How much Horse Power do you think this needs?????

Thanks Ilan
we had the Hovercraft discussion here on his first thread (and I was one of the supporters of that solution)

http://www.boatdesign.net/forums/boat-design/amazon-river-loadum-up-26486.html

Regards
Richard

 

Apex, I did not know this interesting thread...worth to read it. So I suggested an already known solution.

Yes, for "fast" transportation an hovercraft in river conditions is unbeatable. I have a Colombian friend working on the problem of river transportation and it appears that hovercraft is the solution for light loads; it can be built locally ( complete with engine etc...) for less that the price of the Yamaha 150 HP outboard engine moving the same payload boat.

The main problem in rivers is the propeller and transmission that are broken regularly by hitting something...it's very expensive and you can add that the carbureted 2S are very thirsty, and the 4S too expensive. Trials have been made with marine diesels with no good economical results.

Another solution is the flat boat powered by car engines and aerial propellers; it has also its pros and cons.

I think the main problem is economics: marine engines are very expensive and have to be bought in dollars, spare parts are out of reach of most people.

On the other side you can find in Latin America a lot of reliable car engines that can be used on a small boat or hovercraft like the old Nissan Tsuru model, Chevy, Ford Ranger and others, easy and "cheap" to maintain.

 

Here is another data point...

I'm running a mod-V flat-bottom aluminum boat (jon boat style), 26 feet in length, 60-inch bottom width. With a 4-stroke 115hp Mercury outboard, it will plane with 12 people aboard and run about 30mph. However, the boat does have a pocket tunnel. I suspect with a full hull you could easily achieve 30 knots sustained. Also, it has a custom propeller which will make a difference. Despite its 60-inch beam, it is very stable, owing to its flat bottom. Lightly loaded, the same boat will run close to 40mph.

For your needs, in a relatively calm river, you need a flat bottom with square chines. As others have pointed out, the Fugimori may be your best bet with a modern FI 150hp outboard running a well-tuned stainless steel prop. If boat proves stern-heavy, you can add floatation pods to the transom, a practice becoming more common among jon boat builders. If you need to build, the Panga style is not a bad one.

 

Sorry, I'm curious for the reason why not. Please point me to where I can read or explain the reason. Thank you.

 

That was a good one mate!


I recommend to read the thread I posted above!

Same recommendation for Fanie. And do you remember your own thread Fanie? http://www.boatdesign.net/forums/multihulls/multihull-fast-flowing-water-28116.html

Regards
Richard

 

A Fugimori is overpowered with 150 ponies...over 100 HP you're making foam and spray, it will be a waste of gas and money. A panga (we have many here) is not a very good boat in sea but a very good one in flat waters; a 26 feet takes 6 to 8 people with 85-100 HP.

If you want to save the transmission is better to have an aluminum propeller; cheap, easy to repair with a simple LPG torch and zinc alloy, easy also to tune by 1/3 to 1/2 inch of pitch. When it hits something it breaks before destroying the pinions of the transmission. Ok it's better to have some spare propellers...

The problem of expensive outboards on river boats could be -maybe- resolved with aerial propellers and car engines. I see some advantages (and inconveniences) also to this solution; mainly economical. A wood propeller is not very difficult to make and equilibrate, the transmission may be made with industrial and common elements, the complete engine can be found in a junkyard.

Cats are rather fragile on river among rocks, trunks and other obstacles; flat boats stand more abuse, and are simpler to build and repair.

 

Yes, I should have qualified "relatively calm" - what I meant was waters with waves typically less than three feet.

I read the loadem up thread and have not really changed my opinion, other than perhaps Ravencry should find a 30'-33' Fugimori and outfit it with twin 90hp Yamaha two-strokes - they are carbed and, although they will use more fuel, they will likely be cheaper to maintain in the long run.

I regularly run a river here that typically has 3-4mph current, plenty of snags and sandbars that change positions overnight. That is why I run a pocket tunnel. Although the water is murky, with visibility less than six inches, the river tells its tales and I don't hit anything with the prop that I can't see. I should caveat this with the fact that I run a raised helm so I have good visibility which is key for running dangerous rivers.

