hull creased just in front of transom: fix or not?

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May 26, 2024
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Farmville, NC
After 45 years, it was time to replace the floor in my 1979 Sea Nymph SS-170, and I figured if I was doing that, I'd strip it down to the hull and fix everything all at once. (Miraculously, the transom--which is just plywood with an aluminum skin on the outboard face--is in almost perfect condition...all credit to my Dad, the original owner, who kept it trailered and stored it well!)

Of course, all the foam was waterlogged and that all had to be torn out. After getting the whole thing stripped down to the hull, I found that the bottom of the hull--about 3" in front of the transom--is bent, almost creased, about 1" at the highest point. I suspect that it got bent because of the trailer; the back roller sits right at that spot. As a result, water collects right in front of this "hump" and the hull doesn't completely drain when the plug is pulled.

I'm wondering what, if anything, to do about it. I'd be tempted to hammer it out if I could, but there's a stout and firmly attached 2"x3" metal beam a couple inches above this spot, reinforcing the transom, and I can't really get in there with a mallet unless I remove that beam.

When I replace the floor system (including new pour foam), I'm planning to add new aluminum panels perpendicular to the existing braces (in other words, along the length of the boat) so that I can add the foam in "pockets" along both sides of the V-hull, leaving a channel of about 10" clear right down the center, so that the foam won't wind up waterlogged. So, perhaps a 1" pool of bilgewater in the center of the last couple feet of the hull won't really matter. Also, I trailer the boat, and when I get it home after each trip, I can fairly easily tilt it up to run out 95% of any bilgewater (and it'll be stored under a shed). So I don't think it'll have a lot of standing water, and maybe I'm worrying over nothing. But before continuing with the work, I figured I'd ask others who know more about it than I do.

What do y'all think: leave it or try to pound it out--and if the latter, can I pound it out without removing the metal transom reinforcement bar, or should I remove that and then just hit it with a hammer?



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I’ll be curious to hear the opinions of others with your dilemma… first and foremost, I would re-rig the trailer to avoid further damage. Ideally, you want bunks supporting the boat all the way to the transom, with the bunks extending at least an inch or more beyond the transom, keeping the resting weight off the rollers. Personally, I like nylon skids on my bunks vs. carpet - especially with an aluminum boat. Regarding the repair, I think the distinction between a “bend” and a “crease” matters. I would probably attempt flattening a bend with wood block & rubber mallet. An actual crease might give me pause, just realizing that pounding might weaken/split the metal, which would then require a whole different approach to repair. Good luck with whatever approach you take!
I'd be inclined to just clean it up, fill the gouges with JB weld and repaint it so long as there' sno leaks there. If its leaking, then you have less to lose, I'd first support it and not just start pounding on the inside of the hull in mid air. Support the hull with a large flat bock of wood, you want to be forming the hull into a set shape not just banging out a dent. Avoid hitting on rivets if possible but and be sure the metal is warm not ice cold. You won't be able to 'heat' it due to the presence of seam sealer between the layers there.
Work both panels, don't just try to beat the bottom down without helping the transom retake its shape. You will be able to make it better but not likely perfect. Clean up imperfections in the metal with JB weld and sand smooth, then coat the inside seams with Gluvit and paint it when your done.
Depending on the amount of metal that has to be moved, Aluminum in boats is tempered, meaning it can be bent one way but often cracks when bent back...
Unfortunately your rollers are poorly positioned and probably don't have enough rollers to support the hull. If you can't reposition and add rollers, the switch to bunks, easier to add them on. Tough call on your dent with being able to actually see it. Minor dents can be hammered out, but steep dents can crack when the metal is pushed back. Good luck and keep us posted.
What I'm seeing is that flange right below the drain is bent up (see arrows below). Were there originally rivets in that bent up part that pulled out? That cross piece Brenthenze mentions will make it very difficult to work that flange back down. I guess my question is does it leak. If so, then can that cross beam be removed in order to reach the problem area.

The flange may have been bent intentionally if the boat used to have a transom stiffener. Also, there is a rectangular pattern on the hull that looks like something used to be there.

Could the boat have been modified at some point?
If you zoom in the third pic you can see rivets going thru the bent up part of the flange. I'm scratching my head about why that would be done intentionally, but honestly don't know.

This is very seat of the pants and for all I know a dumb idea.. What if: Remove the rivets going thru the bottom and the bent part. Have a very solid backer to go under that part of the tansom/hull. Put 1/4 bolts through the flange, the hull and the solid backer (use washers). Tighten the bolts slowly and evenly. Would that pull the flange back down?

I also noticed the off center rectangular thing. I assumed it was added to address the bend in the hull.

I think @TriBull hit the nail on the head suggesting the rollers be replaced with bunks.
If it is not affecting the ride or causing leaks or other issues, I would probably leave it alone. Pretend like you didn't see it. Someone here has the signature, "Perfection is the enemy of a good job."

Ever see something that looked really good, then you couldn't help but to mess with that one tiny spot and ruined the good work? It's like that. Metal gets bent sometimes. Often, unbending is what causes the problems.

So if no issues, I would not worry about it. If you MUST fix it, then use a torch and warm the area up first and use wood blocks and a mini-sledgehammer.

Either way, I hope it works out for the best.
Just to be clear....are you referring to the depressions in the hull caused by the rollers? If so, I'd leave them alone. Convert to a bunk trailer using as long as bunks as you can (be sure to allow the bunks to stick out at least 2" beyond rear/bottom of hull). You could pound out the depressions from inside hull using a large head rubber mallet, but I would not, even with my OCD!
I'd try to fix it, personally. That lip sticking up is going to catch any trash in the bilge, and also cause water to run out and away from the drain channel into your foam, which is what you're trying to avoid. Additionally, sometimes a dent like that can cause some odd handling problems at speed, although that one is pretty insignificant.

A chunk of 2x4 and a mini sledge should take care of it, I imagine. Work from the top, and beat on the thicker reinforced area, let it pull the hull skin back down. I'd probably run a bead of silicone along it just for good measure when you're done.

Lastly, I'd check that area over close for loose rivets, they may be stretched and need bucking. A leak test would be smart as well, while it's stripped.
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Ok, I see now. A patch or reinforcement was added to the bottom of the hull. The flange was lifted up for access to buck the rivets.

At this point I agree with thill. Leave it alone if it’s not leaking. Trying to fix the flange may open a huge can of worms.
Ok, I see now. A patch or reinforcement was added to the bottom of the hull. The flange was lifted up for access to buck the rivets.

At this point I agree with thill. Leave it alone if it’s not leaking. Trying to fix the flange may open a huge can of worms.

Aw, that makes sense. I would also be inclined to let it go, except for the drainage issue @MrGiggles points out.
I don’t know… I’d be awfully darn tempted to at least clean out under that flange, tap it down with the end of a 2x4, and then seal the entire edge of the flange. But I admit, I have a hard time leaving things alone - and I’ve suffered the consequence on occasion! :oops:
@TriBull How are ya holdin up down there? Some mean weather hittin FLA
Honestly, until this week, it’s been unseasonably dry and hot! Last week temps averaged around 100°. Orlando hit a high of 106°. So far this year, the state has seen quite a bit of tornado damage… The rain this week in South Florida is actually closer to normal Florida weather during this time of year, but with all of the over development that has occurred down there, it now has more impact! But with June opening the hurricane season, the real adventure begins! This year is the highest predicted storm count in history - I sure hope they got it wrong!
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