• Announcements

    • UnderDawg

      A Few Simple Rules   05/22/2017

      Sailing Anarchy is a very lightly moderated site. This is by design, to afford a more free atmosphere for discussion. There are plenty of sailing forums you can go to where swearing isn't allowed, confrontation is squelched and, and you can have a moderator finger-wag at you for your attitude. SA tries to avoid that and allow for more adult behavior without moderators editing your posts and whacking knuckles with rulers. We don't have a long list of published "thou shalt nots" either, and this is by design. Too many absolute rules paints us into too many corners. So check the Terms of Service - there IS language there about certain types of behavior that is not permitted. We interpret that lightly and permit a lot of latitude, but we DO reserve the right to take action when something is too extreme to tolerate (too racist, graphic, violent, misogynistic, etc.). Yes, that is subjective, but it allows us discretion. Avoiding a laundry list of rules allows for freedom; don't abuse it. However there ARE a few basic rules that will earn you a suspension, and apparently a brief refresher is in order. 1) Allegations of pedophilia - there is no tolerance for this. So if you make allegations, jokes, innuendo or suggestions about child molestation, child pornography, abuse or inappropriate behavior with minors etc. about someone on this board you will get a time out. This is pretty much automatic; this behavior can have real world effect and is not acceptable. Obviously the subject is not banned when discussion of it is apropos, e.g. talking about an item in the news for instance. But allegations or references directed at or about another poster is verboten. 2) Outing people - providing real world identifiable information about users on the forums who prefer to remain anonymous. Yes, some of us post with our real names - not a problem to use them. However many do NOT, and if you find out someone's name keep it to yourself, first or last. This also goes for other identifying information too - employer information etc. You don't need too many pieces of data to figure out who someone really is these days. Depending on severity you might get anything from a scolding to a suspension - so don't do it. I know it can be confusing sometimes for newcomers, as SA has been around almost twenty years and there are some people that throw their real names around and their current Display Name may not match the name they have out in the public. But if in doubt, you don't want to accidentally out some one so use caution, even if it's a personal friend of yours in real life. 3) Posting While Suspended - If you've earned a timeout (these are fairly rare and hard to get), please observe the suspension. If you create a new account (a "Sock Puppet") and return to the forums to post with it before your suspension is up you WILL get more time added to your original suspension and lose your Socks. This behavior may result a permanent ban, since it shows you have zero respect for the few rules we have and the moderating team that is tasked with supporting them. Check the Terms of Service you agreed to; they apply to the individual agreeing, not the account you created, so don't try to Sea Lawyer us if you get caught. Just don't do it. Those are the three that will almost certainly get you into some trouble. IF YOU SEE SOMEONE DO ONE OF THESE THINGS, please do the following: Refrain from quoting the offending text, it makes the thread cleanup a pain in the rear Press the Report button; it is by far the best way to notify Admins as we will get e-mails. Calling out for Admins in the middle of threads, sending us PM's, etc. - there is no guarantee we will get those in a timely fashion. There are multiple Moderators in multiple time zones around the world, and anyone one of us can handle the Report and all of us will be notified about it. But if you PM one Mod directly and he's off line, the problem will get dealt with much more slowly. Other behaviors that you might want to think twice before doing include: Intentionally disrupting threads and discussions repeatedly. Off topic/content free trolling in threads to disrupt dialog Stalking users around the forums with the intent to disrupt content and discussion Repeated posting of overly graphic or scatological porn content. There are plenty web sites for you to get your freak on, don't do it here. And a brief note to Newbies... No, we will not ban people or censor them for dropping F-bombs on you, using foul language, etc. so please don't report it when one of our members gives you a greeting you may find shocking. We do our best not to censor content here and playing swearword police is not in our job descriptions. Sailing Anarchy is more like a bar than a classroom, so handle it like you would meeting someone a little coarse - don't look for the teacher. Thanks.

Archived

This topic is now archived and is closed to further replies.

Fra-9816

Weight IRC

15 posts in this topic

Hi,

 

We would like a better rating in IRC (like everyone...) with our prism 28 (0,991) and we think to had more weight in the boat. 1750 kg yet, we think to had 10%.

