Help!

[adelaidem]

Engine alignment ---HELP !!!

Quote : 'Using a feeler gage constantly after every little move,shuffle the engine according to demand until no greater error or misalignment than 0.030mm per 25mm of flange diameter is apparent.'

My engine is hard mounted

My flange diameter is reading 125mm (5") Therefore i assume that i can have an acceptable misalignment of no greater than 0.15mm. This seems to be hard to achieve. Can anyone elighten me on this as i have spent all day trying to achieve this .. advice will be greatly appreciated

 

[snowleopard]

Not a solution to the problem but a pointer - do it with the boat afloat as the hull shape will change slightly when ashore.

 

[adelaidem]

High and dry for 2 yrs I have been told about hull movment, but would be at happy to have it fairly right before she takes the plunge again.

 

[LittleShip]

As previously stated, you need to do this when afloat it cannot be achieved with any certainty whilst on the hard and on wooden boats its a definite No No(I dont know if your is). Take the advice and wait until you’re afloat and the boat is fully supported.

Tom

 

[adelaidem]

So a solid 1"1/2 fibre glass 37 ft will change her shape that much that I cant re-alighn the diesel correct on the hard?

 

[Ships_Cat]

You are doing it fine, if boat is on the hard it is perfectly normal to align out of the water and then check when launched (suspect you will find nothing will change much, if at all). All new boats are done that way as well.

John

 

[twisterkai]

When considering how much a boat will move between high & dry and floating, it depends on the material and the design of the boat. A friend used to have a light weight French boat and while afloat all was fine. However, when she came out of the water, the engine mounts had to adjusted quite considerably to enable the shaft to be removed, thus an extremely flexible hull.

I have a Twister, which we installed a new engine last year. All the alignment & adustment was carried out when she was in the yard. It was checked again once launched and there was no further adjustment necessary. Two boats, similar sizes, two very different end results. There are no hard and fast rules, although one should check alignment regularly.

To answer the initial question, before you start trying to fine tune the alignment, spend a bit of time establishing methods of moving the engine accurately through very small movements. It takes an awful lot of the hassle out of doing it for real. As to the accuracy, 0.15mm is possible, it just takes time, especially if the access isn't great, which unfortunately is usually the case on a sailing yacht. If you have reaonable visibility of the gearbox & shaft flanges then it is possible using the mk1 eyeball instead of feeler gauges. Think in terms of motor sailing to windward in a rough sea and then think of the movement of the flexibly mounted engine. The 0.15mm pales into insignificance, but it's good to start with it as accurate as possible.

Good luck!!

 

[Ships_Cat]

This one is 37 foot, 1-1/2 inch solid lay up, do you think it is going to be bendy? As I said, I suspect not.

John

 

[Stemar]

I shouldn't think it'll be that bendy. I reckon you should get away with it, but I'd check it anyway once the boat's in the water and the rig's up and tuned. A ton or more of force in the backstay and forestay could well make more difference than afloat or ashore.

I just did this job. On Jissel, it's a PITA, but not difficult. My mounts have threads sticking up and the brackets on the engine have nuts that I can screw up & down to adjust the height. If you haven't got an arrangement like this, you'll probably have to add and remove shims under the mounts.

The trick is to get the the engine level port-starboard then, if the engine's too low lift the rear mounts until there's a bit of a gap at the top of the coupling. Now lift the front until things are about aligned and see if you're at the right height. If the engine's high, drop the back until there's a gap at the bottom then drop the front to match. Repeat as necessary. Don't try & do it when you're in a hurry/tired/just had a row with the wife. It needs extreme patience!

The main reason apart from re-engining that you have to do this is that the mounts settle in use., so you probably won't need to worry about side to side alighnment, but if you do, on mine it was a brute force job involving slackening the mounting bolts and persuading the engine to move sideways with a crowbar. The bolt holes in the mounts are probably oval to allow for this.

If you really can't get it good enough, there's always the option of fitting a flexible coupling. I've just fitted the Vetus Bullflex coupling to Jissel. It isn't cheap - from memory about £200, plus a £60 flange for some gearboxes , but it'll handle 2 degrees of misalignment - a couple of mm or even more gap at the plate. (Back of envelope calculation - maths not guaranteed!)

 

[Ships_Cat]

I see you are in Oz. If you can stand moving the shaft aft around 15mm or so then you may wish to talk to the people at Polyflex in Brisbane (http://www.polyflex.com.au/Disc%20couplings.htm) to see if they have a disc that matches your flanges.

Makes alignment childs' play as near enuff is good enuff. I even lined an engine with one up once by just laying a straight edge across the exposed part of the disc until with couplings still bolted up with it (ie not uncoupled) I could not see any distortion of the disc when the shaft was rotated and when ran engine it was fine.

{Edit: I see Stemar has also recommended looking at a flexible coupling - great minds think alike /forums/images/graemlins/smile.gif}

John

 

[Sailfree]

When you next fly align the wing tip when on the ground then again when flying. Next examine the construction- its very strong! Even glass deforms under load!

 

[Ships_Cat]

What a foolish comparison, especially coming from someone who claims to be a civil engineer /forums/images/graemlins/crazy.gif.

Even sillier to seemingly infer that all boats will deflect sufficiently to require realignment of the drive when put in the water. In case of confusion, they all do not.

John

 

[adelaidem]

Yes next time I fly i will be intrested to see how much the the nose and the tail changes shape while in flight will be very intresting indeed

 

[Ships_Cat]

I trust that you have noticed the men out on the wings realigning the engines each time the plane gets up into the air after takeoff /forums/images/graemlins/smile.gif.

John