Backing Plates & Swim Ladder Installation

[Joe D.]

I am going to be installing an Ocean Engineering swim ladder on my CD27 in the next few weeks. On the inside part of the transom, should I use metal plates for the screws to go through and be tightened to in order to spread out the load? Or is it common to simply screw the bolts through and tighten them on the inside part of the transom directly against the fiberglass? I realize the bedding compound is used on the outside of the transom.
I hope my question is clear. Thanks in advance for any help and advice.



donnj2@aol.com

[Ken Coit]

Surely, Ocean Engineering will provide backing plates that match your mounts; check with them. If not, I would ask them to fabricate some from stainless.


Ken
S/V Parfait
Raleigh, NC

I am going to be installing an Ocean Engineering swim ladder on my CD27 in the next few weeks. On the inside part of the transom, should I use metal plates for the screws to go through and be tightened to in order to spread out the load? Or is it common to simply screw the bolts through and tighten them on the inside part of the transom directly against the fiberglass? I realize the bedding compound is used on the outside of the transom.
I hope my question is clear. Thanks in advance for any help and advice.

parfait@nc.rr.com

[Joe D.]

Ken:

Thanks for the info and help. I greatly appreciate it.
Joe D.



donnj2@aol.com

[Bill Goldsmith]

To underscore Ken's comments, a backing plate is NOT optional here. You should use the largest, widest plate that will fit. Due to the significant stresses imposed by a ladder (I know I am not as light as I used to be), the lack of a backing plate will cause the hull to flex at the attachment points and you will get gelcoat cracking and possibly weaken the hull. The design of the CD transom compounds this effect a bit: since it is angled toward the water, the ladder will impose both a shear load and a pulling load. A good backing plate will spread out that load as much as possible.

Another complication is the fact that the hull is curved, and most thick metal backing plate stock is not. Don't be tempted to reduce the size of the plate so the gap in the hull curve is seemingly reduced--you will get point loading at the edges of the plates. Even with the manufacturer's matching plate, you will get point loading on the inside of the hull.
Rather, you may want to consider installing backing plates over an epoxy filler (such as a mixture of West System with their 404 high density filler). Clean and lightly sand the inside of the hull and wet it with unmixed watery epoxy. Then mix 404 into it to a "Peanut Butter" consistency, place it on the inside of the hull where the backing plates will go, and push the plates into the epoxy. Let it cure overnight. (You can clean up any "squeeze-out" before it cures). Now you have a flat surface to contact the plates, with a perfectly shaped filler to match the hull.

If this seems like overbuilding, that's what I had in mind!!


Bill Goldsmith
CD27 #173
Second Chance

I am going to be installing an Ocean Engineering swim ladder on my CD27 in the next few weeks. On the inside part of the transom, should I use metal plates for the screws to go through and be tightened to in order to spread out the load? Or is it common to simply screw the bolts through and tighten them on the inside part of the transom directly against the fiberglass? I realize the bedding compound is used on the outside of the transom.
I hope my question is clear. Thanks in advance for any help and advice.

goldy@bestweb.net

[Mott Blair]

Just a brief comment from personal experience about the strength of the transom of a Cape Dory (30 in my case). About 2 years ago a powerboater (Boston Whaler about 20 ft) decided to play bumper boats coming in to the dock and literally crushed my boarding ladder. He claimed later when we tracked him down that he had not realized that he had damaged my boat. Amazing the gelcoat and glass was without a scratch but the boarding ladder was bent beyond all repair (stainless steel)! The boarding ladder by the way was installed without a backing plate. I was impressed by the blow that we took from the Boston Whaler without any fiberglass damage. He could not deny the damage because part of the broken boarding ladder took a serious deep "core biopsy" of his boston Whaler. So from my experience I am satisfied with the strength of the stern to hold the ladder with or without a plate but I would use one as well. By the way I replaced it with a ladder made by Tops In Quality and I was impressed with their craftmanship.



mblair@coastalnet.com

[Ken Coit]

Mott,

I am glad to hear about that strong transom, but I have one comment. Unless they came at you from the side, it is likely that the Whaler did not pull on your ladder, just push. The backing plates prevent the bolts from pulling out of the transom.

