link stringers to bulkhead or not

There are quite a few good books on the subject of aluminum boat building.

I suggest you pause and do some reading. It is not my area of expertise, so I avoided comment, but I saw the missing mouseholes and black welds which I know are wrong. It would be good to have the reasons for these explained to you so you decide whether to repair, especially whether to expect leaks or critical issues like a broken seam after you hit a wave or two. I am not qualified to explain.

Here is a thread where the builder was not too receptive to criticism and some polemics occurred, but mentions of other good books on the subject are buried in here.

The differences between home built and custom builds of quality boats are important.

Best of luck from a builder.

20 Aluminum Boat Build https://www.boatdesign.net/threads/20-aluminum-boat-build.59925/page-6

 

what exactly do you mean mouse holes are where are they needed?

 

I am not qualified to answer well for you, but aluminum is never or rarely interesected at 3 points. It may be for weld continuity, but really am not certain. Since you are also uncertain, I am asking other contributors to explain the consequences of your 3 point intersects. Mostly wanted to show you books that are available.

 

The reason for mouse holes is to prevent welds "touching" each other.
Why is this important?...well, let's see another example below:



The rider bar has tension and compression when loaded, so there is a load/force, in this transverse direction.
The bracket, that is welded to the long.t stringer is attached to the frame web and frame rider. So a load, from a slam load, or general hydrostatic force, the long.t transmits that load as direct shear, the vertical load of the bkt to the frame web connection.
The long.t is also subjected to bending i.e. tensile and compressive loads...so this has that load in-plane and direct, from the upper surface of the long.t, in this case a bulb bar, and the load is transferred directly (as the bkt is sufficiently stiff enough), horizontally, from the long.t to the bkt, and then comes out at the upper toe of the bkt to the frame rider.

This means that weld, as it is joined to each, has 3 loads, in 3 different directions acting on it, this is called a triaxial stress raiser, like so:


So, the weld is pulled into 3 directions = weaker. In simple language.

When you have just 2 welds crossing, a biaxial stress raiser, if the unit force is non-dimensional parity, the resultant "pull" on the load is 41% greater and a single weld being 'pulled'...so that is an over load of 1.4 times the allowable.
So if now pulled in 3 directions....well, you get the point...

This is why, is is essential to have mouse holes at connections especially in aluminium.

This is a very quick generalisation to get the point across, without going into the structural and metallurgical reasons why this is bad, a triaxial welded joint.

 

Respectfully, his welds are a bit weaker is all?

So, is it necessary to change them? That is my dumb guy question.

 

Respectfully - it is a dumb question!

As noted the above, it is a generalisation of the multidisciplinary effects of a triaxial weld.
Being weaker, is just one of them.

I gave a precise, for the sake of brevity and losing the audience with detailed complex issues that require even more understanding to understand the detailed complex issues involved.
Perhaps my bad in doing so...

 

so basically it ends up stressing all 3 adjoining pieces rather than just one? Another possibly dumb question, would it technically be better to drill those points out where that all intersect?

 

Technically - yes.

But, you would need to be very very careful doing this making sure each one is in the correct location and correct size, and not to drill into the parent metal of either structure.
It would need to be a smooth edge cut not jagged.

The downside is that the resulting 'hole' those edges with small burrs is kind of - straight across - not rounded, as would be the case with a weld.
This leads to more issues, not worth going into at this stage.

But if you have the time, patience and skill, it is worth pursuing. Try it with a few test pieces first, to see if you can, Since no point making a bad situation worse of the remedy makes it worse!
Also, if these are not heavily loaded nor used much boats, and your warranty is only for 1 year... also a thought of no action at all - financially (from your point of view for rework) - may be better?

So, your call really.

