Advice please

[TRevor Lawson]

Hi , I have a couple of questions to any one who can help, Thanks in advance.

Will a 4 mtr rib with a 25 hp on back be faster than a 4 mtr sib ( hon wave t 40 , blow up keel ,alloy floor), given same load, sea conditions etc, just thinking sib has more suface drag ,and flatter bottom?

Also i guess thr rib will be a better/smother ride for same conditions?

Trevor

[Polwart]

Two different models/brands of rib won't necessarily give the same performance so a definitive answer is difficult.

However the rib is likely to be heavier (possibly significantly so) especially if you start to add seats, console, aframe...
The rib is likely to have more of a V-hull than the honwave - v-hull = harder to move through the water.
Once on the plane some rib tubes completely clear the water reducing drag. I'd guess most 25HP/4m combinations will still have some tubes rubbing in the water most of the time.

All in I doubt you will get faster than a similar sized SIB with the same engine - you may not even be able to match it (but both will do very roughly 20 knots). However the ride will definitely be more pleasant on the RIB.

[Max...]

Faster in same conditions is a bit of a red herring though - in the UK anything more than a slight or very gentle moderate sea is a real PITA in a SIB and will limit your top speed far more than the engine. However, a reasonably deep V RIB will think nothing of a moderate or worse sea and will therfore in 'real' conditions almost always be faster. On 'glass' there might be a slight difference but in the real world where moderate is the norm...