Strange shape of port side spray rail on SR 5.4?

C-NUMB · 11 July 2012, 20:41

I am in the middle in the brilliantly fun task of removing antifoul paint from my SR..Several layers of antifoul, primer and than also 2 diferent colours of topcoat paint....

Otherwise the original gel coat is in good condition. Here some pictures of the lover port side spray rail. It has totally different shape than the others, its not straight. I have seen this hull from the inside, it does not look like a bad repair. And its not only filler, its grp beneath when removing the surface. The bottom is straigh, that is not the issue, its only the end of this spray rail that is shaped strangely.

Is this a "feature" ( possible to counter the torque from the engine) or something else?
I think have seen the same on a few pictures here on ribnet but not on all SR( maybe a Navy speck feature?)

jyasaki · 11 July 2012, 21:34

I'd guess someone went at it with some really aggressive sandpaper.

How far along does the curve go? Shouldn't be too bad to take it down to the resin and build it back up.

jky

C-NUMB · 12 July 2012, 05:03

The "curve" is not longer than 30 cm and the spray rail gets wider in the end, the rest of the rail is identical with the starboard side rail. The issue is not that the rail is sanded down, more like the end of it is enlarged....It looks very much like it would been that way from the beginning, or at least mad by purpose.

Other thoughts here?

Hightower · 12 July 2012, 17:44

I seem to remember an old thread about this. Is that commonly called a "Hooked" hull and is generally considered a bad thing?

Hightower · 12 July 2012, 17:55

I've searched the archives and can't really give you anything from the forum, but Googling brings up anything from a manufacturing fault to rotten internals and unsupported boat on trailer. I would have thought that you'd have found some cracks somewhere if it had "sagged" on the trailer.

willk · 12 July 2012, 18:53

Nothing under "Leeway"?

Cookee · 13 July 2012, 06:59

Quote:

Originally Posted by Hightower

I seem to remember an old thread about this. Is that commonly called a "Hooked" hull and is generally considered a bad thing?

A hook generally refers to a running surface rather than a spray rail - it would effectively "pull" down that side of the boat but I doubt it's an intentional shape. Some filler on that would straighten it up and allow you to see if it makes a difference.

C-NUMB · 13 July 2012, 07:36

Thanks for comments. No, hull is not hooked, running surfaces are straigt as can be, its only the spray rail that has this shape. I think i have seen this shape on a picture here on another SR 5.4 but cant remember the thread. It was not related to this topic anyway.

This "issue" has strangely litle impact, geting pretty good speed out of here and handling also. Think need to take the agle grinder out....but still would like to know why its its this way?

C-NUMB · 13 July 2012, 08:04

Look carefully at the picture in post number 6 on this thread:

http://www.rib.net/forum/f8/attentio...ere-42645.html

It looks like the mentioned spray rail is not straight here either, compare to the running surface?

Dry Run · 13 July 2012, 09:55

Here's a pic of a 2008 "MOD Spec" SR 5.4. It looks to me that the inner port spray rail is more flered than the starboard one (albeit in a different way to the OP's)?

johndoe007 · 13 July 2012, 11:27

Quote:

Originally Posted by Dry Run

Here's a pic of a 2008 "MOD Spec" SR 5.4. It looks to me that the inner port spray rail is more flered than the starboard one (albeit in a different way to the OP's)?

OMG I want... no wait I NEED that propellor

ncp · 13 July 2012, 13:47

Quote:

Originally Posted by johndoe007

OMG I want... no wait I NEED that propellor

One of those might give you a better hole shot! Wait, that's another thread....

Dry Run · 13 July 2012, 14:15

Quote:

Originally Posted by johndoe007

OMG I want... no wait I NEED that propellor

Well, if you've got £25k burning a hole in your pocket you can have the propellor along with the rest of the boat!

C-NUMB · 13 July 2012, 15:05

Thanks Dry Run for the picture! Nice SR! Maybe the design have developed during the years(mine is 1992) but now I am convised that it is a feature rather than a bug on navy spec/MOD versions. The story behind this assymetrical shape would be interested to know, but sure there is a reason. Think will leave the angle grinder in the tool box until further notice.

ribraff · 13 July 2012, 16:09

This is intentional and is seen on all the 5.4's, I think it was to try and counteract the chinewalk you get on them at high speeds.

PeterM · 13 July 2012, 16:12

I think I've seen this on a few Avon hulls ...I'll check mine for 'straighness' later !

johndoe007 · 14 July 2012, 01:48

I have my hands full over here, but if you thinking of parting her out I'll take the roll over / righting kit and the prop

searider5.4 · 24 July 2012, 00:45

Hi...

it is the same on my SR5.4 was also worried when I saw it first... then I checked some pics on ribnet and I found it on all the pics.
I think it was the shape of the mould.
Don´t worry .....ride it!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

cheers
Sven

colcreate · 24 July 2012, 07:37

I noticed this contour on my 5.4 when I re-gelcoated the hull. At first I thought it was a bad repair (along with all the others...) but then realised it must have been a feature of the original mould.
It would tend to give the port side a slight lift which might be to counteract the torque of the prop.... then again my mate said I was spending too much time thinking and not enough sanding!
Who wants to grind theirs off and let us know the difference?

C-NUMB · 11 August 2012, 16:46

later on I re checked how straight the hull is. I was wrong, the planning surfaces are not straight as i wrongly said earlier.....In fact there are some hook in the whole planning surface, worst area located pretty close to the transom.

I don't know is it due to tired mould, wrong way of storage or another design feature.

Anyway decided to take it a way. I filled it with lightweight epoxy filler, guess as worst it was like a 3-4 mm hook. I did only the flat surfaces, spray rails left undone at this stage.

Result was interesting. Wot/ high speed handling is better, reduced tendency for chine walking. Also the propeller grip seams to be better. But lost top speed about 0,8 knots, now slightly less than 39. RPM is about the same, 5500(not 100% sure but think it was close to that also before)

I guess loss of wot speed is due to the engine is kind of "lower" (rig doing more resistance than before) as the water now goes straight, as in the past it was directed "down" due to the hook.

Will lift the engine a hole or two to check how that will work. Will let You know the results.