www.iFourWinns.com

I've started my A/C quieting project. It looks like there are three vibration conduction paths:

- the chassis, of course, currently sits on a foam rubber pad on top of carpet; heavy wood screws hold the chassis down, screwed directly into the plywood under the carpet. The screws essentially defeat the foam rubber.
- the coolant hoses; both inlet and outlet hoses are too short and the outlet hose rubs against the chassis, in turn vibrating the hull via its thru-hull which is too close to the unit.
- the air outlet; mine has a galvanized duct splitter that is in contact with the underside of the companionway step well.

I've built a ply/foam/cork/foam/ply chassis isolator, will extend the coolant hoses so they each make a complete loop in free space, and will shift the entire assembly an inch or so rearward to relieve the step well contact.

I'm encouraged and will have results in a few days, I expect.

Tom

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics

Here's the vibration isolator. It's 1/2" pressure-treated ply, 1/4" cork, 1" foam, cork, ply. Each layer is adhered with contact cement. A foam sheet alone is what was originally under the unit - very poorly; the sheet metal edges of the A/C chassis had almost entirely cut through the foam so it offered little isolation, and the mounting screws largely defeated what it might do, anyway.

Thankfully, the panel at the foot of the mid-berth comes completely out with six screws and some convincing with a hammer, so access to the compartment is now easy. The isolator slipped under the A/C unit with little difficulty and I've firmly attached the top sheet to the chassis. It raises the unit 2.5", though, so I still need to replumb the thru-hull coolant hose which rubs against the heat exchanger coil; a 90-degree adapter on the thru-hull will cure that. Once the position is good, I'll attach the bottom sheet to the floor. It is already much quieter.

I'll take some installed shots tomorrow.



Tom

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics

Your filter looks like it could use a little cleaning. Nice job on the isolator work.

_________________
One of 4 Previous (Sold) Boats:
2000 Four Winns 268 Vista

Current Boat: 2004 Chaparral 235 ssi cuddy

The A/C is secured, the compartment is closed and the return grille is back in place.

The result is well worth the effort. Previously, vibration and hum were the principal components of the noise from the unit when in the mid-berth and the hum was clearly audible in the V-berth, carried both by the hull and by the air exiting the forward vent. Now, the primary sound from the unit is the air moving through the return grille, and the vents just blow air, no hum.

In addition to the isolator, the unit was moved a few inches aft to clear the step well, I put a 90-degree adapter on the coolant thru-hull so the hose would clear the chassis, I found that I needed to shim the bottom edge of the evaporator about 1/16" to stop it from buzzing against the drip pan, and the compressor mounts worked best just beyond finger-tight. I put a drop of Locktite on the threads.

Finally, I've got an acceptably quiet A/C in my cruiser! Now to the next project...

Tom

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics

How's it been performing?

_________________
2007 358 T-5.7GXi IB
Previous Boats
'08 H240, '08 V318, '04 268, '04 225

I would say it's performing very well.......

_________________
One of 4 Previous (Sold) Boats:
2000 Four Winns 268 Vista

Current Boat: 2004 Chaparral 235 ssi cuddy

Yes, I think pretty well.

Here are two curves of the last 48 hours, from two USB thermometers; one is in the little locker under the shift control, which is stuffed with USB hubs, serial adapters and voltage converters for the instruments I work with - and the other I placed on top of the AC thermostat, which I've moved to the forward surface of the galley, port side about a foot above the V-berth (right next to the forward AC vent, in fact, but not cooled by it). These USB sensors have a peculiar glitch that produces the plot plateaus you see at ~89F and ~105.5F, but they are otherwise pretty accurate. The locker temperature is usually about 10F above cockpit ambient.

Since the threat of Bonnie had me remove it, I have not had the tarp over the forward deck, but we have had some good late afternoon rains. The AC cycles well except for a few hours at the peak of the afternoon heat when, yesterday, it reached 80F. The 82F peak of today was with me working, in and out of the cabin. Overnight, the compressor runs about five minutes out of every hour if set to 78F, maybe not enough to well dehumidify the cabin. During the day except for the afternoon peak it runs about a third of the time at 78F.