 

I've changed my opinion to a larger Fujimori with twin 90hp Yamaha two-stroke motors. As I said earlier, I am running 115hp on a 26-foot aluminum and the power is usually not wasted. It runs close to 40mph lightly-loaded, and 30mph loaded with 12 people. Any less HP and it would likely not plane with 12 people, especially with a standard prop.

I have run many different boats on rivers over the last 20 years. I have bent/broke two propeller shafts and both of those have been with aluminum props. Now I only run stainless steel props on rivers, but I also run them with (pocket) tunnel hulls. When running on plane, I run through six inches of water, and four inches over short distances (sandbars). It is very hard to hit something with a propeller with a well-designed tunnel hull unless you are not paying attention. The river I run in has visibility less than six inches, but the river's surface and current will tell you where snags, sandbars, etc. are hiding when they are less than a foot from the surface. Also, to my knowledge, know one makes or modifies aluminum propellers that will run efficiently in a tunnel hull. When not on plane, the boat is running slow enough that the rubber/delrin hub on the SS prop takes the hit rather than the gearcase.

Since the OP's requirement is for a heavy payload, I don't think air-powered machines will fill the bill, at least not without a LOT of HP which equals a LOT of fuel. Flat-bottomed aluminum is the way to go.

 

Village;

-The Yamaha sold in Latin America are of the Enduro Line, which are very different from those sold in the States. Practically the lone common feature is the logo Yamaha. The consumption and emissions have nothing in common also. The 2S Enduro have a TBO (time before overhaul) of 1000-1200 hours, that's about one half of the TBO of any 4S.

We use here these Yamaha Enduro so we have direct facts from experience and the difference of consumption is so high that in ONE year (800 hours about) you have over-spent in gas and oil almost the price of a brand new 4S of similar power...

I've spent many hours in meetings with the authorities 11 years ago to convince the fishermen and dive shops to switch to the 4S mainly because of pollution and protection of the reef barrier...We heard a lot of protestations but some switched and after 4 years everybody was using 4S as the advantages are blatantly evident.

The Enduros and small 4S sold in Mexico have not nice amenities like delrin and such transmission savers...directly bolted on the shaft in the old fashion way. As the boats here have to beach 3 or 4 times a days you can imagine the results of hitting with a pretty strong inox propeller ... the pinions of the transmission lose the teeth and sometimes the carters are broken.

Think that in Latin America, where the consumer is not protected and has no way to sue in court (the judges are in permanent sale to the best bidder) the quality of the goods you can buy cannot be compared to the quality of a similar good bought in a First World Country. For example the best warranty that gives you Yamaha in Mexico is 6 months or 300 hours; in clear NOTHING.

The Fugimori are very similar to the boats used in Mexico made by IMEMSA and others, and in Colombia by Eduardoño. A lot of people try to get more speed on such boats putting "big" engines with no results; I made the demonstration 8 years ago with 2 identical 26 feet IMEMSA loaded with the same weight (8 divers) one with a 100 HP 4S and the other with a 150 HP 2S. The difference of speed was minimal (less than 2.5 knots) but the consumption of the 2S was simply almost twice the consumption of the 4S...

About air screws; I can say that a ducted 5 blades propeller is a very powerful fan and moves big loads. That have succesfully been tried in the French Navy about 14 years ago for use in Central Africa.
There are also Russian heavy hovercrafts with no need of high speeds used in Siberia on the rivers all year around (water, snow and ice) and the power used has nothing tremendous.
These kind of propellers have nothing comparable with a plane propeller. The efficiency is rather good.

In Latin America is simpler to go to polyester, almost nobody is qualified for aluminum. Simply too expensive.

 

I thought it was almost ALL said in the "Amazon" thread. And for sure the most economic solution IS a hovercraft. But Ravencry had some arguments against that. Probably the boat he showed us in the first post is a sensible vessel for the use intended, when properly powered of course.

 

Yes Apex almost every thing has been said about the subject. Like you, and my Colombian friend, I think that for fast transportation on river, navigable or not, the hovercraft is the best option. Some other people, in Siberia for example, share this opinion.

And for powering a "classical" boat on river a 4S outboard is a good option. I didn't talk about the 2S with direct injection like the Mercury Optimax and the Evinrude Etec as I have not first hand reports about them. It seems that the Optimax has some problems of reliability but there is not reliable statistics nor reports.