Ken
S/V Parfait
Raleigh, NC

Just a brief comment from personal experience about the strength of the transom of a Cape Dory (30 in my case). About 2 years ago a powerboater (Boston Whaler about 20 ft) decided to play bumper boats coming in to the dock and literally crushed my boarding ladder. He claimed later when we tracked him down that he had not realized that he had damaged my boat. Amazing the gelcoat and glass was without a scratch but the boarding ladder was bent beyond all repair (stainless steel)! The boarding ladder by the way was installed without a backing plate. I was impressed by the blow that we took from the Boston Whaler without any fiberglass damage. He could not deny the damage because part of the broken boarding ladder took a serious deep "core biopsy" of his boston Whaler. So from my experience I am satisfied with the strength of the stern to hold the ladder with or without a plate but I would use one as well. By the way I replaced it with a ladder made by Tops In Quality and I was impressed with their craftmanship.

parfait@nc.rr.com

[Joe Sankey]

Mott: We're planning to install a TopsinQuality ladder on our 30. Which model did you use? FWIW, when installing on a CD22 several years ago I used 1/4" marine plywood (6"+/- squares) for each mount; then fender washers and lock nuts (ss). It seemed to do well. You have to oversize the holes in the ply to allow for tightening on the curve, and fill with caulk on bolts and backing plate.

Just a brief comment from personal experience about the strength of the transom of a Cape Dory (30 in my case). About 2 years ago a powerboater (Boston Whaler about 20 ft) decided to play bumper boats coming in to the dock and literally crushed my boarding ladder. He claimed later when we tracked him down that he had not realized that he had damaged my boat. Amazing the gelcoat and glass was without a scratch but the boarding ladder was bent beyond all repair (stainless steel)! The boarding ladder by the way was installed without a backing plate. I was impressed by the blow that we took from the Boston Whaler without any fiberglass damage. He could not deny the damage because part of the broken boarding ladder took a serious deep "core biopsy" of his boston Whaler. So from my experience I am satisfied with the strength of the stern to hold the ladder with or without a plate but I would use one as well. By the way I replaced it with a ladder made by Tops In Quality and I was impressed with their craftmanship.

sankey@gulftel.com

[Leo MacDonald CD30K]

Hi All,

I would install good backing plates!!

3 years ago I had a stern boarding ladder added by Whitby Boat in Whitby, ON. At the time (and stage of keelboat ownership) all looked fine with each ladder support having a thin aluminum backing plate (approx. 1" x 4"). I have just removed the whole mess because of developing gelcoat cracks radiating out from the top bolt on each support bracket. The backing plate is nowhere near large enough!! Had a difficult time removing the backing plates - they had corroded and the aluminum oxide had swelled to pinch the 1/4-20 stainless bolts (

The current 'plan' is;
I have fashioned ~6" x 6" plywood backing plates and will mount them with 3M 5200 to the inboard side of the transom and reinstall the ladder support brackets (with 5/16" bolt - if they will fit.)

Fair Winds,
Leo

Just a brief comment from personal experience about the strength of the transom of a Cape Dory (30 in my case). About 2 years ago a powerboater (Boston Whaler about 20 ft) decided to play bumper boats coming in to the dock and literally crushed my boarding ladder. He claimed later when we tracked him down that he had not realized that he had damaged my boat. Amazing the gelcoat and glass was without a scratch but the boarding ladder was bent beyond all repair (stainless steel)! The boarding ladder by the way was installed without a backing plate. I was impressed by the blow that we took from the Boston Whaler without any fiberglass damage. He could not deny the damage because part of the broken boarding ladder took a serious deep "core biopsy" of his boston Whaler. So from my experience I am satisfied with the strength of the stern to hold the ladder with or without a plate but I would use one as well. By the way I replaced it with a ladder made by Tops In Quality and I was impressed with their craftmanship.

macdore@aol.com

[Warren Kaplan]

Hi All,

I would install good backing plates!!