I'm an engineer so I'll always be trying to improve it, but this is far better than before - and much more pleasantly quiet.

Tom

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics

Thanks. Mine runs fulltime and only achieves 77 during the daytime. I'm leaning towards its undersized.

_________________
2007 358 T-5.7GXi IB
Previous Boats
'08 H240, '08 V318, '04 268, '04 225

What size is your AC?

Mine is marketed as 6500 BTU but I found that it uses the same compressor as Mermaid's 5200 BTU unit, so I have some doubt. The compressor manufacturer, Matsushita/Panasonic, offers a 6400 BTU unit (R9) but Mermaid uses a 5600 BTU unit (R8) for both machines, it appears, perhaps worthy of an explanation. http://www.macg.panasonic.com.my/pcom/PDF/series_r_spec.pdf and http://www.drillspot.com/products/47484/Matsushita_2R8S3R126A_Rotary_A_C_Compressor

Have you examined your installation? Is it also at the foot of the mid-berth? In particular, might your unit breathe outside air? Look at the photo of mine and you'll see a hint of red-backed fiberglass insulation I stuffed up behind the forward line locker, which is ventilated. The compartment is at a small negative pressure so it drew air. FWIW.

Tom

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics

I don't believe so...but I will check.

Your AC is in the port side compartment, where your feet would be if your in the aft cabin?

My unit is a 5k BTU Cruisair, factory install on the 248/268, and also the 278 to this day. It spits out air at 50 degrees when its 85 in the boat, so its cooling as best its can. I think its just a tad bit undersized. Others with my size boat were able to keep their boat cool just fine, whereas my blue hulled boat wasn't.

If it were drawing outside air into that compartment, would that be the case? The aft cabin was cool, the bow area/mid cabin were not.

_________________
2007 358 T-5.7GXi IB
Previous Boats
'08 H240, '08 V318, '04 268, '04 225

Yes.



Well, 50 degrees is pretty cool, certainly. You don't mean that there is a 35-degree difference between inlet and outlet, though, do you? If so, maybe you've got a blower problem; too little air moving through the evaporator would excessively cool what air moved through it - and not provide sufficient circulation for the volume of the cabin. Does it really blow or is the airflow paltry?

If you suspect that hull color is an issue, the next time you are alongside a similar boat for awhile, turn both boats' ACs off and let the cabins warm up. Is yours significantly hotter than the other? Is your hull hotter to the touch?

Tom

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics

I should clarify. Its 85 in the front of the boat, and the aft cabin is of course cooler. I've added a vent, so I wouldn't think that air flow is an issue. It blows pretty good and hard. Now when I go into the units programming and reset it to the fan speed of 60 and increase it from there, I cannot tell a difference at all. So apparantly 60 is the top speed.

***When we've been at a covered slip, it was able to get down to where we had it set and maintain just fine.

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2007 358 T-5.7GXi IB
Previous Boats
'08 H240, '08 V318, '04 268, '04 225

Very clever idea!

How's that sandwich going to hold up against lateral forces? Like if the boat gets slammed around in chop. Wouldn't want the weight of that assembly to start smacking around that close to the hull. Maybe some long screws out toward the corners of the boards, to act as guides. Through holes larger than the screw diameter and with large fender washers and some isolating bushings on top. That way if the unit shifted dramatically the screws could minimize the range of motion.

I only wish my AC unit was that accessible. It's a pain in the ass getting to the unit in the 348.

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-Bill Kearney, 2005 348 Vista

I think well. I deliberately tried to pull a smaller test piece (about 6" square) apart in tension, and could not. Shear would be much more difficult. There is more than a square foot of adhering surface between each layer - fully glued with industrial contact cement. I doubt it's going anywhere unless I get T-boned by another bow at some speed.

Still, I suppose one could build a strong confinement scheme of some sort that did not sacrifice isolation, but I doubt it is necessary.

Tom

_________________
Tom
Cape Coral

'99 Four Winns 258 Vista
http://www.ustream.tv/channel/bowcam
http://www.ustream.tv/channel/cape-coral-marine-radio VHF
http://67.207.143.181/vlf9.m3u VLF: Lightning, spherics