Rig Tension for Islander 28
Does anyone have any settings information on the recommended rig tension for the Islander 28?
If no one else does before hand, I'll have my manual off the boat in two days...
I bought a Loos Gauge for checking tensions in the standing rig and used it to re-step my mast after I overhauled it back in 07-08. Unfortunately, I bought it after I'd already taken the mast down, so I'll never know what the rigging was set at prior to dismasting.
When re-stepping the mast, I followed the recommendations in the Loos Gauge booklet for 7/32" wire (all shrouds & stays, except splitstay - 3/16"); ~1000 #'s in the stays, ~800 in the shrouds. Since then I've done a bit of sailing and have increased the tension in both by ~100#'s.
I noted to Paul Comte earlier that after re-building the glass beneath the deck plate for the mast step, the mast actually leans forward at the base. So I've added some mast bend into the static location of the rig to bring the masthead plumb with the mast base. Not alot of bend, maybe 1.5" on a vertical stringline.
If you've got the original mast, with 3/32" wall thickness, and original in-line spreaders, then you won't want much mast bend. Maybe someone else can correct me on that. It seems reasonable that the tension that you first settle on should be somewhere close to the original settings, unless you sail your boat really hard. 1/3 of the breaking strength of 1x19 316SS wire (~5400#'s) would be a good upper limit on static tension, especially since you need to worry about galling the threads between stud & turnbuckle as you increase the static load. I always use generous amounts of Silicon spray (wish they sold Mclube here in town) on threaded parts when re-rigging.
The Loos Gauge book has a procedure for re-rigging from scratch, and I believe it says to start with the upper shrouds, then move to the stays, and finally the lowers. I might have that backwards. If we had a professional rigger here in town, I'd hire them to tune my rig correctly once. I'd record the settings, then adjust as necessary based on performance in local sailing conditions. My 10-cents...
i28 rig setup - scan of owner's manual
Here is a scan copy of the rig setup page from our 1979 i28 manual.
Before you begin adjusting, take a good look at the bolts and plates (and deck caulking of same). The rig could be loose because changes in the boat rather than changes in the wire... good luck, paul
VI. SPARS, RIGGING AND HARDWARE
One of the most rewarding activities connected with sailing is tinkering with your boat's rigging and hardware. The best skippers always seem to be looking aloft at the sails and then thinking about new fittings, or new ways of improving old ones. In this way a person acquires a thorough understanding of how and why every piece of sailing equipment works, plus how to repair and maintai n it. As sailors, we too are constantly trying to achieve better and easier boat performance, thus the gear that we install is constantly being improved. What we hope to accomplish in this section is to give you the background information for setting up your boat in the beginning for normal sailing conditions.
When you need more help and information, please consult your local dealer. He is prepared to assist you in obtaining the best type of sailing hardware for your needs in your local area. One may also refer to the annual Lands' End Yachtman's Equipment Guide. This book should prove invaluable to you and your dealer in the selection of the best additional equipment for your boat. The latest issue may be obtained for a minimal amount (approximately $2.50) from Lands' End Publishing Corp., 2241 North Elston Avenue, Chicago, Illinois 60614, and will be an excellent addition to any sailor's library.
WHEN PLACING HARDWARE IN ANY POSITION OTHER THAN THAT SPECIFIED ON THE DECK HARDWARE LAYOUT DRAWING, ALWAYS CONSUL T THE WIRING DIAGRAM TO AVOID CUTTING ANY WIRES OR STRIKING ELECTRICAL FIXTURES.
A. MAST TUNE
UNDER NO CIRCUMSTANCES SHOULD ANY OF THE RIGGING BE SET UP "BAR TIGHT." FOR ALL SAILING CONDITIONS, WE RECOMMEND THA T THE MAST BE VERTICAL AND IN COLUMN, WITH THE RIGGING "FIRM." IT IS VERY IMPORTANT THAT A KNOWLEDGEABLE PERSON WHO UNDERSTANDS THIS CONCEPT OVERSEES THE INITIAL TUNING OF THE MAST AND RIGGING.
You should be able to stand facing the mast, reach out and pull on any stay and see the mast move in that direction. With a light pull or push by hand at chest height, this dockside starting point will have both stays of equal tension with about 1" to 2" of play in the uppers and 2" to 3" of play in the lowers. The backstay and jib stay should be of equal tension and have about 1" of play. If the mast is stepped on deck the rigging will be tighter than a mast stepped on the keel. With double lowers the after lowers will be looser than the forward lowers by about 1" of play. Some of the newer tall rigs have intermediate shrouds, the tension of which should be between that of the uppers and lowers.
On a large mast you may notice a line of rivet heads running up one side of the mast. These hold a 3/4" PVC tube to the inside of the mast for the running of optional instrument wires.
The final tuning of the mast should take place while sailing to windward in a medium breeze of 8 to 10 knots. Sighting along the backside of the mast from deck level will indicate what further turnbuckle adjustment needs to be made to the windward side of the mast. The top of the mast should not "hook" to windward. In a medium breeze the mast should be straight and this is normally accomplished by taking up on the lower shrouds. Always tack, and then make the turnbuckle adjustments on the now lee or slack side of the mast and then sight the mast on the new, windward side, for further corrections. After a few tacks, the mast should be straight! Secure the rigging by inserting cotter keys into the turnĚ buckles, spread them open and cover with tape to prevent any snags!
Special attention should be given to the initial stretch of the rigging, especially after the first sail in a strong breeze. In windy conditions it is actually desirable to have the mast head "fall-off" slightly to leeward, giving the mast a smooth, even curve from head to dock. In a tall rig the intermediates play an important part in controlling the upper mast section and this will be especially noticeable in stronger wind conditions. After a few more sails in strong breezes, the rigging should be checked again for tune as additional stretch will occur.
When racing, the backstay may be tightened to compensate for the extra forward loading applied by the Genoa. At the conclusion of the race it is very important to "slack-off" the amount you "took-up" on the backstay turnbuckle, as this avoids setting up unnecessary strains on the hull and rig. Since you want to keep the mast straight while racing, you will probably tighten up on the jib stay first so when the backstay is slacked off the mast head will hook slightly forward. When the backstay is tightened up, this "hook" will disappear and the mast will be straight.
Too much tension on the backstay is probably the prime reason for mast and rigging failure. It has been found that tension in the backstay can increase 150% to 200% due to the wind load on the headsail and dynamic loading due to heavy seas. The tension on a shroud or stay should not exceed 25% to 30% of the cable's breaking strength at the outside limit. Below are the breaking strengths, in pounds, for 1 x 19 stainless steel wire cable as supplied by the factory:
3/32"= 1 ,200
1/8" = 2,100
1 /4" = 8,200
3/8" = 17,500
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