Spirit of Australia

[785boats]

As stated over in the 'Bluebird thread', I intend building a few more water speed record boats from days gone by.
a few weeks ago I started sketching up some plans for the Spirit of Australia. I ended up taking a small copy of some line drawings to a copy shop & they blew them up to a length of 42". About 1/8 scale.
I intend to try an EDF first so I ordered a fan with an output thrust of 5.4 kg. i hope to keep the total weight well under that weight to at least give it a fighting chance to get up on the plane.
If it doesn't work, then I'll just add an ordinary 1/8 scale hydro setup in it.
Well it has sort of taken over, & the bluebird has taken a back seat again.
I cut most of the parts out of some 1/16" ply & built them up on a 1/16" ply base, using the dry fit & medium ca glue process.
Once the bacic frame work was finished I added the stringers & side skins.
Then the sponsons were built up.

Yesterday, I gave the insides a coat of epoxy resin & cut the foam blocks for the sections.
Next it is the sponson skins & deck skins.

Here's a few pics.

[Fluid]

I trust that you are using at least a 120 mm fan and 10S; regardless of the weight the wetted area is the biggest "drag" and you will need plenty of thrust to get moving well. You know the importance of ample inlet area/low turbulence ducting and the potential advantages of a slightly tapered outlet.

IMO you will need additional aoa on the sponsons compared to the full-scale boat to get it up on plane. IIRC one of the Bluebirds needed aoa added to its original design before the boat would plane off. With the same amount of thrust the jet racer went from a barge to a record-breaker.


.

[785boats]

The boat was sized around a 90mm fan 0n 8s.
To fit a 120mm fan in there & 10s packs would have meant a bigger boat. It did cross my mind, but I ended up with the smaller boat & fan on 8s.
My biggest concern has always been whether the fan can produce enough thrust to get the boat up over the hump & on to the plane.
The inlets are going to be made slightly over scale size to allow the air intake area to be at least the same as the FSA of the EDF. Possibly a bit larger. Although I don't know how much larger is appropriaste.
I read somewhere last night that on jets with a twin intake, it is best to have a divider all the way to the face of the fan. so I will factor that into the design of the intake cowling too.
The thrust pipe will be made to 100% FSA initially, which tapers it down from 90mm to 81mm. But i am prepared to make a couple of inserts down to 90% & 85% for testing.

Thanks for the tip on the AoA for the sponsons. I can make some wedge shaped ride pads to achieve that. Or, reduce the depth of the rear ski. But that will also change the angle of the whole boat too. We'll see how it goes.

[Scott T]

Very cool Paul!! One of my all-time favourites.

[785boats]

Thanks Scott.
I just love the whole story behind it.

Designed it on his kitchen table.
Built it in the shed in his back yard.
Bought the engine for less than $100.00.
Set a world record in 1978 that no one has been able to break since.

I'll try to do it justice.

[Beaux]

Nice , What type of steering would that have ?

[785boats]

Just a small blade rudder in the center

[Beaux]

Cool, that's gonna be a neat boat.

[785boats]

Thanks Beaux. I've always liked the lines of this boat.

So, a bit more work done over the last couple of evenings.
I fitted the skins on the sponsons.
The side skins first, then the ride pads, then the top skins.
It's slowly coming together.

[Beaux]

The wood work is just awesome, a true craftsman.

[JimClark]

Man Paul you are doing some great builds Paul how bout one of the current boat?

[785boats]

The wood work is just awesome, a true craftsman.

Thanks Beaux. But there are some bits that aren't quite right.
I build by that old addage. "Measure twice. Cut once. Fill gaps".

[785boats]

Man Paul you are doing some great builds Paul how bout one of the current boat?

Thanks Jim.
Yes that boat is on the list. I haven't been able to find any drawings for that one yet.
But there are a couple of others I want to build first.
The Crusader is at the top of the list at the moment. I've got drawings for that one.

https://www.google.com.au/search?q=John+Cobb+Crusader&espv=2&biw=1852&bih=889&source=lnms&tbm=isch&sa=X&ved=0ahUKEwiNtNy9yv7PAhWBjJQKHcF2A38Q_AUIBigB

[785boats]

A nice relaxing day today. I decided to make the thrust tube, install the motor mounts, & extend the wires of the EDF to reach the ESC. Then fit it all into the boat.

The thrust tube was made from some 0.4mm ply sheet.
But I had to make a short extension to wrap around the EDF body first, so I could bring the wires out through that & seal them. The whole unit then slides into the thrust tube as it is installed onto the mounts.

The thrust tube tapers down to 81mm as previously discussed. It is easily removable, once the fan is taken out, to allow different ratio thrust tubes to be tried.

The wires of the motor were extended with some #10 gauge wire.

I guess, if I screw the EDF into place, I could give it some juice to see what it sounds & feels like.

I found out today that the motors are made by H.E.T. for the Freewing EDFs so it should be a good power plant.

The extension ring. The motor wires extended & brought through the extension. Just needs some sealant around the wires now.
009.jpg

Thrust tube & EDF mounting blocks.
004.jpg

All sitting in place.
013.jpg

Side view.
014.jpg

[srislash]

Nice work .