Ideal Mounting of Vibration Mount for Self Contained A/C

I am mounting a self-contained A/C unit in the cabin of my new build. the cabin deck is essentially for the purpose of this 3/8" marine Douglas Fir Plywood with 1 layer of 1708/Epoxy resin. Vibration mounting feet are set on 3 layers of 1708/Epoxy resin. The vibration mounts allow for 1/4" holes so I will need a total of 8 holes into the deck to secure the A/C unit.

Option 1... coat the thru holes with epoxy resin to waterproof them and thru bolt the connection with fender washers. However, the downside is that I would have to make an access hatch to access the fastener bottoms if I ever wanted to remove or service the unit.

Option 2... Some clever way to mount studs in epoxy (floor is fairly thin to be doing this) and then put fasteners only on the visible side. However, the downside is if i change equipment I suppose I'll be grinding the studs out. Also, hardware changes are difficult. However, no need for access hatch. (That might be a plus if I am able to fill the area below the deck with flotation foam.

Just wondering if anyone else has a good solution or ideas for this problem?

IMG-2268 https://ibb.co/K5ss08q

 

Can you post an image of the boat and the unit you are mounting. It's pretty hard to help without a picture. But I don't much like the thought of mounting directly to the 3/8 deck. Can you build a subframe that can be dookied to the deck? Condensate has magical properties, it will flow to an exposed fastener every time. Don't most of these just sandwich the inner and outer components with bolts through a 14 inch square cutout?

I see you tried to post a photo, but it didn't take.

 

IMG-2268 https://ibb.co/K5ss08q

 

Condensate has its own pan. Unit is a Flagship Marine 16K BTU unit.

 

Drill oversize hole, install a sex nut or T nut with epoxy into it. Make some marks on the outside of the barrel so the epoxy grips it better, or use screw on T nuts.
Barrel Nuts | Sex Bolts | Chicago Screws | Interscrews | Fastenright https://www.fastenright.com/products/general-fixings/sex-bolts-barrel-nuts

https://www.rockler.com/screw-on-tee-nuts-choose-size-thread

 

I'd mount all that on foam core standoffs.

Use like a 20-26 pound coosa or aquaplas say one inch tbick; then make pieces about 4"x4" or so. Epoxy them onto the deck; then bed the foot in 5200 and screw the fasteners just through the foam core bases. (In the absence of headliner access inside)

This is the no leak method.

A 150mph wind on 2 square feet is a force of

57.6 psf X 2.1 x 2 ft or call it 2400 pounds wind load @ stated conditions and size

4 four inch square bases is 64 square inches

2400/64 = 37.5 psi, epoxy far exceeds

if my calc is bad, be kind, I did at 3am one eye open

probably need to do a screw tearout calc, but I am too tired

another reason for foam standoffs is you can install the unit level that way..

If you only have plywood; you can also make them from plywood; same concept, no roof penetration

 

Maybe I’ll just have to try the lamination under the deck. I have plenty of coosa 26 however I have very limited clearance over the top of the unit. I’ve already calculated that #10 screws would hold it in any sea state I’m capable of. even at 9g comes out to less than 100 pounds per screw.

 

...with a coosa backer and screws from above, you won't need access, but I'd be careful with limiting the unit clearance if it creates heat

 

DarkZ,

Just seeing this thread now.
Did you resolve this?
I have some suggestions if not.
(I'm from Canada. I've been wondering what that refrigeration looking unit was sitting there in your boat pictures.
I decided you were just storing it there or using it as dead weight while glue cured or something. Lol Now I understand why you want a cabin!)

 

Yea, I actually had to do something similar on my other boat, but this post was for the SEASLED. I feel like I prepped the deck enough on that area but I'm probably going to move to a 9K BTU unit based on my calculations. I'll see its lower on the priority list for now, I'm trying to fair the bow area so I can get it painted.