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Old 09 February 2019, 12:00   #1
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Boat and trailer weight ,help please

i was trawling around on here the other day and found a post from an old timer JS i think , it was telling how to calculate boat and trailer weight by weighing hitch weight (with bathroom scales ) and distance ,then moving the boat forward and repeating excercise
measure 1 was hitch weight 92.5 kg ... boat lenth from centre jockey 5.64 metres
measure 2 was hitch weight 140.1kg ...boat (moved forward 200mm ) 5.44m
the other measure i took was centreline jockey to pivot point of wheel 4.6 metres
since reading the post i cant find the post or the formula ,is this water off a ducks back for a structural engineer or similar ? ,any help appreciated
thankyou
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Old 09 February 2019, 12:24   #2
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( Distance to pivot X (difference in weights) ) / movement

4.6 X (140 - 92) / 0.2 = 1100kg

If I remember rightly
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Old 09 February 2019, 12:25   #3
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Boat and trailer weight ,help please

There is a post on here from a very long time ago where I linked to an article in Practical Boat Owner that describes this method... Iíll see if I can unearth it.

Edit: here you go - post 9 in this thread...
Trailer Ponderings
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Old 09 February 2019, 13:14   #4
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Thankyou for that ,super response as usual ,much appreciated
put some meat around the bone .......trailer is 327 kg (i knew that) ......boat is new to me r/c 5.3metre ,twin central jockey , 60hp yam 4 stroke (someone will soon be along to tell me underpowered ) probhably 100 litres of fuel and several electronics etc
amazing really for a boat that is listed bare from factory at 325 KG ,ha ha was originally looking for 4.8m and hoping to get it on unbraked ,think i might of missed the "little lightweight summer runaround " target !! ,had to buy a new trailer before i collected the boat ,lucky i bought 1300kg braked !
hopefully this is a helpfu lesson to all about boat weight !
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Old 09 February 2019, 16:17   #5
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So am i right in thinking if i now move the axle forward 100mm from the 92.5 kg position ,that should deduct another 23.8 kg from 92.5 giving me a hitch weight of 68.7 kg which will suit my discovery nicely ?.
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Old 09 February 2019, 18:53   #6
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Quote:
Originally Posted by Orwell boy View Post
So am i right in thinking if i now move the axle forward 100mm from the 92.5 kg position ,that should deduct another 23.8 kg from 92.5 giving me a hitch weight of 68.7 kg which will suit my discovery nicely ?.
Isn't the disco max nose weight 100kg? I find closer to the max nose weight helps keep the trailer steady.
Unless you want to reduce the nose weight for manual handling I'd stay where you are.
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Old 10 February 2019, 01:26   #7
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Originally Posted by beamishken View Post
Isn't the disco max nose weight 100kg? I find closer to the max nose weight helps keep the trailer steady.
Unless you want to reduce the nose weight for manual handling I'd stay where you are.


I thought it was 150kg for the Disco, depending on vintage. I agree, generally, the closer to the max nose weight, the better for towing.
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Old 10 February 2019, 10:48   #8
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Originally Posted by beamishken View Post
Isn't the disco max nose weight 100kg? I find closer to the max nose weight helps keep the trailer steady.
Unless you want to reduce the nose weight for manual handling I'd stay where you are.
Thankyou both , i am enlightened ,as PD says my disco 4 is 150 kg on removable tow bar ,(250 on fixed bar ) ,so like you say i would be better to use a bit more ,however like you say i also need a bit of handling ability as i have to spin the boat on a sixpence before pushing into my back garden , hence i have moved the axle 200mm forward and now getting 99.3 kg which i feel is good compromise , towed it 425 miles fro collection last w/e with 140 kg hitch weight and must admit it towed a dream ,however i usually only tow 2 miles to launch at my local slip
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Old 10 February 2019, 12:14   #9
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It would be an interesting exercise to pit the theory against empirical evidence. I.e. formula v weighbridge
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Old 10 February 2019, 12:32   #10
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It would be an interesting exercise to pit the theory against empirical evidence. I.e. formula v weighbridge


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