Side deck thickness

[johnnybuoy]

Hello,
Does anyone know the thickness and construction of the side decks on an LM 27 please. I need to know because I am strengthening the shroud anchor plates and it would be good to know this information in order to determine the thread length of the studs that protrude through the deck.
many thanks
John,
Siren.

[tonyp]

John, I've just checked the bolts that I removed when replacing my fore deck and aft side deck cleats. Judging from the rust staining where the bolts went through the deck it would appear that the deck thickness Is 25 mm in both these places.   I presume this is standard, but don't know.

Good luck
Tony

[jandane]

Hi Johnnybouy. The two outer shrouds are simply fastened through the side and onto the hull ....No problem. The two inner are normally fastened into the deck and the plate below deck is around 4x2 cm. The rear of these is often fastened through the roof and onto the connection flange between hull and deck, meaning it can be tightened. The front is often only connected to the roof and can not be tightened very hard, and needs reinforcement. When I tried to trim my mast the way it should be done, I lifted the dech, all the sliding doors to the small cabinets in the cabin fell out and the door to the cabin could not be opened. I made a anchorplate and moulded it into the fibre, in front of th cabin. Now the front, inner can be tightened and the mast curved a bit on the centre, giving 5 dg closer to the wind.
I also reinforced the front stay. If you look, it will very often be attached to a tiny pin. In the front it is easy to attach it with a bolt through the hull

[Brian & Glenda]

Good idea to beef up the deck where the aft shrouds are affixed to the deck. When I bought my 1983 LM32 four years ago, there were two or three very fine cracks in the gel coat of the deck, that extended up to two feet or so aft from the anchor plates of the aft shrouds. I believe that these cracks were likely caused by loads on the aft shrouds lifting the deck thus causing these micro cracks.

I really like Jandane's repair described above, but that isn't what I had done when I wanted my aft shroud anchor plates strengthened.

As part of the purchase agreement, I had a boat yard bond 1/2 inch thick fiberglass backer plates about 4 inches by 8 inches to the underside of the deck to reinforce these points. I later learned that as longer bolts were then required, and as no suitable replacement anchors could be found, the anchor bolts had been lengthened by welding. I understand that the entire length of the bolt below the plate was removed and that a longer bolt with its head removed was then welded to the base of the anchor plate to achieve the required length. I was assured by this reputable boat yard that such a repair would be entirely adequate, and that the welding had been completed by a trade qualified welder. I'll probably always be a wee bit skeptical, and while I have not pulled these anchor plates to check for evidence of failure, this repair appears to have performed well.

I also had the cracks in the deck's gel coat sealed, and they have not reappeared.

I did not do this work myself, so cannot say with 100% certainty what the construction or thickness of my side deck is, but I can say with certainty that my fore deck is of ~1/2" foam core construction, with fiberglass on either side of the core. The total thickness is ~3/4". Whether your LM27 is of the same construction as my 1983 LM32, I cannot say.

Also, I once had to replace the jib sheet track and I replaced the bolts that affixed the track to the side deck when I did so. The replacement bolts are 40mm long, their heads are recessed flush with the top of the track, the track itself is 6mm high and sits on a couple of mm of butyl tape used as bedding material. There was a more than an adequate, but not excessive amount of bolt left to affix nylox nuts when the new track was installed. I did note that if I over-tightened the nuts, then the bottom-side of the deck would compress even though large washers were used between the underside of the deck and the nut, so I suspect that the side decks of my LM32 are also of foam core construction.

Hope that helps!

[tonyp]

Re lower shroud reinforcement, I think our 1979 boat is like Jeffstrud's in that the aft lower shroud attachment has been extended down to a flange laid in the hull just below the cupboard shelves.





I have just got the bits together to strengthen the for'd attachment in the same way. Can you do this, John?

Tony

[jandane]

on the 27, the front plate of the two inner shrouds is fixed inside the cabin meaning a support has to go from cabin roof, via the cupboard to the hull. If fixing it as the aft, outer is fixed, (on the connecting flange between hull and deck) the sliding doors of the cupboard will have to be removed.

[johnnybuoy]

Thank you all for this information,
The aft lower shrouds are anchored in the same way as Jandanes but the forward ones are not and the deck has lifted. 
I am thinking of moving the shroud plate forward so it is directly over the bulkhead and anchoring to a bracket fixed to the bulkhead.
It seems feasible. Has anyone else used this method.
many thanks
John

[Sula]

Jan 22, 2018 17:32:52 GMT johnnybuoy said:

I am thinking of moving the shroud plate forward so it is directly over the bulkhead and anchoring to a bracket fixed to the bulkhead.
It seems feasible. Has anyone else used this method.
many thanks
John

I think I read somewhere on this forum of someone moving both their forward lowers forward, and their aft lowers afterwards, in order to tie them into the bulkheads.  I haven't been able to find the relevant thread again.  As I recall it did result in some minor further restriction of genoa trimming angles.

I've now found the thread(s):
lmowners.proboards.com/thread/217/1982-lm27-construction 
lmowners.proboards.com/thread/224/lm27-construction