Why are props at the back of a ship but at the front on a plane?

[Cadence]

Originally Posted by ZULU40

The canard aircraft is a special proposition. For safety reasons the canard must always stall before the mainplane, this to guarantee that during a stall the nose of the aircraft drops, and airspeed is recovered so that controlled flight can continue. This is known as the stall fuse.

Moving on to a single engine tractor configured canard aircraft, its obvious that unlike conventional tractor types, the flow from the prop will almost completely envelope the canard, and therefore too much within its influence. It is too unsafe and that is why we dont see any except for a tiny few experimental types and Rutans push pull Defiant.

Canards can be more efficient wingplans in some areas of flight, nominally cruise speed, however in order to do so they give up efficiencies elsewhere. Rutans famous VariEze and subsequent LongEze coupled the canards performance with a very good use of weight saving, but the package comes with higher stall speeds, smaller cabins, and longer runway requirements.s

How did drift get to aircraft and canards.

[a64pilot]

Originally Posted by Guy

That is pretty deep man, check out the new Honda jet.

That wasn't done for lift, it was done for cabin room, and to some extent structure.
However there were a few Russian STOL designs that used engine thrust to augment lift

[a64pilot]

Originally Posted by Cadence

How did drift get to aircraft and canards.

More interesting than a tractor configured boat?
However I am real weak in Physics, but believe it is more efficient to pull than push, reason why trains are pulled rather than pushed I think.

A Canard is more efficient to a great extent because both ends are lifting, where a conventional aircraft, the wing lifts, but the tail pushes down, working in opposition like that, is less efficient. Needs to be that way so that if you ever stall the tail, the nose drops and the aircraft will self recover from a stall, if the tail lifted and you stalled it, that isn't recoverable, think deep stall on a T tail jet, it's not usually recoverable.
A very few designs have existed where both ends lifted, but they usually quickly earned the name Widowmaker

[ZULU40]

Originally Posted by a64pilot

More interesting than a tractor configured boat?
However I am real weak in Physics, but believe it is more efficient to pull than push, reason why trains are pulled rather than pushed I think.

A Canard is more efficient to a great extent because both ends are lifting, where a conventional aircraft, the wing lifts, but the tail pushes down, working in opposition like that, is less efficient. Needs to be that way so that if you ever stall the tail, the nose drops and the aircraft will self recover from a stall, if the tail lifted and you stalled it, that isn't recoverable, think deep stall on a T tail jet, it's not usually recoverable.
A very few designs have existed where both ends lifted, but they usually quickly earned the name Widowmaker

Lifting tails are not that unusual. What needs to happen is the lift coefficient needs to be maintained within limits. So in the sum of lifts (we arent dealing with the calculated Cl in a tunnel environment) where tails are 0.9 Cl, Mainplane 1.2 clean, canards if there are any 2.0. In that way the stall fuse is always contrived favourably.

As to canard efficiency, this is only because it isnt in the wake of a preceding wing (unlike some tails). And in the case of a canard, the mainplane as a rule of thumb is 2.5 chords back to reduce wake effects, and where its full span isnt affected anyway

It might seem a mess, but the constraints are well known, most only resurfacing because of the US experimental category of light aircraft, where they appear to be less well known .

[model 10]

Originally Posted by a64pilot

However there were a few Russian STOL designs that used engine thrust to augment lift

So does the C-17.

[Divevac]

Most older large aircraft (like the Navy P3 - Lockheed Electra\Orion) required high speed prop wash to contribute a considerable amount of lift to small wings. I assume it is the same answer for boats: prop wash over the rudder assisting maneuverability under power.

[Cadence]

Originally Posted by ZULU40

Lifting tails are not that unusual. What needs to happen is the lift coefficient needs to be maintained within limits. So in the sum of lifts (we arent dealing with the calculated Cl in a tunnel environment) where tails are 0.9 Cl, Mainplane 1.2 clean, canards if there are any 2.0. In that way the stall fuse is always contrived favourably.

As to canard efficiency, this is only because it isnt in the wake of a preceding wing (unlike some tails). And in the case of a canard, the mainplane as a rule of thumb is 2.5 chords back to reduce wake effects, and where its full span isnt affected anyway

It might seem a mess, but the constraints are well known, most only resurfacing because of the US experimental category of light aircraft, where they appear to be less well known .

I know canards prevent a stall? Should we put them on our hulls.

