Hydrofoils vs trim tabs

Sunfish · 18 November 2006, 08:30

I own an 8m/250hp RIB that I use as a commercial dive boat. I'm finding it difficult to get the bow down sometimes. As a result I'm thinking about either getting those hydrofoil wings that mount to the engine or going for Bennett trim tabs. Money is always tight so I need to get it right first time. Any ideas/views?

G250

PS. moving boat kit (or passengers) around to distribute the weight isn't possible.

samt · 18 November 2006, 08:45

I would prefer the trip tabs, especially after I saw a outboard with half a cavitation plate, the hydrofoils had caught somthing under the water and taken part of the engine with them, the holes you have to drill would have weakened it aswell. I would never want to drill holes it my outboard, and I rekon they'd cause more problems than the trim tabs, I even have trim tabs on my sib.

There are loads of threads on this subject:

http://rib.net/forum/showthread.php?t=16796

Nos4r2 · 18 November 2006, 08:54

From what's been said I'd go for Smart Tabs.

MarkM · 18 November 2006, 09:41

Hydrofoils are for smaller engines, not for 250hp.
I've trim tabs and they do the job.

codprawn · 18 November 2006, 13:38

Get yourself the Volvo - QL interceptor tabs - you can order them at any QL dealer but most still haven't heard of them. They are really easy to fit - cost about £350 for the full kit - and are supposed to be really effective.

I bought a set but haven't fitted them yet - a little job over Christmas!!!

http://www.great-water.com/pages/pro...L_Trim_Sys.htm

For an 8m you need the bigger ones.

jwalker · 18 November 2006, 23:03

Cod, you keep telling folk how wonderful these tabs are. Plainly you've not used yours but have you tried them on any other boat?

codprawn · 18 November 2006, 23:06

Quote:

Originally Posted by jwalker

Cod, you keep telling folk how wonderful these tabs are. Plainly you've not used yours but have you tried them on any other boat?

NOPE but I have read quite a few reviews and they seem to work very well - they are also used on fast cat ferries and high speed patrol boats. As they are cheaper than normal systems and a lot easier to fit I chose them.

jwalker · 18 November 2006, 23:16

There's no substitute for personal experience.

codprawn · 18 November 2006, 23:18

Quote:

Originally Posted by jwalker

There's no substitute for personal experience.

Very true but when people - for example on this forum - pass on gems of wisdom that seem useful then I like to share that knowledge!!!

ribit · 19 November 2006, 14:06

My personal gem of experience regarding hydrofoils is this, having raced boat's in the past, and always with V6 Mercs, I never really considered hydrofoils of any use except on small engines on 12-15ft boats, but when I put an XR2 from a race boat on the 6m ring rib back in 98, things did not go according to plan, there were already holes for an engine bolted to it for display purpose only, so the offset was that I used, coupled to a 26p chopper prop, engine set lower on transom, it was useless 40mph, engine set high 42mph naaa, change to 24p chopper still useless 45mph, 5 bladder 23p much better 52mph, then I remembered a large american style ski boat with a big 7.4 engine with a 5 bladder and a very heavy racey looking hydrofoil, spoke with the guy he said it had never bust and he had given it plenty of stick so I thought I will get one of them and bolt it on the XR2 the 1st XR2 ever with a set of water wings but what the hell, it did work 60mph ish at 5500rpm (if only I could get the other 1500rpm) and a lot more stability plus very low planeing speed for wake boarding given it some very hard use, nothing broken yet although 2 things may help this factor the engine is higher than an ordinary V6 and the engine mounts are for racing, not the easily broken stuff on a standard engine, just my take hope it helps

ribit · 20 November 2006, 18:51

Wavecrosschris, I see your asking if you should put trim tabs on your rib, the reason I did what I did in the above statement is because putting trim tabs on these tiny hulls is crazy, more to go wrong, more to bang on the trailer, and why on a hull no larger than a surf canoe, if it cant be set up without, then it's either overpowered or poor weight distribution or a bad hull, unless of course your looking for crazy speeds that is?

Matal Mickey · 21 November 2006, 18:09

For general inforrmation and this is from practical "on the job" experience.
I had a large RIB that had a bad attitude problem (inbuilt from manufacture). She always was bow high in the water at standstill, cruising, full throttle, loaded or unloaded etc,etc. In large seas she was dangerous! I played with all types of additions to assist this problem. I started with the simplest and most inexpensive, Hydrofoils. Now this boat was a twin installation on legs and approx 260hp each. After initial trials (lots) in all sea conditions it was proved that the hydrofoils cartainly made a significant difference to the attitude of the boat. In other words they actually did do what it said on the tin(so to speak). However they did not satisfy me and left more improvement necessary for safe and comfortable transits. They were left in situ on the legs and trial two started. I fitted trim tabs, the largest type available with financial constraints. I cannot remember the name of these tabs but you will see them in all magazines under the Nautequipe advert. Now they are a good item but my application of them was incorrect, my boat was too heavy hence I continually broke the tab rams. On the trials with these they did in fact prove that trim tabs were the way to go. They changed the attitude of my boat instantly. It was a different vessel completely and much safer in all seas. The change was staggering! Having continued with these tabs and continually changing the rams I finally invested in the largest Bennet Trim Tabs available. At long last and after a bad financial route I settled for these and continued also with the hydrofoils. In actual fact the boat builder is now I believe fitting these tabs and also using the hydrofoils on all new builds? I am at present looking seriously at the Volvo Tabs mentioned earlier in another thread. So in summary:
Hydrofoils do actually work and work well considering their limitations on outboards, drive legs up to and including 260hp, not exactly what it says on the tin.
Trim tabs and only the correct ones are fantastic at altering the handling of badly behaved boats and in fact correctly researched and fitted make the vessel much safer at sea. I must add here that there should be no real reason for fitting any handling device other than for badly set up hulls or inherent bad build qualities? If you see a new vessel that has to have tabs etc fitted by the manufacturer to make it perform properly you have acquried the wrong vessel, personal opinion of course!
I have no experience of the new Volvo intercepter units however all reports are extremely favourable both from the installation and operating views. I also believe they are financial competitive as well? Anyone with these units fitted, I and I'm sure all members, would be very interested to know how they have been received in all aspects?