With the IRC simulation, we will be at 0,980 but the rating will grow slowly after measurement with new shape of the hull in the water.

 

What do you think about the new speed and performance ?

Where do we put the weight for a better shape of the hull in the water ?

Is it a good deal ?

 

Usualy Our boat is a killer in the light wind and the down wind but in other weather, it s not easy to save our rating.

 

Thanks for yur help.

 

post-71105-0-21607700-1352329077_thumb.jpgpost-71105-0-84467700-1352329123_thumb.jpg

Share this post


Link to post
Share on other sites

Hi Fra -

 

This is covered in some earlier threads, but the summary is that adding 3-4% internal ballast won's penalize you and may help slightly (after your official re-weighing and measurement) or result in little change. First recommendation is to have the boat weighed if you have not already done so. Second is that you may augment this savings if you add fixed items that you plan to actually use, like an additional battery, electronics, or autopilot. Best to discuss the benefits of any further addition of weight with the boat designer.

 

BTW, you are now obliged to show us your girlfriends tits, Newbie!

Share this post


Link to post
Share on other sites

mmmm......your boat will be less of a killer in the light and DW when you add weight that's for sure. You might find that adding the weight gets a better rating but also a much worse performance, and then you aren't competitive in any conditions!!

 

its not about getting a better rating with more weight or less sail, it's more a constant search to try and find a combination that suits your boat the best.

 

if you struggle upwind in medium to heavier airs you would be better keeping your light air and DW perfroamnce, but finding a way to improve performance in that zone; more crew weight on the rail?, twisted main with open leech at top? a reef?, a smaller headsail?

 

as an example, your pics show decent breeze and a massively eased outhaul.........I hope that isn't your medium to heavy air setting. ;)

Share this post


Link to post
Share on other sites

as an example, your pics show decent breeze and a massively eased outhaul.........I hope that isn't your medium to heavy air setting. ;)

The pictures don't show that, the main is at full outhaul in the shot with the kite up, it's just the main doesn't go to the end of the boom, fairly normal.

 

Fra, I agree with jolly's post in that you cannot really tun the boat into an all rounder if it's design favours light air and downwind. If you do add weight you'll just create a boat which is more middle of the pack in more conditions. If you want to add weight it's typically fixed into the bilge area around the keel, I would certainly add much less than 10%, you should run a trial certificate with UNCL.

Share this post


Link to post
Share on other sites

I am an IRC measurer and in 2010, I weighed and measured a G&S 30 (ex MORC boat) boat weighed 2728kg and rated 1.000. weighed and measured again with the addition of 145kg of internal ballast on the midship centerline. boat rated 1.003.

Adding weight to a lightish boat will change the fore and aft overhang and transom hight. With the weight, the boats LWL increased by around 0.5m. Longer waterline = faster boat.

They felt that the boat being a little stiffer was worth the slight increase in rating.

 

The boat sails on Lake Ontario where the average wind speed is in the 8-10kt range.

Share this post


Link to post
Share on other sites

I did two test certificat:

First one with 10% of weight more of the boat and the 0,991 become 0,980

Second one with 0,5 m2 less for head sail and 1 m2 less for the main, 0,980 become 0,972

 

But i haven t change the lwp, x, so, etc.... I can t know this numbers.

 

4% of weight (70kg) more and 0,5m2 and 1m2 less for genoa and main sail seems great qnd good deal?

 

 

Share this post


Link to post
Share on other sites

FRA-9816

Adding weight without doing the other measurements does not give you much info. A heavier boat would be slower if nothing else changed, so adding 10% more weight without any other measurments would be expected to reduce your rating.

Adding weight does change the overhang measurements and transom height, so I would suggest that adding the weight will result in a slight increase in rating. I do not know how much credit you get for reducing the main area, but I do know that reducing the genoa results in a reasonable credit. I suggest that you just get your genoa re-measured and it will have shrunk enough to give you at least 0.001 credit.

Share this post


Link to post
Share on other sites

You get a penalty for internal balast, so I would look at strenghtiening the hull with some heavy steel ribs around the keel, just about all production boats are too soft in the hull letting the keel move. Other than that reducing sail. particulay jib size is much more effective than adding wt.

