Backing plates for shrouds
Posted: Tue Jan 06, 2009 5:18 pmI'm just starting to fix up a Mk 1 that I bought last year. It's moored at Toronto in Lake Macquarie.
The first thing is the rigging which definitely needs replacing and I want to strengthen a bit as well (going to 7/32" wire from a mixture of 3/16 and 5/32).
The backing plates under the shrouds look pathetically small, maybe 25 mm wide. Does anyone have any advice on how large they should be, what I material I should replace them with (6 mm stainless?), how best to bed the new ones in to the fairly uneven underside of the deck, etc??
Thanks!
Peter
Dragonfly (formerly Top Knot)
Hi All
Peter that's a good question. I had my Mk 1 re-rigged a year ago and at the time didn't think too much about it, I left everything up to the rigger who replaced like for like. Given that 3/16 wire has a breaking strength of 4,400 lbs it should be OK for many years, but your idea of going up to 7/32 is good because this will give you greater redundancy in the long run as it seems that where rigs fail (unless it is due to poor workmanship) it is usually crevice corrosion on the lower swaged fittings.
Talking of corrosion, I was recently undoing the bolts on the tiller only to have the nuts literally fall apart in my hands, I immediately thought, what if the nuts on the chain plate V bolts are the same condition? I checked them out and they seem OK but will replace them when I get around to it, the thing that is holding me up at the moment is getting at the bolts that are behind the metho stove hood. Rather than pull out the hood I am thinking that the easiest thing to do would be to cut an access hole through the hood and later cover it with a sheet of stainless steel screwed with self tappers.
Another thing I didn't think of when re-rigging was replacing the twin back stays with split back stays, have a look at this for the reasons why: http://www.briontoss.com/spartalk/showthread.php?t=180 . I don't think it's such a big deal, in fact I am not sure I even agree, it's just something to consider.
Somewhere, in previous posts there was a comment about chain plates being a weak point on Top Hat's but as the chain plates on Mark 1s are further outboard and possibly in a stronger part of the deck than Mark 3's (and I don't know if the backing plates are bigger on mark 3's) I don't know if the reference was to Mark 1's 2's or 3's or all models. Anyway, I agree with you that the backing plates on Mk 1's do LOOK pathetic but I am not so sure that they are undersize because the solid deck seems heavily reinforced to take the load..... this compares with my previous boat which had a foam core deck and after a number of years HAD to have triangular stainless steel brackets installed to bind the deck to the hull to stop it from lifting.
It all comes down to what works in the real world, at least one Mk 1 has circumnavigated with standard rigging and chain plates, others have done extensive cruising, so does that mean that the rig has been proved to be OK or does it mean that they were just lucky never to have been is a survival situation with huge shock loads on the rig? I don't know. Given the age and number of Top Hat's built, you would expect that there would be at least one instance of a Top Hat loosing its rig. It would be really be interesting is if anyone on this forum knew of any examples that we could learn from? Also I would be interested to hear from Mark 2 and 3 owners about what changes were made with chain plates on later models.
Cheers
Keith
The backing plates on Tales (Mk III) are as you have described ( aprox 1" x 1/8" stainless steel flat. They look a bit light on to me too but are showing no signs of distress.
Cheers,
Tom
Thanks Keith and Tom. I'm reassured about the backing plates. I'll have a look at them when the mast comes down on Friday and maybe increase the size a little.
My mark 1 doesn't have twin backstays, but has an adjustable yoke with a rope and block arrangement. I didn't know that twin backstays were the norm. Maybe mine was altered in its past life. I know nothing of its history, apart from that it was built in 1973. Maybe Melbourne, or maybe Wyong, I'm not sure.
Cheers
Peter
Peter, I had a look at a Mark 3 on the weekend and it had backing
plates made of aluminium about 3 x 4 inches for the lower shrouds. The
cap shrouds had L shaped aluminium brackets about 14 inches long that
were bolted to the bulkhead. So there seems to be some variation
between boats due in part due to the fact that they could be bought in
various stages for completion by the owner.
Back to your question on how to beef up the backing plates your idea
of using larger plates would work for the lowers but for the uppers,
on my boat at least, the bulkhead is in the way (which is why washers
have been used) and although it would be good to have a bracket made
up to bolt the chain plates to the bulkhead this is a problem because
there is not enough room between the bolts and the bulkhead to fit a
bracket. The way around this is to fit larger V bolts with wider
spacing as per the Mk 3 I saw, but then you would need to fill the old
bolt holes and drill new ones which may weaken the deck right where
you want it to be the strongest! Also where does one find the right
size V bolts?