I'm afraid that these sophisticated 2S are a bit over the abilities of the local mechanics and local gas quality. A computer is needed for any job on them. It's the same problem with the 4S, thus I have proposed the idea of 2 outboards of 50-60 HP as these engines are "carbureted" and as simple as a small motorcycle. Very reliable also; a friend of mine has a Mercury 50 HP with more than 2400 hours running as strong as the first day with simple maintenance. I must add that this friend knows only 2 positions on the throttle; iddle and WOT. That simplifies the tuning of the carburetors...

 

Did´nt know there are two strokes with a "dual system" throttle on the market...

 

If the Fujimori is similar to the Panga (IMEMSA), then that may be the most sensible way to go.

Perhaps the solution is to run two lightly loaded Fujimori boats, each with a 60hp 4S "Bigfoot" outboard. Again, I would be very careful not to underestimate the significance that the design of the propeller itself can lend to performance.

 

Idiot, your statement is totally illogical, like the former other statements:

-1 You have to use the good length of foot as required fot the design. As nobody in the forum, except Ravencry, knows what length is asked by the Fugimori, you can't state that a bigfoot is required.

-2 With 60 HP a Fugimori even lightly loaded won't go far over 15 mph. Maybe 17 or 18 mph if very light. Too much wetted surface as the boat is almost flat, and the wetted surface changes very little with the weight, so the speed. And 15 knots is not a good speed for a such boat. This kind of boat begins to plane at about 10-11 knots and will be fully planing at 16-17 knots.

The goal is to load the boat to his designed weight and to make a decision of speed. 15mph or 13 knots IS NOT ENOUGH speed to take full advantage of planing after the hump of drag in transitional regime. You need to go at least at 16-17 knots and that won't ask for a lot more gas consumption...

At 60 HP the poor little engine is screaming at 100% of its power; it won't last. If you want that an engine lasts at the full potential of its TBO, it must run at 75-80% of its max power. Interesting fact also it's where the torque is at the maximal value and the specific consumption at its best value.

So let's make some very basical powering engineering.

1/ Asking the designed displacement of the boat to the shipyard, and maybe they have the drag values.
2/ Calculate the optimal dead load and its center of gravity so the boat has a good LCG, convenient for the target speed.
3/ Calculate the power needed for the target speed and for the planing boats the power needed to go through the drag hump. In clear to get the boat out of the hole.
4/ Examination of the specific consumptions of the different suitable engines. A fact has to be taken in account; outboards have too small propellers, specially when you go to the higher powers. Morality the efficiency of the propeller of a 60 HP is better that the efficiency of the propeller of a 120 HP as the diameter changes very little.
5/ Other hard fact we are in the rain forest; a carburator is easier to maintain and fix than injection. More if the gas is of low quality. And it appears also that in small engines the injection does not improve really the specific consumption.
6/ That leaves one good candidate:
The FT60BETL 60HP 4S 120kg 4 carburators 19.5L hour at WOT 244gr/HP/h at WOT, 225gr/HP/h at 75-80%.
For comparison the two strokes E60HMHDL 60HP 2S 105kg carburators 25.5L hour 319gr/HP/h burns 31 % more gas for the same power!!!!
7/ the 115 HP is with injection and the specific consumption is higher than the 60 HP. Normal its propeller has a too small diameter, the efficiency is lower. It weights 190 kg.
8/ 2*60HP weight 240 Kg only 50 kg more than the 115HP.
9/ Conclusion: it's very probable that the 2*60HP 4 strokes is the winner combination.
a/each engine weights 120 kg, easy to take out and move.
b/very but very simple engines and very strong.
c/in remote places 2 engines is not a luxury, it's the insurance you arrive.
d/used at 75%, so 90HP the consumption per hour will be around 27 liters/hours, and you can compare with the 60 HP 2 strokes 25.5 liters/hours, but the speed won't be no more 13 knots but 17 or 18 knots. Look know at the total consumption; 18 hours*25.5l= 459 liters with the 2S, 14 hours*27= 378 liters, so 80 liters of gas less...Morality you can go at 17 knots consuming 20% less gas with 2*60HP 4S than 13 knots with the 60HP 2S for the same travel...Just a bit less luggage to keep the weight good.

Now I have to do some true engineering for repowering a 36 feet, so I go back to work.