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Mast to cabin roof fastening

B

bbeach

Bill Beach
I've got my boat all torn apart doing all kinds of projects in
preparation for my cruise. Do any of you ol' timers know if it's
necessary for me to tab/afix the cabin top to the mast to
alleviate the potential up/down pumping of the mast.
I wonder if it's necessary because it's designed for offshore
charter work as is, so why do I need to change it? Seriously,
would like any of your expertise on this. Thanks.
Ps...did the Atlantic City Boat show. Left a msg at the Catalina
pavilion, no one responded.
 
I do not know if I am right, but I am sure you do NOT want to tie the cabin top to the mast. Adds stress to the cabin top unnecessarily. The mast is designed to have its force on thekeel, not the cabin top.
 
<div>Terry,If you have the main sheet lead down the boom to a block at the base of the mast it might make sense to add a strut below decks from the cabin top to the mast to stabalize the upward pull on the deck from the main sheet. Just a thought.Vic C.
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After returning from Mexico a few years back, I decided to investigate this issue. After talking to numerous professionals, I fastened the deck to the mast. You can do it two ways. The first is to connect at an angle from the a point about 12" from the mast and the running to the mast at about 35-45 degrees using either rod or wire rigging. The other is to run rod or wire straight down to the step. Doing it this way, adds a hand hold moving forward. After installing this I've had the boat in 60 kt. winds and 20 ft. seas and I believe there is less working of the deck. I would certainly recommend doing it.
 
Gentlemen
Thank you once again for your thoughts and experiences. Isn't this wonderful! I decided on a compression fitting. First, I replaced and epoxied in the 3/4" ply backing around the mast entry of the cabin roof(CR). Mine had been water damaged from the prior owner's leaks. I carved out a nitch to bed a 3X3 padeye that will be attached to the CR with another 3X3 padeye on the roof sandwiched and thru-bolted. This way, I'll have an extra fastening point/padeye right under the boom just below the vang. I tapped and fastened a strap/tang to the mast 14" below the CR. I attached a turnbuckle in between and voila! One each compression post for under $75. Mind you, I did buy all the stuff at Bacon's in Annapolis, which is all consignment stuff.
Regardless, I feel more comfortable knowing that I've strengthened that area and reduced any potential pumping and canning.
Thanks for your comments. They really help. On to the next project!
Additionally, for those of you that have the stacked bunks in the V-berth, I am finishing the job of making it a proper V-berth with a ton of storage. I'll have pictures on the home page in a couple of weeks with a small write-up (a picture is 1000 words...). Even though I won't be using it under way, it's nice for when you're there.
I'm also using some of the wasted space behind the head in the molded shower stall. I contemplated using the pre-cut holes from the factory recall repair job in the shower seat, but there's not enough room to make it worth while. So, I am cutting an access behind the head and building a cabinet to fit. There's probably another 2 cu.ft. there.
Don't you just love boats??!!
 
Well...... I did this too, but just to give me a strong point for the vang. So, I guess I attached my mast to the cabin top, sort of, against my own advice.
 
Could someone explain the purpose and theory of this mast tie? As I said, I put one int, but not for this purpose; rather to have a stong point for the vang.But why should a keel stepped ;mast, in theory, be attached to the cabin roof. I should have thought that we did not want the cabin roof taking any of the mast forces. And I cannot see how not having it tied will increase pumping. If tying it reduces pumping or movement, then we are tying the mast to the bulkheads (against design, it seems to me) and increases burden on parts not designed for it. (Although, perhaps I have already done that with my vang attachment.) m I would appreciate a design, engineering discussion here if anyone has thoughts. Thanks.
 
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Re; mast to cabin roof fasteningI have seen a number of racing boats that have a steel rod connection from the keel step to the cabin roof. For the most part the purpose of this connection is to transfer the upward forces generated by the halards on the deck when the boat is equiped with halards that run back to the cockpit. If you have such a setup and have not only the main and jib halard but also port and starboard spinnaker halards running through blocks at the mast foot on the deck and back to the cockpit the conection would certainly be necessary to control mast compression and the forces trying to lift the deck independently of the mast. Generraly boom vangs are tied from the mast to the boom and would not create the need for that type of connection.Most of the M38s that I have seen have all halards tied off at the mast and I would not see a need for the connection.Chip Shreeve
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I have only one thing to add to Chipps statements. When the mast is under load, the shrouds are under tension. When resolving these forces, think of the system as being symilar to a archary bow where the mast is the bow, the shroud/chainplate is the draw string and the coach roof is the arrow. I beleive that the M38's coach roof is strong enough for this not to be a problem and I have never noticed any flexing in this area. But, as our boats age and become weaker due to the stresses placed on them, you may be able to notice some flexing and want to add some support.
 
I can say without a doubt that there is less working of the deck with this added tension struct. I again would recommend it to anyone and it is cheap to install.
 
For the life of me I don't know why anyone would want to tie their cabin top to the mast for the purpose of controlling mast pumping. Mast pumping is a result of a loose rig for the conditions being sailed in. Tighten the shrouds and back stay.If you tie the cabin top to the mast and assume that mast pumping will be controlled,your wrong.What you will do is ruin the mast partner at the cabin top, tear up the deck and have an expensive fix on your hands. I race my Charley 38 in all sorts of Great Lakes weather and if I hear the mast pumping we temporarily control it by tightening the back stay. I have a hydraulic backstay adjuster.In port afterwards we tighten the shrouds. On a boat with a bendy mast you cannot do this, but the M38 has a stiff mast.If you do run halyards to the cockpit through blocks at the mast base,it is worth installing a stainless rod from the deck to the mast step to save upward flexing of the deck.
 
This struct is not to stop Mast Pumping, it is simply added to tie the cabintop to the mast to reduce flexing. It works!
 
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