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Re: UK Zip Build

Posted: Mon Feb 26, 2018 8:15 pm
by Hercdrvr
I was thinking the same thing about the transom, it’s not a stock Zip. Do tell, what’s going on back there?
Matt B

Re: UK Zip Build

Posted: Tue Feb 27, 2018 2:06 am
by sproggy
It'll have an outboard lower leg (impeller, gearbox) bolted through a much reinforced keel. Then the powerhead will sit directly over that on a custom mounting plate without all the 'junk' (transom mount, power trim, casing etc) that normally sits between the powerhead and the lower leg. I'll use a 4-stroke in the 30-40hp range - there's very little opportunity to use powerboat performance in the UK but I want smooth and quiet with good economy. Whether I can fit this setup below deck level on a boat as slim as the Zip remains to be seen but at the worst I'll have a 'power bulge' in the rear deck. Fuel and battery will be mounted against the transom either side of the motor with the intention of retaining close to correct weight distribution. Separate rudder, of course.

This will give me a clear transom on which I can impose my barrelback obsession as you can see from the photo. Frames 4 and 5 1/2 will be standard, 2 will be modified by eye to get a fair curve to the sheer once everything's mounted on the build form. Sheer height on the barrel transom is standard so the sheerline in profile should be unaffected. I may add a frame or half frame at position 1 to provide additional support for the motor. The aft part of the topsides will be cold-moulded; the rest will be ply sheet as specified. All, as far as my plans are at the moment, clad in 1/8" mahogany boards finished bright.

I need to work out the details of the gear shift (not too big a deal), exhaust and cooling water routing once I've chosen a donor motor. I don't expect it'll be easy from an engineering point of view but that's part of the fun, right? :D

I don't think this has been done before but I'm happy to be corrected. I'm also happy to be told I'm an idiot because I've missed something blindingly obvious.....

Re: UK Zip Build

Posted: Tue Feb 27, 2018 9:00 am
by BillW
Very interesting!

Yes, this has been done before. I think there was more than one brand name, but one that I seem to recall was "Fageol".
This picture came up when I Googled that name. This one looks like it incorporates steering; maybe not. And it does not seem to
be an outboard powerhead either. Your idea is better in that regard.

You said that in the UK there is very little opportunity for powerboat performance. What did that mean?
I didn't understand that statement.

It will be really interesting to watch your progress.

Bill W.
Fageol.jpg (11.63 KiB) Viewed 4832 times

Re: UK Zip Build

Posted: Tue Feb 27, 2018 9:28 am
by sproggy
Interesting. And no real surprise that this has been tried before somewhere in the world. Looks as if Fageol had all kinds of engine applications back in the day. Using an outboard powerhead, while compromising on height, gives me a modern motor designed for marine use with good parts and service backup even if its not in the original configuration. An outboard powerhead is also lightweight.

In the UK most inland waterways (lakes, rivers, canals) are subject to a 4 or 5mph speed limit. Even places like Lake Coniston where Donald Campbell ran Bluebird for world record attempts (and where he died doing just that) now have a 10mph speed limit. If you want to go any faster you need to be on coastal/estuary waters (which are rarely calm enough to run a hull with so little deadrise at high speed) or on dedicated watersports lakes which aren't generally all that big and where they expect a powerboat to be towing a skier. Unless I'm mistaken I'd have to travel to the Scottish Lochs (1000+ mile round trip from where I live) to find a decent expanse of inland water without speed limits. You guys in the US don't know how lucky you are! Of course you've got rather more space than we have over here... So my Zip will be destined to spend most of its time on the water chugging along at hull speed, not on the plane. I need to make it look good as the people I go past will have plenty of time to check it out :roll:

Re: UK Zip Build

Posted: Tue Feb 27, 2018 10:20 am
by hoodman
There aren't that many waterways restricted by speed over here other than certain areas that are marked as "idle speed" or "no wake." There are lots of lakes that have horsepower restrictions. Where I used to live in North Carolina there were at least 10 large lakes with no power restrictions. We could thank the TVA and Duke Energy for them.

Re: UK Zip Build

Posted: Tue Feb 27, 2018 10:48 am
by Bill Edmundson

Re: UK Zip Build

Posted: Tue Feb 27, 2018 6:06 pm
by JimmY
Lurking with interest....

