choosing for trim tabs?

Gert-Jan Bosch · 04 September 2002, 14:42

I still have my 4.8 mtr. rib (mostro, see www.mostro.gr.) which suffered from chine walking. I got some good advices, and I am working on things like a fuel tank in the bottom/front, and moving the steering console and battery more to the front(thanks for that, Pete 7, scubakid, Charles and Keith! ). I lately read that trim tabs help to overcome chine walking, and give better steering performance and more stability.
Can anybody tell me if they really make a difference, and which trim tabs are the best?
As far as I know there are electric/hydraulic trim tabs, but also completely automatic ones with nitogen gas actuators, which I would prefer since there will be no cables and/or wires to maintain.

Julian · 04 September 2002, 15:31

Trim tabs help to balance the boat. Mainly to keep the boat level although you can use them in a bad sea to trim the boat down as well. They are great for beam seas as the boat will remain level. We use Bennett trim tabs which are hydrolic. I dont know any thing about the gas ones. In 3 years we have had very little maintenance to do on them apart from topping up the oil. Hope this is of some help.

dimitris · 04 September 2002, 15:36

check

www.thehulltruth.com
www.boatsetup.com

Search the forums for trim tabs. I've read a couple of posts according to which trim tabs can improve/solve the chine walking problem.

I've decided (finally) to install trim tabs in my rib (porpoising problem). After some research i've decided to go for bennett trim tabs (www.bennetttrimtabs.com).

I spoke with them and they were amazingly helpful and extremely fast in their response. By the way they offer an automatic version as well

Regards

Dimitris

batfalcon · 05 September 2002, 06:41

Are you sure that you want to install trim tabs on a 4.8 m rib ?
As you realize they are space and power consuming. Forgeting the power (electrical) that they want, the fact that you must install all the mechanism (pump & pipes) in your back seat locker is not something that can overcome easily. Besides that, I think that you can set the trim correctly and avoid all the trouble, since the size of the boat helps.

Mike Garside · 05 September 2002, 07:38

I ordered my Bennett trim tabs from West Marine on-line. They arrived in just over 48 hours from the States and, even with freight charges, UK import duty and VAT, they were still a couple of hundred dollars cheaper than buying them in the UK.

Fitting them took a couple of gentle days and they have transformed the balance of Magellan Alpha. But that's a 4 ton 9m RIB...

John Kennett · 05 September 2002, 20:16

Trim tabs on a big RIB are one thing, but you really shouldn't need then on a small boat.

If it's a last resort, and just to cure the chine walking, then a fixed (ie adjustable with a spanner) set would probably be just as good as a more sophisticated version for a fraction of the cost and effort.

John

batfalcon · 06 September 2002, 07:24

Maybe it's a stupid question, but what exactly are the "chines", (so I may understand what the chine walking is) ?

Gert-Jan Bosch · 06 September 2002, 08:03

Michael,

See Thread "steering problems 4.80 mtr. rib", with last reply on 06-aug-2002.

Gert-Jan bosch

Charles · 06 September 2002, 08:13

Batfalcon, as the Chinese say, a picture is worth a thousand words. The arrows point to the CHINES on the hull.

Gert-Jan Bosch · 06 September 2002, 09:15

Charles,

Although English is not my first language, I think you're wrong.
The arrows on the picture show the strakes, and the chine is the outer edge of the hull, there where the hull meets the "standing up"side of the hull, in this case the the side with the fancy colours......
correct me if I'm wrong!!!

Gert-Jan Bosch

batfalcon · 09 September 2002, 06:35

Either way could you please explain what the "chine walking" is ?
If Gert's opinion is correct, I can't think of any boat that doesn't use this edge !!!
By the way English is not my mother language either, so please use simple terms.

Thanks,

John Kennett · 09 September 2002, 09:44

Charles

Looks like we're ganging up on you -- see below!

Michael

Chine walking is an effect caused by a deep V hull at speed, where the hull is lifted so far out of the water that there is very little lateral (sideways) stability.

The result is that the hull falls over to one side. As the chine makes contact with the surface of the water the force then pushes the hull back the other way, creating a dramatic and potentially dangerous motion.

Most hull designs these days feature some sort of modification to the plain deep V to help counter this -- planing pads, spray rails and variable V hulls can all help, although they are not necessarily the perfect answer.

John