Kelpie
Well-Known Member
I need to replace a few through-hulls and sea-cocks, but not sure how the sizes work out. I can measure the hoses easily enough, but do I need to measure somewhere else instead?
Measuring the diameter of a through hull?
- Thread starter Kelpie
- Start date
Roberto
Well-Known Member
I measured the outside diameters of the through-hulls, then went into asap supplies web site and with their conversion table got the nominal size in inches (1", 1-1/4", etc), once you have that, you may order all the rest (seacock, hose tails, etc).
Just beware there are two different threads, most is BSP, a few fittings (especially those of North American origin) are NPT: a 1"BSP will not fit to a 1"NPT so you have to be consistent
Just beware there are two different threads, most is BSP, a few fittings (especially those of North American origin) are NPT: a 1"BSP will not fit to a 1"NPT so you have to be consistent
Roberto
Well-Known Member
examples
I found my measures
25-26mm outside diameter --> 3/4"
47-48mm OD --> 1-1/2"
17mm OD --> 3/8"
32-33mm OD --> 1"
the diametres are taken inside the boat, on the through hull, measured on the outiside-ish of the thread
I found my measures
25-26mm outside diameter --> 3/4"
47-48mm OD --> 1-1/2"
17mm OD --> 3/8"
32-33mm OD --> 1"
the diametres are taken inside the boat, on the through hull, measured on the outiside-ish of the thread
cimo
Well-Known Member
http://cgi.ebay.co.uk/6-Digital-Cal...UK_Measuring_Tools_Levels?hash=item4cecd9c0f8
this is handy onboard. I use it again and again. cheap enough not to not have one.
this is handy onboard. I use it again and again. cheap enough not to not have one.
VicS
Well-Known Member
The sizes quoted for fittings are the nominal bore and also the size of the thread. (be that BSP or NPT)
for example a 1/2" valve will have a 1/2" thread to fit 1/2" bore pipe
Hose tails will come with those thread sizes but to suit differ hose (bore) diameters.
Hoses come in two sizes ... too large or too small
for example a 1/2" valve will have a 1/2" thread to fit 1/2" bore pipe
Hose tails will come with those thread sizes but to suit differ hose (bore) diameters.
Hoses come in two sizes ... too large or too small
Kelpie
Well-Known Member
So, nominal bore would mean, say, the diameter of the opening on the outside of the hull? This would be easy enough to measure if, um, the boat was out of the water...
Would I be right in thinking that I'll need three separate pieces- the skin fitting, the valve, and a hose tail?
(yes, rather new to this)
Would I be right in thinking that I'll need three separate pieces- the skin fitting, the valve, and a hose tail?
(yes, rather new to this)
PetiteFleur
Well-Known Member
Yes, you are correct, skin fitting + ball valve + hosetail. Make sure you specify Bronze or DZR fittings. Don't use Brass fittings or TONVAL(which is actually only a Brass) as they will dezinctify. Use Sikoflex for the skin fitting and tighten up the back nut. I suggest you fit the hosetail to the ball valve first then fit to the skin fitting. Use PTFE tape. You will probably need a spanner to hold the skin fitting whilst you tighten the valve, depending on the skin fitting design - some have a 'nib' which locates in a similar notch in the grp, some have internal nibs which can be held to prevent rotation, this may need a second person. Use two stainless hoseclips on the hose, positioned diametrically opposite each other. You may not need to renew the skin fitting if it's still in good condition.
Kelpie
Well-Known Member
Thanks 
One more question... do the skin fitting, valve, and hose tail all need to be of the same material, to avoid corrosion?
One more question... do the skin fitting, valve, and hose tail all need to be of the same material, to avoid corrosion?
PetiteFleur
Well-Known Member
Thanks
One more question... do the skin fitting, valve, and hose tail all need to be of the same material, to avoid corrosion?
Simple answer - Yes.
VicS
Well-Known Member
Yes the same material but I would be very surprised if mixing bronze with DZR brass caused any problems.
As said avoid ordinary brass and Tonval.
Bore you asked about. That's the internal diameter of the fitting but is the nominal size, the inside diameter is unlikely to be exactly that (strictly its the ID of pipe that the fittings would screw onto.
When screwing the ball valve onto the skin fitting I would like to use a back nut so that the two can be firmly locked together with the valve in the orientation required ... handle sensibly positioned. I do not like the idea of lashings of ptfe tape to make every thing fit properly ... really it is for sealing tapered threads.
As said avoid ordinary brass and Tonval.
Bore you asked about. That's the internal diameter of the fitting but is the nominal size, the inside diameter is unlikely to be exactly that (strictly its the ID of pipe that the fittings would screw onto.
When screwing the ball valve onto the skin fitting I would like to use a back nut so that the two can be firmly locked together with the valve in the orientation required ... handle sensibly positioned. I do not like the idea of lashings of ptfe tape to make every thing fit properly ... really it is for sealing tapered threads.