Here's a neat solution from a guy who upgraded the chain plates on his
GK24 "Instructions and PDF diagram of new masthead rig
chainplates .... to replace the pathetic & weedy Makefast V bolts,
which I’m surprised have allowed the rig to stay up so long". http://www.gk24.org/content/view/121/29
Cheers
Keith
Hi guys interesting subject I have owned three tophats mrk1, 2, and 3 I always thought the chain plates looked weak on all three but i have survived a 50knt storm and had no problems. the mrk3 though has the smallest backing plates i have ever seen roughly 1inch x1inch i do have the intention of changing this, but there is the problem of the uneven deck for the plate to sit on.
I assume they made it uneven for extra strength of the deck. I did'nt know the mrk1 had the chain plates further out can any one tell me how they learned of this? the stainless cover over the stove which hides the chain plates on the port side unscrews and slides out very easy so i would'nt think it was worth cutting out any holes in the stainless. Bedding in the u bolts I woulnt use anything else but sikka flex.
would love to hear any one eles view
Hi Bornfreee2 (and others...)
I am interested in your comments -- "survived a 50knt storm" -- and would like to learn of your experiences in a tophat in heavy weather and others also... and any recommendations you might have for handling.
I know there are lots of far more experienced people on this site than myself and would love to hear about some of the bigger trips others have done... cross bass straight big coastal passages etc.
Karl
Hi Karl on your photos page on page 4 there is a mrk1 top hat I used to own her.
I left sydney with lady crew 730am with a 25knt sw forcast she started to fly up the coast we headed 20 miles out to sea as we had no engine I wanted to clear all land. Let me say the waves were bigger than i had seen before looking back now i think because the air is colder down here than QLD and denser you get a bigger wave so was a new experence for me.As it does night fall came and we were just of newcastle when i saw the dreaded lighting coming from over newcastle and it was black as. of course i had been shit scared of stockton bight and now my worse nightmare was coming true. Being a typical skipper i sent the crew forward to put the storm jib on (could'nt understand why she did'nt want to go forward) anyway it hit and my heart was in my mouth, we hove to for 6hrs this is the bit you will like to hear. that long keel did its job and she rode over ever wave not a drop of water came into the cockpit unfortunitly land was getting closer so it was into the wet suit and outside i had to go boy is it comfy inside that cabin i put her back to it under storm jib only and headed back out to sea my crew god bless her came out as well mainly to lean over the side but she kept me company.we sailed out 15mile and stayed hove to i went down below to read and the crew stayed in the cockpit were she informed me there was a ship coming thinking she was a dramitist i kept reading when she informed me it had stopped right behind us i lept out of bed only to find out we had the navy there that is another story i estimate the waves were around 5m and the tophat gave me no concern at all i gained experiance from it but it certainly had its scary moments
Hi Born Free 2,
When I bought Storm Petrel a mk11 the rigging and chain plates had just been replaced with heavy duty stainless. I will put a picture of the shroud fittings that were fabricated for the refit (I have a couple of spares) on the photo section of this site. They look to be made from 5/16 inch stainless plate and appear a lot more solid than the U-bolts that they replaced (which I still have). It cost the previous owner close to $4000 to get the boat's rigging totally replaced and strengthened. Seems expensive (he passed on the receipt) , but I am glad he had it done.
Your Newcastle adventure would have been quite exciting. Out of interest, did you decide to go to an an inboard on your current boat?
Mark
William,
Please don't leave us hanging, what's the navy story?
Phillip
SEAKA
Ok phillip when I got out into the cockpit I found there was a navy ship pulled up right behind us so I grabbed the hand held vhs and put a call out to them, and said I was surprised that they were out here where they informed me coast guard port stephens were worried about us so they had put in for a search and found us.
I said to them that we were ok as we thought the weather was getting better were they informed us they had just got a weather fax and it was going to get worse and they suggested we get a tow in. so i end up saying ok where they got on to the water police who after about a couple of hours came out and threw us a line which i tied around the mast lots of fun in those waves. and they started towing us in, what a sight seeing huge police boat being blown off the top of the waves as she tried to keep her speed down as she was towing us. Now the yacht had became a submarine and waves broke right over our yacht this went on for about three hours we were wet cold and tired, we finally saw the entrance to port stephens were we were helped to tie up. bit of interest here when we opened the boat up the bilge was full of water and everthing was soaked dont know were it came from but it was a mess also i would say think carefully about a taking a tow it was great to be back inside but we went from being very comfortable to a quite a severe motion
Mmmm,
It would seem that sometimes the view from the shore is different to what is going on at sea, especially when viewing the interface between land and sea.
On my Mk1 I see the foreward hatch as the weak point, as far as water entry is concerned.
Phillip
SEAKA
Hi Mark I was looking at those photos of your backing plates even though they are very well made I cant see them being any stronger than the original, because its mainly the backing plates which are taking all the weight and yours are still doing that so I would think they would be the same strength. If I was to re do mine I think I would use a stainless steel strap bolted and glassed into the hull like the old wooden and ferro boats. I agree with you $4000 for them is over the top
The first thing is the rigging which definitely needs replacing and I want to strengthen a bit as well (going to 7/32" wire from a mixture of 3/16 and 5/32).
