Playing around with a 10 m trailer cruiser

Very nice, Will! Your craft is somewhat larger than mine and from the shape of the V I imagine it's meant for rougher water, but we do seem to be thinking along similar lines
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Right now I'm pretty much beat, things are insanely intense at the shop right now.... if I'm more awake later tonight I'll get a few more pics up here.

 

Actually, Stu brings up a very good point. People spend way too little time considering the setup of their trailers.... worthy of its own thread me thinks.... will do so shortly....

 

Having spent the last two years driving the solar car's trailer across the province.... I have to agree. Not nearly enough thought goes into the construction of these rigs. People will spend $70k on a decked-out F350 to haul their precious new toy, and then trust the rig to a set of $200 surge brakes. Amazing, really. I'm lucky to have good brakes, good electrics, good bearings and a solid frame on the one I've been hauling lately..... I see an awful lot who aren't so fortunate.

 

yes the trailor is very important ,,your investment rides on it ,,,boats dont like to feel thier wieght...im modifieing my trailor with tractoro trailor air ride..dual wheels ,,2 one ton tractor axils,,hydrolic breaks ,,keel is 4ft 11 inchs ,,lowering the boat 3 more ft ,,reason is ,I like lake erie,but it freezes,,I like chesepeke bay and the gulf ,,but it is hard to be there all the time..you gotta be realistic ..hitting a pothole at 45 mph,,,,is no good ,,and you just cant avoid them all,, all the time,,plus I got to keep her under 13 and a half ft ,,,,,,,Ill sneek buy with the 10.5 beam ,,but not on the hieght,,,,,,longliner

 

Another update....
(Work's been getting in the way of boating again- haven't been able to play with this one much lately!)
Thanks to all who have commented on the hull bottom.... latest drawings below; I've smoothed everything out and made sure there's no concavity where there shouldn't be, etc. (Stations and waterlines in the bow area read as convex outward except for the first couple of inches at the stem, where they tend to be pretty much linear to very, very slightly concave.) I think I'm getting more or less happy with it, but if I get time this summer I'd like to build a model to pull around just to be sure....
Got some suspension bits for the solarcar back recently, all done up in gorgeous glossy coloured anodizing.... thinking of the type of beefy bolted-aluminum construction lazeyjack mentioned a few days back, maybe have the beams anodized up and clearcoated- it's gotta look good on the ramp, right?

 

looking good!
I don't have much experience with jet installations, but I do know that they are pretty fussy about the waterflow around the intake. You might want to ask one of the myriad of knowledgeable chaps around these parts about the 'pad' that you have on the bottom....
I still remain unconvinced about how well you can make a jet perform at intermediate speeds. I know you have some concerns about maintenance, but a sterndrive would probably be simpler, cheaper, more economical and avoid any of the wandering issues that others have mentioned....

Now - when are we going to see some profile and arrangement pics - just rough sketches will do....c'mon, I'm getting excited about this 'little' project!!

 

quite simply put, a screw gets aa grip on the water a jet does not, jets are maintanence free, sterndrives are quite the opposite, but maintained well can last for years I have several worked 6000 hrs
jets often cost more than the engine, see HAMILTON JET, ask for Trever and tell him Stu said so!!)

 

Stu - yes, that's what I was getting at...I too have had sterndrives. I spent at most $1000 AUD per year servicing my last one (on a boat kept in the water btw, which always increases maintenance on s/drives) and never had a problem. In the scheme of things, it wasn't really a significant factor for me. From an efficiency and overall cost point of view, I think they're hard to beat for a midsize boat.

I've started a trailer thread. Would welcome all comments....
http://www.boatdesign.net/forums/showthread.php?p=145581#post145581

 

true, I,m off to NZ to fit one of the bigger Volvo ones , on 20th, has the 310hp diesel 5.7, never seen this one, but then I,m only picking up again after 6 years, give you a bell sometime!! ciao

 

That would be the D6 I presume. The 40 foorter that I posted was designed to have the 350hp version of the same engine. Meant to be very good. But bloody pricey - 85 grand (AUD) including the DP leg!

Have agood trip - make sure you take some pics and we look fwd to your report....

 

Will,
The drive nacelle was based on a paper published by Ultradynamics, which proposed it as a well-tested and proven means of getting better jet immersion than the more traditional cutaway in the keel. I'm going to run both it and the drivetrain proposal by the folks at Hamilton to determine whether my proposed jet drive is, in fact, possible. If they say it can't be done efficiently, the Volvo DPH sterndrive with one of their D4 motors (or a Yanmar) would be the other option. Probably from the rebuilt market because I would not be thrilled about dropping eighty large on a driveline.
Layout, arrangement and deck/superstructure drawings are on the way, but I'll have to keep you waiting until next week- I'm moving halfway across the province this week and so time is in short supply.
Enjoy your trip, Stu

 

Got some news today from Ian Gillon at HamiltonJet (they seem to be both incredibly quick and incredibly helpful!)
Now, I know that as a jet maker, their main interest will be in selling their products, so one would expect a report that strongly pushes their own unit as being the absolute best. But that's not what I got back from them. Ian sent a couple of neat and concise summary calculation pages, an explanation of how to interpret them, and some comments on how the jet options stack up against both claimed and actual propulsive coefficients for prop drive options (lower than sterndrive makers usually claim, but when the calculations are done on the same mathematical basis the jet has about the same overall propulsive coefficient- around 50% give or take a few points). The math makes sense and the numbers work out, albeit somewhat differently from what conventional wisdom about high-speed jet drives would indicate.
Based on the thrust curves HamiltonJet gave me for the Yanmar 180 hp 4cyl and 220 hp 6cyl engines with an HJ274 pump and appropriate gearing, here's what it looks like the boat would do (speeds given as cruise/max, knots)
_______Empty (2.5 t)___Full (3.5 t)
180 hp____23/27________18/23
220 hp____26/30________22/27
I would tend to leave the exact engine choice open for now, suffice it to say that I'm convinced a marine diesel in the 180-220 peak hp range (not necessarily a Yanmar of course) would suffice to get the performance I desire with a jet. The key seems to be to use a large diameter, low RPM impeller compared to the diameter and RPM you'd have in a normal high-speed jetpump or propeller in a similar application.
Ian also explained that the stern lift Ranchi Otto mentioned earlier is real, but only at speeds well above 25 knots; it's apparently the result of high boat speeds forcing more water past the intake than the jet can accept, thus the water flow over the intake actually has a positive pressure at the trailing lip of the intake. Apparently it's not an issue in the speed range I'm considering.

 

I am just curious about your layout.

Because the propulsion will be around 5' len, 2.5' wide and 2.5' heigh (HJ274 + yanmar 6BY220). This raw engine dimension. Need to add some more space for floors and side tickness, sound proofing, engine move on silentblocks, mechanical accessibility etc ...

I do not think this can be hidden under a floor.

 

Layout / general arrangement plans are coming. I have my hands rather full with fibreglass mould-making at work until tonight, plus moving. I'll post some sketches very soon.
The jetpump itself will be hidden under the cockpit deck; I'm trying to find creative uses for the top of the engine box which will have to occupy a fair bit of the cockpit and will protrude slightly into the saloon.

 

Whenever I'm stuck with an engine-box, I tend to have the fwd 1/2 as part of the saloon dinette seating and the aft 1/2 as aft-facing cockpit seating. It seems to work pretty well.