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  #1   IP: 24.247.10.191
Old 09-10-2007, 12:35 PM
harvey harvey is offline
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exhaust hot section restoration

I have followed other A4 owners problems with great concern due to my own restoration efforts on my Tartan 34C 1971. The hot section has been my greatest problem. The system redo has worked fine, new water lift unit (Moyer), however the close conditions that exist around the Tartan 34C engine and exhaust compartment has been a large concern to me. Even with the hot section wrap (Moyer), new temp sender and gauge the interior cabinet temp is so high that the wood surfaces close to the hot section can and has scorched. This has lead me to remove the top and side of the compartment during engine operation. Some of the hot section was within 1" to a wood surface. The heat build up in this area is quite high so I am looking into installing a 10,000 hour 250 cfm 12 volt vapor proof fan, that will operate as a direct compartment air exhaust fan operating in the on position when the engine is on. I will have to provide air make up to allow good air flow i.e. negative air preasure. Also I need to line the interior of the hot section compartment with a thin reflective thermal insulation material 1/4 to 1/2" designed for hot zones.

My concern is based on the high temp scorching that showed up on my wood surfaces. I read a report on the effects of hot pipes both water and steam on wood surfaces for long durations, and high moisture levels this report showed that combustion can and has happened when wood is close to hot pipes like when residential hot water heating pipes pass thru wood floors combustion can happen at low temp levels surrounding the pipe like 150 degrees F. dry bulb , this report list some case history however the school was still out on this.

I will not stand around for the school doors to close on this one. With so many folks redoing there exhaust system this topic needs to be covered, fire on board, well you know the rest of the story.

Harvey
Tartan34C 1971 hull #107
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  #2   IP: 138.89.222.198
Old 09-10-2007, 02:37 PM
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BadaBing BadaBing is offline
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same issue

Harvey,

I dont kow if you saw my post re this problem on my T30 but I share your concern. The funny thing is when my hot section was poorly insulated with FG insulation and some stove pipe covering there didnt seem to be as much heat build up. I'm beginning to wonder if the corosion in the pipe caused an increase in resistance to the exhaust gas moving and contributed to more heat. I am planning on reusing my old water lift muffler as it seems to be the only part of the old system that worked. I'm also replacing the bilge vert fam so adding another vent fan sounds like a very good idea.

I also plan to see if I can rerout the hot section a bit to take it lower in the compartment to give it some added space from the wood and bulkhead.

Im sure something is out of wack here I cant belive this boat ran this hot for the last 30 years.

Bill
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  #3   IP: 38.118.52.41
Old 09-10-2007, 02:57 PM
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Harvey,

Thanks for your valuable report! My guess is that the rather confining engine cover on your Tartan may present more of a challenge than on boats with more open compartments.

Thanks again for you heads-up,

Don
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  #4   IP: 207.206.237.78
Old 09-11-2007, 04:07 PM
wlevin wlevin is offline
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Harvey
I also have a T34C, and faced the same problem you face. The hot section of the exhaust that led to the muffler in that small, vertical enclosure that leads out the top of the cabin had scorched the plywood, especially where it entered the enclosure low down, but the pipe also heated the inside of the enclosure enough so I couldn't keep my hand on the surface for long.
I wound up pulling the enclosure apart (taking the opportunity to have the muffler reworked) and thoroughly wrapped the new hot section I made from black pipe with several layers right back to the engine. Then I arranged a sheet metal buffer (baffle?) between the pipe and the plywood case, setting it in so there was a small air space between the wrapped pipe and the metal, and between the metal and the plywood. I also put a thin sheet of insulation on the inside surface of the plywood enclosure. Lots of fussy work, but it solved the problem.
Bill on Otter
T-34 C # 453
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  #5   IP: 138.89.229.154
Old 09-11-2007, 04:42 PM
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starting to put it back togeather

I decided that the system I had seemed to work fine up till the pipe rusted through. I'm betting the corrosion inside the pipe may have restricted the exhaust flow some as well causing the hot section to be hotter. Since it seemed to work properly before I am going to put it back together much the same way, but this time I am using brass pipe. I just returned from the plumbing supply house and they were able to put together the parts I needed, unfortunately I needed to add a couple threaded unions to make some lengths work out.

Brass should hold up longer the galvanized. I actually got a good deal on the parts because the inside sales person took pity on me (not to mention I am a builder) so the parts came to $160 vs the $320 counter price. Galvanized would have been much less expensive but I have read there are problems with toxic fumes let off Galvanized when heated as much as this area will be heated. Black pipe would have worked but would have rusted out even faster. I'm thinking brass will last twice as long, only time will tell. Since I have this all torn apart I'm going to give the engine a good scrub and a coat of paint. Something about a shiny engine seems to automatically increase the value of a boat.

I'll shoot some pics of the progress and then new exhaust system as well. I also picked up a new blower to add some air movement to the engine compartment.

Bill
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