Topic: Campbell's Bluebird K7 model advice needed. (Read 9942 times)

Imagewerx · « **Reply #25 on:** October 07, 2018, 08:58:32 pm »

Quote from: C-3PO on October 07, 2018, 05:21:30 pm

caveat emptor
Imagewerx - You might find some more info interesting on this link - https://www.modeljetdrives.com/bluebird-k7-hydroplane.html

John W E - I will see if I can locate the video and publish on here

C-3PO

Thank you again!

Taranis · « **Reply #26 on:** October 07, 2018, 09:02:53 pm »

A great project you have there, I'm watching with interest

Hopefully we can all learn from your discoveries.
Regarding hull shape. Even a lowly club 500 will turn 90 degrees at full speed if the rudder travel is small. Excess rudder travel causes undesirable results.
My 44" Shannon will turn very hard with only small jet nozzle travel so no rudders but hull shape nothing like flat

Taranis · « **Reply #27 on:** October 07, 2018, 09:18:13 pm »

This is a club 500. quite small but these ride very much out of the water so the basic below water line shape could easily be concealed under a bluebird with parts scaled to suit

Imagewerx · « **Reply #28 on:** October 07, 2018, 09:24:29 pm »

Quote from: Taranis on October 07, 2018, 09:02:53 pm

A great project you have there, I'm watching with interest Hopefully we can all learn from your discoveries.
Regarding hull shape. Even a lowly club 500 will turn 90 degrees at full speed if the rudder travel is small. Excess rudder travel causes undesirable results.
My 44" Shannon will turn very hard with only small jet nozzle travel so no rudders but hull shape nothing like flat

Thank you for this and the photo above.How long is that hull?

Taranis · « **Reply #29 on:** October 07, 2018, 09:26:51 pm »

That question just taught me something I never twigged

tape measure in hand! I guess it's called a club 500 for good reason

500mm hull

Imagewerx · « **Reply #30 on:** October 07, 2018, 09:34:15 pm »

Quote from: Taranis on October 07, 2018, 09:26:51 pm

That question just taught me something I never twigged tape measure in hand! I guess it's called a club 500 for good reason 500mm hull

Aaahhh ok.I think a 210mm long jet drive pump would be a bit OTT for something this size.

Edit......I get the reason now for showing me this.

Taranis · « **Reply #31 on:** October 07, 2018, 09:34:54 pm »

I'm thinking that to allow for the possible weight involved in your working model compared to this, you would need all of that hull below the water and as your model got faster it would/should rise to look like it's hydroplaning

Taranis · « **Reply #32 on:** October 07, 2018, 09:39:59 pm »

Quote from: Imagewerx on October 07, 2018, 09:34:15 pm

Aaahhh ok.I think a 210mm long jet drive pump would be a bit OTT for something this size.

A single jet drive along the keel plus motor would fit easily and a battery either side?. All below the water line with K7 on top. The problem being these hulls are only styrene and not really strong enough

Taranis · « **Reply #33 on:** October 07, 2018, 09:49:50 pm »

Just kicking a ball about here obviously

idea crunching

Imagewerx · « **Reply #34 on:** October 07, 2018, 09:50:36 pm »

Quote from: Taranis on October 07, 2018, 09:39:59 pm

A single jet drive along the keel plus motor would fit easily and a battery either side?. All below the water line with K7 on top. The problem being these hulls are only styrene and not really strong enough

I've never used brushless motors before,so this is all a VERY steep learning curve for me.I have chosen this partly on a whim,and partly on what other people have used in similar sized boats......
Turnigy AquaStar 3974-2200KV Water Cooled Brushless Motor

Turnigy AquaStar 3974-2200KV Water Cooled Brushless Motor

Imagewerx · « **Reply #35 on:** October 07, 2018, 09:51:56 pm »

Quote from: Taranis on October 07, 2018, 09:39:59 pm

A single jet drive along the keel plus motor would fit easily and a battery either side?. All below the water line with K7 on top. The problem being these hulls are only styrene and not really strong enough

Thanks,all food for thought!

Taranis · « **Reply #36 on:** October 07, 2018, 09:52:36 pm »

Well yes that is a beast

but probably suited to a 40mm drive. Presumably you can fettle it down the line with different LiPo options

Imagewerx · « **Reply #37 on:** October 07, 2018, 09:57:50 pm »

Quote from: Taranis on October 07, 2018, 09:52:36 pm

Well yes that is a beast but probably suited to a 40mm drive. Presumably you can fettle it down the line with different LiPo options

And if I understand these things correctly,a relatively low kv count meaning more torque than a higher number.

Taranis · « **Reply #38 on:** October 07, 2018, 10:00:09 pm »

Quote from: Imagewerx on October 07, 2018, 09:57:50 pm

And if I understand these things correctly,a relatively low kv count meaning more torque than a higher number.

Is that a low KV count? With a fresh charged 4s LiPo that would hit 33,000 rpm

What is the jet drive specified RPM ?

Imagewerx · « **Reply #39 on:** October 07, 2018, 10:13:04 pm »

Quote from: Taranis on October 07, 2018, 10:00:09 pm

Is that a low KV count? With a fresh charged 4s LiPo that would hit 33,000 rpm

What is the jet drive specified RPM ?

Maybe not thinking about it now

.Don't know about the jet drive as there's very little technical info about it.

Taranis · « **Reply #40 on:** October 07, 2018, 10:17:43 pm »

Best to experiment. 2S 3S 4S 6S etc as long as your motor is spec'd to the necessary voltages and the ESC too.

