'll need to loosen the coupling bolts, pull coupling apart then bring back together, using a feeler gage verify space between two coupling faces is within .08mm at the 12,3,6 and 9 O:clock positions.

On the hard, I'd verify shaft thru cutless is centered and ease of turning the shaft...if that's good I'd wait on playing with the feeler gauge for anything other then getting a rough number (.15-.2mm) as it can change after boat goes back in.

[Navatech]

I was told that proper alignment is done IN the water, not on the hard, since the boat sitting on the metal drums is by definition somehow "twisted".

A "rough" alignment is done on the hard and the final alignment is done in the water... The reason is that the supports do not support the hull the same way it is supported in the water... And therefore it's possible that the hull will be "twisted" somewhat when out of the water... Furthermore, the longer the boat has been out of the water the more time in the water it needs to "untwist"...

If so, how can you pull the shaft, even for a little while, without risking to keep permanent company to the fish and other marine life?

As long as the shaft is in place you won't join the fish... You don't need to pull the shaft all the way out... You only need to pull the coupling a little way and you don't have to remove the coupling bolts all the way...

I also remember that last year my mechanic had pulled the shafts for checking because I had a bent prop fin by a rope. So he pulled the prop to send to the shop and pulled the shafts also while he was at it. In the process he changed the cutlass bearings. How did he do the alignment in the hard? Maybe my alignment needs some revision.

Only your mechanic can tell you what he did... I think that at this point a realignment is in order... Rough on the hard and final in the water (a day or two after you have been put back in the water)...

[Yannis]

Thanks guys.

Or, it may also be that after I bent that prop fin I had to also return home, which was another 200 miles (with a bent prop) - I imagine that issue alone might destabilize a strut.

What I don't want is to have to redo my struts at this point in time where I'm ready to splash and go and all technicians are extremely difficult to find.
I know though that the "engine mounts/strut/alignment" chapter is for next September... Together with the tank...

Sometimes I sit back and watch on you tube those nice new boats - no matter the size - where everything seems so NEW ! where everything works by itself, without your having to bend into awkward positions to fix ... where captains and crew are smiling and they don't seem tired at all ... for a few instances like these I envy them... what about you guys?

[Carl]

Maybe things are different in your neck of the woods, but around here it doesn't matter if you shell out 40k, 100k or a million and change.... When you take possession of a new boat expect problems...then expect long delays trying to get the problem or problems rectified. On top of the problem you get to make heavy monthly installments to the bank.

Choose your poison...


200 miles on a banged up prop...that can beat up a plywood strut pad allowing a crank or two on strut bolts....my opinion anyway.

[Yannis]

Thanx Carl.

What is strange though is that even those self securing nuts needed half a crank. I would think that this type of nut would never loosen up.

[Yannis]

Personally, instead of a plywood pad, I would either get a manufactured FRP plate or I would build up an FRP plate myself... If the latter I would look into vacuum techniques...

Does anybody know what size and thickness should this new strut pad be?
Would you also consider any hard wood such as iroko, instead.
Thanks.

[Navatech]

Maybe things are different in your neck of the woods, but around here it doesn't matter if you shell out 40k, 100k or a million and change.... When you take possession of a new boat expect problems...then expect long delays trying to get the problem or problems rectified.

Having served most of my naval service on a brand new vessel - I was part of the launching crew and, in my maritime experience having worked on a vessel from her 2nd voyage through her 4th voyage and then a few more voyages afterwards I can categorically state that if you would graph the technical issues against the vessel's life what you'll see is a huge spike during the first year of operation (when all the yard SNAFU's come to light) followed by a drastic drop (the so called warranty repairs after which you'll see a slightly upward line with occasional drops (regular maintenance sessions)...

[Navatech]

What is strange though is that even those self securing nuts needed half a crank. I would think that this type of nut would never loosen up.

NyLoc nuts, as their name indicates, have a section that's made out of nylon and which has a slightly smaller diameter then the screw... When you install such a nut the nylon will cause friction resisting self unthreading... However, if you run them on and off several times the nylon will loose material and friction...