3 years ago I had a stern boarding ladder added by Whitby Boat in Whitby, ON. At the time (and stage of keelboat ownership) all looked fine with each ladder support having a thin aluminum backing plate (approx. 1" x 4"). I have just removed the whole mess because of developing gelcoat cracks radiating out from the top bolt on each support bracket. The backing plate is nowhere near large enough!! Had a difficult time removing the backing plates - they had corroded and the aluminum oxide had swelled to pinch the 1/4-20 stainless bolts (

The current 'plan' is;
I have fashioned ~6" x 6" plywood backing plates and will mount them with 3M 5200 to the inboard side of the transom and reinstall the ladder support brackets (with 5/16" bolt - if they will fit.)

Fair Winds,
Leo

Leo,
Consider soaking those plywood backing plates in some epoxy before mounting. I did just that when I installed a new fitting for my bowrail. Soaked a piece of plywood in West System epoxy for a while then let it cure overnight. Then I epoxied it to the underside of the deck in the chain locker where I was going to install the new bowrail fitting. Adhered real well and consequently I could drill the holes thru the deck and the backing plate all at the same time. No problems with alignment of the backing plate holes and deck holes that way.
Warren

Just a brief comment from personal experience about the strength of the transom of a Cape Dory (30 in my case). About 2 years ago a powerboater (Boston Whaler about 20 ft) decided to play bumper boats coming in to the dock and literally crushed my boarding ladder. He claimed later when we tracked him down that he had not realized that he had damaged my boat. Amazing the gelcoat and glass was without a scratch but the boarding ladder was bent beyond all repair (stainless steel)! The boarding ladder by the way was installed without a backing plate. I was impressed by the blow that we took from the Boston Whaler without any fiberglass damage. He could not deny the damage because part of the broken boarding ladder took a serious deep "core biopsy" of his boston Whaler. So from my experience I am satisfied with the strength of the stern to hold the ladder with or without a plate but I would use one as well. By the way I replaced it with a ladder made by Tops In Quality and I was impressed with their craftmanship.

Setsail728@aol.com

[Warren Kaplan]

Hi All,

I would install good backing plates!!

3 years ago I had a stern boarding ladder added by Whitby Boat in Whitby, ON. At the time (and stage of keelboat ownership) all looked fine with each ladder support having a thin aluminum backing plate (approx. 1" x 4"). I have just removed the whole mess because of developing gelcoat cracks radiating out from the top bolt on each support bracket. The backing plate is nowhere near large enough!! Had a difficult time removing the backing plates - they had corroded and the aluminum oxide had swelled to pinch the 1/4-20 stainless bolts (

The current 'plan' is;
I have fashioned ~6" x 6" plywood backing plates and will mount them with 3M 5200 to the inboard side of the transom and reinstall the ladder support brackets (with 5/16" bolt - if they will fit.)

Fair Winds,
Leo

Leo,
Consider soaking those plywood backing plates in some epoxy before mounting. I did just that when I installed a new fitting for my bowrail. Soaked a piece of plywood in West System epoxy for a while then let it cure overnight. Then I epoxied it to the underside of the deck in the chain locker where I was going to install the new bowrail fitting. Adhered real well and consequently I could drill the holes thru the deck and the backing plate all at the same time. No problems with alignment of the backing plate holes and deck holes that way.
Warren

Just a brief comment from personal experience about the strength of the transom of a Cape Dory (30 in my case). About 2 years ago a powerboater (Boston Whaler about 20 ft) decided to play bumper boats coming in to the dock and literally crushed my boarding ladder. He claimed later when we tracked him down that he had not realized that he had damaged my boat. Amazing the gelcoat and glass was without a scratch but the boarding ladder was bent beyond all repair (stainless steel)! The boarding ladder by the way was installed without a backing plate. I was impressed by the blow that we took from the Boston Whaler without any fiberglass damage. He could not deny the damage because part of the broken boarding ladder took a serious deep "core biopsy" of his boston Whaler. So from my experience I am satisfied with the strength of the stern to hold the ladder with or without a plate but I would use one as well. By the way I replaced it with a ladder made by Tops In Quality and I was impressed with their craftmanship.

Setsail728@aol.com