Rod in cabin just aft of keel stepped mast

[RickDelaune]

Jim, We are just splitting hairs !!! Everything you and I have talked about has to do with supporting the mast. To say that the only reason to use a panting rod is to stop the deck from being pulled up by halyard loads may have some truth in this application. So are we to say that boats built without a panting rod all had halyard stress at the base of the mast and there for the desks would be pulled up ???? Just not the case my friend !!! In the interest of designing lighter stronger hull to deck and interiors structures the designers stopped using full bulkheads ( Catalina 30's, Easterly 30's, Beneteau 30e's, etc ) to gain more head room. And whether there was a deck stepped or keel stepped mast made no difference. Although the deck stepped mast would push down on the deck and really no need for the panting rod. However there are a number of boats with keel stepped masts that do not have a panting rod and the bulkheads do not come off the bottom or the decks pull up due to the mast loads. You put 3800 psi on a backstay adjuster and the mast is like an arrow loaded by the shrouds and the hull sides with out proper structure the deck will rise whether there are deck mounted halyard leads or not. And the hull will flex at least 6-10 inches. (Experienced this on a One Off 3/4 Ton 34 foot sailboat. By the way, the boat I refer was "Swampfire" which won the 3/4 Ton worlds in 1974 and eventually became the Ranger 32.) And you have not even put up a sail with the deck lead halyards. The only way to stop this is with a panting rod or turnbuckle with an eye pad on the mast. Halyard loads are not even close to that. I was always taught that if you took a chain saw and cut in front and behind the chain plates on the hull and deck, the mast should be able to stand on it's own. If the designer does not triangulate the left,right, up and down loads of the mast it will not stay in column. That's where the panting rod comes in.
Enjoying our mast structure dialogue, Rick

[CLady]

It may have to do with tying the deck down.

[chasfgr]

Originally Posted by George DuBose

I thought a compression post went under a deck stepped mast to keep the base of the mast from coming into the cabin?

That's right - this is the opposite, a tension strut - mine is wire not an SS rod.
Mine is specifically fitted to prevent the mast collar from being hoisted aloft by any of the 10 mast-collar pulleys.
Set-up the same tension as the inners, ie less than caps and more than secondaries.