Volvo IPS, trim?

[lutor]

Hi everyone,
I'm sharing with some other designers the possibility to use IPS system on a new 42 powerboat design. Having investigated about existing boats that has IPS system installed, I've noted that some user noticed problems in control the Trim (pitch) of the boat with the IPS system.
They explained that the boat, in pre-planning mode and until 15 knots have a very high tau (trim angle), than when arrived close to the top speed the boat begin to pitch as she is searching her equilibrium without finding it (dolphin style, we call in Italy).
I've tried to made some calculation and also with savitsky, at around 10 knots a boat equipped with IPS has trim problems...
I think this will be something that volvo must investigate as the IPS have no means to trim the propulsion.
If someone of you have most informations, pleas post here.

Ciao,
Alessandro

[woodboat]

I was under the impression that IPS was meant to replace inboard technology thus trim would come from trim tabs or any device normally used on inboards.

[cyclops]

In the press release no where is a trim function mentioned. I did not see enough bulk to have one. It is a direct replacement for NEW inboard hull designs ONLY.

[gonzo]

Yes, they are only sold to manufacturers. To modify an inboard hull would require major re-engineering of the structure and the hull bottom shape.

[marshmat]

My understanding is that Volvo expects the IPS to be installed with fairly substantial trim tabs. The drive itself can't trim; neither can the inboards it's supposed to replace. It has its advantages and disadvantages; not all hull shapes will benefit from the technology. A hull designed for IPS will not look or ride like an inboard-engine hull; Volvo leaves it up to the designer to ensure that the boat will behave properly with their motors.

[yipster]

lutor, you may try contacting volvo, keep us informed!

[lutor]

Originally Posted by yipster

lutor, you may try contacting volvo, keep us informed!

Sure,
as soon we understand which direction to follow with the systems, as soon I will contact Volvo for more infos not shown on the brochures.
I will give details on the forum if something interesting and new come out from my discussion with Volvo.

In the mean time, thank you guys for your point of views.

Alessandro

[D'ARTOIS]

Actually I have heard about this problem too - on the METS I have been looking at the IPS but isn't it a fact that the actual place of the engine plays a vital role?

[cyclops]

IPS is REALLY going to get all the not perfect N. A. and designers canned pronto. Plus, they could close a few company doors if the go directly to full production. ----------Can you grasp at all, the gigantic trim tabs and controls for the screwups? Most should wind up in court.

[gonzo]

It is the same we all see on inboard installation. Owners end up installing huge trim tabs, wedges under the stern, moving batteries, etc. I/Os and outboards hide many of those design problems.

[cyclops]

How many years does it take to get it right? Lets go back to inboards and shafts. At least they did not need trim tabs to run, with people sitting everywhere in the boat.

[gonzo]

Yes they did. Or haven't you been around boats ever?

[lutor]

Well, Impost an article that I found about a test on a boat equipped with IPS.
The boat has trim tabs installed, but the test guy says that he don't found any reason to use them.
My ask is, "is that guy payed from the yard in order to give positive impressions of the boat?".

Anyway it is a fact that this opinion can help us to better understand the possible trim problems with the IRS.

here's te article
http://www.boaterslife.com/tiara-yac....1419.3.12.htm

[cyclops]

I ride in Hackers and Gar Woods during the summer. They ride as well as anythig else of similar size and capacity.

[dougfrolich]

With IPS Drives the Thrust line is parallel to the running surface- blindly using a method for predicting trim equalibrium that assumes the thrust line intersects the CG, will result in a problem. If the designer does the job correctly then performance should improve slightly vs a traditional inboard installation.