Reply
 
Thread Tools Search this Thread
 
Old 27 August 2013, 16:27   #1
Member
 
JamesF's Avatar
 
Country: UK - England
Town: Sidmouth
Boat name: Various
Make: Avon, Ribcraft
Length: 4m +
Engine: Mercury 40, Honda 50
Join Date: Nov 2012
Posts: 249
Surprised by an SR4

I went home for the week last week to helm the leeward mark laying boat at a national championships for sailing dinghies. I had expected to be distinctly underwhelmed by the boat it was a visiting one kindly lent by another nearby club.

A 1989, rescue-layout SR4 deluxe. With a 20hp motor. And a prop guard.

I was just a bit worried that, if we got conditions like we usually get for a nationals, I'd have plenty of power to get me into trouble, and nowhere near enough to get out of it.

First surprise: we got a week of bright sunshine, gentle but generally sufficient breeze, and almost flat seas. Wooo: .

Second surprise: big seas notwithstanding, 20hp is actually just about adequate for an SR4.

This is carrying a lightweight crew of two, 30 or so litres of fuel, safety kit, two big lumps of concrete, two anchors and towing two large inflatable buoys. It's not exciting quite the opposite: a set of bearings and a stopwatch says we took 8 minutes to cover 1.7 nautical miles at WOT, which works out at about 13 knots. But it was on the plane, and with some throttle left over once it got there, if you felt like slowing down (oddly enough, I didn't).

With the same kit on board, it will also plane quite happily up-sea into a couple of feet of swell. It won't plane properly with three people.

It's actually pretty well balanced with a 65kg engine too there didn't seem to be a lot of difference with 20kg less than I'm used to. Perhaps just a touch nose-heavy, but not a lot.

So if anyone ever thinks of rejecting an SR4 out of hand for looking woefully underpowered it might just be OK for a while until you can find a 40 for it.

For actual safety boat work in strong winds the following day many capsizes to assist and two rafts that needed towing and felt more like stuck anchors than boats the full 40hp was much appreciated.
__________________

__________________
JamesF is offline   Reply With Quote
Old 28 August 2013, 06:05   #2
Member
 
Country: UK - Scotland
Boat name: Wildheart
Make: Humber/Delta Seasafe
Length: 5m +
Engine: Merc 60 Clamshell
MMSI: 235068449
Join Date: Apr 2007
Posts: 4,610


I ran one with 25 gee gees for a while.

Driven plenty of club boats with the same set-up.

Thing is with rescue boats you rarely stay on the plane long enough to notice the difference between 15 & 25 knots...... abd yes, there is a lot of HP frenzy on here.

At risk of sounding like a road sign in a housing estate...... 20's plenty!
__________________

__________________
9D280 is offline   Reply With Quote
Old 28 August 2013, 15:44   #3
Member
 
JamesF's Avatar
 
Country: UK - England
Town: Sidmouth
Boat name: Various
Make: Avon, Ribcraft
Length: 4m +
Engine: Mercury 40, Honda 50
Join Date: Nov 2012
Posts: 249
That said, for boats that might need to go inside the surf line in anything more than a couple of feet of swell, I still say 40hp with manual tilt (gas-assisted, preferably) is much safer than 25hp or anything with power trim/tilt. Less likely to end up upside-down.

Landing the 20hp power tilt boat (no power trim) would have been nerve-wracking in proper waves, whereas it's not much more than routine with our usual 40hp manual tilt boats.

For more sheltered waters, though, 20 seemed fine, and 30 would probably be plenty. The current crop four-stroke 30s seem to be just about the right weight.
__________________
JamesF is offline   Reply With Quote
Old 29 August 2013, 03:33   #4
Member
 
Country: UK - England
Town: Dorset & Hants
Boat name: Streaker/Orange
Make: Avon/Ribcraft
Length: 4m +
Engine: 50Yam/25 Mariner
Join Date: Apr 2007
Posts: 5,551
Quote:
Originally Posted by JamesF View Post
That said, for boats that might need to go inside the surf line in anything more than a couple of feet of swell, I still say 40hp with manual tilt (gas-assisted, preferably) is much safer than 25hp or anything with power trim/tilt. Less likely to end up upside-down.

