Hi Gra, Welcome to LM owners. The deck of the LM27 is indeed a sandwich construction. It's about 15mm thick, with a wooden core Jan will probably correct me on this but I believe the core is of balsa for stiffness and lightness. The deck has slightly raised non skid areas where the sandwich is a bit thicker. The deck is bonded to the hull. The outward protruding seam is hidden inside the rubbing strip.
The hull is a solid layup and by modern standards quite heavy. My 42 year old boat was surveyed recently and the surveyor was expecting to find some spongy areas on the deck - he didn't! I believe that the construction was very good and the hull layup is excellent. My hull shows no sign of osmosis. I recently had a bow thruster fitted and the man cutting the hole said mine was among the best and thickest layps he had come across.
The only areas of concern that I have ever seen on other boats were stress cracks around the inner stays. Jan will provide more information but I believe that the early mark 1 hulls were recalled in order to carry out a modification to accommodate the stress in these areas which I believe consisted of a frame bonded to the hull. Mine didn't get recalled and I have had to produce my own mods. If there is no additional support the deck can warp when sailing in heavy winds and in my boat the sliding panels in the cabin lockers used to drop out!
Regards
Michael Legg
Last Edit: Oct 17, 2016 18:31:24 GMT by oceandancer
Oceandancer...thanks for your confidence. Yes, the hull and sides of the cockpit/cabin are solid. The deck and roof is of a sandwich construction. If it is plywood or balsa I cannot tell yet, but will find out. The front inner shrouds are only attached to the deck with a shroud plate fixed to the deck with two 10 mm bolts but the rear shroud plate is attached to a turnbuckle which is attached to the hull or to the line of screws bolting the cabin's sides to the hull. A strange solution but I guess it was made as a compromise not to disturb the sliding panels above the berths. It has given some cracks in the topcoat on many a LM27. The problem comes up when trimming and trying to curve the mast a bit forward. Forst time I really trimmed the mast, the sliding panels fell out and I could not open the cabin door as the whole cabin has been lifted some milimeters up. Most LM sailors are sailing with very loose inner stays which makes the mast curve leeward and thus opening the sail too much close to the mast. I became tired of this and had made some modifications and the mast stands perfect now, with stays as tense as should be. (Normally it is said, you can tighten the turnbuckles as much as you can with normal hand tool) As you see, it is just a little plate attached to the inside of the shroud plate, attached to a modified turnbuckle which is attached to an anchor plate which is moulded onto the keel with 4 layers of glassfibre. On fact I had the same problem with the front stay, lifting the deck up when being trimmed, but also here I made a modification.
I have made some different and rather more fundamental mods. I don't consider that it changes the design significantly but I have moved the inner stays forward and backward in order to position the fixing points near to the bulkheads below where I have anchored them. You do loose a few degrees of boom swing but not much. I have in-mast reefing and a straight mast is vital to efficient furling.
Here are some pics of my mods to the lower shroud attachment points to keep the deck from flexing.
The lowers have been moved forward and aft by 10 inches (25cm). This does mean losing several degrees of boom swing but I have not found this to be a problem.
On the aft lowers a stainless steel strop and rigging screw is attached using a ring nut to the underside of the deck fitting.
The rigging screw attaches to a fitting which is bolted through the bulkhead with a wooden pad bonded on the other side for strength.
Attachment limit reached see LM27 construction.
Mick
Last Edit: Oct 26, 2016 18:47:35 GMT by oceandancer
My LM has been modified in a similar manner to the photos with a combination of solid rod and cable tensioned by bottle screws these mods carry the load down to the horizontal shelf/stringer at the rear of the settles. There is absolutely no sign of any stress crazing at any point of fixing. my hull no is 8008
