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Through Hulls

Fitting the through hull mechanical seals was a real nightmare.  Firstly, when I made the through hulls themselves, I reamed them out to the correct 16mm.  But after welding, they had pinched a little and needed re-reaming.  This meant that they were not completely smooth.  Once I tried to fit the 5\8ths bar in, it was such a tight fit that the slightest burr on the bore scratched the bar and it jammed solid. 

I fitted a bar with a slot cut down it into the drill and slid a piece of 800 grade emery through the slot.  Then I stuck the bar into the bore and polished it up.  Then polished up the bar itself on the lathe.

I tried loads of different sized O rings and eventually went for 2.5mm x 15 which went through with silicone grease and a bit of a shove.  I had to also machine a gradual taper onto the bar to persuade them through.  If there was not enough taper, the O ring chopped and I had to start again.

I think the way to do this again would be to machine the bore to only something like 15.5mm, weld it in and then ream it after.  This would make the bore smoother.  O ring size and taper is critical and everything has to be utterly utterly smooth.  Not the slightest scratch. 

This took ages, but they are all done.  Rudder, dropweights and VBT control.

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