The backing plates under the shrouds look pathetically small, maybe 25 mm wide. Does anyone have any advice on how large they should be, what I material I should replace them with (6 mm stainless?), how best to bed the new ones in to the fairly uneven underside of the deck, etc??
Thanks!
Peter
Dragonfly (formerly Top Knot)
Hi All
Peter that's a good question. I had my Mk 1 re-rigged a year ago and at the time didn't think too much about it, I left everything up to the rigger who replaced like for like. Given that 3/16 wire has a breaking strength of 4,400 lbs it should be OK for many years, but your idea of going up to 7/32 is good because this will give you greater redundancy in the long run as it seems that where rigs fail (unless it is due to poor workmanship) it is usually crevice corrosion on the lower swaged fittings.
Talking of corrosion, I was recently undoing the bolts on the tiller only to have the nuts literally fall apart in my hands, I immediately thought, what if the nuts on the chain plate V bolts are the same condition? I checked them out and they seem OK but will replace them when I get around to it, the thing that is holding me up at the moment is getting at the bolts that are behind the metho stove hood. Rather than pull out the hood I am thinking that the easiest thing to do would be to cut an access hole through the hood and later cover it with a sheet of stainless steel screwed with self tappers.
Another thing I didn't think of when re-rigging was replacing the twin back stays with split back stays, have a look at this for the reasons why: http://www.briontoss.com/spartalk/showthread.php?t=180 . I don't think it's such a big deal, in fact I am not sure I even agree, it's just something to consider.
Somewhere, in previous posts there was a comment about chain plates being a weak point on Top Hat's but as the chain plates on Mark 1s are further outboard and possibly in a stronger part of the deck than Mark 3's (and I don't know if the backing plates are bigger on mark 3's) I don't know if the reference was to Mark 1's 2's or 3's or all models. Anyway, I agree with you that the backing plates on Mk 1's do LOOK pathetic but I am not so sure that they are undersize because the solid deck seems heavily reinforced to take the load..... this compares with my previous boat which had a foam core deck and after a number of years HAD to have triangular stainless steel brackets installed to bind the deck to the hull to stop it from lifting.
It all comes down to what works in the real world, at least one Mk 1 has circumnavigated with standard rigging and chain plates, others have done extensive cruising, so does that mean that the rig has been proved to be OK or does it mean that they were just lucky never to have been is a survival situation with huge shock loads on the rig? I don't know. Given the age and number of Top Hat's built, you would expect that there would be at least one instance of a Top Hat loosing its rig. It would be really be interesting is if anyone on this forum knew of any examples that we could learn from? Also I would be interested to hear from Mark 2 and 3 owners about what changes were made with chain plates on later models.
Cheers
Keith
The backing plates on Tales (Mk III) are as you have described ( aprox 1" x 1/8" stainless steel flat. They look a bit light on to me too but are showing no signs of distress.
Cheers,
Tom
Thanks Keith and Tom. I'm reassured about the backing plates. I'll have a look at them when the mast comes down on Friday and maybe increase the size a little.
My mark 1 doesn't have twin backstays, but has an adjustable yoke with a rope and block arrangement. I didn't know that twin backstays were the norm. Maybe mine was altered in its past life. I know nothing of its history, apart from that it was built in 1973. Maybe Melbourne, or maybe Wyong, I'm not sure.
Cheers
Peter
Peter, I had a look at a Mark 3 on the weekend and it had backing
plates made of aluminium about 3 x 4 inches for the lower shrouds. The
cap shrouds had L shaped aluminium brackets about 14 inches long that
were bolted to the bulkhead. So there seems to be some variation
between boats due in part due to the fact that they could be bought in
various stages for completion by the owner.
Back to your question on how to beef up the backing plates your idea
of using larger plates would work for the lowers but for the uppers,
on my boat at least, the bulkhead is in the way (which is why washers
have been used) and although it would be good to have a bracket made
up to bolt the chain plates to the bulkhead this is a problem because
there is not enough room between the bolts and the bulkhead to fit a
bracket. The way around this is to fit larger V bolts with wider
spacing as per the Mk 3 I saw, but then you would need to fill the old
bolt holes and drill new ones which may weaken the deck right where
you want it to be the strongest! Also where does one find the right
size V bolts?
