A couple of newbie questions....

tweeds · 19 April 2016, 22:43

I'm thinking of getting a 4 metre 'heavy duty' SIB, with aluminium floor. Is it okay to be trailing it around with a 25hp engine on the back? On a RIB the transom is integral to something a lot more structural; would the loads on the engine in transit affect the bonding of the transom to the tubes?

Now for afloat.......... SIBs look great on flattish water; would you take it on the Solent in a 20 knot breeze?

Thanks

Gareth

jeffstevens763@g · 19 April 2016, 22:55

Gareth

I have a Mercury 365 hd with a 25hp Suzuki on it and trailer every where with no probs just make sure you have the transom supported on the keel and on the tubes. I lift the engine up and put a block of HDPE through the engine mount to support whilst traveling and strap down to prevent movement.
The RNLI use sibs ok they are 5 m boats but they go out in some horrendous seas the limit is expearence and what your prepared to go out in, do a course RYA must be plenty around the Solent and your learning in the water you want to sail in.

Cheers

willk · 19 April 2016, 23:20

Quote:

Originally Posted by tweeds

Now for afloat.......... SIBs look great on flattish water; would you take it on the Solent in a 20 knot breeze?

20kts is a Force 5. In the lee of a shore that might be fine - but I'd say it was going to be fairly horrible in a SIB further offshore.

HDAV · 19 April 2016, 23:23

Why not a rib?

tweeds · 19 April 2016, 23:28

Price really, as well as what seems available.

Is there anywhere other than eBay to look for older bargains?

Max... · 20 April 2016, 00:08

SIBs are great fun in the waves (ie 20kts) but really for playing about close to shore. You need to take care though and be sensible and watch the weight distribution or you're a snip away from flipping...

Taking a long journey in bad conditions in a SIB is another story and can get very slow, scary, tiring and uncomfortable very quickly.

Check B&O, Apollo Duck, forums, Gumtree, Friday Ads, boatyards, fishing, sailing clubs. eBay is best chance though, check the eBay SIBs spotted topic for examples.

HDAV · 20 April 2016, 13:46

Forums like this and gumtree are good to keep an eye out or put up a wanted ad.

tweeds · 20 April 2016, 22:02

Thanks for the replies. Given I want it to support my son windsurf training in Hayling Bay, I guess it's probably a rib I need. Budget is the challenge there.

Poly · 20 April 2016, 22:56

Quote:

Originally Posted by tweeds

Given I want it to support my son windsurf training in Hayling Bay, I guess it's probably a rib I need

Interestingly I'm not sure it is.

Windsurfers tend to go out in conditions where everyone else is coming in! Willk is right that for normal boating 20 kts would not be too much fun in a SIB for long periods. The normal school of thought is rough weather = bigger boat. BUT windsurfs, big waves, close to shore, aren't ideal for big boats.

If it were me, I would be looking at the sort of thing the surf rescue guys use - small, fast, highly manoeuvrable, easy to right if it goes wrong, soft floor if you get thrown about etc...

Gwozhog · 21 April 2016, 04:21

The engine will do more abuse WOT on the water to the transom than it could ever do on a trailer.

Max... · 21 April 2016, 08:25

Quote:

Originally Posted by Gwozhog

The engine will do more abuse WOT on the water to the transom than it could ever do on a trailer.

Why??

Gwozhog · 21 April 2016, 14:07

Quote:

Originally Posted by Max...

Why??

Fantastic question and I would love to answer it. I pretty sure nobody is doing what the general lee is doing when they trailer. Now I'm not sure how you ride around on the water but when I'm WOT and I pass another boat that throws a pretty big roller my SIB occasionally has looked like the general LEE in the pic below. Not sure if you have ever pulled a skier behind your SIB either but it has quite a bit of force on the transom too. So if your boat is properly inflated on the trailer and you are keeping all six of your wheels on the ground and not breaking any laws on the roadways you should not have a problem trailering with an outboard on the transom. Hope that answers your question.

jyasaki · 21 April 2016, 16:09

Generally, when you're on the water, the force on the transom is unidirectional - a twisting force from the prop pushing forward, with the motor mount keeping the motor from flipping backwards. Force is mainly forward on the transom, but may vary as swell is encountered.

