Seaplane not speeding up enough while in water to take off

[Second Hand Rocket Science]

See title! Should I make some critical design changes with pre-determined effects which will enhance the take-off capabilities of my aircraft? Or just moar boosters?

https://imgur.com/a/t5OfgwO

[ColdJ]

Assuming the physics works the same in KSP2 as in 1 then you need to add some hydrofoils to the underside of the hull and floats. Made from structural pylons that have 2 elevons each. Elevon either side of the pylon, angled so that from behind the whole thing looks like an arrow pointing down. Turn off pitch,roll and yaw and have them adjusted to a deploy that causes them to raise up in the water as you move forward. This not only will raise your craft out of the water but also decrease drag, allowing you to achieve a take off speed.

[Second Hand Rocket Science]

https://imgur.com/a/NeU7RDZ

Is this what you mean?

Also, this is KSP1 with Deferred Rendering and zTheme. It does look a little like KSP2 lol

@ColdJForgot to quote you lol, so just mentioning you since you can't edit in a quote after posting

Edited August 8 by Second Hand Rocket Science

[Lisias]

I think he meant something like this:

https://forum.kerbalspaceprogram.com/topic/27292-what-did-you-do-in-ksp1-today/page/2153/#comment-3813618

 But somewhat smaller as you only need to get above the water a little bit.

Do you know an addon called Retractable Lifitng Surface? I think it may help you a bit, as the hydrofoil will be only a source of drag once airborne.

Edited August 8 by Lisias
Hate posting on mobiles

[Second Hand Rocket Science]

4 minutes ago, Lisias said:

I think he meant something like this:

https://forum.kerbalspaceprogram.com/topic/27292-what-did-you-do-in-ksp1-today/page/2153/#comment-3813618

Ah! I'll try a similar design. I'll put one on the base of each pontoon and one at the front of my hull

[Lisias]

5 minutes ago, Second Hand Rocket Science said:

Ah! I'll try a similar design. I'll put one on the base of each pontoon and one at the front of my hull

You  ninja'ed me!

Anyway, you only need to lift a bit from water, as your wings will do the heavy lifting - you only need enough to overcome the water's extra drag.

Once airborne, the hydrofoil is only a source for aerodynamic drag. You may want to check Retractable Lifting Surfaces!

[Second Hand Rocket Science]

https://imgur.com/a/cSGoxJU

Now we have another problem, when landing with the hydrofoils installed, it flips on contacting the water.

PS: This is my stock save, I don't use any mods apart from graphics/Restock and such, stuff that doesn't cause compatibility issues when I delete mods

Edited August 8 by Second Hand Rocket Science

[jimmymcgoochie]

I would suggest more engines and mounting them lower down. A single jet engine so high up is creating a nose down torque which will push you deeper into the water when trying to take off. Moving your wings forwards will give you more lift at the front too, though you will need to be careful to keep it balanced when in flight.

A lot of tricks that real seaplanes use to take off (clever hull design, ground effect etc.) don’t work with KSP’s physics, but adding a sizeable angle of incidence on the wings (make the front edge higher than the back edge to produce more lift at low speeds) can help; see the PBY-5 Catalina, for example.

[DennisB]

6 hours ago, Second Hand Rocket Science said:

See title! Should I make some critical design changes with pre-determined effects which will enhance the take-off capabilities of my aircraft? Or just moar boosters?

https://imgur.com/a/t5OfgwO

Others already mentioned the lack of thrust. I think, another issue is drag in the water. You have the two floats and the main body swimming in the water. I suggest to put the floats deeper, and make them probably larger, so the main body of the plane doesn't touch the water even at zero speed, and put the foils onto the floats.

This is my design, which worked on Laythe with the thrust of four fan drives. Water landing and takeoff at 4:00.

 

Edited August 8 by DennisB

[Lisias]

2 hours ago, Second Hand Rocket Science said:

Now we have another problem, when landing with the hydrofoils installed, it flips on contacting the water.

PS: This is my stock save, I don't use any mods apart from graphics/Restock and such, stuff that doesn't cause compatibility issues when I delete mods

Krap.

We need to find a way to retract the hydrofoil.

In time, I think you only need the ones in the central hub - once you get enough speed to lift from water, the engines will probably be able to keep the craft in balance - and you will have less weight e drag to carry while flying.

Additionally... Perhaps instead of a single big hydrofoil, a bunch of smaller ones would be enough? You don't need to get too high, you only need to let the hull to be high a couple inches about he water and get speed enough to the wings do their job.

Or perhaps the robotics could help?

 

49 minutes ago, jimmymcgoochie said:

A lot of tricks that real seaplanes use to take off (clever hull design, ground effect etc.) don’t work with KSP’s physics,

But some do, and this is what makes he thing interesting! Trying to see!

 

49 minutes ago, jimmymcgoochie said:

but adding a sizeable angle of incidence on the wings (make the front edge higher than the back edge to produce more lift at low speeds) can help; see the PBY-5 Catalina, for example.

