Use Sampson Post for anchoring?

[markpierce]

My Sampson post is welded to a steel deck.

 

[markpierce]

How much weaker is bronze than steel?
The essence of this conversation is that stoppers need to be strong.
So why choose a weaker material than the norm ... steel.

The bronze fitting attaching the tiller to the rudder post broke on my father's sailboat. He got a new fitting consisting of quarter-inch thick stainless steel which never failed.

 

[garbler]

I would say most all production GRP vessels regardless of price range offer Sampson posts that are decorative and unsuitable to the tonnage of the vessel and rough conditions.

Wooden Hulls: A properly built wooden post on a wooden hull of suitable scantlings must include serious deck and below deck fortification. I mean major transverse or deck beams with partners at the deck penetration that are locked into one pair of beams and depending on vessels tonnage with additional blocking fore and aft. The major beams should have full depth lodging and hanging knees bolted to deck beams to prevent surge loads from starting the deck covering boards or plank shear. The proper post will step to the keel or stem gripe depending on location. This step should preferably include longitudinal support members spanning two or more frames or floor timbers. The base of the post must be secured against movement. If a forepeak bulkhead is present it should be heavily fastened and fitted along the perimeter and deckhead and the post heavily bolted to it using backing blocks at least 2X the width/depth of the post.

Fiberglass Hulls: Most builders rarely support or frame out a post for real ground tackle loads. The school of prevalent thought is vessels park in marinas, i.e., ground tackle of secondary importance. Many of your better trawlers do nothing more than insert a teak or apitong post alongside a plywood forepeak bulkhead. Often the post is tabbed to the bulkhead or bolted and being the anchor locker it’s wet, poorly ventilated and prime for fungal growth if not plywood delamination since few builders treat raw edges of plywood. These bulkheads are basic five to seven lam plywood that rarely is even 100% tabbed to the hull skin. They are frequently tabbed one side only in three to four areas along the perimeter or if lucky the full perimeter. However the tabbing tape is often laid up and bonded to the face veneer only which is false security. If the builder was saavy enough the forepeak plywood should be best grade and the veneer routed back at least 3” along perimeter both sides for full tabbing using epoxy resin. Like wood construction the deck penetration for the post needs to be fortified with hat-section stiffners that partner to spread lateral loads into the deck structure and I should this bulkhead needs to be tabbed or fastened to the deckhead also to prevent deck pumping and starting seams and joints.

Before closing let me address another frequently encountered type of structural counterfeiting. That is the Sampson post of welded SS with the large deck plate. There are several variation of this almost none are legitimate. This plate will frequently and proudly display large through bolts but to the curious who pokes their head inside their is nothing but washers or small backing plates on the deckhead underneath. No support members attached to the hull fabric. Sometimes there is a piece of SS pipe fitted
( often stanchion or railing scrap ) flattened, bored and lagged to something below but mostly for show. The point is that most or many Far East trawlers are decked with plywood and overlayed with plank and seam teak decks. These decks should not be asked to carry the jerking live loads of ground tackle in a blow.

Steel & Aluminum Hulls: They are easy. Frame it and weld it.

Like the Sampson post every fitting associated with your ground tackle must not be compromised. Here is one of two bow cleats from a well respected builder that ripped out of the foredeck during a blow. Too light, poorly installed the vessel a Constructive Total Loss.

 

[psneeld]

Did that cleat rip out because the forces were more upward than horizontal?

 

[Nomad Willy]

Spectacular post Garbler,

Decorative deck hardware .... sad but true.
My original (Alum/SS) Samson Post (admittedly not the ideal combination of materials) but was so decorative I got talked out of it. It was easy. As attractive as it was I didn’t like it. Anyway it was attached much like the one in your pic. Looks like it got ripped off sideways rather than being used as a lifting eye.

Picture was the day we bought Willy.
I have forgotten about that awful Danforth. No longer have it. Have one the same size but it's a "S" w forged shank. Genuine Danforth.
But the post mount was very deck dependent. At least the pull was low on the post.

 

[garbler]

Did that cleat rip out because the forces were more upward than horizontal?

Good question and the answer would be a lot of both. The weather was a moderate Nor’easter with 5-7’ steep close swells sweeping into this harbor. The vessel was secured on a well maintained harbor mooring, plenty of scope and weight. In witnessing the storm it was easy to see almost all the boats near the harbor entrance or outer mooring field were pitching and diving heavily into these swells. These swells didn’t have much fetch or recovery intervals so the bows were being driven down and under enough that loads on these cleats would have been both shear and tension or lateral and vertical.

The lateral loads in combination with poorly installed small hard edged backing pads created localized shear and rupture of the deck laminate. But with the bow diving into the troughs and being submerged by the next swell the forces would have been to literally pull the fitting off the deck. This particular boat may have survived had it broken from the pendant earlier and been driven ashore at the back of the harbor which was soft bottom.

