Laurent Giles 'Jolly Boat' Exeter |
29er GBR 074 Tynemouth |
J24 (Sail No. 4239) Dartmouth |
List classes of boat for sale |
Effect of weight on boat speed |
Post Reply | Page <12345> |
Author | |
Sam.Spoons
Really should get out more Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3398 |
Post Options
Quote Reply
Topic: Effect of weight on boat speed Posted: 24 Oct 20 at 4:35pm |
Yup.... 'precisely'
|
|
Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish" |
|
NickA
Really should get out more Joined: 30 Mar 05 Location: United Kingdom Online Status: Offline Posts: 783 |
Post Options Quote Reply Posted: 28 Oct 20 at 10:06pm |
There are two kinds of 3000 class dinghy hulls, one weighs about 79kg and the other about 55kg. The light version is faster, but mostly because is requires less wind to get planing. When it's windy enough for both to plane the weight doesn't matter so much and they're about the same speed. In very light wind the difference is also small .. I guess, because it's hull length rather than displacement that's speed limiting. In marginal planing conditions a lighter boat will be surprisingly faster... Otherwise not to much, though acceleration in gusts is better.
|
|
Javelin 558
Contender 2574 |
|
Sam.Spoons
Really should get out more Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3398 |
Post Options Quote Reply Posted: 28 Oct 20 at 11:01pm |
Yes, that's my feeling too, sub-planing and waterline length is king, when everybody's planing hull form is the decider (and irrelevant in a strict one design as they are all the same shape) it's only in marginal planing where hull weight makes a significant difference*. Of course that is slightly frustrating for me sailing a boat who's whole raison d'être is to plane early and fast, with an old and moderately overweight hull. Equally eating a few less pies (and drinking less beer, but that would be a step too far) could easily compensate for the 5kg difference...
* it was much the same when I was racing Raceboards except the benefits of early planing were magnified tenfold compared to dinghies, and the benefits of abstinence were similarly magnified on those marginal days...
Edited by Sam.Spoons - 28 Oct 20 at 11:04pm |
|
Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish" |
|
whitsundays
Newbie Joined: 21 Oct 20 Location: Australia Online Status: Offline Posts: 4 |
Post Options Quote Reply Posted: 05 Nov 20 at 9:40am |
A boat sails since it displaces more water than it weighs. More weight consistently implies more inertia, so the heavy boat needs more capacity to get to a similar speed. On the off chance that you analyse two in any case comparable boats, the heavier one will sit lower in the water, making more frictional and wave obstruction also.
|
|
Whitsundays Yacht Charters
|
|
Sam.Spoons
Really should get out more Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3398 |
Post Options Quote Reply Posted: 05 Nov 20 at 1:42pm |
Somebody said this elsewhere and it is incorrect, at least insomuch as a boat floats because it displaces exactly the same weight of water as it weighs (a boat's weight is often termed it's 'displacement').
Edited by Sam.Spoons - 05 Nov 20 at 1:43pm |
|
Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish" |
|
Guests
Guest Group |
Post Options Quote Reply Posted: 05 Nov 20 at 2:21pm |
Yes indeed. And, as mentioned before, that is not an explanation of *why* a boat floats. It floats because there is hydrostatic pressure acting on the wetted surface area of the hull, and the resulting force is equal and opposite to the weight of the boat.
|
|
Sam.Spoons
Really should get out more Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3398 |
Post Options Quote Reply Posted: 05 Nov 20 at 2:39pm |
Perhaps I should have said "when a boat floats it displaces exactly the same weight of water as it weighs"?
|
|
Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish" |
|
423zero
Really should get out more Joined: 08 Jan 15 Location: United Kingdom Online Status: Offline Posts: 3406 |
Post Options Quote Reply Posted: 05 Nov 20 at 3:00pm |
Plus it's less dense due to air space in Hull.
|
|
Robert
|
|
Sam.Spoons
Really should get out more Joined: 07 Mar 12 Location: Manchester UK Online Status: Offline Posts: 3398 |
Post Options Quote Reply Posted: 05 Nov 20 at 5:58pm |
Windsurfers float and most don't have air space inside
|
|
Spice 346 "Flat Broke"
Blaze 671 "supersonic soap dish" |
|
423zero
Really should get out more Joined: 08 Jan 15 Location: United Kingdom Online Status: Offline Posts: 3406 |
Post Options Quote Reply Posted: 05 Nov 20 at 6:05pm |
They are full of foam.
|
|
Robert
|
|
Post Reply | Page <12345> |
Forum Jump | Forum Permissions You cannot post new topics in this forum You cannot reply to topics in this forum You cannot delete your posts in this forum You cannot edit your posts in this forum You cannot create polls in this forum You cannot vote in polls in this forum |