Mast Rake

[Fascadale]

Here are photos of the boat I bought last year, an Invicta 26

and

It was not until after the season that I took a good look at the photos.

What do forumites think of the mast rake ?

I think the for and aft trim of the boat is OK. I cannot judge her sailing performance against an identical boat but I feel she should be able to point higher.

Unfortunately it is not easily possible to adjust the rig as it stands, the forstay bottlescrew is fully extended, the one on the backstay as tight as pos.

I am going to replace the standing rigging this winter so I can easily make alterations to the mast rake.

I would very much appreciate any advice on this one

Thanks

Paul

 

[Talbot]

Certainly is raked forward, and I prefer a rake aft of a few degrees.

You could always insert a couple of shackles forward and get the backstay shortened and see if that makes any difference before the expense of new rigging.

 

[johnalison]

It does look forward-raked but it could be raked to port which is why it appears to be more raked in the second photo.

 

[colvic987]

looks as if the forestay has been fitted incorrectly when the furling equipment was fitted, and to much of the forestay has been chopped on installation, have you used the boat this year, if so have you had some bad weather helm.

Looks like you will have to rake the mast back quite a bit to get it to resemble the correct angle, maybe an extra foot at the masthead.

was the boat received by you in 'mast up' condition, or was it down, and did it already have the furling equipment already fitted...

but it can be quite difficult to notice it fully from a photo, you will need to do some measurements with the main halyard, and see what you come up with.

fernhurst books 'illustrated sail rigging and tuning', would be the cheap way to go at the moment so you can understand how the rigging and sail works...

 

[savageseadog]

Conventionally it should be raked back by about as many degress as it is forward now, 3or 4 degrees? It does depend on the sail and boat balance so isn't cast in stone.

 

[sailorman]

i would suggest 9" rake aft

 

[ctelfer38]

You might be interested in looking at this http://www.yachtsnet.co.uk/boats/s45806/s45806.htm
/forums/images/graemlins/cool.gif

 

[Guest]

If the mast foot has different position then you can also rake the mast back/reduce forward rake by moving the foot forward a notch or two. Which will also reduce any excessive weather helm. Moving the top of the mast back (by extending the forestay) will have the opposite effect of increasing weather helm.

 

[Fascadale]

Boat bought with mast standing.

The surveyor said nothing about the rake and I didn't really notice it until I looked at the photos afterwards....too excited by the purchase I suppose.

Its OK in the port/starboard plane, I think in the second photo the boat is rolling to port which creates that odd aspect.

The previous owner did have the mast down and did fit a new genoa so the rake may have resulted from that.

Difficult to judge the weather helm without having sailed another Invicta. I do get the feeling that I am reefing early (c18kts of wind) to avoid weather helm

This image

shows a very vertical mast, I thought to-days preference was for a rake astern.

Thanks for your comments

 

[Fascadale]

Simon

Just seen your comment.

Should I understand from what you say that the weather helm is more dependant on the centre of effort rather than rake.

I would have thought that the same rake would be achieved by either altering the position of the top or bottom of the mast.

Thanks

Paul

 

[Guest]

[ QUOTE ]
Should I understand from what you say that the weather helm is more dependant on the centre of effort rather than rake

[/ QUOTE ]
Yes, exactly, weather helm is determined by how forward/aft the centre of effort is (compared to the centre of lateral resistance of the hull/keel). By moving the foot of the mast forward, you're moving the centre of effort forward. By moving the top of the mast back, you're on the contrary moving the C of E back. So the mast ends up at the same angle, but the amount of weather helm is different.

The fundamental difference between the two of course is that, althought the same angle of rake may be achieved either way, in the first case the whole mast is physically further forward than in the second case, and with it the sail plan.

 

[VicS]

I am not clear in my mind if you mean that the back stay adjuster is screwed in fully or whether you just mean that it is fully tensioned.
If the latter , ie there is still some adjustment available on the back stay, then try the suggestion to extend the forestay with a shackle or two. BUT remember shackles are not recommended on standing rigging so change to a proper toggle if that is the permanent solution until you get the new forestay made.

However the first photo looks OK while the second looks very odd so before you do anything else check the side to side adjustment my using a halyard to measure down to the deck or toe rail on each side. Also try to determine the actual extent of any forward rake by suspending a heavy weight on a halyard on a windless day, That will hang vertically and you will be able to see exactly how much rake there is.
(If you are so inclined and can still remember your schooldays trigonometry you could the calculate rough figures for the amount by which the forestay needs extending and the backstay shortening. I'll give you an idea what to try.)

Regarding the position of the mast foot. It looks to me as though it is a full tabernacle. Unless that is adjustable or there are any signs that it has been moved then I would not touch it.

Start by checking it sideways and do it by measurement with the halyard not by eye.

 

[VicS]

Thre are some good pictures of an Invicta in the galleries on the Truro Boat Owners Association website which might be of interest.

TBOA Gallery

This is one of them

Compare the mast with the horizon using a square or the corner of a sheet of paper and you'll see a good rake aft

 

[Fascadale]

Vic

Thanks for the photo link

The mast is indeed in a full tabernacle which is solidly bolted through to good backing plates so that will definitely not be moving

The back stay adjuster is fully tightened

Fairly certain the side to side aspect is OK

I like the idea of using trig to calculate what the length of the stays should be: I'll have to look around the attic for the old 4 figure tables, or maybe one of the kids can show me how to do it with a calculator

Cheers

 

[john_morris_uk]

[ QUOTE ]
Certainly is raked forward, and I prefer a rake aft of a few degrees.

You could always insert a couple of shackles forward and get the backstay shortened and see if that makes any difference before the expense of new rigging.

[/ QUOTE ]Possibly - but I agree with VicS in his post where he points out that you should be careful about the loading on shackles. Some shackles would not take the load of a fully tensioned up forestay. A proper toggle might be better.

 

[smth448]

If the mast is raked too far forward that would move the centre of effort of the rig forward resulting in lee helm rather than weather helm. If the boat is carrying excessive weather helm now then raking the mast back will only make it worse.
It is possible that the previous owner raked the mast forward to try to reduce weather helm.

If you have to reef early to avoid weather helm it could be that the sails are baggy and need to be recut or even replaced. How old are the sails? If the backstay is as tight as it will go then it could be that the rig is slack resulting in a saggy forestay which will increase the fullness in the genoa.
There was an article in YAchting Monthly a few months ago where someone was experiencing similar problems and Tom Cunliffe went out on his boat for a day and tweaked some things hear and there and improved sail shape.

Good luck