Maybe I should rephrase / calrify:
Quote:
Originally Posted by miles
both gearbox's were standard gearbox's. The bigger BIGFOOT gearbox's would make for even more interesting testing, as it swings a MUCH bigger prop, which should give better low down power. Both gearboxes looks the same to the naked eye.
|
Yeah, absuolutely, but my point was that at a high level, drag through water at the sort of speeds Ribs travel at is roughly proportional to the square of the speed & the cube of the frontal area of the object. - I.e Gearbox size is quite important!
My merc has a relatively slim gearbox (as I said, comparable to my old Suz 25Hp), but my old Yam (55Hp - so as close as in the HP dept) has a monster of a box that the production line shared with a 90Hp (so bigger to cope with the higher HP).
I'm just saying that to do a true scientific test there is a lot to take into account, and your test is the closest we've seen to date, for which
.
(and realistically, what are the chances we (even as a collective) can get "smilar" engines/ hulls etc in the same place at the same time?)
Quote:
Originally Posted by miles
I like my cavitation plates to be a bit higher than the bottom of my keel. This allows me to get better fuel economy, as there is less drag, as less of the motor is in the water. Both motors were mounted at the same height, as my transom is a fraction too high. This meant that they both were fitted as low down as possible, with the brackets of the motor hanging onto the transom.
<snip>
Both motors are non-trim and tilt. Both were set to the lowest pin. However the honda's lowest pin is a tad bit higher up than the yamaha's lowest pin, but very, very close!!
|
I have an interesting parallel to that comparison. Forth cruise last year . Here's me with my 1980s vintage premix 2- stroke, one of the other boats, granted not the same hull, but the youthful helm had not got the concept of fine tuning the trim, and had parked the 1990s auto mixing 2- stroke on the bottom pin.
Both 5m ribs, both with oldschool carbed 2-stroke 60 Hp engines, so ballpark similar.
Their engine was hard down the whole trip and it looked like they were towing the Bellagio fountains behind them with the spray coming off the leg etc. I trimmed mine as high as it would go, as I usually do.
FF to halfway through the cruise. They had drained a 25L tank, I was only halfway through a 30L tank, and I had travelled Port Edgar - Granton to join the fleet before we started.
That trim angle is CRUCIAL to performance & economy - hence my asking.
, higher servicing costs.
