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[knoby]

I have a fibreglass funnel on my tug, do you guys usually insulate the funnel inner from the boiler flue, & if so how do you do it?

I have thought about sleeving it with metal sheet, but wondered if that wouldn't just transmit the heat to the funnel anyway, unless i left a gap around it

The funnel has a 50mm inside diameter & the flue is 25mm diameter.

Any thoughts/suggestions would be great.

many thanks Glenn

[Bunkerbarge]

This is my take on the subject.  Wrap it with string and then cover it with foil tape.  It ensures good coverage and is very flexible as well as being neat.  It does get boring though!!

[HS93 (RIP)]

if you want to reduce the heat in it get a sheet of ceramic matting in 2mm from Polly eng/Bruce

http://www.pollymodelengineering.co.uk/sections/bruce-engineering/materials.asp

you can wrap it with heat tape from the likes of demon tweaks to cover the matting I think they do 1mm  as well it bends very easy used on boilers below the wrapper. I think   http://www.chronos.ltd.uk/acatalog/Shim_Packs_and_Gasket_Material.html  do the 1mm which is all you need.

if you cool the exaughts from the engine to much as it goes up it will come back as droplets.

Peter

[knoby]

Thanks guys, to be honest I was more thinking of insulating inside of the fibreglass funnel than the metal flue of the boiler.The flue itself doesn't get excessively hot, just didn't want to risk damage to my lovely funnel. Hadn't considered the cooling effect condensing the exhausted steam though,

There is some boiler insulation material left, so I'll start by temporally fitting some on the inside of the funnel & see hoe we go on initial sea trials.

many thanks for your input

Cheers Glenn

[gondolier88]

Hi Knoby,

Insulating material works by trapping air- just leave an air gap of at least 5mm around the flue- as long as a naked flame doesn't touch it GRP is fairly heat resistant anyway.

To help further make sure the outer GRP funnel has a flow of air through- leave an air gap or drill holes at it's base.

Doing this will be far and away enough to insulate the GRP funnel.

Greg

[HS93 (RIP)]

sorry I thought you where doing it to save getting burnt by touching it more than anythink, thats why I said about over cooling it and the 1mm thick stuff, in that case just stuff some of that stuff up the inside of the funnel, few blobs of super glue will hold it, or as MHB use thin doublesided tape on there boilers to hold before the planking goes on, then a few blobs of glue .(as you wont be planking the inside of the funnel).

Peter

[knoby]

Thank you gents, thought it would be ok to leave it as it is, but I just wanted to check.

many thanks Glenn

[Bunkerbarge]

Glenn whether your flue gets excessively hot or not it is infinately easier insulating the outside of the flue than it is trying to insulate the inside of the funnel.  Either way you are preventing the heat getting from the flue to the fibre glass but, as has already been mentioned a good air gap will be extreemly effective.  

I insulated the outside of the flue, not only because it was easier, but also because I wanted to keep the heat in the flue to maintain the exhaust outlet temperature and try to keep condensation to a minimum.  Insulating the exhaust pipe along it's length is also for the same reason.

[787Eng]

Has anyone seen or used this product before. Looks like it could be good stuff 

http://bvmjets.com/Pages/heatshield.htm

Mark