trim tabs

[seafariskye]

On a small RIB (up to 7/8 mtrs) trim tabs are not of much use (no that high free board, low boat weight, easy to move things on the boat to correct trim (i.e. leaning left or right ), engine trim use etc etc )!!!

I put the trim tabs on my 7m because due to the heavier inboard, and the thought was to bring the nose down and stop or cut down the slamming in a head on sea, the thought of actually trimming the boat, on a beam sea was there, but was not that important to me really.
The difference is quite noticable, when getting going, and on a long head on journey, if the weather is ok, then they are simply trimmed all the way up, and clear from the water, so do not affect performance and all that.
The original question was putting them on a 7m - and how effective they are/would be - my experience - made a difference, and would fit them again, if need be.
Have been on an 11m with trim tabs, and the difference was virtually Bog all, much more on the 7m.

Easyiest was is for you to come up to sunny Skye and take a spin (well it is sometimes sunny)

Pete F

[Dirk Diggler]

Manos, thanks for that last post, all crystal clear now!!

Why study "basic naval architecture" when I can always ask you.

As for a serious discussion, how about reviving your old thread about the problems of drilling holes in stainless, and the possibility of a forest fire. I liked that one!

As for my degree, I thought I might study Greek Mythology, maybe research your boating knowledge.

[John Kennett]

Hey Manos! Calm down!
And Dirk, try not to wind him up. Please!

For my 2p worth (possibly over priced!) there is no question that trim tabs will work on small boats, but I would still question the need for them -- by small I mean under about 7 metres.

For fore and aft trim a reasonable weight distribution plus the engine trim should be sufficient. On the other hand a small boat with a diesel engine may well benefit from trim tabs.

For lateral trim I'm not convinced that trim tabs would be particularly effective on a small RIB. In conditions likely to make their use necessary, the course driven will be endlessly changing as you drive between the waves so the trim would have to be constantly adjested. One more thing to fiddle with!

On a bigger boat they have several applications: to compensate for windage; assist with getting over the hump onto the plane; keep the bow down in a head sea. The first of these is fine, but I can't help thinking that there ought to be more efficient ways of dealing with the other two situations.

Having said all this, I doubt that the average powerboat driver has the skill or knowledge to use trim tabs effectively anyway. From a quick glance around the Solent on a busy day it's clear that most can't even master the most basic for and aft trimming and bounce around with their bows pointing to the sky . . .

John

[Dirk Diggler]

Originally posted by John Kennett
Having said all this, I doubt that the average powerboat driver has the skill or knowledge to use trim tabs effectively anyway. From a quick glance around the Solent on a busy day it's clear that most can't even master the most basic for and aft trimming and bounce around with their bows pointing to the sky . . .

John

John, I am suprised at your last post, you are obviously an intelligent man, but are you seriously suggesting that the average rib owner has greater skill and knowledge by virtue of owning a rib.

I always thought that the majority of rib owners bought them because they lacked the necessary skills required in close quarter manouvering, hence the large inflatable fender that they come equipped with. IMHO

[seafariskye]

Here Dirk

See in your boat type box thing it says ' A very disappointing Falcon

just to keep the peace and all that - why not start a new thread telling us why ?

Not Stirring or anything...

Pete F

[John Kennett]

Originally posted by Dirk Diggler
John, I am suprised at your last post, you are obviously an intelligent man, but are you seriously suggesting that the average rib owner has greater skill and knowledge by virtue of owning a rib.

Absolutely not. I include RIBs in the generic term powerboat. What ever made you think anything different?

I always thought that the majority of rib owners bought them because they lacked the necessary skills required in close quarter manouvering, hence the large inflatable fender that they come equipped with.

I don't know about the majority, but I can certainly think of a few cases where this applies!

John

[Julian]

Hi Dirk

Whats up with your Falcon then???.


Julian

[Dirk Diggler]

So you load em and I fire em. I don't think so.

All that I'm prepared to say is that the Falcon represents good value for money, ( I have to say that cos I've got a punter) as long as you accept the fact that you only get what you pay for.

Not wishing to upset our South African Members, I think my Falcon is a classic example of the obvious lack of skilled workers in SA.

I believe you can buy one of these boats, ie: hull & deck, tubes, console seats etc for less than the price of a tube from Henshaws, me Greek mate could probably confirm this.

The boat is good looking, and has a good turn of speed with a 115 four stroke mercury, but the ride and handling, together with the banging, crashing and rattling is pretty poor.

To finish, I would say that if you are on a tight budget, or you aren't interested in quality, then a Falcon might be worth considering.

[Julian]

Hi Dirk

Interesting to know thats all. Allways good to get people opinions of boats etc.

