Reinforcing a transom ladder

[Voiding Sounds]

My '73 came equipped with a huge plastic folding ladder that connected to mounts deck mounts on the bow. It was brittle with age and required repeated improvisation to get swimmers out of the water last summer.
I have a new transom ladder I want to install but I have a question about reinforcing the mountings. Where I'd like to mount the ladder, there is a void between the transom fiberglass and and lazarette lining roughly between 3/16" and 1/2".
I know some transom jobs like the scuppers call for adding a piece of plywood between the fiberglass but I'm not sure I'll be able to access this section. I've considered trying to fill the are where the hardware will mount with thickened epoxy, or drilling the liner oversized and using a metal bushing/collar/spacer to make the area around the hardware solid, and then installing a backing plate.
Am I overthinking this? Would a couple of backing plates (2" wide 3/16" aluminum strips) inside the laz be enough to support the ladder? I want to overbuild this a little, my friends and I are big guys and I would hate to have the ladder damage the transom.

 

[Jacktar]

My 83 and tons of other boats came from the factory with just fender washers on through bolts from the ladder bases so maybe you do not have a void or a void problem?

 

[Voiding Sounds]

Yeah, I don't think this is a void as in poor quality glass layup. Just space between molded parts. If Catalina was just slapping a fat washer on and calling it good that is reassuring since I'll be doing something heavier-duty.

 

[Leeward Rail]

At least on our 1987 "new design", the transom has no void.

There is a gap between the liner and the actual hull, on the fuel locker side (where the outboard mount is). IN that location the fasteners are between the liner and the transom.

In both cases, ladder and outboard mount, there are backing "plates".

Here's a shot of the ladder backing plate, inside the starboard locker, on the transom.

 

[rpludwig]

our '84, original design has ~ 3/16 void.....squeeze some thickened in there, sure, backing plate no harm or large fender washers are adequate...don't overthink it...

 

[Gene Neill]

@Leeward Rail ... Well whadda ya know. Mine is identical. I always assumed it was the work of some PO, but apparently it's factory.

 

[Hardhead]

At least on our 1987 "new design", the transom has no void.

There is a gap between the liner and the actual hull, on the fuel locker side (where the outboard mount is). IN that location the fasteners are between the liner and the transom.

In both cases, ladder and outboard mount, there are backing "plates".

Here's a shot of the ladder backing plate, inside the starboard locker, on the transom.
View attachment 150788

My 87' has the fiberglass backing plate shown on the boarding ladder, but the outboard bracket is only backed by 1 1/4" fender washers from the factory. Must depend on what fellow was putting them together. I'm going to add backing plates to the outboard bracket, but honestly, the 1 1/4" fender washers seem like they have done a good job for 30 years.

I've never removed the outboard bracket yet - does anyone know if there is generally a void in the transom layup the outboard bracket is mounted through? Strangely enough, my entire transom sounds hollow (relatively sharp and high toned), when tapped. Seems strong though-

 

[Voiding Sounds]

Thanks for all the advice. Yesterday I installed the ladder and used 2, 2" strips of 1/8" aluminum for backing. Seemed rock solid with my 200lb self standing on it.


I didn't have the outboard aluminum perfectly straight when I drilled the lower but I think it will be fine. I'll cut the bolts and reinstall it tomorrow with butyl and be ready to retrieve swimmers.

My 87' has the fiberglass backing plate shown on the boarding ladder, but the outboard bracket is only backed by 1 1/4" fender washers from the factory. Must depend on what fellow was putting them together. I'm going to add backing plates to the outboard bracket, but honestly, the 1 1/4" fender washers seem like they have done a good job for 30 years.

I've never removed the outboard bracket yet - does anyone know if there is generally a void in the transom layup the outboard bracket is mounted through? Strangely enough, my entire transom sounds hollow (relatively sharp and high toned), when tapped. Seems strong though-

Tapping on the port side sounds about the same as the starboard side on my boat. My outboard mount has wood spacers and backers installed, which are due for replacement.

 

[Leeward Rail]

The easiest option is to not allow large people aboard. It's much easier to do MOB recovery on 5' 2" brunette and redhead gymnasts and also less stress on the ladder.

 

[Sacto Dave]

Well, since I’ve got my motor mount off, here is what my ‘73 transom gap looks like:

 

[Voiding Sounds]

The easiest option is to not allow large people aboard. It's much easier to do MOB recovery on 5' 2" brunette and redhead gymnasts and also less stress on the ladder.

My wife isn't the jealous type, but if I added a petites-only guest requirement it would probably dim her enthusiasm for sailing.

Well, since I’ve got my motor mount off, here is what my ‘73 transom gap looks like:

Yep, that's pretty much what I found. Outboard side looks like your second pic, inboard looks like the last one.

The plan for the weekend is to head to the lake for some sailing and swimming. Should be a good test of the ladder mounting and positioning.

 

[agprice22]

Remember that the transom is primarily plywood. I would over-drill those holes, fill them with thickened epoxy, and redrill the correct size in the center of the filled epoxy, so your bolts do not pass directly through plywood. G10 also makes a great backing material although I do use aluminum often.

 

[Sacto Dave]

Well, that sounds like good advice. Here is what I’m repairing:

Remember that the transom is primarily plywood. I would over-drill those holes, fill them with thickened epoxy, and redrill the correct size in the center of the filled epoxy, so your bolts do not pass directly through plywood. G10 also makes a great backing material although I do use aluminum often.

 

[agprice22]

Well, that sounds like good advice. Here is what I’m repairing:
View attachment 152933

Are you re-mounting a motor bracket? If not, epoxy the holes with thickened epoxy. Then remove 1/16” of the epoxy on the outside to apply gelcoat.
If you will re-mount a bracket, over-drill the holes, fill them with thickened epoxy. Then drill the correct sized holes. Mount the bracket using butyl rubber. On the other hand... if you wanna stir up ALL sorts of fun... mount it with 3M 5200!... JUST KIDDING!

 

[Sacto Dave]

@agprice22 - I am remounting the bracket.
But that leaves me with 10 extra holes. I read gelcoat may have subpar adhesion to epoxy.

Are you re-mounting a motor bracket? If not, epoxy the holes with thickened epoxy. Then remove 1/16” of the epoxy on the outside to apply gelcoat.

Just looked it up. Appears it will stick fine:
https://epoxyworks.com/index.php/applying-polyester-gelcoat-over-epoxy/