Tie bars?

larby · 20-02-2009, 09:54 PM

Can anyone tell me why tie bars are usually at the back of the motor instead of the front? Could they be attached to the front of the motor, say to the steering arms instead? I can't see how it would make any difference or put any undue stress on the steering arms?
I'm probably overlooking something though, hence my asking.
My yams seem to have had ties on both the front and back, i'm looking to run it with just front if i can.

Cheers in advance, James

BluFin · 20-02-2009, 10:17 PM

James,
There isn't a simple answer but there are a fair number of articles on and around the web.

Tech Sheets & info on Tie Bars

Tony Davis · 20-02-2009, 11:17 PM

Sea Star do a front mounted catamaran tie bar kit.

Jon Fuller · 21-02-2009, 12:17 AM

A tie bar under tension is a happier tie bar than one under compression. Most setups have the props 'turn out', so it all works nicely with a link at the back.

Also, the mechanical attachment to the rear mid section is way, way better than the silly little tiller on the front.

Burty · 21-02-2009, 02:06 AM

i'm going to put it nicely! fit the tie bar at the back or risk the chance of dying!!

larby · 21-02-2009, 09:03 AM

Quote:

Originally Posted by BluFin

James,
There isn't a simple answer but there are a fair number of articles on and around the web.

Tech Sheets & info on Tie Bars

LMAO, cheers for that one!

Quote:

Originally Posted by Tony Davis

Sea Star do a front mounted catamaran tie bar kit.

Just to add a bit of confusion!!

Quote:

Originally Posted by Jon Fuller

A tie bar under tension is a happier tie bar than one under compression. Most setups have the props 'turn out', so it all works nicely with a link at the back.

Also, the mechanical attachment to the rear mid section is way, way better than the silly little tiller on the front.

Now that makes sense to me! I guess a tie bar under compression will be likely to try to bend. The attachment of the rear tie bar isn't what i'd call substantial though! So.....

Quote:

Originally Posted by Burty

i'm going to put it nicely! fit the tie bar at the back or risk the chance of dying!!

Considering these words of wisdom, i think i'll just fit both again! They'll both have to be quite long anyway, and i don't really want my engines flailing in opposite directions!

Cheers for the help again guys, don't know what i'd do without this place!

James

Matt · 21-02-2009, 10:57 AM

Mmm. Not so sure about that - Unless the geometries are all 100.000% on, the tie bars could end up fighting each other.

Quote:

Originally Posted by larby

Considering these words of wisdom, i think i'll just fit both again! They'll both have to be quite long anyway, and i don't really want my engines flailing in opposite directions!

Cheers for the help again guys, don't know what i'd do without this place!

James

Tony Davis · 21-02-2009, 11:46 AM

http://ww2.seastarsteering.com/OUTBOARD/oboard.htm

larby · 21-02-2009, 01:44 PM

Gaaaaahhhhhh!!! :head explodes:

Well i know that the mounts for the rear tiebar don't look strong enough to do on their own, and i definately can't afford to go have a pair of wing plates made up!

James

Burty · 21-02-2009, 06:03 PM

why not??, ask Cyco or Dan on here for a price to make you a set

larby · 21-02-2009, 06:11 PM

Well i'd have to get not just the wingplates but new tie bars too, so once posted i can't see the bill being under £500, which is money i just don't have at the mo, especially if there is another option!

James

Tony Davis · 21-02-2009, 07:24 PM

Is the steering going to be cable or hydraulic?

larby · 22-02-2009, 08:04 AM

It's twin ride glide at the mo, would love it to be hydraulic, and it will be as soon as i have the money, which isn't right now!

Once it's hydraulic i'll go down the side mount route with a pair of big wing plates and a bar across the back!

James

Burty · 22-02-2009, 03:00 PM

cant you run a cable down each side with wing plates and a tie bar at the back?

larby · 22-02-2009, 06:23 PM

Well at the mo it fits into the steering tube on each engine and steers via the steering arms. I'd imagine mounting it on the side to a wing plate would be quite tricky and i can't really see an advantage gained from it.
With it being twin rigged with the engines tied together there won't be much strain on the jesus bolts so i don't see any issues there, as the engines cancel out each other's torque.

From what i can see so far, the only argument supporting putting the tie bar on the back of the engines is that they prefer to be stretched, not compressed. That said, if it's a sturdy enough unit not to bend under strain, with good rose joints at the ends, i can't see it being an issue?
Don't get me wrong, i'm not just disagreeing with everything people are saying, I'm just trying to make sense of it in my mind and look at all the options!

Also it'd be a lot cheaper to have it attached at the front as i wouldn't have to start getting wing plates made. It seemed to manage fine like this when it was a ski race boat?

James

larby · 22-02-2009, 06:37 PM

I've just been on the latham marine site, they offer a front mount system complete with front mount tie bar...

From the latham site;

ALL MULTIPLE OUTBOARD INSTALLATIONS require one or more tie bars to keep the motors parallel and equalize loading. Boats running 65 mph or more with multiple outboards should use an external tie bar assembly; either with the LATHAM side mount cylinders and wrap plates or with the LATHAM front mount cylinders. The front mount cylinder and tie bar system will allow the driver greater latitude for independent trimming and tilting without damage to tie bar or motor components.

James

Burty · 22-02-2009, 06:52 PM

Quote:

Originally Posted by Burty

cant you run a cable down each side with wing plates and a tie bar at the back?

like this

Ciao · 22-02-2009, 07:05 PM

As Geoff Purves ran the Donohue/Hicks boat so well for many years, why not ask him?

larby · 22-02-2009, 07:23 PM

Quote:

Originally Posted by Burty

like this

Never seen one done like that with cables before, looks neat. Thats an option then, if i need to go down the rear tie bar route and get wingplates made, i may as well do that!

Quote:

Originally Posted by Ciao

As Geoff Purves ran the Donohue/Hicks boat so well for many years, why not ask him?

I've got a few pics of how it was laid out then, It started out with front mounted cables and rear tie bar, then moved on to side mount hydraulic with rear tie bar. I don't deny that a rear bar is doubtless the best option, but it's another expense i don't need if i can do it another way. Surely if latham make a front mount setup then it must be ok?

James

Ciao · 22-02-2009, 07:28 PM

Quote:

Originally Posted by larby

Never seen one done like that with cables before, looks neat. Thats an option then, if i need to go down the rear tie bar route and get wingplates made, i may as well do that!

I've got a few pics of how it was laid out then, It started out with front mounted cables and rear tie bar, then moved on to side mount hydraulic with rear tie bar. I don't deny that a rear bar is doubtless the best option, but it's another expense i don't need if i can do it another way. Surely if latham make a front mount setup then it must be ok?

James

Rig it the same way Geoff did - spend the extra Guernsey £ - Why reinvent the wheel?