Crack inside transom

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HARD_WAY
Posts: 12
Joined: Wed May 24, 2023 10:51 am

Crack inside transom

#1

Post by HARD_WAY »

Good Morning:

A google search with the same subject revealed a 10 year old post in here by "giddy" that finished off with the discovery of a crack in the transom of their Alumaweld Intruder.  I'm in "the same boat" as they say!   The cracks are around the bottom bolts that go through the hull to the outboard but only on the inside piece of aluminum. It seems like thinner material than the outside skin and there is quite a bit of space between the two layers. My questions;  What is in that space? and; Rather than just weld up the cracks, should I cut the damaged aluminum out and inspect whatever is inside that void? (then perhaps replace everything with something a bit more substantial?) 
 
I also have small cracks in an area of the hull that is not accessible from the inside. All of my issues appear to be from hard use and are not associated with corrosion or a weld failure. In all cases the plate is cracked. Can these be welded from the outside successfully by a pro?

Her name is Hard Way and she comes by it honest. I've had her for 2 decades, fishing the Pacific, Atlantic, and the Gulf. We've been in allot of scrapes  together and I won't let her go without a fight. Any guidance is appreciated. 

thanks in advance. 
kmorin
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Location: Kenai, Alaska

Re: Crack inside transom

#2

Post by kmorin »

Hard_Way,
To directly answer your question about the inner transom plate; yes you should open up the void to see what's inside.  If the inner plate is the liner to a void that was created as a 'sandwich' or double sided built up 'box'(?) then it may not have been stiff enough internally? The bolt heads compression and tension loads (tightening would cause compression and engine thrust would cause tension pulling aft at the top set of bolts) were/are pulling on inadequate thickness of plate to take the loads.

What caused the cracks? ( I'm not sure) That may be the lack of panel reduction braces.  That is flat bars or angles inside the box/void that would support the inner plate/panel to be stiff enough for the loads at the bolt heads?  By having more bracing inside (?) the panel area(s) would be reduced making any thickness of plate 'stiffer' in resistance to compression plus vibration. 

A 1/8" plate may be stiff enough to hold the loads if the internal bracing were on a 3" spacing in both directions? 

I'd cut out the inner box plate that is cracked, and increase the thickness to 1/4" or even 3/8" and try to add bars to the transom.... then cut keyhole or 'pocket' weld allowances in the inner plate so the inner edges of these added flat bars/extrusions could be welded from the inside - to the inner plate.  This would reduce the panel size of the inner box/void side so it was stiffer than the original design/build.

One thing I've seen in lots of plate boats is the wear and tear happens more on the trailer than in the water.  IF the engines are not tipped down and have a wood 'traveling block' in the mount? then there is a lever arm of the wt of the engine trying to bend the transom plates where the bolts connect the engine.  The forces of an outboard on the transom at 70mph on the highway are considerably higher than at 25-40 mph on the water while running.

This also holds true of boats riding on rollers instead of plastic covered bunks- the rollers' only support the boat on a few square inches while the bunks are hundreds of times that area.  Therefore a boat on rollers is seeing a 60-70mph 'bump' or seam in the highway distributed over a few 10-12 rollers at 2-3" sq inches or 36" ^2 to sustain the entire momentum of the boat.  That force is hundreds or even thousands of times greater than bunks supporting hundreds of square inches while traveling.  Hulls that are fine in the water can still be damaged by incorrect trailering methods.

If the hull cracks that might be welded from outside only are coated with bilge water or other deposits inside the hull- they won't weld very well.  The only method I can think of is TIG from the outside- but that will still bubble the interior contamination into the root of the weld and that usually results in cracking.

I think the question of why the other area cracked is the big issue at this point?  Pictures are always helpful in trying to suggest repair work on a welded aluminum hull.

Hope this helps your deliberations about how to repair your boat?

