Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[1967Brutus]

Hi all,


Can anyone help me with the following:

I have purchased a wooden hull, waterproofed inside and out with Epoxy.
In that hull installed is a sterntube (as far as I can see brass tunnel) that needs to come out alltogether without damaging the hull.


I intend to heat the tube to the breakdown point of Epoxy and pry it loose.
The trouble is: How do I apply heat without damaging the hull? I mean, I can most likely not use a burner or I will char the hull.

I can think of inserting a sacrificial "shaft" and run some high current through it, but what source do I use for that current?
Perhaps I can let that shaft protrude far enough to be able to heat one end with a flame but I am not sure how hot things have to get to get the heat soaking all the way through.

Maybe I can run hot air from an electric paint stripper through but how do I duct that hot air?

Anybody any experience with a job like this?

All tips, hints or tricks are welcome.

Thanks in advance,


Bert

[1967Brutus]

Never mind, 5 minutes after posting, I found the Portasol soldering set I forgot I had... It contains a very tiny burner so small that I can put the burner head IN the tunnel.

Took all of 5 minutes to loosen the Epoxy.


Getting the tunnel out is a matter of elbow-steam but pretty straight forward: Twisting to break friction while pulling.
Excruciatingly slow, but doable.

[Capt Podge]

Well, thanks for posting up this solution Bert - I've got a similar situation to deal with further down the queue of models for rebuilding.


Cheers,


Ray.

[Treble]

To limit the spread of heat to adjacent areas would suggest you look at using La-Co Cool Gel.  It ain't cheap , but it is good . Once you got it you will be surprised how many uses you'll find for it.  I use a similar American version , which is water soluble , and I can hold a 15mm copper pipe in one hand whilst soldering on a fitting a relatively short distance away with only the gel barrier between. Trevor.

[JimG]

If you don't have a small enough burner then you could use a soldering iron. One of around 25 watts generally has a bit the right size to go inside the stern tube and heat it up.
Jim

[1967Brutus]

To limit the spread of heat to adjacent areas would suggest you look at using La-Co Cool Gel.  It ain't cheap , but it is good . Once you got it you will be surprised how many uses you'll find for it.  I use a similar American version , which is water soluble , and I can hold a 15mm copper pipe in one hand whilst soldering on a fitting a relatively short distance away with only the gel barrier between. Trevor.

I was actually amazed how limited the spread was, as it was: the tunnel was some sort of home made piece using copper fittings, one of them had outside thread and was basically "cast-in" in Epoxy. The entire tunnel loosened in a matter of minutes, but the thread formed in the epoxy held and I could screw the tube out rearwards for a good part. I had to remove that Epoxy with a drill bit afterwards.

[1967Brutus]

I was actually amazed how limited the spread was, as it was: the tunnel was some sort of home made piece using copper fittings, one of them had outside thread and was basically "cast-in" in Epoxy. The entire tunnel loosened in a matter of minutes, but the thread formed in the epoxy held and I could screw the tube out rearwards for a good part. I had to remove that Epoxy with a drill bit afterwards.

I tried that with a 75 Watt soldering iron, but it did not do much, purely due to the minimal heat transfer through the contact area.
The hot gasses from the tiny flame however, wow...
I could hold my fingertip at the other end of the tunnel (where the combustion gasses exited) and never felt any heat, but the entire tunnel from rear to front came loose within minutes nevertheless.

Just to tease you guys a bit: This is the NEW tunnel and prop...

https://www.modelbouwforum.nl/attachments/20240107_230537-1-jpg.566442/


https://www.modelbouwforum.nl/attachments/20240107_230548-1-jpg.566439/

(Yup... it's a variable pitch prop... )