Cummins/Arneson questions

Hi Folks,

I'm new to the forum, although I have been lurking for a while, and I am quite interested in surface drives.

I have a Cummins 6BT which I am planning to put in a 22' crew boat style welded aluminum pleasure/work boat (yet to be built, so I can design around the propulsion system), and I am quite interested in the Arneson surface drives. At 160 HP stock, and 250 - 300 with minor modifications I think the ASD6 would be the best fit, but my budget does not allow for new drives. In the used market ASD8's seem to be much more common. Would an ASD8 with a zf 280-1 be workable on a 6BT, or is that not enough engine?

Cheers,
Eli

 

Welcome to the Forum Eli.
Re the 22' ally crew boat which you will build in due course, are you planning on designing her yourself, or do you have a set of plans already?
If you have plans already, do you have any links or drawings that you can post?
I am just wondering why you specifically want to use an Arneson surface drive, as opposed to (say) an outdrive leg?

For reference, here is some info on the ASD8 - http://www.twindisc.com/downloads/ASD08.pdf

And on the Cummins 6BT - Cummins 6B / 6BT / 6BTA 5.9 Technical Specifications https://www.sbmar.com/engine-info/cummins-6bta-specifications/

And some info re the ZF 280-1 gearbox mentioned - https://www.performancediesel.com/wp-content/uploads/DS-ZF_280-1.pdf

 

Hi Bajansailor,
Thanks for the reply, and the links!
I'm pretty familiar with the 6BT, as I own a dodge first gen, and do all the work on it myself, but not sure how the power ratings on the drive and transmission would match up with it. I love the reliability, and the fact that I know the engine fairly well. The engine I have has not been marinized, and is from a low mileage truck. I found an ASD8 with the ZF 280-1 for sale, which is why that gearbox in particular. I will be designing her myself, with the help of a friend who is a retired ally boat builder. Plans are just in the early concept stage, but looking at a small cuddy cabin up front, forward controls, open back small cabin, self bailing deck, 6' wide plate for the hull bottom flairing to 8' at the gunnels, 10 - 14 deadrise at the stern, increasing forward. I'm building for the Georgia Straight (West coast of Canada), so not offshore, but does get pretty rough, think 50 knot winds, 80 knot fetch, tides, not that I would want to go out in that with this size of boat. I have always been fascinated by surface drives, and like what I have read about maintenance and efficiency. I am also quite interested in a tunnel hull surface drive configuration such as The Integral Vented Surface Drive http://nava.ca/power.htm Currently looking for more info on that system.
An outdrive leg would be my next choice, and I can probably get something used for a reasonable price in my area.

Cheers,
Eli

 

Thanks for this update Eli.
Re marinising your Cummins, others on here have experience of this, but it will not be an easy job.

Re designing the boat yourselves - please be aware that it is not as simple as it might initially appear.
Especially so if you want to use a surface drive - these are very complex beasts indeed.

Do some research on aluminium boat plans available 'off the shelf' - here are some typical examples.
Mono-Hull Boats | Aluminum Boat Plans & Designs by Specmar http://www.specmar.com/aluminum-boat-plans/monohull-boats

Specmar even have a boat with a surface drive, although it is a bit bigger than 22'
26 FT Orca, surface piercer drive (1305) | Aluminum Boat Plans & Designs by Specmar http://www.specmar.com/aluminum-boat-plans/monohull-boats/26-ft-orca-surface-piercer-drive-1305

These folk downunder have a wide variety of aluminium boat designs which are probably worth browsing for reference -
Plate Alloy Australia - 7m Monohulls http://www.platealloy.com/7m-mono.htm

Range | CNC Marine https://cncmarine.com.au/range/

Aluminium kit boats, Australian Designed Boats, Boat Plans | Turtle Marine https://www.turtlemarine.com.au/page/alloy-boat-kits/

Alum Boat Designs | Designer Boats http://www.designerboats.com.au/alum-boat-designs/

 

Surface drives are a specialised thing, and that is the reason they are not commonly seen on "ordinary" boats. One hitch is you can't trim the boat that easily with them. You can trim the drive down to drop the bow, but if circumstances have you wanting to raise the bow, you can't raise the drive without losing traction, as the prop rises out of the water. That sort of mandates having a boat that is inclined to run nose up and porpoisy, and using tabs or interceptors to accomplish the trim function. But if the boat does not have a design that allows the bow to rise easily, you have a problem.

 

I’m very skeptical that your planned use of Cummins truck motor will work out well as a marine motor.
Truck motors are usually derated for marine use rather than increasing hp.
I see you’re familiar with sbmar.com, so I’d suggest that you post your idea on that forum for some real expert advice.

 

I suggest you start with a statement of requirements (SOR). I know this advice is everywhere in the forum, but it is the best. Do you need a surface drive, or is it something you want to play with. Surface drives are not a good choice for a first time builder and designer. They are very finicky to make work properly. Also, why do you want to design the boat? If you are doing it as a hobby, which I support, think of what you are designing and building as a prototype. That means is won't be very good, but is a learning experience. After you launch it and find the defects, start cutting, welding and modifying until you get something decent. At that point, you will be able to design and build a better performing boat. All in all, it is a lot of fun.

 

Thanks for all the input!

regarding designing my own boat(s), I have designed and built two welded aluminum boats so far (an 11 footer and a 21 footer) and both considerably exceeded performance expectations.
I think it’s a fascinating process, and will probably have two more behind me before tackling the boat in the thread above. I also have hands on advise and assistance from a retired fabricator who was a partner in a boat building company for many years.
On the Cummins front, I have acquired a Borg Warner AS1 71 (1:1) plus damper, adaptor, and oil cooler, and I’m working on lining up the sae 3 bellhousing. If I can, I will design around the stock horsepower, with any boost being primarily for getting over the hump. My understanding (and I will be doing more research on this) is that the Cummins 6BT marine engine is the same block and head as the pickup engine and the marine ones I’ve seen are all rated well over the pickup truck’s stock 160. I plan to run inside keel coolers, and a dry exhaust, so the engine side should not be an overwhelming project.

Regarding surface drives, it is definitely something I would like to play with, and if I go for a non trim able design ala nava.ca I would be quite prepared to cut and weld until it runs the way I want, if it’s necessary.

Thanks to bajansailor for the design links - I have spent quite a bit of time studying similar designs on the internet, including from some of our better west coast designers. I have admired several of the specmar designs for quite some time.

If anyone has suggestions for surface drive design reading please let me know.

Cheers,
Eli

 

Not sure if I am permitted to post links, but here is a YouTube timelaps of the 11 footer I just finished.

 

Thanks for the Youtube link Eli - you and your friend are obviously very accomplished at aluminium boat building.
Your skiff is a nice design, and she certainly goes along nicely.
She dos look rather 'heavy' though, especially with that double bottom floor - dare I ask how much she weighs?

Re the design of your bigger 22' boat, will you do it the same way as with the 11' skiff, re building the model first?
(Or did you use a CAD program for the design initially?)

 

I think its probably 250-300 lbs. I should figure out how to weight it It is a little on the heavy side for its size, but I really like self bailing decks, and I wanted to be able to beach it wherever without worrying about it. On the plus side it handles more chop than it would if it were lighter.

I think so. I will print the grid onto heavy card stock next time. It was actually a really fun process, and I did several models till I had one I liked. I looked at CAD options, but there is not much out there for Mac, at least not cheap. I have used Onshape a bit, but it's not really optimized for boat building. From what I hear DelftShip is one of the best free/cheap options out there, so eventually I'll arrange a windows setup to try it. I would like to be able to model the displacement and CG more accurately.

Cheers,
Eli