Landing the 20hp power tilt boat (no power trim) would have been nerve-wracking in proper waves, whereas it's not much more than routine with our usual 40hp manual tilt boats.
Can you explain why ?
__________________
PeterM is offline   Reply With Quote
Old 29 August 2013, 06:21   #5
Member
 
Country: UK - England
Town: Southampton
Boat name: SMH Rib / War Shot
Make: Ribtec / Scorpion
Length: 4m +
Engine: 10hp Yam / 150hp opt
Join Date: Sep 2003
Posts: 1,894
RIBase
Got a 30hp on my current one and it's great.
__________________
Searider is offline   Reply With Quote
Old 29 August 2013, 06:45   #6
Member
 
mister p's Avatar
 
Country: UK - England
Town: LONDON
Make: SR4/ZODIAC/3D
Length: 4m +
Engine: 30T/40T
Join Date: Oct 2011
Posts: 1,433
Have a 30 on mine, with a 4hp wing, 60 litres of fuel in two tanks, 180kg of P's, anchor chain plus supplies for the day.
We get 18 knots with this rig and it planes from 6 knots within 2 seconds thanks to hydraulic trim tabs. In the chop we get down to 15 knots.
Attached Thumbnails
Click image for larger version

Name:	IMG_0663.jpg
Views:	136
Size:	208.1 KB
ID:	84781   Click image for larger version

Name:	IMG_0660.jpg
Views:	140
Size:	44.4 KB
ID:	84782   Click image for larger version

Name:	IMG_0582.jpg
Views:	173
Size:	135.0 KB
ID:	84783  
__________________
mister p is offline   Reply With Quote
Old 29 August 2013, 13:54   #7
Member
 
Razorbill RIBs's Avatar
 
Country: UK - Wales
Town: N. Pembrokeshire
Boat name: Various
Make: RIBs & Hovercraft
Length: 9m +
Engine: Outboards
MMSI: Various
Join Date: May 2009
Posts: 1,357
RIBase
Quote:
Originally Posted by mister p View Post
Have a 30 on mine...We get 18 knots with this rig
Surprised at that, sure I read of one on here doing 50 knots with a 40 recently
__________________
Dan Worth
www.razorbillribs.co.uk

Follow us on Facebook http://www.facebook.com/#!/group.php...17306504953480
Razorbill RIBs is offline   Reply With Quote
Old 29 August 2013, 16:45   #8
Member
 
JamesF's Avatar
 
Country: UK - England
Town: Sidmouth
Boat name: Various
Make: Avon, Ribcraft
Length: 4m +
Engine: Mercury 40, Honda 50
Join Date: Nov 2012
Posts: 249
Quote:
Can you explain why ?
I can try .

The short version: you want enough power to stay just behind the crest of a sizable wave, you want ample steerage, and you don't want to have to worry about bashing the prop on the pebbles.

The long version: (I tried to be brief, but failed...)
Landing in flat or fairly flat seas is easy burble slowly in to a few pairs of waiting hands and switch off. Equipment makes next to no difference, and it's by far the best and safest way if conditions allow. We always do this if we can.

If it's crashing in though, you want the boat out of the water if the transom is just far enough away from the water to avoid the next wave (which is partly your own wash), that's nicely judged. If you've not got a winch, it's harder to pull a boat full of water, and even if you have it doesn't do the D-ring at the bows any good.

The way we've always done it is to start your run in from somewhere outside the surf, pick a wave and follow it in just behind the crest. That usually means running in on the plane. Keep the power on as the wave breaks and cut to neutral so that you're going fast enough to carry speed onto the beach but before the prop hits the bottom. With manual tilt and some speed on, the engine will come up with a little assistance from your crew (almost on its own if it's gas assisted), and it won't do it any damage even if the skeg hits the beach. There's probably a one- or two-second interval between cutting the throttle too early (wave over the tramsom) and cutting it too late (bent prop).