codprawn · 21 November 2006, 18:22

I will be fitting the interceptors to my RIB in the next few months. They are a lot cheaper than the others as they come complete with the indicators and switches etc as standard. Also on a big RIB that gets a hammering they say you should use dual rams on normal tabs which increases the cost quite a bit.

Matal Mickey · 21 November 2006, 18:35

Yes, twin or dual rams are most certainly better and stronger. Unfortunitely it was dual rams that I continually broke on my initial tabs. The Bennet Tabs were much, much stronger and suffered no damage or breakages. If in doubt simply go for the best. I most certainly would be interested to hear your comments and results when you fit the Volvo items. Thanks.

nik · 21 November 2006, 18:55

do trim tabs add to drag and increase fuel consumption?

Matal Mickey · 21 November 2006, 19:19

Regarding drag and fuel consumption, these are my personal findings and results. No, they do not cause drag as we know it. Consider that the tabs etc are actually raising the stern under way and extending the length, fractonally, of your hull. If fitted and utilising correct operating procedures, you will actually use your trim tabs on flat good seas, good cruising speed and achieve better fuel consumption. There is a myth that tabs are only for foul weather etc,etc. This is incorrect, they enhance all movements and attitudes of the vessel and correctly used in all conditions and weathers are brilliant. Also consider the old favourite questions "tubes in or out of the water". Well if your tubes are in contact with the water under way you are actually causing drag and increasing your fuel consumption, fact! If your tabs or hydrofoils are raising your stern under way, then you are actually assisting the vessel through the water by decreasing drag and assisting fuel consumption, fact. This is very brief for such a complicated subject. I hope it is of use to all. So again to summarise:
These items do not cause drag and yes they most certainly assist fuel consumption. Again my personal opinions.

wavecrosschris · 21 November 2006, 20:28

Quote:

Originally Posted by ribit

Wavecrosschris, I see your asking if you should put trim tabs on your rib, the reason I did what I did in the above statement is because putting trim tabs on these tiny hulls is crazy, more to go wrong, more to bang on the trailer, and why on a hull no larger than a surf canoe, if it cant be set up without, then it's either overpowered or poor weight distribution or a bad hull, unless of course your looking for crazy speeds that is?

hmmm, I know i'm putting tabs on my boat and know they'll work! - I used to build rc powerboats (before I bought a bigger toy) and if they work on a 100cm 30mph model, they're goana work on a half-ton rib with slightly too much weight on the stern. I have bought a set of Plastimo tabs which are on adjustable rams. Basically, I know the only time I need to trim the boat (keep the bow down) is when I'm carrying people - I will just wind them down a bit when I'm carrying more load, which will give lift when I need it. When it's just me, they can run level to the hull and just increase the planing surface.

My RIB does have slightly too much power for its size (not over the max rating on the transom though) but like anything with excessive power, superbikes and cars alike, it's the person on the throttle that says whether it's in control or not.

Can't see why you wouldn't want tabs and advise not to have them - everyone I have spoken to, from the dealer I bought the boat from - a main Yamaha dealer to people with SR4's on this forum, all say tabs work?!

wavecrosschris · 21 November 2006, 20:58

Quote:

Originally Posted by Matal Mickey

I must add here that there should be no real reason for fitting any handling device other than for badly set up hulls or inherent bad build qualities? If you see a new vessel that has to have tabs etc fitted by the manufacturer to make it perform properly you have acquried the wrong vessel, personal opinion of course!

So anyone with a sunseeker Tomahawk 37 , princess 45, fairline turbo 36, er, Class 1 race boat... (i could go on!) and they all have trim tabs, has aquired the wrong vessel? or have i got the wrong end of the...

Millermob · 21 November 2006, 21:02

Quote:

Originally Posted by wavecrosschris

So anyone with a sunseeker Tomahawk 37 , princess 45, fairline turbo 36, er, Class 1 race boat... (i could go on!) and they all have trim tabs, has aquired the wrong vessel? or have i got the wrong end of the...

What about Scorpion, they seem to put trim tabs on many of their ribs, they're one of the top rib manufacturers, surely they can't be wrong.

Freddie

wavecrosschris · 21 November 2006, 21:04

Quote:

Originally Posted by Millermob

What about Scorpion, they seem to put trim tabs on many of their ribs, they're one of the top rib manufacturers, surely they can't be wrong.

Freddie

funny, lol i was just looking at the scorprion website and couldn't see any tabs in the pics so didn't put them in my post - but knew the one that did the round britain must have had them!