posted 09-16-2009 06:15 PM ET (US)        

Part of the damage involved physical removal of the aluminum backing plate which is mounted in the bow of the 18' Outrage (most boats have a sampson post bolted into this plate.

The plate on my Outrage has evidence of what I will term "severe" corrosion with significant pitting. If this was once a smooth plate of metal, it is not anymore.

However.

There is still substantial thickness to the plate and screws can be securely fastened to it.

I believe that one of the factors in the failure was the corrosion of the plate, which caused a mechanical separation of the plate from the underlaying fiberglass and resin in which it was originally encapsulated at the factory. Once this corrosion/pitting reached a critical point, the backing plate was simply floating under the surface on a field of powdered metal - no longer affixed to the hull.

Here is my question:
Is it a total waste of time to re-secure this plate to a new bed of resin and fiberglass? The new resin bed would mould to fit the current contours of the plate, and if/when sealed properly against water intrusion, it should not corrode further.

I am not concerned in any way about reduced strength of this plate at this time - but the corrosion must be arrested.

On a related note - I think that this is yet another example of where Whaler (and probably most builders) didn't seal bolts from water intrusion - and over time, water penetrated the threads of the bolts and in the anaerobic environment inside the hull, was not allowed to evaporate and began corroding this plate.

posted 09-17-2009 10:54 AM ET (US)            

I do have some Aluminum plate in my stock of loose material, but per Tom's post, now I'm considering using StarBoard. My only concern with that is that resin/glass and gelcoat don't stick to it very well...

...and I'd like to eliminate any voids in there once it is finished off with gelcoat and re-drilled and tapped for threads.

Was planning on using an appropriate amount of sealant in the holes before inserting the bolts for water tightness.

posted 09-17-2009 12:31 PM ET (US)            

I will observe that approximately 1/3 of the thickness of the original plate has eroded/corroded away into a coarse powder. Given the fact that I store my boat indoors, much of the damage must have been present before I bought the boat.

I'm also considering some kind of support/brace that would provide strength from underneath the pulpit to reduce the leverage force on the backing plate.

Thoughts?

posted 09-17-2009 12:37 PM ET (US)            

You're worried about corrosion right!

posted 09-17-2009 09:46 PM ET (US)            

Both in how to access the plate, (Dave, how did you find out it was less than 100% ?) and how a phenolic resin board can have the same thread holding ability as aluminum (or some other metal).

For example: lets use 1/2-13 bolts. The tap drill size is 27/64 (or .422) the tap will then cut threads (major diameter) that are 1/2 " (or .500) in diameter. the difference (between major and minor diameters) is .078 or .039 per side; a little more than 1/32 of an inch.

That strikes me as not much, I'm "old school", but admittedly when it come to composites they can be pretty darn impressive.

posted 09-18-2009 12:51 AM ET (US)            

Jay -- I doubt that the thread holding strength of WhaleBoard is as strong as aluminum but I am also equally sure it is more than strong *enough* for this task.

Like I said the commercial boats still use aluminum even though it corrodes. The recreational boats get the WhaleBoard because I presume it is easier to deal with.

posted 09-18-2009 09:00 AM ET (US)            

You're right - it is just under the fiberglass skin, and yes - a wave swept the pulpit from the boat.

The 4 through-bolts securing the pulpit to the backing plate were still secured, but the backing plate was not secured further to the boat other than being imbedded in the hull. I will remedy that by drilling some 1" holes down into the hull that will be filled with a filler epoxy/fiberglass and then drilled and tapped for some countersunk bolts that will secure the plate to the hull (and will be flush with the surface of the plate) before glassing over the plate to finish the repair and re-installing the pulpit.

I was fairly surprised at a couple of things.

First and foremost, that the damage even occurred. As I said - the corrosion must have reached a point where there was no longer a structural bond between the plate and the surrounding hull, allowing the fiberglass skin to be the only remaining holding strength of the plate...when the wave raked the boat, it simply tore the fiberglass. Believe me - and I'm sure you guys have experienced the same thing, perhaps with other "toys"....at the moment it happened - after I had secured passengers, items and pulled the pulpit aboard the boat (it was attached to the anchor chain via a tensioner) - I was ready to cry. I broke my favorite toy. That's not fun.

Second, I was surprised at the level of corrosion evident on the backing plate. For awhile, I fretted and wondered if I had a saturated hull, etc - even though the foam that was exposed in the incident was bone dry.

Third, I guess the conditions suprised me. It was a fairly rough day on Lake Erie, but the three sisters that were responsible for the "conditions" portion of this incident were unusually large even for the afternoon we were out. In a sea of 4-6 footers, these were easily between 8 and 10 feet. Everything that was "up" in the boat ended up "down". I broke the plastic mount for the fire extinguisher that was mounted under the leaning post. The arch cracked in three places, etc. You get the idea.

I'll say it for the thousandth time on this board - thank God for Mills Canvas, otherwise we would have been standing in calf-deep water on the deck. As it was, there was quite a bit of water aboard and we both got wet feet from the ordeal, but the canvas, despite popping some of the buttons up front, shed most of the third wave.

I will describe the incident: We were running out into Lake Erie from the River Raisin into a stiff East wind. The current was against the wind and we were in the ship channel trying to get out far enough to gain the depth required to run along shore back to the campground at Monroe.

When we encountered the waves, we climbed the first and leaped off it's face. The engines "barked" and the stern hit the top 3' of the second wave, which "tripped" us, causing the hull to basically "faceplant" into the third wave. I don't remember how much of the wave we plowed through, but there was blue/green water on the windshield of the Mills canvas.

posted 09-18-2009 10:12 AM ET (US)            

Jerry -

Regarding the aluminum stock in my basement - it was purchased at a boatyard - so it is marine-grade and anodized. I bought extra when I made the backing plates to mount the arch to the gunwales.

posted 09-18-2009 11:07 AM ET (US)            

Please photograph that part with a tape measure or scale against it as appropriate. I requested information on it when I was designing the bow-mounted trolling motor components for my 18 and no one had anything definitive on this piece.

posted 09-18-2009 11:29 AM ET (US)            

It is a "modified pentagon" shape that is essentially a 6"w by approximately 4"h rectangle with a squat, 1"h triangle on top of it toward the bow.

posted 09-19-2009 01:41 AM ET (US)         

There are two large diameter bolts at the back, countersunk into the pulpit teak, then there is the Marinium cleat, which has four 3/8" x 3" machine bolts into the plate, clamping it down so to speak, then as the pulpit passes over the gunwale lip, there are two 3/8" through bolts going completely through both glass skins, with large washer and nut on the bottom side. I think these are important, as they would take, and prevent, any uplifing force.

If you re-do it, you might use this method of attachment.