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Author Topic: Offshore Racing Boat - Best to build light weight or heavy?  (Read 6476 times)

craig dickson

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Offshore Racing Boat - Best to build light weight or heavy?
« on: December 17, 2014, 08:05:25 pm »

Hi Folks


My topic question might appear somewhat simple compared to the more technical topics that we enjoy. However I am interested to hear your opinions as to whether you recommend building a boat that is as light weight as possible or perhaps more on the heavy side.


Assuming that the chosen IC power plant has sufficient grunt to get the boat well on its chines and planing as it should, what is your preference in respect of the overall weight of your boat?


Is it best to build with minimal weight?
Or better to make it heavier?
Or does it not matter a jot so long as the boat it properly trimmed and adjusted?


If you have a preference, please enlighten us with your opinion(s).... :-)


Cheers
Craig

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w3bby

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #1 on: December 18, 2014, 03:01:36 pm »

Are you talking layup of the hull or overall weight?

As light as possible without losing strength... Building a light boat enables you to use weight, should it be required, to trim your boat optimally for the running conditions.

On M-course racing or other courses with sharp turns you will benefit from better acceleration with a light boat. However, if you are going to be banging about on the sea then a heavier layup is probably a good idea.

spearfish99

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #2 on: December 18, 2014, 05:00:20 pm »

Hi Craig,
 I would err on the side of a bit more weight. Possibly because that's the way mine usually come out!   Seriously, I think that balance is more important than the overall weight per se.  I know that lots of people quote the 30% from the transom C of G almost as gospel, but my observations over the years, it depends very much on the hull form. I know that we are probably talking deep v , but the angles of the v can vary quite a lot.

 From memory, my old Swordsman had a reasonably forward balance but ran nice and flat especially in rougher water. I am hoping that my A class Crusader 3 when it gets finished runs similarly.
 
Also think that one needs to consider the drive format i.e. do you use a stinger type drive , angled underwater drive or what ? Personally, where I can, I use what I would call conventional fixed sub surface drive angled down from the bottom of the hull. I don't say this is best, but it is what I get on with best given the type of hulls i want to run.
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craig dickson

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #3 on: December 18, 2014, 07:25:29 pm »

Hi and thank you for your interesting input :-))


To answer the questions asked:
I am talking about the overall all up racing weight of the boat, assuming C of G in the correct place.
I am interested primarily in the boats that race around oval courses as opposed to an "M" course requiring tight turns. Including those with surface drive and submerged drive.
Although all contributions and considerations are of interest to me here. :-))


I totally accept as I am sure all will agree, that the light weight boat has a big advantage in terms of better acceleration, compared like for like.


However on a big oval course (such as the ones we have in BMPRS events), does that advantage come at a cost?
The reason why I question this, is that throughout the many exciting 2014 races, although we had great dry weather in the main, there were plenty of  occasions when the wind was extremely blustery! And there were memorable occasions of wind getting under the hulls of boats of all sizes and shapes leading to some spectacular flips and somersaults!


So as I see it, my train of thought is that a boat with extra weight as low as possible in the hull could be beneficial as follows.
1) Less top heavy means less chance of flipping over.
2) The natural extra inertia may help reduce the impact of a sudden gust of wind.
3) Similarly in the event of a small collision with say a buoy or another boat, less chance of the boat being violently knocked off course and a potential stop.
4) If the extra weight comprises of reinforcement materials in the base of the hull, extra strength and stiffness is an added bonus.


Now of course I am not suggesting that boats should resemble tanks, because tanks are known as being slow! Some might say that heavy boats will naturally be slower, but my thoughts are that so long as the power plant gets the hull riding sufficiently on plane so that the wetted area is identical to a lighter weight counter part, the straight line top speed should be just as good. Debatable perhaps?


In terms of acceleration, the other consideration other than going from zero to 60mph, is change of velocity in respect of turning ability. The lighter boat may require less force to turn it especially in a sharp turn. I say "may require less force" because if comparing two identical boats, the turning force needed for the heavier of two identical boats will depend upon where the extra weight is distributed. If the extra weight is all at the bow and transom,  inertia will require more force to turn it. If the extra weight is all around the mid section of the hull perhaps the boat might be more likely to spin when not wanted in a sharp turn?


Tell me please if you disagree as I am only thinking aloud here. My feeling is that weight could be used to big advantage in terms of making a boat more capable of winning races.


Having sought your opinions in my opening topic, I thought it only right to give my take on this which is much open to discussion. ok2


Enough from me as I have rambled on long enough!


Craig
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Brigadair

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #4 on: December 18, 2014, 08:26:14 pm »

Hi Craig and all.




Clearly many variables, and no right or wrong answers because of this.


However, build it heavier rather than lighter in my opinion for the type of "off shore" racing on big inland lakes which we do. For the aforementioned reasons, along with others. Weight should be low as possible. C of g position from stern to bow obviously important, depending on boat, design, setup etc etc.