Cheers,
Kevin Morin
Kenai, AK
kmorin
HARD_WAY
Posts: 12
Joined: Wed May 24, 2023 10:51 am

Re: Crack inside transom

#3

Post by HARD_WAY »

kmorin

thanks, I am in the process of selecting the shop to do the work and needed some guidance on the direction the repair should go. At least conceptualize with them and then ascertain whether the shop candidate can do what needs to be done or not.  I am just understanding how to upload imagery on this new site and will attempt that with my phone next.
However, the outboard has always traveled with one of those spring loaded supports and the boat rests on long flat plastic coated bunks. I use some rollers to guide the bow to the center when I load up but are not in play while on the trailer. I think operating her in rough water, one sideways contact with a submerged sea stack while drifting (removed my skeg), a couple dead heads, and one tree @ 15-20kts in a Texas reservoir likely did me no favors back there. the cracks up front are in the back of what seems to be unsupported outer hull between the keel and the first chine just under the anchor well up front. There is no access to this pocket and no drainage. The plate is bent inward on both sides a little unevenly but no discernable impact marks. ?? the rollers that I just mentioned are well ahead of the bent areas. I fear contact with rough water has just beat the plate inward and it has begun to crack where it meets the first rib, ?? IDK.  Again photos are on the way...

 
HARD_WAY
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Re: Crack inside transom

#4

Post by HARD_WAY »

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Last edited by HARD_WAY on Wed May 24, 2023 5:41 pm, edited 1 time in total.
HARD_WAY
Posts: 12
Joined: Wed May 24, 2023 10:51 am

Re: Crack inside transom

#5

Post by HARD_WAY »

C630B5A7-8B0A-4F76-91D5-E573656530C5.jpeg
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kmorin
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Location: Kenai, Alaska

Re: Crack inside transom

#6

Post by kmorin »

Hard_Way,
First the transom bolt doubler 'pan'.  It appears this is a bent piece of sheet and the bends look like they were done with a knife edge brake die?  This resulted in a weakened piece of metal due to the strain hardening of the bend areas; by not using the correct (4T Radius Upper Nose Bar - Die) to form a more rounded curve in the bend. 

That 'too-tight' radius then cracked over time along the hardened and embrittled edge of the 'pan' from the compression of the bolt adding strain to the lower nut/washer assembly and pulling the middle of the 'pan' inward toward the transom.  This 'too-hardened' area then cracked due to the bend radius conversion of the original sheet material spec.s then flexed by many cycles of load as the engine stress on those lower bolts cycled from compression to relaxation.  So the edge cracks were the original design flaw and the horizontal cracks came from continued deflection of the face of the 'pan' after the bent edge failed.  You can see the two vertical tracks in the face and leg of the 'pan' where the lower die marred the sheet material during the bending process.

Releasing the lower engine mount bolts, and scoring the (what appear to be) vertical welds holding the pan to the transom, will allow the removal of the 'pan'.  Replacing it with a welded edge 'pan' or one bent with the correct die set (very difficult to get done in many shops who refuse to accept the Machinists' Guide to bending aluminum alloys!) and either reinforced w pipe sections to hold the bolts, or bars or other extrusion shapes to reduce the panel size of this 'pan' assembly's area will work fine to increase the strength of this area. 

I'd want to use 5086 instead of 5052 as it appears was done originally?  The 5086 will strain harden and fail along the bend line if not done to recommended nose bar radius.  But using 3/16" or 1/4" material and welding the edges to flat bar will work too.

Remember to insure the batteries are fully disconnected from the engine and hull before welding. Also make sure the outboard engine's 'brain box' is disconnected inside the cowling so there is possibility of TIG AC High Frequency passing through either electrical component.

As to the bow/forefoot crack near the rib/bulkhead that could be welded from the outside but may take several passes w/ repeat cut out and re-welds because predicting what will be inside and could float up in a weld; is not realistic to do from AK.

This crack suggests the interior/exterior framing of the bottom panels in this area are inadequate.  I'd consider asking for a set of tapered 'spray rails' be added wrapping upward and forward as is shown the end of a bottom rail/longitudinal in the photo of the crack.  These would be used to reduce panel size, increase the stiffness of these panels and stop and 'oil canning' or flexure of these panels in collision or just running hard in to a chop. These can be 'stitch' welded to the hull panels from the outside where the crack is welded only where the rail/long will pass over the crack; at first. Then the rest of the crack would be filled in after the new hull stiffener longitudinals were added.  I'd add 3 longs, spaced from keel to chine evenly and I'd use a 1-1/4" x 1-1/4" by 3/16" angle for each of the new stiffeners- tapered by 4X cross section at the bow stem and aft end I'd use a 3"-4" circle of plate so that the end of rail weld is not stopped in the middle of a hull panel w/o distributing the potential crack area over a circular 'patch' or hull doubler.

