Engine room questions

As per a previous post I am cutting out my 200 gallon mild steel saddle tanks. Between the engines and the tanks there is a wall built tight against the tanks made out of 1/4 inch plywood and acoustic tile. The plywood is glued to four 2x2 hardwood posts that are bolted to stringers at the bottom and saloon floor joists at the top. My question is are these posts structural or can I permanently remove them?

When I have the tanks out I am thinking of doing some improvements to my engine room. A lot of the acoustic tiles are in pretty scuzzy condition. I wouldn't mind removing them completely on the walls. Don't know if that will increase the noise in the saloon. Wondering what others have done.

I'd say the 2x2s are structural. But you could **** can the plywood and tiles.

Not enough info given to tell if they are structural. Need to understand the whole structural system of the deck to make that call. Best thing to do is assume they need to go back in, or get someone familiar with structure engineering to take a look.

How are the tanks held in place? 2X4s maybe?

Boat decks, unlike a house are not generally set up to span long distances without support.

If you need to remove the pillars to get the tanks out thats one thing. Leaving them out for the long term is hard to say from the backside of a keyboard but in my opinion probably not the best idea.

As far as plywood attached to them, well in my opinion you cannot get too much wall space in a engine room. Every inch of vertical space in an engine room is a inch that can potentially get something screwed to it in the future. I would want every bit of vertical walls I could get for future equipment mounting.

GordC said:

...The plywood is glued to four 2x2 hardwood posts that are bolted to stringers at the bottom and saloon floor joists at the top. My question is are these posts structural or can I permanently remove them?

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Two separate issues here - I think there's a high probability that the posts are providing some structural support to the saloon floor. Which may be providing structural support to the saloon walls. Which may be providing structural support to the boat deck / flybridge, and so on. I would absolutely replace them, and would even consider temporary bracing as they are removed.

The plywood...that's harder to say. Plywood does provide quite a bit of bracing, but the "glued to" makes it look like the builder did not intend that. How thick? 1/4"? 1/2"?

The plywood (and tiles) have quite a few effects. You've already noted the sound reflection / absorption possibilities, but they also insulate the tanks from heat transfer from the engines. Repeated heating and cooling of the tanks will increase condensation inside (and possibly outside) the tanks - that is a "bad thing"(tm) and something that should be avoided whereever possible.

The ability to attach things inside the engineroom needs more thought. The panels should be mechanically fastened (not just glued), and there may need to be additional spacing / insulation on the tank side to prevent fasteners from penetrating the tanks. So 1/2" ply ( thicker) might be more appropriate.

A downside of the panels is that they hinder inspection of the tanks as well as air circulation around the tanks (to help dry any external moisture). And removing them might make it easier for a fire to spread. It might affect air intake to the engine (ok, this one seems unlikely), it will likely affect the ability to close off the engineroom to suffocate a fire, and it will certainly affect the function of any fire suppression system.

Those are the impacts off the top of my head.

My suggestion would be to re-install them but make them removable for inspection.

The 2x2's probably wouldn't be structural w/o the plywood. A 2x2 is kinda skinny for a structural post. My guess is that they are not structural.

I had a supprise when I found out the gap in a floor beam in the salon (above the engine) was not original. Some PO cut it out (a 2X4 spanning 2.5') thereby greatly increasing the access to the engine compartment. When I discovered it was not original I had already gone through 7' seas many many times. I really like the access and decided it was good enough for me too.

manyboats said:

The 2x2's probably wouldn't be structural w/o the plywood. A 2x2 is kinda skinny for a structural post. My guess is that they are not structural.

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Well, that's a guess with potentially enormous consequences. The compressive strength of hardwood is at least 5,000 pounds per square inch. If the 2x2s are "dimensioned/nominal", that's over 11,000 pounds per post. If they are actually 2x2, it's almost twice that. Per post. OK, the bolts and so on weaken this, but the potential cost of increased flex in the saloon floor might be catastrophic. And the cost of replacing them is trivial. Why take the risk?

Edit: If you really want to delete the posts, get a dial indicator ($35 from Harbor Freight) and measure deflection in the saloon floor before and after removing the posts. That will give you an objective measurement that you might not feel by jumping up and down in the same spot.

