hi

I want to install two speakers which require a 130mm diameter hole. The speakers need to be installed onto a surface which has an enclosed space behind them with some volume (ie, no good installing in bulkhead, as nothing behind them). In the photo below I have found what I think might be a good spot (see circles in red), which is a fibre glass panel at the bottom of the bulkhead. The volume is made up of the whole area under the V-birth.

My question is, structurally, is it unwise to drill 130mm holes in each side in this location of the boat, I think the glass is at least 4mm think. I was thinking I could use a ply backing which also has a whole in it to give a bit more rigidity.

Holes generate a "stress raiser" in the surface, which may possibly lead to failure, Windward Passage 2 had this occur with holes in the deck (I think for a compass?). In your case, the main structural area is probably the bulkhead, and your boats much smaller with less applied loads.....! If you increase the strength with some glassed or epoxy glued 8mm marine ply behind the hole you should be OK. not sure how hard it is to access to do this.

Only other concern maybe that the area you have indicated looks to be a water tight area for buoyancy area. Putting speakers into this space will compromise any air tight space you may have there. Not sure if this is really an issue. Nice tidy cabin. Looks great.

Why not install them under the settees. I did this in the Boomerang and get great acoustics. If you use the storage under there you will have to be careful as I found out. Occasionaly the wires on the back will get knocked off.

shoodbegood said...
Northshore 27, beautiful little boats, enjoy!

Thx

I use 3 way bass reflex speakers mounted on the bulkhead in about the spot above the shelves in that picture, they might fit in that gap. I bought them from the Salvos op shop, $10 a pair. Superb quality book shelf items. The reflex vented bass enclosure gives a stunning performance. The Salvos here always have a good turn over of quality units.

Datawiz said..

Excellent idea Ramona - wish this thread had come up before I spent many hours making (sanding, filling, varnishing) a pair of timber speaker enclosures to mount on the bulkhead :(

Often dead pensioners have really top class equipment. The really good stuff gets taken by the workers but in my local there is always a choice. I was so impressed with the performance of mine I went back and bought another pair for my sail room.