I hope this helps your discussions with the repair shop?

Cheers,
Kevin Morin
Kenai, AK
 
 
kmorin
HARD_WAY
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Re: Crack inside transom

#7

Post by HARD_WAY »

Mr Morin:

Thank you so much. That is precisely what I needed for my discussion with my shop candidates. Removing and fabricating a more robust pan is what I will do. I like the spray rail idea too. I will return to post results!
Thanks again
DW & hard way
HARD_WAY
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Joined: Wed May 24, 2023 10:51 am

Re: Crack inside transom

#8

Post by HARD_WAY »

quick update:

the outboard, floor, and gas tank are all out and a shop and I are working on scheduling. The pan actually goes right up through a catch basin like area ahead of the outboard to the top edge of the transom. It is also welded to the floor section and contains the drain hole. It is almost completely hollow. The vertical crack in the earlier photos runs along the one piece of aluminum inside there that sections off the area that holds the outboard to the boat just below the lower bolt holes. There is no wood between the layers where the motor attaches and there is nothing in the void below that section either. the horizontal crack crosses both chambers as you can see. We will likely zip up the cracks and reinforce the area with a secondary pan section that is welded rather than bent over top of the damage area.
I found four small pits under the gas tank where some beer cans had been lodged for who knows how long. They are at least 2/3 as deep as the plate is thick so we will weld those up too.

estimated cost; around $2600
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gandrfab
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Re: Crack inside transom

#9

Post by gandrfab »

Thank you for the update.
as always, more pictures, please.
HARD_WAY
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Re: Crack inside transom

#10

Post by HARD_WAY »

What I’m calling “basin”. The top rail of the transom with the holes is double thick as the “pan” that extend through the “basin”.
What I’m calling “basin”. The top rail of the transom with the holes is double thick as the “pan” that extend through the “basin”.
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HARD_WAY
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Re: Crack inside transom

#11

Post by HARD_WAY »

The rest of the “pan” below the “basin”. The horizontal crack runs along the only support (perpendicular welded aluminum plate) inside the entire pan. That goes up through the “basin” and it’s welded above it.
The rest of the “pan” below the “basin”. The horizontal crack runs along the only support (perpendicular welded aluminum plate) inside the entire pan. That goes up through the “basin” and it’s welded above it.
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HARD_WAY
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Re: Crack inside transom

#12

Post by HARD_WAY »

60E13BE5-7CC7-4FB2-A938-E24AF8FD231B.jpeg
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The bend inside the pan. Areas with or without the crack.
The bend inside the pan. Areas with or without the crack.
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gandrfab
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Re: Crack inside transom

#13

Post by gandrfab »

I have known 'the “basin” as the splash well.
HARD_WAY
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Re: Crack inside transom

#14

Post by HARD_WAY »

10-4, we will continue forward with splash well.

I experimented with the garden hose pressed firmly against the cracks in the bow and I got water to show up inside the bilge. There is a drain along the keel in the center of that first bulkhead but the length of the keel is covered by a support. As the support meets subsequent bulkheads there are small openings to allow drainage. I tried to get my endoscope in there and forward but it's a pretty tough spot. However, I found a lead sphere in there that I dismissed as a errant 2 oz fishing weight. However there is no shank on it or evidence that there ever was one. Interestingly it rolls freely along the keel and fits pretty neatly through each bulkhead but seals the terminal drain hole. Is this a feature or indeed an artifact of fishing days past? I'll attempt some photos with the phone forthwith.
HARD_WAY
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Re: Crack inside transom

#15

Post by HARD_WAY »

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Inside the support along the keel
Inside the support along the keel
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HARD_WAY
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Re: Crack inside transom

#16

Post by HARD_WAY »

So the business that quoted $2600 (& materials) were recommended and supposed to be "the best". Well I agreed to their price and thought I'd get out on the water this season but they were too busy for me apparently. After stringing me along until mid July they ghosted me.... I had someone else do it for a fifth of their quote. I don't think I can get her back together fast enough to chase salmon this year but I am happy with the results otherwise. Next time Im here, it will be with fish on the deck !! cheers
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