PBO Sept 2004 ???

wragges

wragges

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Nottingham, UK
www.minstercomputers.com
Hi All,

Can anyone provide me with a copy/scan/email of the Fibreglassing a P-bracket on p79 of the Sept 2004 PBO?

I know I can buy a copy from the library service but I'm not sure I can part with £1.50 for 1/3rd of a page of A4. I'd be happy to send it to the RNLI but I feel the heavily advert-ladened mags make enought out of us already.
 
[ QUOTE ]
Fibreglassing a P-bracket on p79 of the Sept 2004 PBO?

[/ QUOTE ] I think you will find that it is HERE
 
G'day VicS,

Nice find, but not what I expected, perhaps they had limited space to fit all required and important information into.

Like 'alignment Critical' but a single word on how to preserve it. Also shocked to see a recommendation to just add more material on the outside, increasing drag, weight and possible cavitation of the prop, at the very least a loss in prop efficiency.

If a 'P' bracket has movement it's not going to get better, if left it will get a lot worse and chew bushes off the shaft.

I have seen 'P' brackets flexing on new hulls to the point that new bushes had to fitted every season, a simple addition of more glass over the area was all that was required, 30 minutes and all done including a top coat and all in epoxy.

But the bracket has broken its bond it should be removed and rebuilt without extra lumps on the underside.

Just my 2 bobs worth.

Avagoodweekend......
 
I suggest that the article is not worth the digits it is written on. There is very little possibility that you will arrest movement of the P-bracket with a bit of filler. You really need to address the problem at source.

When I did mine I wrote up the job for the Sadler website. Here it is. Note that mine was not replaced due to looseness but due to damage to the cutless bearing housing.

As supplied, the new bracket differed from the old, in that it was about 3 inches longer and aerofoil section all the way up, whereas the old one widened into a rectangular section where it entered the hull. I managed to remove the old one without grinding at all, to minimise dust. A 2 lb lump hammer and old wood chisels were up to the job, although the chisels were not happy when they hit metal parts! I was not too impressed by Sadler's handiwork. As advised, two short lengths of stainless steel angle were bolted through the hull each side of the bracket using 8 mm countersunk bolts but the through-bolting of the three was done very poorly. It appeared that everything was offered up to the hull, with wet GRP between all, then two 5 mm holes drilled through the lot at an angle of about 45 degrees. Long, spindly bolts were then fitted and tightened, giving very poor mechanical strength and lots of possibilities for movement. However, I will say that no movement was apparent under hand loads.

The reason for this strange arrangement is that, due to the offset location of the P-bracket in the hull, the steel angles are at differing heights on each side. To improve this I built up the hull on the lower, central side with glass and epoxy, allowing two 8 mm bolts to be bolted straight through the angles and bracket, giving far greater strength. With no epoxy at all the bracket was very stiff indeed. Once I had included the epoxy everything seemed quite satisfactory.

I cut 3 inches off the new bracket using an angle grinder. New holes through angles and bracket were drilled using a hand held drill, not the best arrangement, but accomplished OK using cobalt bits. Finally, everything was covered with layers of glass and epoxy, then covered in a layer of epoxy mixed with filler. All looks OK, alignment of the shaft and bracket was very easy and the shaft turns very freely with no evidence of movement at the Aquadrive connection. Finally, the shaft was checked for straightness using a clock gauge, and found to be OK, just in case we still experience the same knocking.

The photos show the old and new P-brackets and the holes in the hull to which the angle brackets are bolted.

IMG_2210.jpg

IMG_2215.jpg
 
G'day Viv,

I see what you mean about workmanship, plenty of bog on the left side, or did the screws get set deeper? I wonder why the screws were placed so close to the centre reducing the leverage and increasing the load.

I hope the white bits are scrapes and not low resin spots.

Avagoodweekend......
 
The hole spacing is a consequence of the angle size selected, which was 1 inch. I would have preferred to use 2 inch angle but I didn't really want to drill a new set of holes, and the existing one had been OK for 20 years. Replacing the transverse bolts and increasing their diameter to 8 mm made the whole job far stronger.

The photo shows antifouling on top of Gelshield 200, with GRP beneath that. I don't think the white bits are anything significant, certainly no evidence of bad construction of the hull. I tapped the old P-bracket out and I think what you are seeing is just the resulting gouge.
 
Hmmm

Not that using PBO's forum makes you feel guilty though. Does it?

Prid pro quo.

Donald
 
Vyv,

Your experience mirrors mine on my Sadler29 precisely. The only difference being that my angle-plates were aluminium rather than S/S ... hardly ideal.

In my case the P-bracket was loosened by an unfortunate encounter with a mooring rope in Portland Hbr. However the original was also badly de-zincified which I put down to it never having been bonded to the anodes (think we've discussed this elsewhere).

One useful thing I learned from the saga is that it's a lot easier to align a P-bracket to an engine than the other way around. (maybe that's how most builders do it, but my Sadler came with the P fitted but the engine 'loose').

Vic
 
Vic,

Yes, the alignment was a real eye-opener. Without a great deal of difficulty I was able to achieve shaft rotation with far less friction than previously. The new cutless bearing and P-bracket aligned themselves perfectly.

With the shaft coupling aligned correctly and the shaft passing centrally though the stern tube, the old P-bracket was visibly tilted. Taking the shaft out and lining it up centrally in the cutless bearing put its axis at least 1/2 inch off the axis of the stern tube.

Vyv
 
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