My Summer wine has been fitted with lowers before i bought her, but over the course of the season i have noticed that the foredeck compresses when the lowers are pulled tight. There is no strut on the boat or any post between the underside of the deck and the top of the front tank. 
The lowers are led to a turning block(from the side deck) which is /was screwed into the underside of the deck and then down to the hog and then to the thwart. I think simply putting in a post would cure it but then i have no idea how to build boats i just sail them.
I would be most grateful for any tips.

There was an article by Henry Wright in one of the old year books (in the 80's I think) which used a wire strop from under the foredeck to the hog. This had a bottleneck screw to tension it. This stopped the deck flexing.

Perhaps some one has a copy they can scan and post a lonk to it?

oops, do not know what a lonk is. Should have read link.

I suspect this is the old problem of high rig tensions and loads on a high-tank hull.  To sort this out you do need a proper bit of engineering, as well as taking the load from mast gate to the hog you need to look at opposing the tension of the lower shrouds from gunwhale to mast step.  This isn't that difficult to do, but is difficult to do and make it look pretty

I'm surprised there is no support between the hog and the foredeck (just in front of the mast gate). Even a light post!

See photo at this link for a way to strengthen the hull (ignore the thick wooden king post). Not sure if you'd want to go for this though.

the boat has a low bow tank. i have thought about the post from the top of the tank to the underside of the foredeck but was a little concerend abotu where the pressure would go. i should also have said that the foredeck sinks when the lowers are pulled on rather than rises. i have tried to take a line down from the front of the gate to the top of the tank but on investigating the internals of the tank ( through a handily placed hatch) there isnt much to support the pressure.
Would an angled post work say from frnot of mast step to the forward end of the gate??.

Hamish, is there a beam underneath the foredeck (running fore/aft)? My boat has a bit of wood running from the gate to the chute, as well as a couple of sideways ones to support the deck. There is no strength in the very thin ply deck at all.

I'm confused, if the deck curves upward, and the problem is the lowers pulling the hull in, then the deck would go up - surely.

As it seem (are you sure it is really) to have been converted to a low bow tank (unlike the boat in the picture link), then the hull should be stiffer, but the deck is going down.

No mention of the shrouds/jib when pulled tight imapcting the deck shape.


Conculsion - something else is happening - but I don't know what.

the deck is pulled down when the lowers are pulled on due to the position of pulleys. It could be stopped by a re route of string and cables or a post fitted in front of the mast under the deck with support built into the low tank.

Regarding "a little concerend about where the pressure would go" - if you put a strut between foredeck and the hog (NOT the top of the tank) then that would be plenty strong enough.