Or adding a obscene amount of flaps. It also helps, and don't induce drag while cruising.

 

50 minutes ago, jimmymcgoochie said:

I would suggest more engines and mounting them lower down.

More engines can do the trick, but check your fuel consumption on cruising - you will carry more weight too.

Mounting the engines down is tricky on a design like this one - engines are terribly brittle when in contact with water, you will loose them on landing over water.

[Second Hand Rocket Science]

2 hours ago, DennisB said:

I suggest to put the floats deeper, and make them probably larger, so the main body of the plane doesn't touch the water even at zero speed, and put the foils onto the floats.

I tried this, but it exacerbates my problem of flipping tenfold. The floats bite into the water when landing at just about stall speed and flip the entire craft with a force of around 15 Gs. 

3 hours ago, jimmymcgoochie said:

A lot of tricks that real seaplanes use to take off (clever hull design, ground effect etc.) don’t work with KSP’s physics, but adding a sizeable angle of incidence on the wings (make the front edge higher than the back edge to produce more lift at low speeds) can help; see the PBY-5 Catalina, for example.

Added an angle of incidence, quite small (around five degrees). All it seems to have done is made my aircraft pitch up pretty hard with SAS off in flight, necessitating nose down trim, which makes it pretty difficult to land, since taking your finger off the pitch means it just starts gaining altitude.

2 hours ago, Lisias said:

Additionally... Perhaps instead of a single big hydrofoil, a bunch of smaller ones would be enough? You don't need to get too high, you only need to let the hull to be high a couple inches about he water and get speed enough to the wings do their job.

I have no idea how to make these hydrofoils, every attempt I've made and they are making no difference to performance. I've not been able to test the latest iteration of hydrofoils since I can't do a water landing with the lowered floats, but I doubt they'll work either. It's a pylon with an elevon on the front and back mounted horizontally using robotics to lower it into the water when I land, which I had hoped would solve the flipping issue, since I believed it was the hydrofoils that were responsible. It seems it's simply the floats. I think instead of trying to fix this clearly flawed airframe, I'm going to make another design from scratch, and hopefully it'll be more successful.

[Second Hand Rocket Science]

OK, new problem. I raised the floats and it now almost flips, then tips back up the right way. However, when the foils are deployed and the aircraft gets to about 15 m/s the nose digs into the water, bites, and the aircraft starts to pitch down, then becomes about 3/4 submerged and nearly 90 degrees in the water, then floats back to the top. I would post a video, but imgur is being picky and not letting me upload. Is this a CoM problem? Or does it need another foil under the nose? Which poses more annoying engineering problems...

[DennisB]

Are your foils adjustable? As I tested my design, I accelerated close to the speed, where it got unstable, changed the inclination, and looked if it made it better or worse.

Another question regards the flipping. Are your floats still like in the pictures? Maybe you should make them longer to make flipping less likely. If you look at my plane, the floats have about half the length of the entire plane.

[Second Hand Rocket Science]

6 minutes ago, DennisB said:

Are your foils adjustable? As I tested my design, I accelerated close to the speed, where it got unstable, changed the inclination, and looked if it made it better or worse.

Another question regards the flipping. Are your floats still like in the pictures? Maybe you should make them longer to make flipping less likely. If you look at my plane, the floats have about half the length of the entire plane.

I've checked and my foils still aren't working. I've tried four or five different designs and none of them make any difference to my performance in the water. My aircraft can't get over 15 m/s because the entire fuselage is always submerged, and the floats can't be lowered any further, because it just flips landing.

I seem to have fixed the flipping by replacing the nosecone for a much longer, pointier one. It cuts into the water instead of biting into it and yanking the front underwater. 

[ColdJ]

@Second Hand Rocket Science

We seem to have drifted from my original suggestion. You want the smallest pylon and smallest elevons. You want to use elevons because you can adjust the pitch till you find the best angle. You can retract them once airborne so that they are only lifting surfaces and won't cause significant drag. I have successfully used this method in the past.

If you can get me your original craft file then I can modify it for you.

[Vanamonde]

You need more power, for one thing. You're only reaching 17m/s and a plane that size could not take off at that speed even on land. 

[Lisias]

2 hours ago, Vanamonde said:

You need more power, for one thing. You're only reaching 17m/s and a plane that size could not take off at that speed even on land. 

The Wheesley is a decent engine for the size, I had walk from heavier planes using 4 of Junos that gives me 2/3 of the trust of a single Wheesley (a single juno gives us 20KN, a single Wheesley does 120KN).

IMHO the OP is in need of flaps. They are incredibly useful for taking of and landings, and will help counteract the torque of the Wheesley at the current configuration.

