Teething Problems

Robert1 · 29 March 2004, 13:07

Hi,

I lauched my Ribcraft 4.8 on Saturday and it was superb! Boat was really easy to handle and within minutes I felt comfortable putting in the tightest spots! The engine was superb and sounded awesome! However, I did have one problem...

When on the plane, I got a lot of spray coming up over the transom. This spray was mostly directed away from the boat, but some water was coming in. I'm no expert but it clearly wasn't right. How can I stop all this transom spray? (It was both sides of the outboard leg but worse on the side with the elephant trunk, which was in the up posistion). I can only describe it as two 'fountain like' sprays of water coming up from the transom area. Can anyone tell me how to correct it? Is it to do with incorrect trim?

Thanks,

Robert

Pete7 · 29 March 2004, 13:19

Rob hi,

Assuming the engine is the right length for the hull and has been trimmed correctly so the prop is horizontal then it is likey that the engine hasn't been fitted at the right height and you are getting spray from the front anti cavitation plates. Try jacking the engine up a hole.

Pete

Robert1 · 29 March 2004, 13:29

Ribcraft fitted the engine...Surely they woudnt have done it wrong?

jwalker · 29 March 2004, 13:39

Quote:

Originally posted by Robert1
Ribcraft fitted the engine...Surely they woudnt have done it wrong?

Robert1 · 29 March 2004, 14:43

Thanks for the suggestion, Pete. I'll have a word with Ribcraft. Anyone else got any ideas?

simmons0 · 29 March 2004, 15:38

Theres not really anything else down there that might cause that.

Once the engine has been lifted, if that is the problem expect an extra few knots top speed

Robert1 · 29 March 2004, 15:53

I have spoken to Jason at Ribcraft and he has diagnosed the problem:

'Our transoms have a greater angle than most for increased grip and planing ability when loaded, I.e. you can get the engine trimmed in further. Hence most of our hulls when planning run with the engine trimmed slightly, if you trim the engine out slightly the spray will go away.'

This makes sense and I will try it next weekend. Roll on Saturday!

Robert

P.S.
Pete, refering to your post, this would explain why the prop would not have been horizontal to the waterline.

Alex Brown · 29 March 2004, 19:40

Hello Robert,

I had a similar (what I thought was a) problem as you when I first got my boat...... Assuming the trim would be about right if I left the needle in the middle, and with the engine looking pretty level I thought that was all there was to it, but no

Image on the right shows when I first got the boat, and had level trim.... image on the left shows trim at the 3/4 mark which is my standard cruising level.

In my case, lifting the engine (not an easy task) did not prevent the water coming over the transom, and it also only increased my top end by half a knot or thereabouts, so the engine went back down to where it was originally.

Robert1 · 30 March 2004, 08:46

Alex, so trimming the engine away from the transom solved your problem? The spray shown the the pic on the right is what I have been getting.

Robert

Garygee · 30 March 2004, 12:11

Hi folks

I always calibrate my trim gauges so its shows level when the cavitaion plate is level with the hull.

Just get a long length of wood and set the engine cavitaion plate parrallel with the hull using the wood as a guide.
Just hold the wood along the hull and trim the egine until it lones up with the wood.

Next most trim sensors can be adjusted, often onlt two srews to loosen, turn the sensor till the trim gauge reads level and tighten the screws.

After a while you stop using the trim gauge and run with what "feels right" for the conditions. but at the start i found the gauge useful.
On my previous 4.8 the engine trim made a hugh difference to the handling & performance of the RIB.

Regards Gary

Robert1 · 30 March 2004, 12:14

Gary,
Did you have this problem on your 4.8?
Robert

Bilge Rat · 30 March 2004, 12:18

I've recently been playing with the trim on my engine after finding the steering pulling to one side, by trimming the engine up a bit i can get the boat to ride slightly higher at the bow, the boat runs straight even to the point i sat and had a cup of tea at 30 knotts no hands

and she ran dead straight, the bow raised makes it a lot dryer ride when its choppy and i've attained a few more knotts - which is always a good thing

R

JCW · 30 March 2004, 16:18

Robert,
with the engine trimmed in there is a tendency for water to splash into the transom well, with the boat trimmed out this should not happen. As Gary said, the trim on this size of boat makes a massive difference, and it will not be long before you get a feel for what is right and wrong. My experience of helming larger boats is that the trim has less effect than on my 4.8.

Alex Brown · 30 March 2004, 18:24

Quote:

Originally posted by Robert1
so trimming the engine away from the transom solved your problem?

Yeap, that's right.

From 'default' level trim on the guage to full up trim on flat water, there is very little difference to the handling of the boat apart from lots of water going high at the back.

I do find however, that when the engine is trimmed down, the boat is very keen to lean to port, especially when working in choppy water.

In my case, I'm not sure if calibrating my trim would work though Gary.... when the guage reaches the top, straight after that, the engine goes into shallow mode which might not be so good when bombing along at 40 knots.

-Alex

Simon Guest · 30 March 2004, 20:12

Hi Robert,

Don't worry, it's not really a "problem" is it, it's learning to use the trim properly. (And Ribcraft do know how to set their boats up correctly.)

What the others have said is right, and also what I experience (with the same boat). Trim too far in and you get the spray. (Of course, trim too far out, and you get wobble, aka chine walk.)

Have a fiddle next time you're out. In the meantime, enjoy your Ribcraft - what a great little boat!

cheers,
Simon

PS: Just going into the third season with mine, which you can see here: http://www.rib.net/forum/showthread....&threadid=1183

Garygee · 30 March 2004, 20:51

Hi Robert

Well I could get if to do it if I wanted to

But saying this it never did it when the engine was trimmed correct for the conditions.

Dont panic, have a play you will soon feel whats right.

Start in calm conditions as once their is some chop you change your trim not only for the load/speed but for what the waves.sea is doing. Keep this out of the equation for now.

Trim is a thing that needs to be learned, and all too many people dont learn it to their loss. Once you learn to trim a RIB propper you can be doing 25kts in in conditions that others that dont understand trim are bouncing all over going 15kts.

As far a bigger boats & trim, well i never move the trim on my 7.8 is best fully in for all conditions. Have tried many positions but makes almost no difference.

Regards Gary

Robert1 · 30 March 2004, 21:08

Thanks very much Pete, simmons0, Alex, Gary, Bilge, JCW and Simon. I am now confident I can address the 'problem', sort it out, and learn how to make my boat perform better. Thanks guys - I feel I may need to draw on your experiences again at some point in the future. I'll post some pics of last Saturday's launch in the gallery when I get a chance so you can see the boat.

Cheers! Robert