Thermal protection around exhaust riser

[Mr. Close Reach]

Looking for some feedback on a fix here:

I recently engineered a new exhaust riser which is working nicely, however it comes up a bit closer to the underside of the cockpit sole and when running the engine for more than an hour creates a "hot spot" you can feel when standing in the cockpit.

I have two layers of thermal wrap in this area, but I'm also considering gluing a 5 x 5 ceramic tile (underneath the sole, above the riser) to insulate it from the heat.

Does this seem worthwhile or am I kidding myself that it would actually help?

[Mo]

How close is the top of the riser from the floor? Are you feeling the floor warm on your bare feet or through deck shoes?

[Mr. Close Reach]

How close is the top of the riser from the floor? Are you feeling the floor warm on your bare feet or through deck shoes?

less than half inch, so probably too close. the floor is hot on bare feet, but not so hot that you feel it in deck shoes!

[krazzz]

I come from an automotive racing background and we used a rubberized mat with a reflective foil layer that reflects/blocks heat. Works very well and would be perfect for your application. There are a lot of varieties of it. Her is an example that just happened to be the first one to pop up on amazon.

http://www.amazon.com/Thermo-Tec-14620-Heat-Sound-Suppressor/dp/B004PILLZG/ref=sr_1_1?ie=UTF8&qid=1407508749&sr=8-1&keywords=heat+sound+shield

[Mo]

You might want to look at dropping that height down a couple of inches if you can...that will make a big difference. The stuff Krazz has there sounds good...just have to ensure it won't ignite. Here's one way I tell if the heat is OK.

In hot sun conditions, lay your hand on the inside hull wall of a dark colored boat (white are significantly cooler). It will be very warm and that's fine...typically heat above an engine area is about the same. Note that if you get a resin smell from a heated area, Ie: above your exhaust it is indeed too hot.

FWIW and general information: at the start of most fiberglass boat fires (smoldering or slow starters) people in the area notice a "resin" smell as if someone is working with fiberglass. Later it will flash (ignite) if the source of heat continues. Keep in mind this usually happens with smoldering electrical fires but it's something to keep in mind.

[Mr. Close Reach]

I come from an automotive racing background and we used a rubberized mat with a reflective foil layer that reflects/blocks heat. Works very well and would be perfect for your application. There are a lot of varieties of it. Her is an example that just happened to be the first one to pop up on amazon.

http://www.amazon.com/Thermo-Tec-146...t+sound+shield

Thanks Krazzz, just placed the order. I still like my ceramic tile idea (if it works for the space shuttle...) but will give this a shot. It claims to resist direct heat up to 300 degrees and ambient 2000 degrees.

[Administrator]

If it's warm on top, it's a whole lot warmer on the bottom.

I would be concerned about this.

Bill

[Mr. Close Reach]

If it's warm on top, it's a whole lot warmer on the bottom.

I would be concerned about this.

Bill

Ok...the oracle has spoken. Sounds like I have one more project this weekend!

[toddster]

Hmm... and I was thinking that warm spot was a "feature" not a bug. At least during winter time. It's right under the helmsman's seat on my boat.

[Whippet]

Re-route?

i also have a C&C (but a 27) and my hot section comes within an inch of cockpit floor. Believe it has been that way for 33 years and I havent noticed excessive cabin floor heat with my MMI wrap in two layers (although i will give the bare foot check this weekend).

I have been observing other C&C exhaust systems around the docks. Some take an approach of bending the hot section up along side of the cabin floor into the lazerette to reach above the waterline. Assume you are constructed of black pipe so have some flex in the design. I might try this approach with next rebuild.

[Administrator]

I couldn't find a reliable reference on the flash point, but there is lots of information out there about off-gassing and the onset of structural degradation occurring at surprisingly low temperatures.

I do know this from my experience as a volunteer firefighter . Once ignition occurs, you may assume you have lost the boat.

With an older boat and one or more prior owners, you never know what you'll find, and discovering the presence of a hot spot like you're describing doesn't mean it's ok. Neil may know if ABYC speaks to this issue. Mo may have some field experience as well.

Bill

[romantic comedy]

You might try and increase the air flow in that area. If you mount the tile spaced off by a 1/4 to 1/2 inch it might solve the issue. Might be worth a try if shortening that height is trouble.

Try a fan, just for fun. It may be interesting to see.

[ndutton]

Calling this a concern is an understatement. I have fought a fiberglass fire, a Columbia 45 hull still in the mold. I'll tell ya, once it starts it burns very fast, something like tossing a Christmas tree branch into a fireplace. A 30 foot sailboat in the water takes 10 minutes to burn to the waterline. 10 minutes.

Neil may know if ABYC speaks to this issue.

Here is an excerpt from ABYC Standard P-1, Recommended Practices for Exhaust Systems, Section 1.5.8. It was the only mention of shielding and frankly not that helpful.
Protective guards, jacketing or covers shall be provided wherever persons or gear might come in contact with the exhaust system where the temperature exceeds 200°F (93°C).

One of the features on my hot section wrap, something that was there when I bought the boat, is a wrap of expanded steel mesh on the hot pipe under the heat wrap. I can't say for certain that it has any value but it seemed to me it might so when I replaced my hot section I also replaced the expanded steel.

[Mo]

Calling this a concern is an understatement. I have fought a fiberglass fire, a Columbia 45 hull still in the mold. I'll tell ya, once it starts it burns very fast, something like tossing a Christmas tree branch into a fireplace. A 30 foot sailboat in the water takes 10 minutes to burn to the waterline. 10 minutes.
Here is an excerpt from ABYC Standard P-1, Recommended Practices for Exhaust Systems, Section 1.5.8. It was the only mention of shielding and frankly not that helpful.
Protective guards, jacketing or covers shall be provided wherever persons or gear might come in contact with the exhaust system where the temperature exceeds 200°F (93°C).

One of the features on my hot section wrap, something that was there when I bought the boat, is a wrap of expanded steel mesh on the hot pipe under the heat wrap. I can't say for certain that it has any value but it seemed to me it might so when I replaced my hot section I also replaced the expanded steel.

Doesn't take long. The boat in this video was my friend Phils...a C&C 30. Odyssey is right behind her on the inner marina. I do believe an electrical malfunction was the cause. The heat and smoke were such that no one could get to it and fight it once it flashed. The video is very early on in the fire...there were 3 engines on scene and the fire tug responded.



The skipper of the tug positioned her between both rows of boat and held position. Then he opened up with water cannons and knocked it down. At the time it was flames and black smoke. The fire went out when she slipped below the waves.

I was doing Paramedic OJT with Hampton Fire and Rescue (Hampton Va) back in 95 and we had a huge yacht catch fire. The power yacht had to be 70 feet long....she folded in on herself in slow motion and just about every engine and tug in the area were on that as well. We put so much foam on it....it too went out when it went under.

[YOUTUBE]Jtgwa2-ONN8[/YOUTUBE]

PS: Fred Reese was down there and walked by about an hour earlier and smelled resin. He couldn't tell where it came from and thought someone was working with fiberglass. He didn't see any smoke...another case where someone smells resin before flash.

[ndutton]

In an odd way the fire reacts like the products of combustion are more flammable than the initial fire, like an escalating chain reaction. For on the water fires the typical sequence is get the hoses or water cannon going ASAP which does very little but is effective at filling and sinking the boat which finally quenches the fire.