On a trailer, the force is bi- or multi-directional, as the motors weight pendulums fore and aft, and side to side, as road irregularities are encountered. It becomes more pronounced as the motor is "balanced" in a raised position with the center of mass perched on top of the transom.

I am not claiming that forces are larger while trailering (though I also wouldn't be surprised if they are), but they are definitely different. I use a transom saver to stabilize the motor and transfer some of that energy to the trailer frame.

jky

Poly · 21 April 2016, 17:41

Quote:

Originally Posted by Gwozhog

Fantastic question and I would love to answer it. I pretty sure nobody is doing what the general lee is doing when they trailer. Now I'm not sure how you ride around on the water but when I'm WOT and I pass another boat that throws a pretty big roller my SIB occasionally has looked like the general LEE in the pic below. Not sure if you have ever pulled a skier behind your SIB either but it has quite a bit of force on the transom too. So if your boat is properly inflated on the trailer and you are keeping all six of your wheels on the ground and not breaking any laws on the roadways you should not have a problem trailering with an outboard on the transom. Hope that answers your question.

You've not seen British roads! Its certainly possible that the wheels on a sib trailer bounce over potholes, kerbs or speed bumps even with sensible driving.

When it is on the water the boats is supported over a relatively large area, and when landing on water it has a relatively cushioned landing. When on a trailer, many sibs have poor support at the actual transom.

Some SIBs will actually spend longer on the trailer travelling to the water than being used afloat; many of those miles will be at 2-3x the maximum speed on the water and so the frequency of the vibration from towing will be quite different.

The engine itself is partially supported by the water (both through bouyancy and by lift) most of the time, only momentarily is the entire weight of the engine ever acting vertically on the transom.

That said, I'd tow a sib with an engine on the transom, with some extra support
that (a) helped to stop it bouncing around and (b) transferred the load direct to the trailer rather than via the tubes.

cala · 10 June 2016, 17:20

How far out to sea is it safe to take a 360s yam ?

Poly · 10 June 2016, 17:42

Quote:

Originally Posted by cala

How far out to sea is it safe to take a 360s yam ?

That very much depends...

This weekend a group of sibs will hopefully travel around 70 miles. They'll never be more than a few miles from shore, although that doesn't mean there is a safe or easy escape plan at the nearest shoreline. They do have the safety of others nearby, and whilst it's not a perfect forecast it is still relatively sheltered.

Max... · 10 June 2016, 18:10

Quote:

Originally Posted by cala

How far out to sea is it safe to take a 360s yam ?

As Poly indicates - how long is piece of string?!

Depends on so many factors - experience, crew make-up, bottle, weather, local area, engine size, solo or in a group, rescue services etc - obviously some factors far more important than others. Personally if not in convoy I would not generally go more than a mile or less from the coast as round here the next land 'out' is France so no island hopping etc just coastal hugging and then you can go as far as you like fuel and stamina permitting.

All small SIBs are generally Cat C:

C. INSHORE: Designed for voyages in coastal waters, large bays, estuaries, lakes and rivers where conditions up to, and including, wind force 6 and significant wave heights up to, and including, 2m may be experienced.

cala · 10 June 2016, 18:21

Thanks Poly and Max, very informed advice, i was really only thinking of 1 or 2 miles max for fishing in good weather.

HDAV · 10 June 2016, 20:09

Quote:

Originally Posted by cala

Thanks Poly and Max, very informed advice, i was really only thinking of 1 or 2 miles max for fishing in good weather.

That's fine and what they are often used for just make sure you have an effective method of communication if you do have an issue.

Marine vhf radio is the norm.