I am running slower motors on my model than those supplied and works perfect so trial and error is the way unless directly copying anothers success. You will teach us more than we can offer you

Imagewerx · « **Reply #41 on:** October 07, 2018, 11:53:23 pm »

Quote from: Taranis on October 07, 2018, 10:17:43 pm

Best to experiment. 2S 3S 4S 6S etc as long as your motor is spec'd to the necessary voltages and the ESC too.

I am running slower motors on my model than those supplied and works perfect so trial and error is the way unless directly copying anothers success. You will teach us more than we can offer you

I'm starting with a 4S which is well below what that motor can handle.Not sure I'm a good role model though

!

Onetenor · « **Reply #42 on:** October 08, 2018, 06:24:29 am »

You might find the boat goes in fits and starts or porpoises. You have to think about the way she runs on the plane. She lifts above the water so lifting the intake out of the water in fits and starts as she loses and regains thrust. I would go for an EDF or even an I/Ce DF. That's an Electric Ducted Fan or Internal Combustion engine Ducted Fan That is a multi bladed fan in a duct much like a jet turbine but without the fire. Or the expense. Oh yes downthrust under a hull is something you don't want. Nor inside the hull either. One lifts the null in the wrong place. The other pushes down causing more drag Put that unit in a model of a Jet Speedboat as used on Marine lakes for joy rides

grasshopper · « **Reply #43 on:** October 08, 2018, 10:18:35 am »

On another tack, if you aren’t too fussy about scale on water looks...

The sponsons protrude further forward than the central hull, what’s to stop you using something like thinnish lexan between, and for for the length of the sponsons, creating a sledge /stepped flat hull effect?
With enough grunt she should plane on the back edge of the lexan step and the underneath of the jet drive outlet (or flaps either side).....handling might be interesting but it could work.

There’s another thread on here where someone 3D printed a jet drive and used a flat bottomed hull for experimentation that seemed to go well, you’d be replicating that hull shape after a fashion.

Taranis · « **Reply #44 on:** October 08, 2018, 10:27:15 am »

Nice idea

Imagewerx · « **Reply #45 on:** October 08, 2018, 07:56:22 pm »

Quote from: john mantova on October 08, 2018, 06:24:29 am

You might find the boat goes in fits and starts or porpoises. You have to think about the way she runs on the plane. She lifts above the water so lifting the intake out of the water in fits and starts as she loses and regains thrust. I would go for an EDF or even an I/Ce DF. That's an Electric Ducted Fan or Internal Combustion engine Ducted Fan That is a multi bladed fan in a duct much like a jet turbine but without the fire. Or the expense. Oh yes downthrust under a hull is something you don't want. Nor inside the hull either. One lifts the null in the wrong place. The other pushes down causing more drag Put that unit in a model of a Jet Speedboat as used on Marine lakes for joy rides

Thank you for your thoughts John.The jet drive as a propulsion system came first and was the most imporant part of this project,the idea to use Bluebird K7 to mount it in came later and is of secondary importance.
I could shift my weight around on my jetski to stop it from porposing.Get the right amount of weight over the jet pump to keep it hooked up.Enough weight over my front foot to keep the nose down and just the right amount of leaning forward to help as well.Even Campbell and the Norris brothers didn't get it right and had to mess around with ballast to,which I think this boat is going to need any way being well under it's scale weight by a very large amount.As long as it stays hooked up and doesn't cavitate (keep the throttle nailed as much as possible) it will get more downforce to keep it stuck to the surface rather than bouncing over any chop that might be there.Or at least that's the theory based on my experience with a 130kg jetski.I believe that a conventional prop driven boat that loses drive for a second or so every time the prop comes out of the water will not lose out to a jet drive with greater drag but almost no loss of drive.

Imagewerx · « **Reply #46 on:** October 08, 2018, 08:02:49 pm »

Quote from: grasshopper on October 08, 2018, 10:18:35 am

On another tack, if you aren’t too fussy about scale on water looks...

The sponsons protrude further forward than the central hull, what’s to stop you using something like thinnish lexan between, and for for the length of the sponsons, creating a sledge /stepped flat hull effect?
With enough grunt she should plane on the back edge of the lexan step and the underneath of the jet drive outlet (or flaps either side).....handling might be interesting but it could work.

There’s another thread on here where someone 3D printed a jet drive and used a flat bottomed hull for experimentation that seemed to go well, you’d be replicating that hull shape after a fashion.

I'm not sure what you mean by this,can you show me an example please?

Arrow5 · « **Reply #47 on:** October 09, 2018, 02:32:29 pm »

If you are not locked into Campbell why not consider the fastest boat in the world, the late Ken Warby`s Spirit of Australia and the Mk.2 Spirit of Australia to be driven by his son David Warby. Much better layout for 300+ mph, K7`s design max was 250mph. The 45 degree ramp bow of the hull and slope of the sponsons was an aerodynamic disaster above the design speed. I think grasshopper`s idea was for a toboggan-like sheet between the sponson, not good.

Imagewerx · « **Reply #48 on:** October 09, 2018, 08:35:41 pm »

Quote from: Arrow5 on October 09, 2018, 02:32:29 pm

If you are not locked into Campbell why not consider the fastest boat in the world, the late Ken Warby`s Spirit of Australia and the Mk.2 Spirit of Australia to be driven by his son David Warby. Much better layout for 300+ mph, K7`s design max was 250mph. The 45 degree ramp bow of the hull and slope of the sponsons was an aerodynamic disaster above the design speed. I think grasshopper`s idea was for a toboggan-like sheet between the sponson, not good.

If I can't get the plans for Bluebird,that will be another option.A very nice looking boat with quite a bit of Bluebird to it's design

.

Arrow5 · « **Reply #49 on:** October 09, 2018, 09:49:34 pm »

I wouldn't say that the cowling and fin were much of K7

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Author Topic: Campbell's Bluebird K7 model advice needed. (Read 9942 times)