Re: UK Zip Build

Posted: Wed Feb 28, 2018 2:09 am
by sproggy
Bill Edmundson wrote:This not unlike Saildrive. ... drive.html
Not unlike them in principle except that all internal combustion saildrives use heavy diesel motors. The 28hp version in the above link weighs 348 pounds - not bad for a diesel inboard but too much for a Zip. And who wants a diesel Zip anyway?! :lol: I reckon an installation based upon a Honda BF30 (for example) would weigh something below 150 pounds. There are electric saildrives available too but the prices are prohibitive and they protrude too far below the hull - cutting up a 10 year old outboard is one thing but cutting up a brand new, expensive electric saildrive would be a step too far.

I have seriously considered (and not completely discounted) making the Zip electric-powered, direct-driving the outboard lower leg with an electric motor mounted inline above it. I'd be able to water-cool the motor using the flow from the impeller and no exhaust or gear linkage to worry about. It's just that range concern - would going electric limit potential use of the boat and/or require carrying too much battery weight?

Happily either option involves the same basic drive method that I'll build the hull to take so I can keep my options open regarding power source until much later in the build. Who knows - by the time I have to take the decision there might have been a breakthrough in battery technology or a change in legislation (there's talk of banning internal combustion motors from some waterways) that makes the decision for me.

Re: UK Zip Build

Posted: Wed Feb 28, 2018 7:24 am
by Bill Edmundson

You hurt my feelings! I have diesel in my Tahoe! I just threw sail drive out as proof of concept.

I had a 27' Hunter sailboat. It weighs 8000#. An 8HP diesel would push it 6MPH. Set-up the way you're proposing, it could probably fit under a seat. I would you wouldn't need more than a 10 gallon tank (or less).

I lied about my feeling being hurt. :wink:


Re: UK Zip Build

Posted: Wed Feb 28, 2018 8:04 am
by sproggy
Hurt feelings aside, I guess the diesel in your Tahoe is a bit more effective than a 28hp twin? A larger boat like the Tahoe, designed for an inboard, won't notice much difference between a petrol (gas) or diesel.

But you've got me thinking - if I could find a used saildrive leg/gearbox and switch the diesel for a PWC motor that might be interesting..... ... 3512285039?

or ... 3451294088?

Way too long, though, by the look of them - I'd have to shorten the leg a load. I guess yachts use larger-diameter, slower-spinning props compared to the typical outboard.


Re: UK Zip Build

Posted: Wed Feb 28, 2018 8:41 am
by hoodman ... drive.html

I don't know if you've seen this or not but I've always thought it was a really cool idea. If you replace the weight of an engine with an equal amount of batties the range might be adequate. Or those plans might help you out with trying to adapt your outboard.

Re: UK Zip Build

Posted: Wed Feb 28, 2018 10:21 am
by sproggy
Yes, I've seen that and spent a good while thinking about it. But I have my doubts that a couple of v-belts would be up to the job if talking about 30-40hp. It would at least need a toothed belt designed to handle the power/torque. Something like a Harley or BMW F800 final drive, for example. I took that solution to be aimed at lower-powered (lower-speed) boats. Maybe just my incorrect assumption based upon the physical size of the electric motor in the photos?

The only benefit I can think of to running that setup over one with the motor driving the outboard shaft direct is that you can change the gearing via the pulleys. Higher power electric motors seem to spin much slower than an outboard (sub-2000rpm?) and there's only so much you can account for with a different prop so you'd possibly need a 1:3 pulley ratio to put that right. Possible with this design, not possible with mine.

I know that Glen-L design is an old one - I wonder how recently anyone has used it?

Re: UK Zip Build

Posted: Fri Mar 02, 2018 4:59 pm
by 283
BillW wrote:Very interesting!

Yes, this has been done before. I think there was more than one brand name, but one that I seem to recall was "Fageol".
This picture came up when I Googled that name. This one looks like it incorporates steering; maybe not.]
That fageol engine looks like an early pod drive.

Re: UK Zip Build

Posted: Mon Mar 05, 2018 7:40 am
by sproggy
Back to the Zip....

I've dry-assembled the stem, breasthook and frame 5 1/2 - all OK except I can't figure out whether the breasthook is supposed to be joined to the stem by anything other than epoxy? Done a forum search and not come up with a definitive answer, nothing in the book or instructions. Any attempt to join the two using screws would seem to mean driving them into ply end-grain. My gut is telling me to trust the epoxy and not worry about adding screws with questionable additional holding strength. What have others done?

Re: UK Zip Build

Posted: Mon Mar 05, 2018 9:11 am
by 283
Use screws, mostly for clamping/assembly.

Make sure you set them back far enough so they are in the way when you start fairing.