 

Thats kind of where I am at with it. I was just debating whether I wanted to weld the longitudinal stringers to the bulkheads. I primarily build flat bottom boats 16-24 foot with 60-84 inch bottoms which are corrugated. The corrugations on them are pretty much in place of the longitudinal stringers. I don’t have much experience with these V Hull. I have only built about 2. This is my third. I saw a boat down in Venice La. That I liked and went and jigged it out. They ride beautifully but are so wet. It’s like getting 5 gallon buckets of water thrown on you when your stuff a wave low speed. The faster you run them the better they ride.

 

So, you're at an impasse, with regards to risk v rewards, in terms of time and costs.
Thus, is there a warranty for these boats once delivered?
And you previous boats, how long a ago did you build them..and what feedback have you got so far?

Since building with aluminium, is all about quality, in every sense.
And thus, does that also translate to the client they are buying quality and willing to pay extra for it too?
Or, they just don't care will buy anything boat that is silver coloured and shiny!

 

Built over 100 flats. Have only come back for adding stuff on. One boat got rear ended and before the motor broke from the tree it tore about a 10” strip directly where the bottom of the mounting bracket was. Do a lot of shallow water now fishing boats with tunnel hulls. I didnt weld the longitudinal stringers to the bulkheads on the other 2. Looking at it now before putting the floor in I figured I would see if that was a big no no and it was crucial that I did. These aren’t spec’d out transcontinental boats.

 

Nice range of boats.
So, in this case then, perhaps it is more prudent to just address the shall I or shall I not attach to the WTB, issue only, on this current boat.

As for the welds shown, give the above, it may be a case of better let sleeping does lay, and be food for thought on your next builds.
Always better to start wanting to produce the best, given the new knowledge, than trying to correct one half way through, for maybe very little gain, financially - other than quality build.

 

I could go on with pics all day

 

The Welds aren’t bad, it was just Uhhh bad welding wire…. Argon was bad….. new welding machine….. glove had a hole in it…. Lens was dirty…. Give me a minute, I know there some more reasons they weren’t good that day
Na, I love furthering my abilities and I hope to continue to get more knowledge here throughout other builds. Maybe ask opinions before jumping into a phase.

 

That is an impressive line up in your photos above!
I like how on some of the boats you have managed to have the exterior rubbing strakes act as longitudinal stiffeners for the hull shell - especially useful as the hull plating is very flat there.
And they are probably massively strong, relatively, re the close spacing of the transverse frames.
However the design could probably be 'improved' in future, whereby you have less material (and less welding) for the same strength, which should result in less total cost of build (and more profit perhaps?).

If you do not weld the longitudinal to the bulkhead, how are you going to terminate the longitudinal before it meets the bulkhead?
Is it just going to 'stand off' maybe a 1/4" or 1/2" (or more), or will it be snaped at an angle so you don't have an abrupt end?

Here are a few random hull structure photos I took of a couple of vessels being built at Alnmaritec in Northumberland, England 12 years ago, to try to show how important mouse holes are.
They are found everywhere! And with CNC plate cutting, they can all be programmed for the machine to cut them perfectly.
Alnmaritec were building a 12 metre Oil Spill Recovery Vessel for our (small) Oil Terminal here.

Here is a photo of hull frames set up on a patrol vessel that was being built for the River Thames in London.



And a photo of the frames set up on the port hull of 'our' OSRV - you might have to save the photos to your computer and then 'blow them up' to see the mousehole (and other) details.



Here is a view looking down into the cargo hold in the starboard hull of the OSRV, showing the bottom longitudinal stiffeners meeting the bulkhead - but they also have gussets / brackets going up the bulkhead to help distribute the loads into the structure. Note how the flanges on the brackets are snaped at each end.



And another OSRV bulkhead photo, with stiffeners on the bulkhead as well.
This is all way in excess of your requirements for your boats - but the OSRV is 'only' 39' long, built to cruise at a modest speed (8 to 10 knots) - and she was built in accordance with the Rules (I cannot remember which ones, possibly the Lloyds Register rules for Special Service Craft).