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Old 07-09-2020, 08:39 AM   #321
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Ha, I'm glad you asked! I was very concerned about this because aluminum is a VERY good conductor of noise. WINGSPAN measures an average of 75 db at 2000 to 2300 rpm with doors closed (It doesn't really go much higher when doors are open). I haven't measured it at 8 knots, but it would be materially quieter. If you are interested I can take that measurement this weekend.



I was very concerned about noise and we took a lot of measures right from the start to keep noise in check. You can spend a large amount of money on noise mitigation and I didn't want to do that (I'm really really cheap).



Starting from the design phase, I put the engines completely under the cockpit deck. The forward bulkhead of the engine bays is watertight (noise seeks out air gaps) and we insulated the entire bay with Sounddown to help capture noise bouncing around the engine bays. One problem, the original builder did a poor job of affixing the insulation in a number of areas and I suspect much of it will have to come down because it's only held by tape in the area over the tunnel. But because of the location of that insulation, I suspect it won't have a major impact on noise in the cabin. If it does, I'll figure out how to mechanically reattach it. However, the builder who finished the boat reattached the Sounddown where necessary in the main portion of the engine bays so most of that is very solid. I originally wanted the watertight bulkhead not to overlap the cabin sole, but the NA couldn't physically make that happen with the length limitations I gave him, so the compromise is we now a little overlap; which means the forward couple of feet of the engine bay extends below the sole at the aft couple feet of cabin. To help overcome that, we added 1 pound psf mass loaded vinyl under the vinyl flooring in the cabin and the flooring itself was a commercial product selected because it helps trap airborne noise. I've also added a couple soft rugs to help capture airborne noise - if those help, it's probably not noticeable without equipment.



My 28' lobsterboat with 110hp Yanmar measured at 80 db at cruising speed of 13 knots and WINGSPAN's 75 db at 17 knots sounds materially quieter. You wouldn't think 5 db was a big difference, but you can carry on a conversation at 17 knots without losing your voice. Frankly, I'm pretty satisfied with how that came out. I have not been in rough enough conditions to assess how bad the wave slap on the tunnel will be. I suspect it will be unnerving.

Wow. 75db seems very respectable. Back when I was trying to quiet down my Genset that sits right under my feet basically, I was getting 88db readings! Like I said, my boat is pretty noisy.
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Old 07-09-2020, 11:00 AM   #322
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When I saw the reference to VHB tape I assumed it would be used to hold the metal clips. I agree that tape to foam isn't a good idea.
Ah, you could be right and it would probably work well for that purpose. I probably misunderstood.

Although VHB seems to suffer from the same problem as 5200 - you have to have some clamping pressure and be able to get to access the area.
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Old 07-09-2020, 09:15 PM   #323
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When I saw the reference to VHB tape I assumed it would be used to hold the metal clips. I agree that tape to foam isn't a good idea.

My Soundown is held in place by large fender washers with screws through them and into the wooden underside of the sole. I realise you don't have wood, hence the clips. Once those are reliably fixed in place then you will have options for something with a decent amount of surface area to spread the weight of the Soundown out, beyond high point load failure conditions.
Sorry, yes I mean the VHB for alum clip/bracket holding to the hull, then continue with however is best to hold the sound material to the clip/bracket, exactly as you've said. You can afford to have quite a few per panel then if you are worried about the VHB holding the weight. I certainly was, but further reading suggests it will have more than enough holding power with a small piece on its own, let alone what I was thinking!

I'm thinking of VHB in lots of places too: our strongall aluminium build has almost no stringers, bulkheads or even gussets, so there is nowhere to hold up wiring and pipe runs. I'm hoping the VHB can help with attaching brackets instead of welding. Given how hard welding is to 12mm aluminium due to heat dissipation, I'm hoping VHB is my lifesaver in lots and lots of situations! Post-covid I can report back...
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Old 07-13-2020, 10:09 AM   #324
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Sorry, yes I mean the VHB for alum clip/bracket holding to the hull, then continue with however is best to hold the sound material to the clip/bracket...

I'm hoping VHB is my lifesaver in lots and lots of situations! Post-covid I can report back...
Sorry, I misunderstood. Please, let us know how it works and what you used it for. It's a product I was totally unaware of.
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Old 07-23-2020, 04:53 PM   #325
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More progress on our project. Engines gi in next week. Starting to look like something now. Still a ways to go though.
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Old 07-28-2020, 07:56 AM   #326
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Good news, Larmex! It's interesting how different our construction sequence is. Stay on top of 'em and don't cut them any slack on making progress. I think my biggest mistake was to assume everyone was working in good faith - I exhibited too much patience with BS and people not answering my questions. In hindsite, I believe my patience and courtesy was used against me.

I'm looking forward to seeing some details of your electrical and mechanical installation.
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Old 07-28-2020, 08:13 AM   #327
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Hey BK, Engines went in a few days ago, shafting is next. They are happy to do a live FaceTime tour at my request, but for the most part still shots are fine. Wiring will be interesting and inside finishing/carpentry as well. They are getting a lot of new business and are trying to finish up current projects asap. Canít remember if you had a fire suppression system in the engine rooms. It is something that I overlooked. Do you recall the ER sq footage (if you did install a system)?

I trust that you are having a great summer on Wingspan? She is a beauty.
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Old 07-28-2020, 10:10 AM   #328
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That's all good to hear. I do have an ER fire suppression system (Fireboy). It was the last thing I chose to install and the first thing I'd cut if money was an issue. I think they are a marginal value but I don't love them. I mostly dislike the idea that the engines will shut down without my permission if they trigger.

I don't think I ever got my engine bay square footage. I spec'ed a fire suppression system and they originally installed one bottle in one engine bay and said "that meets specs". When I questioned how a fire in the starboard bay would trigger the bottle that was located in the port bay I just got a deer in the headlights look. They also didn't have an engine shut down system included (which is required by Fireboy).

When my new builder took over I had them correct this with a second bottle and sensor in the starboard bay along with the required shut down system. One thing they couldn't do that you might be able to figure out - have two shut down systems, one tied to each bottle, so if port bottle triggers it only shuts down port engine. You can then decide whether to trigger the starboard bottle manually if you feel its warranted.

To me, that's an ideal compromise that allows you to maintain maneuverability if there were a fire in one engine bay.

And yes, having a good summer. Unfortunately, I got her home after it became too hot to cruise, so it's been day trips only. But I've got her set up to single hand so I've been out regularly. Just waiting for it to cool down now.
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Old 07-28-2020, 01:16 PM   #329
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They are looking at two free standing systems with auto shut down and a manual override. I haven’t seen a price yet but it sounds costly. I once had a slow leak in a canister shut down both engines in 10’ seas. Never want to go there again. Thanks for your input. I value your opinions!
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Old 07-29-2020, 09:42 AM   #330
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Sometimes I scratch my head on how necessary those system are in boats like ours. I'm sure someone will make valid points to the contrary - but our hulls are not going to melt out from under us, and that puts us in a completely different risk category. Your engine and electrical will be in a space with no significant flammables (with the possible exception of some insulation), your fuel tanks are in a separate watertight area, and you will probably have fuel shutoffs on each side of the watertight bulkhead. So how much additional safety does a Fireboy system provide vs ports that allow you to shoot in chemical extinguisher from a hand held?

If money is not a big object, it's certainly a safer choice to have one. But...

It sounds like you already have experience with them, so you know what you're getting into. Besides, my wife would point out that I'm worth more dead than alive...
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