Hobie Cat Forums

It is currently Thu Jul 31, 2014 12:38 pm

All times are UTC - 8 hours [ DST ]




Post new topic Reply to topic  [ 6 posts ] 
Author Message
 Post subject: Upwind trim
PostPosted: Tue Jun 10, 2014 7:25 am 
Offline
Site Rank - Deck Hand

Joined: Thu May 15, 2014 11:51 am
Posts: 7
Hi guys, I'm fairly new to this, so treat me like a beginner... I've read the H18 performance manual but this hobie is boggleing my mind sometimes.... When try to point upwind, sometimes I feel like the leeward hull is just being driven deep into the water (no trapezing, both hulls are in the wet) rather than generating forward acceleration. Sail and boat trim will feel good (windward hull fully planed off, leeward hull generally on plane with an occasional burble of roostertail that rises up along the rudder castings), but a gust just seems to "sink" the leeward hull and reduce performance. No luffing or anything, it just feels like a microburst pushing downwards on an otherwise moderate wind day.

Anyone ever had a similar sensation? I don't really know what it happening, so I'm not sure how to react. I'm not luffing up into the gusts (intentionally anyway, but perhaps I am pointing up almost to a luff? I don't know). It just feels like that leeward hull goes deep _without_ raising the windward hull and I decelerate when I feel like I should be accelerating. I'm wondering if I need to adjust my rake or focus on mast rotation perhaps


Top
 Profile  
 
 Post subject: Re: Upwind trim
PostPosted: Tue Jun 10, 2014 11:09 am 
Offline
Site Rank - Captain

Joined: Mon Jan 27, 2014 1:34 pm
Posts: 41
Location: Bellingham, Washington
Do you have a bridle vane or another way to read apparent wind?
It may be that the gusts are coming at you from an angle different than the wind.


Top
 Profile  
 
 Post subject: Re: Upwind trim
PostPosted: Tue Jun 10, 2014 12:12 pm 
Offline
Site Rank - Captain

Joined: Wed May 25, 2011 3:15 pm
Posts: 98
Location: Buffalo, NY
It really could be any of a number of things. It sounds most to me like you're pointing too high, or that the gusts are actually headers. If you sail with more mast rake you'll be able to improve pointing ability, but in general a Hobie will not point nearly as high as you might expect if you're used to sailing monohulls or dinghies. Optimum upwind angle for a Hobie is 50-60 degrees true wind (or ~30 degrees apparent wind), again depending on your mast rake, weight, weight positions and a whole slew of other factors. Most of it is based on "feel" of the tiller, as you seem aware, so you just need to sail a bit more to get a feel for it. Experiment!

Mast rotation shouldn't have any effect here, it's primarily used to control the fullness of the mainsail and the sail entry to the wind.

http://www.hobieclass.com/site/hobie/ih ... HobieU.pdf

_________________
Mike
Image
'79 H18 standard 'Rocketman II' sail #14921


Top
 Profile  
 
 Post subject: Re: Upwind trim
PostPosted: Tue Jun 10, 2014 2:30 pm 
Offline
Site Rank - Old Salt

Joined: Mon May 09, 2005 10:25 am
Posts: 2528
Location: Jersey Shore
Are your rudders locked all the way down and is your helm balanced? The first thing that comes to mind when someone says their boat won't accelerate in a puff is rudders being out of balance. You should also make sure you have the rudders on the correct sides of the boat and measure your toe in/ toe out.

sm


Top
 Profile  
 
 Post subject: Re: Upwind trim
PostPosted: Tue Jun 10, 2014 4:34 pm 
Offline
Site Rank - Deck Hand

Joined: Thu May 15, 2014 11:51 am
Posts: 7
srm wrote:
Are your rudders locked all the way down and is your helm balanced? The first thing that comes to mind when someone says their boat won't accelerate in a puff is rudders being out of balance. You should also make sure you have the rudders on the correct sides of the boat and measure your toe in/ toe out.


Rudders on the correct side of the boat? I thought I was certain that the rudders and daggers were symmetrical?(!) I've got a bushing kit on the rudder pins and nylon washers on the rudder bolts, I also put some waterproof duct tape on the old-style castings I have to brace my plastic rudders... I've adjusted rudder rake to a weather helm and everything locks down like it should (I even used the hobie print-out template!) I have the rudders aligned within +/- 1/8" from the center of leading edge to the center of the trailing edge, though they are plastic and have some slop.

ToddE wrote:
Do you have a bridle vane or another way to read apparent wind?
It may be that the gusts are coming at you from an angle different than the wind.
I have yarn on the bridle... I think I should buy that bridle fly though...

SabresfortheCup wrote:
the gusts are actually headers.

Yes! I payed attention today and noticed huge headers... I have to be way more aggressive on the tiller on days like today I think. Yesterday I was sheeting in to "power up in a gust" that was actually a header instead of falling off to catch it...

SabresfortheCup wrote:
Optimum upwind angle for a Hobie is 50-60 degrees true wind (or ~30 degrees apparent wind), again depending on your mast rake, weight, weight positions and a whole slew of other factors. Most of it is based on "feel" of the tiller, as you seem aware, so you just need to sail a bit more to get a feel for it. Experiment!

Mast rotation shouldn't have any effect here, it's primarily used to control the fullness of the mainsail and the sail entry to the wind.


I logged a 12 mile round trip today (moderate wind, but not able any reaching in the narrow bay... lots of tacking and jibing) in about an 1h15m and played around a bit... I think you are right, I'm just pointing too high: I've been trying to target within 45 degrees off the true wind. I'll have to go look study the polars... I glanced at them once in that hobie U document, but didn't pay real close attention. I'll make sure I'm at least 50 off the true wind until I get my senses adapted.


Top
 Profile  
 
 Post subject: Re: Upwind trim
PostPosted: Tue Jun 10, 2014 5:19 pm 
Offline
Site Rank - Captain

Joined: Wed May 25, 2011 3:15 pm
Posts: 98
Location: Buffalo, NY
Srm is referring to the rudder tiller arms... They aren't straight, they bend slightly inboard on the older style system. If you take them off and put them on "backwards," i.e. The starboard rudder on the port side & vice versa, the rudders will significantly toe in. If you've measured the toe of the rudders on a day that you're having the issue, and the rudder toe is correct, then this isn't your problem.

You are correct, the rudders and daggerboards are symmetrical.

Note again that pointing ability depends on your rudders and your mast rake. With more rake and higher performance rudders, 45 degrees true wind angle should be entirely possible.

_________________
Mike
Image
'79 H18 standard 'Rocketman II' sail #14921


Top
 Profile  
 
Display posts from previous:  Sort by  
Post new topic Reply to topic  [ 6 posts ] 

All times are UTC - 8 hours [ DST ]


Who is online

Users browsing this forum: No registered users and 2 guests


You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum

Search for:
Jump to:  
Powered by phpBB® Forum Software © phpBB Group