Maximum efficiency prop for a WIG boat

I appreciate your feedback, Ken and others. This craft is not for going up rivers and lakes but for traveling up Puget sound to North of Vancouver Island and into some of those Fjords ... and beyond

Concerning the WIG website you mentioned, I've been told that most there are completely clueless, and the one or two pros sort of gave up. I know aerodynamics so well it's in my blood, so let's not discuss that part, OK?

 

Impressive,

how does that go together with a Diesel propulsion, and a non sensible surface prop (plus additional weight and lalala...)?:?: :?: :?:

No, Starman.

You are just another example of a guy searching for confirmation of his preconception, no matter what the experts say.

When asking the experts, one should rethink a biased opinion, or prove them wrong.

Regards
Richard

 

Starman,

I warned you myself about most of the enthusiasts on that forum. Clueless as those are, there still are some very insightful posts by real experts, and references both in those posts and in the documentation on site are scholarly work with empirical data to support it. No public forum will be populated only by experts, including this one. This site has all sorts of people who propose ridiculous ideas and insist they know more than the experts. The purpose of a forum such as this one or the se-technology forum are to let non-experts ask questions and get reasonable advice, or at least peer review.

So, a question about your design that comes screaming into my head:
Could you please explain how overpowered (with ridiculously in the same sentence), travel (presumably meaning distance traveled or range) and aircraft can reasonably be used in the same context?

The one WIG I have actually been in while flying is a UH-18spw. As a hovercraft it holds up 6 large adults easily, and while I haven't gone fast with that many people in it I have gone 60 or so with 3 people who totaled over 600 lbs. Top speed is 70+ as a hovercraft, I frankly don't know how fast mine goes. Edit: Mine is a UH-18sp, no wings.

As a WIG, I've seen one take off with 3 people and go 55-60 mph.

It's not a very good WIG by the standard measurements, in the sense that it flies slower as a WIG than it does as a hovercraft. In spite of that it flies with 85 total horsepower for the duration of your fuel supply if you have room and inclination to do so.

Those numbers aren't very impressive to a WIG person, but this machine actually works as advertised. It's not even designed to be a "good" WIG, it's just a recreational hovercraft that you can put wings on and go cruise. It's another thing you can do with a hovercraft you may already have, if you're into that.

I consider the UH-18spw to be a good example, because you with aerodynamics in your blood will no doubt design a better WIG than that, so the numbers I gave would no doubt be less impressive than yours.

So why is it that your apparently 4-place WIG (based on the Lippisch drawing that has vanished from this thread) requires 500 hp on board in order to go 90 mph? Why is it that something purpose-built as a WIG weighs 3 times as much as a 6-place hovercraft? Where the heck are you going to put that extra 400 hp engine? Have you even been in a car that has 400 actual hp?

I don't present myself as any sort of an expert. My only qualification is that I have actually been on real water going over 60 mph on an air cushion machine I built with my own hands, and that I've been running air cushion vehicles for about 15 years now. And that I have directly watched 4 separate WIG designs which successfully carried at least one human, in person.

The UH-18spw, I've seen any number of people build that --Edit: usually with bigger engines -- and try to get it airborne. The ones who thought a huge engine was the answer generally didn't even get it off the ground. With WIG craft, horsepower is NOT the solution to a bad design or a bad implementation. Horsepower generally doesn't speed you up or make you fly better. All it does is reduce your final payload capacity and lower your range.

On the other hand, I've seen several people build it per plan and get it to fly just fine.

You, with aerodynamics in your blood, probably know something that none of the other aeronautical engineers in the world know. I'm guessing, because none of them add huge engines that won't have any benefit, nor will they generally put in an engine which is not used during flight.

Best of luck.

 

Frankly, looking back at this thread, I don't really understand why you're arguing so much.

You made a proposal for a vehicle. Just about everything anyone is telling you says that you would get a better solution by spending less money and having less complexity. There are other concerns about the nature of WIG craft and with operating at high speed on water, but these are problems that can be worked through with discussion and reading and some experience with something a little bit slower.

Most of the objections I have regarding operation on rivers probably apply every bit as much on your stated cruising ground as they do where I've been driving.

