Limber holes in stringers, location thoughts?

Hi,
I’ll move this to the top…thanks Siri, so it’s lumber holes instead of “limber” if anyone has the power to change the title.

Are there any “rules”, best practices, or do’s and don’ts with the location and size of lumber holes in stringers?

I’m looking to do two holes through my stringers, one towards the stern and one about amidships for the fuel tank compartments. The stringers are 6”-8” tall and I have some 1-1/4” fiberglass tube I was going to put in the holes to line them.

 

It is Limber, not Lumber.... lumber refers to wood.

Usually one places them close to the frame, reason being, if any water/moister is resting on the upper face side of the stringer, it tends to collect near the frames - as this is often dependent upon how you have attached the stringer to the frame.
So, when the vessel pitches, the water also tends to run to the locations where it has difficulty in moving away from......thus limber holes tend to be close to the frame location, so this allows the drainage down into the bilges.

If you're concerned about fuel tanks...then these are called 'stoppers'. This should be located on every stringer either side of the FTB.

 

Built some 3/4 and 1.25 inch tube on a jig. Placed some water on the up hill side and saw where it pooled then shop vac it up and marked. Then went to each extreme end and did one there as well. When the boats in storage any water that leaks from the hatch can run through the spots I found.

Did the ends based off experience from seeing boats have issue. Mine are a bit taller but not much. I've only rarely seen a boat have an oopsie level once or twice. 8/10 times they are either on their nose or rear with some kind of list. Nothing worse than dewatering a boat sitting on its butt with water on the far side of a non limber stringer.

Probably not enough to solve the big issues but there were a few times 2x boats ago that would have been helpful.

 

I suggest using a slightly larger tube and cutting it in half so the hole is semi-circular and bond it to the hull before the stringers go in.Locations need to be the lowest point in each zone for gravity to help you.It will need to be a bit longer than the thickness of the stringers and the glass over the stringers can then bond to the surface.Trim back when the stringer bonding is in.As for location,everywhere water can collect is a good policy.It may be necessary to run a split tube beneath the engine(s) in the direction of the pump if you need to get bilge water to the bilge pump and maintain an oil containment compartment under the engine.The tubes ought to go in before the stringers,but I have a feeling that this may not now be possible.

 

Did mine in the round in a standard pipe i.d. so that I could use rubber stoppers to block them if need be. I've port and starboard fish tanks as well as raw water hyd oil cooler as well as refrigerant coolers. When they need a clean out or winterizing I can block the limber holes and keep the fish scale/ jelly fish funk out if the main bilge and use a shop vac to clean it up.

Probably overkill but nothing I hate more than stinky bilge.

 

No need for liners.
1 1/4 " sounds good.

(Limber hole is correct terminology.)

 

Thanks all. I was really looking to ask if a couple 1-1/4” holes in the stringers would have any structural concerns but reading between the lines it seems like it should be ok.

 

So long as the depth of the stringer has not reduced by 50% or more, you're ok.

 

I used a ton of frp pipe and fittings from litek composites in torrence, didn't think to use them for limber holes but would have been a lot faster and could have used thread plugs if need be. Might be something to try.