Most of the bmprs boats enjoying some success over the last 12 months, were certainly not of anorexic nature!!
Regards


Garry

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Brigadair

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #5 on: December 18, 2014, 08:27:55 pm »

Forgot to add




All of my three boats are heavyish but too light, and will be weighted more next year for better reliability.


Garry
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martno1fan

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #6 on: December 21, 2014, 11:43:05 pm »

Heavier will be much more stable than a lighter hull in rough water.Andy Uttleys c class Arrow was hard to beat and only missed out on the championships by a few points,he missed 3 meetings if i remember right but didn't lose many he entered.I built that boat heavy at over 11lbs and she was super fast and stable ,so much so hes just bought another for racing again but this time in d class.He specifically asked me to build it on the heavy side because he loved the way she handled.
A friend racing his in Trinidad in endurance was leading the championships over there with his last i heard,shes also built heavier.
As most hulls are built using poly resin you need that weight for the stiffness otherwise the hull will twist under the torque of more powerfull motors so you wont gain any advantage been light far from it.
If the hulls built from epoxy that's not so much an issue but even then a heavier boat can out perform a lighter one especially in race conditions when the water gets quite choppy so as Garry says you'd probably need to add weight.How many races have you been in where the water stays flat calm ?,none id bet.
This said go for it built it light and let us know how you get on but my honest opinion is build it too light and you will struggle when the going gets rough.
Mart
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black magic racing

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #7 on: December 22, 2014, 05:39:50 pm »

I have two very very heavy boats,A phase 2 and a mhz chief,having said that we all also know how fast these boats are as well,they  can out run most boats on the circuit today,its alright building a heavy boat but think about what you are going to power it with?
mine do have the engines to make sure that the weight and engine combination works well,just a shame my throttle finger doesnt {-) %% %%
i think theres a place for both light and heavy boats,i run some very light ones as well which do work well on calm days,
to be honest if a boat is built half decent it will perform well,and lets face it alot of it is down to how you drive it.flat out in windy choppy waters is not always the best way %% but boy it adds for a great days racing {-) O0 O0 O0
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craig dickson

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #8 on: December 27, 2014, 07:38:49 pm »

Thank you very much for your input guys :-))


I am pleased that I am not alone in thinking  that a heavier boat provided that it has sufficient power, can have substantial advantages :-)


Kurt, your Throttle finger is exactly why your presence always delivers excitement on race day! :-))


Craig
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Den W

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #9 on: December 28, 2014, 03:28:15 pm »

IMHO...build lightish do not compromise on quality, but put weight add-on points in strategic places, i-e forward -mid-ships and aft , just glass in a couple of 5mm x 25mm stainless bolts with a penny washer silver soldered on, along the keel line.................simples
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MPM

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #10 on: January 02, 2015, 10:43:48 pm »

Ive had this chat with a few customers over the last few months about this...

light boats tend to jump over the chop.. Building an overhaul heavy boat makes the boat cut through the chop alot better because you have the weight in the boat... the kenetic energy has been loaded into that heavy boat keeping the boat prop in the water... jumping out the water you loose power.


martno1fan

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #11 on: January 03, 2015, 01:05:06 pm »

Ive had this chat with a few customers over the last few months about this...

light boats tend to jump over the chop.. Building an overhaul heavy boat makes the boat cut through the chop alot better because you have the weight in the boat... the kenetic energy has been loaded into that heavy boat keeping the boat prop in the water... jumping out the water you loose power.

Couldnt have said it better myself,also having your stinger slightly up from the keel line by quite some way keeps the transom planted which really helps,some have them exiting as near the keel as possible which can make the boat ride too high in the water in my experience but thats another subject lol.
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craig dickson

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #12 on: January 08, 2015, 07:48:24 pm »

Hi All


This is just a quick reply to thank each of you for your helpful and interesting responses to this topic. Your shared experience and advice given is much appreciated. :-))


Thank you all. :-))


Craig
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martno1fan

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #13 on: January 09, 2015, 11:25:12 am »

If you ask 10 people you will get 7-8 dif answers.you gotta decide which bits of info will help you.Theres not always a right or wrong way to do things just different ways that will give you similar results but thats what makes it fun  :} .If we all did things the same way life would be pretty boring so why not experiment and come to your own conclusioins ,you never know you might find a way of doing things that give you that edge over others.
Mart
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phillnjack3

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Re: Offshore Racing Boat - Best to build light weight or heavy?
« Reply #14 on: May 13, 2021, 07:49:51 pm »

light offshore looks  bit silly when it gets choppy.
youl will never see a lightweight offshore boat in the real world.
too light and it will flip up back and over and also chinewalk like mad.

and dont forget to balance it both ways. left right and forwards backwards. centre of gravity for offshore needs to be
1/3rd of waterline from the rear of boat, not rear of anything over hanging..
I run my boat in the sea 60 inch boat and its around 15 to 18 pounds all up when tanks are full. if realy rough I might add a pound or 2
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