Many older boats certainly used 2by4s or similar for support to the decks.

My Albin uses something like 1.5 by 3.0 harder but looks like teak or similar hardwood.

My Silverton entire interior decking was supported by single 2 bys notched onto the stringers and tied into the cross braces...they were only pine or fir.

Huge homes are built up of 2 bys...yes the walls are webbing to give additional support and in this case it may or may not be...but the 2 bys could definitely be structural.

Without a picture or visit...hard to say....spacing would be critical but to save space 2 by material certainly could be OK if not too tall.

Thanks guys, lots of good stuff. You have convinced me to reinstall them and screw plywood to them that can be removed for tank inspection. Good point about fuel tank temperature. Does anyone have any suggestions for material to put on the plywood, if any, or other parts of the engine room to replace very tired and damaged tiles? I wonder if the original tiles are asbestos?

In the better safe than sorry column, keep or replace the 2x2's.


In the: are they necessary column? maybe.

Are there vertical supports on the inboard stringers? Do the 2 x 2's align with the house walls? The fact that they are just inboard of saddle tanks indicates they are pretty close to the hull sides. Most really important vertical supports are inboard far from hullside support and bulkhead support.

The tiles do very little, and by current best practice on a small vessel like this acoustic absorption insulation adds very little to noise reduction. It is better to spend time and money on the overhead and the forward bulkhead where there are accommodation's on the other side of the panel.

Fuel tank thermal insulation is interesting, as cooler fuel enhances performance, but installing thermal insulation on panels where there is air circulation behind won't provide much if any insulation. And even if the space was sealed after a time the temps would equalize and your thermal insulation would be ineffective.

$0.02

I

GordC said:

Thanks guys, lots of good stuff. You have convinced me to reinstall them and screw plywood to them that can be removed for tank inspection. Good point about fuel tank temperature. Does anyone have any suggestions for material to put on the plywood, if any, or other parts of the engine room to replace very tired and damaged tiles? I wonder if the original tiles are asbestos?

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Lots of boats don't have those crappy tiles lining the engine area and covering the tank with no issues as far as the tanks heating up.

I'd cover the plywood with something easy to clean, like Formica.

although they clean easier, formica has sound reflective properties rather than sound absorbing properties. Probably would be echoing the engine noise throughout the boat.

Here is what I put in the engine compartment of my old sailboat. Muffled the hell out of the gas engine. http://www.soundown.com/Section%201%20PDFs/Products.pdf Can't tell you where I got it from, or someone would be annoyed where 12' of it went...... It's not cheap. BUT it is effective.

The bad thing about soundown is it is 'relatively' heavy with the lead sheet in the center. It does not like being adhered to overheads well (or for long) I have had luck using battens, and fender washers to help the adhesive stick to surfaces (especially overheads). Another technique is to mount it to a 1/4" plywood panel so the plywood panel is easier to attach to bulkheads and overheads. My current vessel has a similar product (no lead core though) glued to the underside of the cabin deck between stringers. More is better I think.

"More is better I think."
You're right there Cappy, when it comes to noise more is always better.

"The bad thing about soundown is it is 'relatively' heavy with the lead sheet in the center."
The weight "mass" of the product is what makes it perform. Lead is not used much anymore, today its mass loaded vinyl, same weight, same performance.

Using an adhesive and mechanically fastening with screws/fender washers and/or battens is always recommended for insulation with a mass barrier. Done right and it's not coming down.

cappy208 said:

Here is what I put in the engine compartment of my old sailboat. Muffled the hell out of the gas engine. http://www.soundown.com/Section 1 PDFs/Products.pdf Can't tell you where I got it from, or someone would be annoyed where 12' of it went...... It's not cheap. BUT it is effective.

The bad thing about soundown is it is 'relatively' heavy with the lead sheet in the center. It does not like being adhered to overheads well (or for long) I have had luck using battens, and fender washers to help the adhesive stick to surfaces (especially overheads). Another technique is to mount it to a 1/4" plywood panel so the plywood panel is easier to attach to bulkheads and overheads. My current vessel has a similar product (no lead core though) glued to the underside of the cabin deck between stringers. More is better I think.

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