Share this post


Link to post
Share on other sites

as an example, your pics show decent breeze and a massively eased outhaul.........I hope that isn't your medium to heavy air setting. ;)

The pictures don't show that, the main is at full outhaul in the shot with the kite up, it's just the main doesn't go to the end of the boom, fairly normal.

 

Fra, I agree with jolly's post in that you cannot really tun the boat into an all rounder if it's design favours light air and downwind. If you do add weight you'll just create a boat which is more middle of the pack in more conditions. If you want to add weight it's typically fixed into the bilge area around the keel, I would certainly add much less than 10%, you should run a trial certificate with UNCL.

 

I looked at the right hand UW pic and thought I saw a massive draft depth, like about 400mm from the boom line. Maybe it's an illusion?

 

thinking on this some more; the only reason I would add weight to a boat is to try and achieve some more stability if it was too tender. Most people I know in IRC racing take weight out so that they go faster and have more fun!!

Share this post


Link to post
Share on other sites

I looked at the right hand UW pic and thought I saw a massive draft depth, like about 400mm from the boom line. Maybe it's an illusion?

Gotcha - yes agreed in that photo outhaul is eased but I think it's pretty light air

Share this post


Link to post
Share on other sites

Hi Fra 9816

I raced against you at Cowes week this year on a j97 in what was a petty well mixed irc fleet (97's, A31,Corby 30, x332, j92's and a big heavy swan to name it a few) all pretty similar rating and each having there day depending on the conditions.... We might have even got a bit too close on a few occasions....!

 

You guys seemed to have pace to burn in any sort of flat water and certainy were quick enough downwind. If I remember rightly the Prisim 28 was one of the early 'planning' offshore keel boats - pretty much designed to go fast downwind but maybe giving away too much grunt to be in it upwind .. Also probably not as refined as today's irc lead mines !.

 

Have you considered doing some keel mods? Maybe get the weight down where it helps, possibly a different or more forgiving profile? Also the sails might benefit from being slightly reduced / flatter - again to help getting it uphill in more breeze. Final thought - how well do all your systems run? How easy is it to change gear? Do you have your max and min setting dialled in?

 

I am not saying that I have any of the answers or want to be trying to teach you how to 'suck eggs' but I think you have a cool wee boat and would be interested to see how things pan out.

 

Pom

 

 

Share this post


Link to post
Share on other sites

We have a much larger boat with similar issues to what you are describing FRA 9816. We are very quick in light airs and downwind, but lack pace and height upwind and reaching.

 

The lack of ability to carry sail upwind or reaching, having to de-power much earlier, rounding up in the gusts are all symptomatic of a lack of stability which the IRC rule penalises very, very harshly in smaller (<50ft) boats.

 

We have just started some simple modifications to add weight to the bulb by adding two lead castings. The effect of this will be the same as adding 7 crew to the rail of the boat (43ft).

 

The rating will go down and in nearly all conditions we will be quicker - so it's a definitie win-win.

 

There will be a penalty in downwind performance, but this is hugely mitigated by the ability to compete on the breeze, hold lanes, etc.

 

IRC is a pretty stupid rule in the sense that it can penalise very, very harshly boats that are not radical or extreme, but lie marginally outside a set of measurements. You can have a good day out and sail well, beating all the boats of similar size only to discover you're motherless last in the IRC results. You need to work at measurements and stability to get yourself closer in the box to what the rule likes.

 

PM me if you want some info on the keel modifications.

Share this post


Link to post
Share on other sites

Have you considered doing some keel mods?

 

That's the route IRC optimisation of ex-IOR boats or ex-IMS boats has often taken i.e. rules where, unlike IRC, stability is penalised. I haven't heard much of people installing internal ballast for IRC optimisation, although I guess that's less expensive (as in €€€€).

Share this post


Link to post
Share on other sites

if I understand,

 

it's not too bad to do main sail and genoa with less surface aera.

it's not good to add lead because it will be internal ballast

 

 

remove the keel and add heavieris too expensive for us.

 

to modify the keel is hard and expensive ?

 

http://www.casimages.com/img.php?i=121115115910419815.jpg

 

 

I can't hope have a polyvalent boat and work the weakness without cut the good point of the boat ?

Share this post


Link to post
Share on other sites