True, we've been saying some of your ideas don't make sense. The thing is, the solutions we're offering are much simpler and much cheaper and will certainly get you going further on a tank of fuel, and have a higher probability of actually reaching your speed goal.

 

I explained that four times and won't do it again, so if you haven't seen it by now you never will, partly because i deleted it. Nor did you see or understand what i said about stability and range. Nor did you see what I said about span dominated versus chord dominated ground effect nor even try a little bit to understand the implications of what that was all about. Not just you by the way, but the others too.

 

The village idiot always underestimates his enemies, doesn't he.

But you are right, I didn't come to a boating forum to ask a question about water prop efficiency. I posted here on the propeller forum so I could get a bunch of freaking armatures who know nothing about aerodynamics and can't read to pat me on the back on an idea that doesn't meet their limited scope of experience.

There may have been someone out there with enough intelligence, open mindedness, and knowledge of aircraft stability and aerodynamics to study what I was saying, and they might have learned something.

You all objected to everything, when you could have asked. For example the high gross weight is because the design range is 3000 miles and so it needs to carry a lot of fuel. I SAID it was a long range vehicle in the first POST! And the diesel? Don't get me started, I can chop your little tiny head off. I know you were just trying to be helpful in your own perverted way, but you know, go take a flying leap.

I realize I was an idiot for going further on about this than just the prop efficiency and I do appreciate the answers about prop efficiency.

 

You are wasting our time and efforts mate. And it is quite obvious that you are NOT the aerodynamics expert you claim to be.

Bye, bye...........

 

My ideal cruising boat would be a hover craft lifting spud barge with an out drive.

An air prop (by my rule of thumb) will create 5 lbs of push for each HP ,7lbs being the "theoretical" max.

A water prop can easily do 20lbs per HP with 25lbs being common on a good setup.

So to save 4/5 of the fuel the water push is my choice.

There are many localities that restrict anchoring with complex laws.

The cruiser would simply NOT anchor , just jack it self 5 ft up its spuds.

Then 2 black balls would be exhibited "AGROUND" , no laws against that (except in the FL Keys).


The wakes of passing marine motorists are seldom over 5ft , so the cruising should be fine.

FF

 

Dude.

Chord dominated lift puts the G in WIG. It's part of what causes a WIG to stay close to the surface. It rapidly loses its efficiency and stability as it gets out of ground effect. Regular aircraft (at least low speed aircraft) have span dominated lift usually, so they are efficient and stable in free flight. We got it. You showed a Lippisch WIG in a post before I made my first post. I figured you were following that design for the most part, which is a known quantity.

What it seems to me that you were suggesting (if my memory is correct, and it may not be) is that you want to be able to fly higher than a typical WIG wants to fly, and get some more stability by increasing the span. That's a huge and well-documented problem all by itself, if that's what you're really driving at.

But you're putting the cart before the horse, which is why everyone is talking about engines and weight and props while ignoring your WIG-specific questions.

There's a fundamental flaw in what you're telling us about your machine. It's like asking about automotive tire tread patterns, and you're showing a drawing of a car with square wheels. Chord dominated vs span dominated ain't gonna make any difference if you can't fly to begin with. Range ain't gonna happen if you're carrying that much extra weight that has nothing useful to contribute. You're permanently removing the ability to carry 3 or more passengers -- OR that much weight in fuel -- because you want to drag around some unnecessary equipment.

If you deleted your posts, you must have been so incredibly embarrassed by whatever was in them that you couldn't bear to have anyone read them, right? FWIW netiquette disallows that for very good reason, and enough so that most forums I've been a member of won't allow you to delete a post. Netiquette also dictates that if you need to edit a post it should be for clarification only, and it should be evident that the post was edited to any user.

So, had you explained exactly once, clearly, and left that post there, then we could revisit it and discuss it intelligently after we dealt with the fundamental problems we all saw as people who had real experience with certain aspects of your project. Instead you felt the need to ignore our concerns with those fundamentals, the results of which will change any facts we might be able to give you regarding your other questions.

On top of that, you've started using profanity and insults in combination.

I think Richard is right. You're wasting all our time and effort.

