Attaching Boarding Ladder to Transom

[Rowa]

[Moderator's note. This post revived a thread that had been dormant for nine years and was discussing a different topic in a different forum. The thread seeks advice on making a modification and has been moved to the REPAIRS and MODIFICATIONS forum for discussion. The first question has been re-written to be direct questions rather than a survey questions to see how many readers might possess the knowledge necessary to answer a question. An illustration of the specific ladder to be mounted as been included to allow readers to better understand the the questions being asked.]

Q1: when attaching a swim ladder to the transom on a boat with a Unibond hull, between through-bolting with a backing plate or using "lag bolts" which method should be used?

Q2: if lag bolts are to be used, what kind of lag bolts should be used and what size lag bolts should be used?

Q3: between two methods of mounting a Garelick model 19684 telescoping boarding ladder on the transom of a 2003 150 SUPER SPORT, which would be better:

1. mount the ladder with its mounting brackets just below the transom [top], and let it expand by gravity, then collapse the steps and secure the ladder when not in use; or,
2. mount the ladder just above the water line but then need to fold-down the ladder into the water?

and when answering you should take into account the area of the transom that is or is not reinforced internally.

Fig. 1. The Garelick model 19684 boarding ladder that is under discussion.

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[jimh]

Q1: when attaching a swim ladder to the transom on a boat with a Unibond hull, between through-bolting with a backing plate or using "lag bolts" which method should be used?

Through-bolting is always to be preferred for mounting a boarding ladder. In the case of a 15-foot boat, the weight of a person attempting to board the boat from the sea could exceed the weight of the outboard engine. As can be inferred from the method of mounting the outboard engine, through-bolting with backing plates is clearly preferred for handling loads of that weight.

Further, the particular boarding ladder you intend to use projects outward from the transom as it goes into the water, which will create a tremendous turning moment at the point of attachment to the transom. Expecting "lag bolts" or large wood screws to be able to have sufficient purchase into the embedded wood in the Unibond hull to tolerate such large forces is unreasonable.

Q3: between two methods of mounting the Garelick model 19684 telescoping boarding ladder on the transom of a 2003 150 SUPER SPORT, which would be better...

Generally the most significant factor in using a boarding ladder is how deep into the water the lowest step of the ladder will be located. For this reason, a boarding ladder is typically mounted to the transom in a manner that puts the hinge point lower on the transom in order to increase the depth of the bottom step in the water, and the ladder is stowed in an inverted position when not in use. This approach is implied in the illustration in Figure 1, which shows the ladder in an inverted position when telescoped to smaller size.

[jimh]

...when answering you should take into account the area of the transom that is or is not reinforced internally.

In order for readers to comply with this criterion, you need to furnish readers with a diagram that shows the location of embedded wood in the transom for the particular boat you will be mounting the ladder. It is not reasonable to expect readers to know exactly where reinforced areas are located on the transom of the boat you will be using.

[jimh]

Another element to consider in a boarding ladder is to have a railing or grab bar available at deck height to assist the swimmer in climbing aboard the boat.

[Rowa]

[This post only quoted a great deal of the initial post, but contained nothing else.]

[mud-channel]

A [transom boarding ladder with a] platform with railings is nice.

As stated, through-bolting [a boarding ladder to the transom] is preferred.

My Martin Marine, Whaler-focused, welded, stainless, through-bolted swim platform is great. If Martin Marine were to make a [Whaler-focused, welded, stainless, through-bolted swim platform ] for your boat it would fit like a glove and make ingress and egress rock solid and easy.

Fig. 2. A transom boarding ladder with platform and railings.

IMG_1296.jpeg (180 KiB) Viewed 465 times

[A Martin Marine Whaler-focused welded stainless through-bolted swim platform is] high quality all around, and expensive