At low tide, when the beach dries out to sand with a shallow slope, the technique's a bit different. You can follow a wave in so far, but there comes a point when you need the boat firmly on the plane to minimise its draft you want to get in as close as possible. So you open the throttle to WOT and punch through the last two or three waves, then cut to neutral at the right moment as usual. You can afford to cut the throttle earlier from that speed, and roll off the throttle a bit more gently if you feel like it. If the boat drops off the plane before it hits the beach, that was probably too slow. In those conditions, it's sometimes a bit all-or-nothing either take a wave over the back or finish up some considerable distance from the sea.

Having a smaller engine or having power trim/tilt have much the same effect not enough power when you need it. You need to be able to get enough power into the water to sit just behind the crest and get back there if you slip off the back. If you slip off forwards, you want to be able to power off it and into the back of the one in front. Either way, the result is probably the same heading for the beach on the front of a wave, which is a Bad Thing. The worst case if it happens is a capsize it's been done by others before me, and I've nearly done it myself.

The most difficult set-up would be a small engine with power tilt and no power trim (like the surprising SR4). Because it can't tilt the engine with much more than idle throttle, you have to tilt up as much as you dare before the run in, and leave yourself enough time between cutting the throttle and hitting the beach to tilt the engine the rest of the way up. That means that you're committed to having limited power and not much steerage the perfect recipe for being overtaken by a wave, pushed about sideways and rolled over. Power trim/tilt that works under way is better, but still difficult. More power helps, but not much if you're trimmed up.

More power and an engine tilt system that you can unlock and forget is ideal. That way, you have all the control you need on the run in, and the power immediately available if you need to make corrections. You're less likely to end up a passenger.

Quote:
Have a 30 on mine, with a 4hp wing, 60 litres of fuel in two tanks, 180kg of P's, anchor chain plus supplies for the day.
We get 18 knots with this rig and it planes from 6 knots within 2 seconds thanks to hydraulic trim tabs. In the chop we get down to 15 knots.
And what a fun and capable looking set-up it is . And another SR4 surprise (for me): it's possible to squeeze an auxiliary engine neatly alongside the main one, and have enough space for steering!
__________________
JamesF is offline   Reply With Quote
Old 29 August 2013, 16:49   #9
Member
 
Country: UK - England
Town: Dorset & Hants
Boat name: Streaker/Orange
Make: Avon/Ribcraft
Length: 4m +
Engine: 50Yam/25 Mariner
Join Date: Apr 2007
Posts: 5,551
Ah..didn't realise you were talking about actually beaching the boat.
__________________
PeterM is offline   Reply With Quote
Old 29 August 2013, 17:15   #10
Member
 
JamesF's Avatar
 
Country: UK - England
Town: Sidmouth
Boat name: Various
Make: Avon, Ribcraft
Length: 4m +
Engine: Mercury 40, Honda 50
Join Date: Nov 2012
Posts: 249
Oh yes. It might be a help for rescues in surf too (the cause of our other SR4 capsize; I've never tried it myself), but for doing that sort of thing regularly I'd have to join the SIB club .

Edit: on reflection, a similar follow-the-wave technique might work for surf rescues in a Searider. And then you're back to needing the power again. I wonder if 30 would be enough (maybe if it had a slightly flatter prop than usual...). Can't see it ending well with 20hp, though.
__________________

__________________
JamesF is offline   Reply With Quote
Reply

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off





Copyright 2002- Social Knowledge, LLC All Rights Reserved.

All times are GMT -5. The time now is 21:26.


Powered by vBulletin® Version 3.8.8 Beta 1
Copyright ©2000 - 2017, vBulletin Solutions, Inc.