Engine Power Ratings

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AusHover
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Engine Power Ratings

Post by AusHover » August 2nd, 2015, 10:31 pm

Hi,

Still trying to decide between the Geoduck, Prospector and Explorer. Leaning more towards the first two as the drop in speed for the gain in payload for the explorer is not worth it for my needs/wants.

Does the prospector call for 72hp @ 4,000rpm? What about the geoduck? I can only see these sorts of specs for the smaller models. Just trying to choose the model taking into account engines available.

I realise it will be less than linear when extrapolating the increase in hp to get an increased speed but what sort of speed are people getting with higher hp at the same rpm on either of these 3 models? I need to cover distance and have the ability to push into headwinds.

Cheers

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bphillip2
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Re: Engine Power Ratings

Post by bphillip2 » August 4th, 2015, 9:27 pm

The Prospector with the original 1.4L engine has a reasonable weight for its size. Larger 4 cylinder engines like the 1.8L EA-82 engine made the craft undesirable to me. A more spartan Geoduck with the 1.3L would out pace most 1.8L Prospectors. Usable speed is much more complicated than just adding power. If there is any wave action at all the Explorer will leave the smaller craft behind, and using much less power. Out in the Sound the 55hp prototype Explorer would leave the 80 hp1.8L Prospector in its wake. The smaller craft with high base loading just could not handle the water as well.

If I understood what exactly you were trying to do I might be able to help better.

AusHover
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Re: Engine Power Ratings

Post by AusHover » August 5th, 2015, 3:44 am

Hi Bryan,

Thanks for that reply, understood.

After John Carter suggested the Honda Fit L15A7 engine, I've been looking at other engine options and trying to see what is economically available and then build the correct craft based on the engine. The Honda engine is readily & cheaply available with very low mileage and could be tuned for power and torque below 4,500 RPM.

I will be building in Papua New Guinea now which will be extremely hard to get parts so I'll have to personally fly in everything I need from Australia.

It will be used for coastal voyages (initially around 80km/50mi each way) as well as exploring offshore islands and inland rivers.

I guess I was wondering what power and toque curve characteristics are desirable for a sev and can I get higher top speeds through different engine selection. Like John, I'm a pilot, I'm not a designer so not looking to redesign the sev - I think it's wonderful whats been done already, just looking to make it work with a newer, more available engine if I can.

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jchovernut
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Re: Engine Power Ratings

Post by jchovernut » August 6th, 2015, 11:34 pm

From the sounds of it, the 20' Explorer would be the craft best suited for your needs: coastal & off-shore excursions. Indeed, the 55hp Explorer performed exemplary on the 1400mi Alaska Adventure. It hauled quite a load, too. There were just a couple instances where higher hp would've helped bucking headwinds, but as Bryan said, wind=waves & increasingly uncomfortable rides!

My tendency towards the Honda Fit L15A7 is an attempt to modernize the plans, & utilize an engine that is quite popular with the experimental aircraft crowd, thus a large knowledge-base to draw upon for installation & operational advice. I'm also considering turbo-normalizing to compensate for altitude, & increase torque at lower rpm. I have tall swamp sawgrass to push through at times, so I'm looking for low-end push, not necessarily high-end top speed. For now, I have to depend on 300hp airboats to blaze the trails! ;)

So, if you were considering a Prospector, I'd up-size to Explorer; you'll enjoy the trips to the islands much more!! ...& take more new-found friends ;)

John Carter
www.hovernut.com
John Carter
SEVs: Vanguard, FanTastic, Prospector, Explorer
Others: StarCruiser, UH-18P, RX2000
http://www.hovernut.com

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bphillip2
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Re: Engine Power Ratings

Post by bphillip2 » August 7th, 2015, 9:21 pm

For more open water use the Explorer will hold better average speeds. You need more hull, not more engine. The Explorer does not cost much more time or money to build, the drive, controls are the same. The hull and skirt are just larger.

AusHover
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Re: Engine Power Ratings

Post by AusHover » August 7th, 2015, 10:38 pm

Thanks for that John & Bryan,

Then what engine weight range is allowed and how many HP@RPM does it call for? How effective is overpowering assuming you could keep the same weight?

Will the 84" paddle prop allow for higher speeds compared to the 72" IVO or 75" Powerfin, assuming all else is the same?

Cheers

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bphillip2
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Re: Engine Power Ratings

Post by bphillip2 » August 11th, 2015, 1:40 pm

The larger the prop for a given hp the more thrust you get, within reason. The 76" is notably better than the 72" in the case of the Prospector. Our 76" prop is also wider allowing reduce rpm and noise.

I would try to keep the Prospector to a 1.3L engine, 60hp and 220 lbs. The Explorer can accept larger 4 cylinder motor. Rpm needs to be 4500 or less.

AusHover
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Re: Engine Power Ratings

Post by AusHover » August 11th, 2015, 7:52 pm

Thanks for that, much appreciated.

AusHover
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Re: Engine Power Ratings

Post by AusHover » April 4th, 2020, 7:26 am

bphillip2 wrote:
August 7th, 2015, 9:21 pm
For more open water use the Explorer will hold better average speeds. You need more hull, not more engine. The Explorer does not cost much more time or money to build, the drive, controls are the same. The hull and skirt are just larger.
Sorry to bring up an old post! Based on this, would a mariner be able to hold better average speeds compared to an explorer on coastal waters?

Thanks!

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bphillip2
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Re: Engine Power Ratings

Post by bphillip2 » April 4th, 2020, 7:33 am

Yes

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