I'm installing a new inverter/charger that requires some heavy (#4/0 AWG) cable from the battery box and so I would like to keep the run as short as possible. See image attached looking aft. The blue box on the left side is the inverter/charger and the battery box is above the engine compartment at the top right of the image. I'm thinking I can drill a hole in the bilge section with the vacuum bag in it and connect that with another hole just forward of the fuel filter in the engine compartment. The black conduit with the wires in it runs within the stringer along that same side and pops back up at the aft end of the compartment. I've fiddled around in there with some wire and sticks, lost a magnet, and done some knocking, and I get the impression that there is a void that should connect exactly where I need to be. I feel pretty good about this, but thought it's worth asking around first. Is there a rule of thumb when cutting into structural members?
Conduit holes in structural beam and stringer
- Thread starter Marrigoround
- Start date
Not sure what boat you are working with but, most production boats use an inner liner that forms the cabin and is only tied to the hull in specific places.
One option for you that would limit the number of holes being drilled is to drill straight from the locker to the bilge area and use the existing hole from there to the engine compartment. You would be adding only 2 holes to the liner and they don't have to be too big. Just enough to handle the wiring.
Have fun,
One option for you that would limit the number of holes being drilled is to drill straight from the locker to the bilge area and use the existing hole from there to the engine compartment. You would be adding only 2 holes to the liner and they don't have to be too big. Just enough to handle the wiring.
Have fun,
It would be helpful to know what make and model boat you have.
As @victorhoisington said, what you are looking at is a liner. Some parts of it may be structural and some are not. The structural portions will have something in them besides air, there will be wood or foam that is encapsulated in fiberglass.
If the section is relatively thin walled, say ¼" or less, that is not a structural member. Sometimes the only way to find out is to drill a small hole, if the skin is penetrated quickly it is probably not a structural member. If drilling reveals wood or foam it is structural.
You are correct that drilling holes in structural members is not to be taken lightly. The hole should be as small as possible and the inside of the hole should be coated in epoxy to seal the wood or foam. One device that might prove to be helpful is an endoscope. I've used one to poke around in areas of the boat that are not otherwise visible.
As @victorhoisington said, what you are looking at is a liner. Some parts of it may be structural and some are not. The structural portions will have something in them besides air, there will be wood or foam that is encapsulated in fiberglass.
If the section is relatively thin walled, say ¼" or less, that is not a structural member. Sometimes the only way to find out is to drill a small hole, if the skin is penetrated quickly it is probably not a structural member. If drilling reveals wood or foam it is structural.
You are correct that drilling holes in structural members is not to be taken lightly. The hole should be as small as possible and the inside of the hole should be coated in epoxy to seal the wood or foam. One device that might prove to be helpful is an endoscope. I've used one to poke around in areas of the boat that are not otherwise visible.
Thanks guys.
The boat is a 1987 Hunter Legend 37. Judging by the existing holes, I'd say the thickness is around 1/4". You can see the same structure continues on into the engine mount where one conduit hole is quite a bit thicker.
I think I'm going to go for it...
The boat is a 1987 Hunter Legend 37. Judging by the existing holes, I'd say the thickness is around 1/4". You can see the same structure continues on into the engine mount where one conduit hole is quite a bit thicker.
I think I'm going to go for it...
That should be ok. Keep the holes as small as possible and put them on the middle, e.i. Not too close to top or bottom of the beam your are drilling through.
The one place I would be most careful is around the engine mount because of the huge amount of stress on that part of the structure. The engine mounts probably run fore and aft and are solid wood covered in a thick layer of GRF. The engine mounts have to transit the torque of the motor, the thrust, and the vibrations to the boats hull.
If you can avoid going through those structural members you will be better off.
If you can avoid going through those structural members you will be better off.