[ZULU40]

Originally Posted by Divevac

Most older large aircraft (like the Navy P3 - Lockheed Electra\Orion) required high speed prop wash to contribute a considerable amount of lift to small wings. I assume it is the same answer for boats: prop wash over the rudder assisting maneuverability under power.

Unusual case tho
Orion has the highest power to weight in the RAAF, and can blow the doors off the F18A from slow to go. Russians do the same with the Bear. They slow down, jets keep behind, Bear lights it up and poof gone. Jet fighters even on reheat cant accelerate fast enough.

Orions narrow wingspan serves it well as its a low altitude ASW aircraft, and its clipped wings thus provide enhanced status to manoeuvre at sea level. You are right the lesson is similar tho, energised flow keeps the control surface alive.

[ZULU40]

Originally Posted by Cadence

I know canards prevent a stall? Should we put them on our hulls.

they dont prevent stalls at all

[Cadence]

Originally Posted by ZULU40

they dont prevent stalls at all

I thought they did on experimental aircraft way back when. I just don't see it boat related?

[Rorzech]

I would think it's just common sense that is the end which is usually in the collision, and like I hear all the time is if you're going to have a collision then aim for the least expensive part. Who wants to be running aground prop first all the time and snagging all the old nets and rope floating in the water? You can go and put the heavy engine in the front of your boat if you like and I'll keep mine where it is.

[Flyingriki]

Originally Posted by ZULU40

they dont prevent stalls at all

Incorrect.....

[daga]

Have you looked at Voith-Schneider drives? (Voith | VSP Voith Schneider Propeller) They do not use props at all but one or more 'drives', frequently at the front of the boat.

[buzzstar]

Originally Posted by JasonDS

I'm interested in humorous and technical reasons. I'm no engineer (as you can tell) but don't hold back on the technical reasons, I can always look up big words.
Has anyone ever build a ship our boat with the main drive at the bow (not counting bow thrusters) ?

I, like the op, quoted above, am not an engineer, but I can look up both the difficult technical words, as well as the often more elusive and devious simple ones, in particular those which may cross over into technical jargon, as well as into languages other than my own. Accordingly, feeling I was best equipped to deal the the humor potential, I replied, by stating the following:

Originally Posted by buzzstar

Let's face it, no one disagrees the canards can fowl the improperly positioned prop.

Originally Posted by ZULU40

The canard aircraft is a special proposition. For safety reasons the canard must always stall before the mainplane, this to guarantee that during a stall the nose of the aircraft drops, and airspeed is recovered so that controlled flight can continue. This is known as the stall fuse.

Moving on to a single engine tractor configured canard aircraft, its obvious that unlike conventional tractor types, the flow from the prop will almost completely envelope the canard, and therefore too much within its influence. It is too unsafe and that is why we dont see any except for a tiny few experimental types and Rutans push pull Defiant.

Canards can be more efficient wingplans in some areas of flight, nominally cruise speed, however in order to do so they give up efficiencies elsewhere. Rutans famous VariEze and subsequent LongEze coupled the canards performance with a very good use of weight saving, but the package comes with higher stall speeds, smaller cabins, and longer runway requirements.s

At first, as a result of my inadequate engineering background, I thought I had been looking up the wrong words or using the wrong dictionary. The one dictionary I own free and clear, that is not loose in it binding, is by a fellow named Bierce, who may have disappeared in Mexico while flying very high. After some thought, it occurred to me the engineer making the last post may not have understood me at all. So, for the engineers (nothing to do with being from Aus, since the latter, with due respect to the Canadians, are America's closest living relatives) please reference this: Canard also extends to flyers even older than he Wright Flyer; it is also French for duck. I understand that it may also mean hoax. Ducks are fowl (which is not the same as foul, even though a foul in American baseball may cause some to duck. Please refer all added questions to a moderator; I can see trouble ahead no matter which way I may attempt to wiggle out of this one.

[a64pilot]

Originally Posted by Cadence

I know canards prevent a stall? Should we put them on our hulls.

They do in effect prevent a stall. They way they do that is so long as the aircraft is within CG and operated within its limits, the canard will stall first, before the main wing. What that does is lower the nose and prevent a main wing stall, so the canard stalls preventing the aircraft from stalling so to speak.
There have been other "stall proof" designs, the old Aircoupe comes to mind, the way it prevented a stall was the elevator simply didn't have enough authority to raise the wings angle of attack high enough to stall.
However nothing is stall proof as it requires the aircraft to be operated within limits, particularly CG limits, and sometimes stall proof designs can be a real problem to recover from a stall when the aircraft is operated in a manner inconsistent with its type design.