Julian

[Julian]

Out of interest what size was the Falcon you had, was it the 7 mtr one. If your looking for a scorpion there is a few second hand ones on the Scorpion website.

If you want a run in one to get an idea how they handle give me a shout and i'lll take you for a run.

Julian

[Dirk Diggler]

Years ago, more than I care to remember, I bought 3 or 4 boats from a guy in Edenbridge, I think the house name was Pootings or something like that, it might even have been the village name.

The boats were known as Fondas, excellent bit of kit, available part built for home completion. He offered me a job once when he saw one that I had completed for a mate.

[matiboy]

ribs with low seated tubes will be less prone to a glass boat at chine walking, however

with a small lightweight deep vee speedboat I have found in the past that 3 factors can produce an annoying ride, which could be cured by trim tabs ?

torque of powerfull engine can produce tilt (engine trim can help cure sometimes )

single handed driving - no choice but to sit on the right of boat giving poor weight distribution- very very annoying

certain sea conditions- never really been able to figure out why

Now with people on board you can boss them around to change trim by playing musical chairs

Surely trim tabs would give the opportunity to play around with sideways trim. All airplanes have them fitted ( ailerons) !!

Reality is they are the last thing you would think of spending money on given their price & given you may only use them occasionally

[crazyhorse]

Just got in, and how we have gone from do I go with Trim Tabs yes or no?


To my mate can sort you out a second hand scorpian, is beyond all belief.


The best rib to buy is going to be a real upsetter for some and probably will be the biggest thread ever going?.So we will leave that one in the bin for the moment. As some of us will have no mates after that one hits the Net.

Your decision is based on the information here and your own conclusions,after maybe discussing it with Bennet Trim Tabbs and then see how you feel.

http://www.diy-boat.com/Pages/Archiv...rb/powerb.html

Good luck.

[Arek Pawelek]

I never used trim tabs, but I'd seen something like that in Zodiac catalog. That's optional for their RIBs, both Zodiac and Bombard. They are no power-lifted. I don't remember the price. Friend of my and Andre, put that thing(tabs) on his Bombard DB 600, as I remember. You have to ask Andre for contact to Kurczak - He'll tell more about handling boat with that gizmo
One more thing: my other friend put trim tabs on 4,5 m Fletcher with 200 HP Mercury! With throttle on 2/3 and on calm water He was flying virtualy on tabs and propeller!!!

[Julian]

crazyhorse

I never said i could get Dirk a second hand scorpion. I told him there were a couple for sale on the website , nothing else.

Julian

[Brian]

I have just been out for a blast round the bay and when I got back decided to look at my tabs.
(Firstly the starboard tab wont depress-but i'll find out why and try and fix that).

What surprised me was that from hi-up to max-down, the tab seems to move remarkably little. Certainly not "big spades digging in, causing huge drag, horrible fuel consumption etc etc".

My (Bennett) tab instrument measures the tab settings from zero to 20.
IF IF this is in degrees, then the setting is likely to have the (desired) effect without, it seems, much of a penalty.

Anyone care to comment.

Brian (the one who has got to be back by 17.00 to watch tele!)

[Alan Priddy]

Brian, I cannot comment on how the tabs work on your boat but when my tabs are working (properly) I can bury the bow so low in the water that it laps over the tube. This came particularly handy when we were in New York using the boat as a taxi (remember that day Charles?) in the Hudson River which is full of dead bodies, logs, and complete sides of houses!! the bow would hit the debris first and give us a chance to cut the throttle before any damage was done.Alan P

[Julian]

Afternoon Brian

The trim tab could be lack of oil or where it has been left standing the slt could be trapped between the rams. Some WD 40 should solve this problem. We have a similar sytem with 0-20 degrees down etc. Ours dig in quite a way though. Maybe a different ram etc. Was it nice out on the water. Is your boat still in the Scorpion yard.

Julian

[Brian]

Alan P. / Julian

Hmmm.
I checked the Bennett website but could find no mention of angle of depression of the tab between max and min.
My rams (two on each tab) extend about 2 inches (max to min), pushing the tabs down, as I said about 20 degrees.

Judging by what you said Alan, this is by no means enough. You imply they should go down 40/60/80 degrees??
Have e-mailed their tech support for an angle figure.

Julian. What do you think your angle is (if you will excuse the question)?
What do you mean by your problem with "sit" trapping between the rams?

PS Brought Cyanide back to Torquay early December.
Torbay today was smooth, slight breeze, overcast but I was bored. Also no one out there to play with, everyone seems to be doing something called work. Whatever that is!

[Julian]

Hi Brian

Sorry I made a spelling mistake, I meant Salt stuck between the rams. Ours go down 4-5 inches or so. Again like alan our bow can go down very low. Have you checked your oil resevior, maybe you need to top her up a bit.

Julian