 

Listen, Kroberts, you aren't so bad, but I wasn't embarrassed by my posts, I just don't want to make the great effort to explain the design theory behind this to people who look at some of the details and complain about them without trying to see the bigger picture, and I would rather leave all the 'experts' in the dark until I get this thing flying. I made some very good points and they were completely blown off, and it's because it hasn't been done this way before so you can not see it. It's true that this design might have some problems, I am well aware of what those problems might be, and they have nothing to do with what you guys think. I had no intention of getting advice on design here and I apologize for wasting your time, just assume you are looking through the wrong end of the telescope, which is an assumption you can not make.

And you can rest assured that I won't waste any more of your time with design theory. I didn't ask for or want your opinions (except for prop efficiency), but you give it anyway and then complain about it.

Making things up and disagreeing with them is the international sport of the forums.
__________________

Edit: And THIS is a real jewel:

 

Starman,

If you're not after design advice, then why are you here? Look at the forum you're in. What is a discussion about chord dominated lift vs span dominated lift if it's not a design discussion?

Up until that post I thought I had a reasonable handle on what you were asking, even if I wasn't taking it in the order you thought I should take it in. Now I have absolutely no clue what you're talking about.

You're trying to protect a potential patent? Fine by me, just say that.

Yes, I and pretty much everyone else did blow off some of your points, in the interest of clarifying or correcting what we saw as critical design flaws.

I'm not an engineer, but WIG craft are not a theory for me. I have in my garage a machine which could be converted into a WIG in less than a weekend. I've helped convert the same model of machine to a WIG, and it took a weekend. I'm familiar with them, first-hand in every way except actually flying one. My objections are not theoretical in any substantive way. My objections are that machines which were less "out there" than yours have failed to fly, in my presence. WIG craft, by just about everyone's assertion, are more sensitive to design changes than aircraft are, and can potentially be more deadly in testing a bad design.

You must realize that in order to answer your questions we need to know something about your design. You must realize that those people who have any sort of experience in anything even similar to what you're doing will speak up when they see something they consider to be a problem. That's what we're doing.

Good luck and have fun.

 

I came to findout about efficiency of water props, I think that's the title of the thread, in case you missed that, or my first post.

Yes, I looked at the forum I'm in, it says "props", that's why I'm here.

There is no discussion about chord versus span lift. I mentioned it and it was ignored.

There's NO discussion, get it? I'm beginning to suspect your intelligence.

I have no interest in patents, I just don't want to teach you, why can't you get that?

Also, your little toy airboat has nothing to do with aerodynamics, it is a flying mistake with no aerodynamic engineering behind it. Just go away, I will soon.

Edit: by the way, Daiquiri had intelligent comments but misunderstood what I was getting at due to the limited words I used and I didn't want to iron it out with him.

 

Starman, the question about propulsion efficiency cannot be properly adressed until we have something like a basic idea of the resistance of the craft as a function of speed. As I mentioned before, overcoming take-off resistance is a balance between drag reduction and thrust. The thrust characteristics of ventilated propellers (which is what we would have in your case) has a dip in the speed region, where the WIG actually needs high thrust. If my memory serves me correctly, there are some WIG's propelled by outboards, and in those cases, the propeller is actually controlling/limiting the flying altitude.

All fully submerged propellers (air or water) obey the same physical laws. High thrust at low speeds come with low efficiency and vice versa. Again, without knowledge of the craft's drag it is not possible to say anything like "Air propeller has x % efficiency"; it depends primarily on speed, thrust and propeller diameter. So: a preliminary drag curve is essential in order to have a starting point for the design spiral.

 

Daiquiri did not misunderstand a single word, be as sure as I am. He just knows what he is talking, you don´t.

As mentioned before, you are a waste of time....

Go, build your crap and dream along for your 3000 miles Arneson transporter.

Richard

 

Go to the home page and look over on the upper left where it says 'Design', then look a bit lower and to the right of that, what word do you see there, you *****? Then look down the list and see what word comes after sub- , which word is that?

What he said is something I'm already quite aware of but it wasn't that pertinent to the design, and you have no idea what I know .. and yet you seem so sure.

You are wasting your own time here, Richardo, but if it's fun then go for it. I must say, I enjoy lowering myself down to your level.