Confessional: admit to boat-related things you've never quite understood...

[dancrane]

...please don't bother posting if you think you know it all.

Here's one to get the ball rolling, which often occurs to me whilst at the boat, although the question isn't actually a sailing one.

What the hell does self-tapping mean? Every how-to video or description of equipment-assembly seems to use 'self-tapping' screws/bolts. What does it mean?

 

[Tranona]

...please don't bother posting if you think you know it all.

Here's one to get the ball rolling, which often occurs to me whilst at the boat, although the question isn't actually a sailing one.

What the hell does self-tapping mean? Every how-to video or description of equipment-assembly seems to use 'self-tapping' screws/bolts. What does it mean?

Exactly what it says. Taps its own thread in the material. As opposed to threads already tapped in the material. Difficult to think of any term that is more explicit to describe the process.

 

[vyv_cox]

Exactly what it says. Taps its own thread in the material. As opposed to threads already tapped in the material. Difficult to think of any term that is more explicit to describe the process.

The tip and a few millimetres are hardened to start the cut into the material. As opposed to wood screws in which this is rare.

 

[JohnGC]

Exactly what it says. Taps its own thread in the material. As opposed to threads already tapped in the material. Difficult to think of any term that is more explicit to describe the process.

Not to be confused with "self-threading" screws which look like mini taps.

 

[jerrytug]

Re yacht designs..
I've never grasped the point of reversed sloped transoms, like sugarscoop types. Yes waterline length allows more hull speed, but why slope the transom forwards, why not have it vertical. Thus giving more space in the cockpit, or the aft cabin, or a lazarette. You could still have a gate and steps, etc.
Another design point I can't get my head around is overhangs. I can read that overhangs give greater waterline length when heeled. Fine, but why would you not want the 'extra length' when NOT heeled?
Tumblehome on the topsides is another design feature I don't get. Why?
Good idea for a thread!

 

[oldbilbo]

"....admit to boat-related things you've never quite understood... "

Enjins.... lectricks.... racing types who, the slower they go, the louder they shout....

 

[prv]

I can read that overhangs give greater waterline length when heeled. Fine, but why would you not want the 'extra length' when NOT heeled?

That one's easy - because you're a racing boat and the measurers will give you a less favourable rating for the longer waterline. But they only measure with the boat at rest.

Pete

 

[Woodlouse]

That one's easy - because you're a racing boat and the measurers will give you a less favourable rating for the longer waterline. But they only measure with the boat at rest.

Pete

That, and you have less wetted surface area so less drag in conditions where the extra waterline isn't required.

 

[lw395]

Re yacht designs..
I've never grasped the point of reversed sloped transoms, like sugarscoop types. Yes waterline length allows more hull speed, but why slope the transom forwards, why not have it vertical. Thus giving more space in the cockpit, or the aft cabin, or a lazarette. You could still have a gate and steps, etc.
.....!

Keeps the weight out of the ends of the boat, where it slows you down.
Cruising boat designers tend more toward your way of thinking than racers...

 

[jerrytug]

I understand the racing measurement explanation thanks P. But I don' t get yours Woodlouse. Do you mean overhangs are designed to provide better fuel consuption but lower speed, when motoring with the boat level not heeled?

 

[MYStargazer]

I think I now know the difference between polyester and epoxy. I was thinking that polyester was a type of epoxy because it is two-part, but it seems this is not so.

http://www.ybw.com/forums/showthread.php?378786-Anyone-know-if-this-is-available-in-bulk/page2

 

[Woodlouse]

I understand the racing measurement explanation thanks P. But I don' t get yours Woodlouse. Do you mean overhangs are designed to provide better fuel consuption but lower speed, when motoring with the boat level not heeled?

No, I mean when sailing in light airs, when the boat is not heeling over there is less boat in the water and so less drag for the same sail area.

 

[jerrytug]

No, I mean when sailing in light airs, when the boat is not heeling over there is less boat in the water and so less drag for the same sail area.

Oh I see, that makes sense now, interesting! Thanks for the explanation!

 

[jerrytug]

Keeps the weight out of the ends of the boat, where it slows you down.
Cruising boat designers tend more toward your way of thinking than racers...

Yes I see, it keeps the *structural* weight out of the ends of the boat (so she pitches easily and is easy to trim) , while maintaining a longer WL length. Very interesting. thanks!

 

[Habebty]

What is "tumblehome"?

 

[Tranona]

What is "tumblehome"?

Maximum beam of the hull is not at deck level, but lower down. So looks fat from ahead or astern. Partly driven by rating rules and partly by (IMHO misplaced) aesthetics. Very popular with some designers about 40 or more years ago!

 

[greggron]

What is "tumblehome"?

http://en.wikipedia.org/wiki/Tumblehome

 

[jsl]

What is "tumblehome"?

It's that inward curve of the topsides, so that the beam on deck is less that it is down near the waterline. It helps to provide a less-distorted underwater shape when the hull is heeled.

 

[Woodlouse]

Back in the days of Victory I think tumblehome was used to keep the weight of the upper decks down. It also served to keep the weight of the cannon on those decks a bit more in towards the centreline.

 

[FurryWritingDesk]

Fascinating; I never knew that my boat had tumblehome. If someone had told me before (without explaining), I'd probably have asked what I need to do to treat it!