The most secure nuts are the castellated nuts (when secured with wire or a cotter pin...

Does anybody know what size and thickness should this new strut pad be?

The size should be, AT LEAST, as big as the existing one and, if you have the space, make it bigger... Up to about 150% of the original size would be good...

Would you also consider any hard wood such as iroko, instead.

The whole point of going with a non-wood panel is to eliminate any possibility of rot... If you're going to use wood it doesn't matter much which wood you're going with...

And yes, going 200 miles with a banged up propellor might cause enough vibration to loosen your nuts (no pun intended)... However, if BOTH of your struts needed tightening (which is the case as I understood it) then I'm not sure that's your only issue...

[Tony Meola]

http://bertram31.com/proj/tips/bronze_shaft_alleys.htm

http://bertram31.com/proj/struts/strut_backing.htm

Yannis

these two articles will help. The strut pad replacement in the one includes how to fix it if it damages the hull. That step you can skip.

[Yannis]

Was it Adam Smith who wrote "The wealth of Nations"? Here it is "The wealth of the Bertram Owner". Thanks guys.

[Carl]

Hmmm...so your thinking the nuts loosened up as in backed off...

I was thinking the wood pad crushed a little allowing you to further tighten nuts past the original stopping point.

6 of 1 and half a dozen of the other...


Then again...unless you snugged the nuts down yourself...you don't know how tight they were to begin with.

[Yannis]

so your thinking the nuts loosened up as in backed off...

Yes, while everyone here thinks that the pad collapsed etc...

unless you snugged the nuts down yourself...you don't know how tight they were to begin with.

yeah, which I didn't, so I cant be sure how tight they were ...

Whatever the reason, in September I will have to rethink the whole topic. I only hope the setup will last until then (and the 1000 or so miles that I will put on the boat over the summer).

I also checked the nuts of the steering system... they're all loose too, I suspect the vibration of the engines at idle.

[Hyena Love]

B28's have a different strut pad set up, relative to the B31. Essentially, there is no need for the addition of a plywood strut pad in the B28. That was addressed at the factory with the pad already glassed in place.

Alignment - as in minor adjustments - is not really that big of a deal. First time or two, it seems like a big deal. Then, its just another job. So, just learn how to do it. Its going to come up again in the future, so there is no time like the present to learn how.

I would not run my boat a 1,000 miles with bad alignment. Nothing good could ever come of that, and there are some bad things that can happen. Its one of those deals where its cheap to do it right today, and potentially expensive to fix/repair down the road.

[Navatech]

I also checked the nuts of the steering system... they're all loose too, I suspect the vibration of the engines at idle.

Yannis, it's always a good idea to check and verify that nothing has shaken loose from one season to another... You might want to invest in a so called torque wrench... Tightening by hand is OK but if you want to be sure that stuff is secure a torque wrench will actually measure how hard you tighten the bolt/nut... And, if you keep a record of your values you will be able to differentiate between what you think/remember and what you're actually doing...

As for vibrations, there's a reason that in aviation just about everything on the engine is secured with wire... Boats will float even without power... Practically for ever... Planes won't stay in the air without power...

As for a crushed pad, as I said earlier, if you keep a careful eye on it, it won't be much of a risk to just tighten up the nuts and take the wait & see position... On the other hand, alignment is a much less forgiving issue... If you know you might have an alignment issue don't wait for it to get worse... Vibrations (and the damage) only get worse over time!...

The initial alignment is that of the shaft and it's ancillaries (struts, log)... All the rest (gear, engine) is then adjusted relative to the shaft... Since you're out of the water it shouldn't be that hard to get the running gear (shaft, strut, log) aligned... Then, after being a day or two in the water, you can get the engines & gears aligned...

[Tony Meola]

http://www.yachtsurvey.com/Alignment2.htm

http://blog.boattrader.com/2013/05/inbo ... nment.html

Yannis

I know you have nothing else to do, so here are a few more links for your reading pleasure.

[Yannis]

I hear you all and thanks.

I'll discuss with my mechanic and revert.