 

[psneeld]

Thank you. A lot of hardware failures are caused by poor application/mismanagement by owners.


Just checking. A cleat should survive a mooring situation...not all dock tie ups though.


Most securing hardware is based on sheer not tensile strength and many don't seem to forward think the application enough.

 

[FlyWright]

To me, the deck in Garbler's photo looks very thin. Admittedly, I've only cut into one deck, my own, but it was much thickerer than that! I estimate mine was 3-4" thick at the foredeck.

Are foredecks that are this thin commonplace?

 

[psneeld]

To me, the deck in Garbler's photo looks very thin. Admittedly, I've only cut into one deck, my own, but it was much thickerer than that! I estimate mine was 3-4" thick at the foredeck.

Are foredecks that are this thin commonplace?

Decks are all over the map and sometimes...just a few inches apart, they are reinforced...where the hardware should have been placed but wasn't.


Almost no linehandling hardware is designed for a lifting moment, that's why I asked.


Even a thin glass deck or tiny hardware can handle a sheer (lateral) moment (which ground tackle or dock lines should handle) but does not do well in tension (lifting) forces.

 

[garbler]

Deck laminates and construction vary significantly depending on design, construction and budget. The deck piece in the photo measured approximately .320” or about 5/16”. Not super heavy but typical for North American built performance cruising sailboats in the 7-10 ton displacement range. The problem is the builder’s lack of understanding and implementation of sound deck fitting procedures. Quick and dirty because the cleat foundation was essentially inaccessible to the average person. Violation on two counts in my book; (1) Inadequate installation lacking sufficient backing plate surface area and deck reinforcement , (2) critical deck hardware with foundation inaccessible to visual inspection and/or service.

Cored or sandwich decks are always thicker than solid glass decks it’s just the nature of the construction. Properly built solid glass decks should always include heavier perimeter flanges. Such flanges are necessary for the hull to deck joint attachment and necessary to support deck stanchions. Often the builder increases the size of these flanges or removes the core altogether for critical deck fittings forward since working access is limited in the bow. A hull with some flare, a tight close chain locker and thru-bolts for deck fittings = access problem. Too many boat builders today regard deck fittings as nothing more than final build stage accessories. Go look at some builders drawings and see how much specifications or detail is noted for deck fitting installations.

Many deck structures on sailing vessels that race or are sold as performers deliberately keep the deck mold weight down. Weight up high is always a concern for many of today’s boats. Hence sandwich or cored panels with balsa, Divinicell, Klegecell closed cell foams. Stiff and light weight but special techniques are required for thru bolting deck machinery or fittings.

As for vertical loads well if it’s a commercial hull with lifting or streaming gear then padeyes and terminal fittings are everywhere they need be. Same with lots of older sailing craft that use deckhorses and deck blocks.

 

[psneeld]

One thing to consider....boatbuilders are not thinking their boats are world cruisers or should routinely anchor out in hurricanes.


One should know and understand that....


never read in any literature to the contrary....

 

[Hippocampus]

Ps- depends on the boat. There’s different audiences for boats. Some are directed at world cruisers and are designed and built to function in serious weather, high lat or the southern ocean. My concern is EU A rating. It implies at the time a boat is newly completed it will function and survive force 8 to my understanding. Think people sometimes misunderstand this rating. It doesn’t mean the vessel will tolerate the use and abuse of cruising.
Once was involved in a small boatbuilding company. This was before prepreg, CF and even current resin infusion/vacuum bagging being commonly done. Back then you could pretty much cost out production by weight of the vessel. Strong heavily built boats cost more. Properly done systems cost more. Backing plates instead of washers, eliminating core under fittings, and proper sized and quality fittings cost more. In the current era strong light boats achieving that level of build cost even more.

 

[Shrew]

There is a cleat aft of the sampson post in the original picture. Are we sure that he is affixing the rode to the sampson post while anchored? This could just be a chain stop for holding the anchor on the bow roller. He may be using the cleat with the anchor line once the anchor is set.

 

[psneeld]

Ps- depends on the boat. There’s different audiences for boats. Some are directed at world cruisers and are designed and built to function in serious weather, high lat or the southern ocean. My concern is EU A rating. It implies at the time a boat is newly completed it will function and survive force 8 to my understanding. Think people sometimes misunderstand this rating. It doesn’t mean the vessel will tolerate the use and abuse of cruising.
Once was involved in a small boatbuilding company. This was before prepreg, CF and even current resin infusion/vacuum bagging being commonly done. Back then you could pretty much cost out production by weight of the vessel. Strong heavily built boats cost more. Properly done systems cost more. Backing plates instead of washers, eliminating core under fittings, and proper sized and quality fittings cost more. In the current era strong light boats achieving that level of build cost even more.

Of course....I should have said "the vast majority of power boatbuilders"......


.....and all this sprung from the original post about a samson post on a trailer sailor "looking" like it might not hold a 50,000 pound boat through a hurricane.