 

7 hours ago, Second Hand Rocket Science said:

OK, new problem. I raised the floats and it now almost flips,

The problem on the plane, IMHO, is that the most of the engine's trust is being wasted on the torque that by its time makes the nose to submerge, completely screwing whatever trust the engine would be giving you due the drag the water is exercising on the whole plane when it happens. And it's a lot of drag...

I think the you can walk with just the Wheesley if:

• lots of Flaps are added, making the taking off easier
• something be put slightly ahead of the CoM, coercing the water to work for you instead of against.
  • yeah, a Hydrofoil.

Give a peek on this seaplane I just smacked together:

"0" will deploy/retract the flaps. Activate them for landing and taking of on water or ground.

"9" will deploy/retract the hydrofoil's angle of attack. Activate it for taking of, but not for landing on water.

Whole Slide Show here. Give it a peek for more insights and to download the craft.

[ColdJ]

@Second Hand Rocket Science

Ok. That is the first upload I have done to KerbalX in years. I did my best to replicate your design, added hydrofoils and airbrakes. Went out and tweaked it on the water. When you reach 70 ms gently pull back on the stick and you will rise out and fly. Try to get down to 30 ms or less to land in water. Have the Airbrakes locked on to help with this when landing. Top speed is about 208 ms cruising in air.

Successfully tested in water and on runway.

https://kerbalx.com/ColdJ/Seasplain

[ColdJ]

@Lisias That brought back memories.

https://kerbalx.com/ColdJ/The-SEAL-Hydrofoil-3

[Second Hand Rocket Science]

Are you able to send a short video of the Seasplain taking off from the water? I'm starting to think this isn't about the plane but the pilot  the Seasplain can't get over 30 m/s when I'm flying it and the foils don't seem to make a jot of difference when they're extended or not.

[ColdJ]

5 minutes ago, Second Hand Rocket Science said:

Are you able to send a short video of the Seasplain taking off from the water? I'm starting to think this isn't about the plane but the pilot  the Seasplain can't get over 30 m/s when I'm flying it and the foils don't seem to make a jot of difference when they're extended or not.

Lucky I was on, you didn't ping.

Sorry but I can't do videos. By any chance are you using BD armory?

It adds armor to all parts, making them heavier. Really mucked me up years ago when I was setting a water speed record, till I removed the patch.

From the pics you can see the speeds I reached. 81 ms a second on water.

[Second Hand Rocket Science]

No, I only use a massive suite of graphics mods. No parts mods apart from Restock+, which only adds a few parts which fill gaps in the stock lineup. Can't play without it anymore. Anyway, yeah. I'm starting to think that maybe it's sea conditions? Does Parallax change water physics? It gets up to about 15 m/s and then starts biting into the water, and hitting every wave, slowing it down by about 5 m/s every wave. It can't possibly get to take off speed. It also does the same thing that my original Mockingbird design does which is if you get to anywhere near 20 m/s it bites so hard into a wave it flips the entire craft.

I even saved your foils as a subassembly and added them to my own design, and the problem persists.

That was the best I could describe it. Imgur is such an annoying site, and it won't let me upload this video either. But whatever.

[Lisias]

3 hours ago, Second Hand Rocket Science said:

No, I only use a massive suite of graphics mods. No parts mods apart from Restock+, which only adds a few parts which fill gaps in the stock lineup. Can't play without it anymore. Anyway, yeah. I'm starting to think that maybe it's sea conditions? Does Parallax change water physics?

Now that you mentioned it... I missed an important detail...

You are using Canards in your plane, and when the thing gets underwater, it ends up working as an Hydrofoil by accident, and should not allow the nose to go so deep.

Can you redo your initial video, but with F-12 hit (showing the Force Vectors)? This will help to see how the lifting surfaces are behaving, probably giving us a hint of the problem...

[ColdJ]

13 hours ago, Second Hand Rocket Science said:

No, I only use a massive suite of graphics mods.

I believe you have answered the question as to why you are having problems.

If you have Scatterer or maybe something like it, it defaults to a setting that creates physical wave effects, sounds nice but causes havoc with anything in the water, When I was creating my Thunderbirds mod and had those effects turned on, it was making the dropping, using, and picking up of Thunderbird 2's pod in the water near impossible. Thankfully there is a setting to turn off the physical interaction. You still get the nice visual effects of the waves but not the chop that is killing your sea plane.

[Second Hand Rocket Science]

 

5 hours ago, ColdJ said:

I believe you have answered the question as to why you are having problems.

If you have Scatterer or maybe something like it, it defaults to a setting that creates physical wave effects, sounds nice but causes havoc with anything in the water, When I was creating my Thunderbirds mod and had those effects turned on, it was making the dropping, using, and picking up of Thunderbird 2's pod in the water near impossible. Thankfully there is a setting to turn off the physical interaction. You still get the nice visual effects of the waves but not the chop that is killing your sea plane.

Aw hell, I had suspected that, but my reasoning was that a purely graphics mod wouldn't feature a full rework of the water physics! Let me go and find out how to turn off the water physics revamp and I'll get back to you