Here's a neat solution from a guy who upgraded the chain plates on his
GK24 "Instructions and PDF diagram of new masthead rig
chainplates .... to replace the pathetic & weedy Makefast V bolts,
which I’m surprised have allowed the rig to stay up so long". http://www.gk24.org/content/view/121/29
Cheers
Keith
Hi guys interesting subject I have owned three tophats mrk1, 2, and 3 I always thought the chain plates looked weak on all three but i have survived a 50knt storm and had no problems. the mrk3 though has the smallest backing plates i have ever seen roughly 1inch x1inch i do have the intention of changing this, but there is the problem of the uneven deck for the plate to sit on.
I assume they made it uneven for extra strength of the deck. I did'nt know the mrk1 had the chain plates further out can any one tell me how they learned of this? the stainless cover over the stove which hides the chain plates on the port side unscrews and slides out very easy so i would'nt think it was worth cutting out any holes in the stainless. Bedding in the u bolts I woulnt use anything else but sikka flex.
would love to hear any one eles view
Hi Bornfreee2 (and others...)
I am interested in your comments -- "survived a 50knt storm" -- and would like to learn of your experiences in a tophat in heavy weather and others also... and any recommendations you might have for handling.
I know there are lots of far more experienced people on this site than myself and would love to hear about some of the bigger trips others have done... cross bass straight big coastal passages etc.
Karl
Hi Karl on your photos page on page 4 there is a mrk1 top hat I used to own her.
I left sydney with lady crew 730am with a 25knt sw forcast she started to fly up the coast we headed 20 miles out to sea as we had no engine I wanted to clear all land. Let me say the waves were bigger than i had seen before looking back now i think because the air is colder down here than QLD and denser you get a bigger wave so was a new experence for me.As it does night fall came and we were just of newcastle when i saw the dreaded lighting coming from over newcastle and it was black as. of course i had been shit scared of stockton bight and now my worse nightmare was coming true. Being a typical skipper i sent the crew forward to put the storm jib on (could'nt understand why she did'nt want to go forward) anyway it hit and my heart was in my mouth, we hove to for 6hrs this is the bit you will like to hear. that long keel did its job and she rode over ever wave not a drop of water came into the cockpit unfortunitly land was getting closer so it was into the wet suit and outside i had to go boy is it comfy inside that cabin i put her back to it under storm jib only and headed back out to sea my crew god bless her came out as well mainly to lean over the side but she kept me company.we sailed out 15mile and stayed hove to i went down below to read and the crew stayed in the cockpit were she informed me there was a ship coming thinking she was a dramitist i kept reading when she informed me it had stopped right behind us i lept out of bed only to find out we had the navy there that is another story i estimate the waves were around 5m and the tophat gave me no concern at all i gained experiance from it but it certainly had its scary moments
Hi Born Free 2,
When I bought Storm Petrel a mk11 the rigging and chain plates had just been replaced with heavy duty stainless. I will put a picture of the shroud fittings that were fabricated for the refit (I have a couple of spares) on the photo section of this site. They look to be made from 5/16 inch stainless plate and appear a lot more solid than the U-bolts that they replaced (which I still have). It cost the previous owner close to $4000 to get the boat's rigging totally replaced and strengthened. Seems expensive (he passed on the receipt) , but I am glad he had it done.
Your Newcastle adventure would have been quite exciting. Out of interest, did you decide to go to an an inboard on your current boat?
Mark
William,
Please don't leave us hanging, what's the navy story?
Phillip
SEAKA
Ok phillip when I got out into the cockpit I found there was a navy ship pulled up right behind us so I grabbed the hand held vhs and put a call out to them, and said I was surprised that they were out here where they informed me coast guard port stephens were worried about us so they had put in for a search and found us.
I said to them that we were ok as we thought the weather was getting better were they informed us they had just got a weather fax and it was going to get worse and they suggested we get a tow in. so i end up saying ok where they got on to the water police who after about a couple of hours came out and threw us a line which i tied around the mast lots of fun in those waves. and they started towing us in, what a sight seeing huge police boat being blown off the top of the waves as she tried to keep her speed down as she was towing us. Now the yacht had became a submarine and waves broke right over our yacht this went on for about three hours we were wet cold and tired, we finally saw the entrance to port stephens were we were helped to tie up. bit of interest here when we opened the boat up the bilge was full of water and everthing was soaked dont know were it came from but it was a mess also i would say think carefully about a taking a tow it was great to be back inside but we went from being very comfortable to a quite a severe motion
Mmmm,
It would seem that sometimes the view from the shore is different to what is going on at sea, especially when viewing the interface between land and sea.
On my Mk1 I see the foreward hatch as the weak point, as far as water entry is concerned.
Phillip
SEAKA
Hi Mark I was looking at those photos of your backing plates even though they are very well made I cant see them being any stronger than the original, because its mainly the backing plates which are taking all the weight and yours are still doing that so I would think they would be the same strength. If I was to re do mine I think I would use a stainless steel strap bolted and glassed into the hull like the old wooden and ferro boats. I agree with you $4000 for them is over the top