Crusader.

[785boats]

Here are the rudimentary beginnings of John Cobbs' Crusader. The next boat in the line of 'World Water Speed Record Boats' that I'm building.

Again in 1/8 scale like the others. So a total length of around 46".

I'm not confident that the EDF will work in this one because the inlets are even smaller in proportion than the Spirit of Australia that I've just completed.
But I'll make them bigger & open out the cockpit as an air inlet so we can give it a damn good crack at working with an EDF.
I've got no problems with converting it to a prop rider if the EDF doesn't work.
Here's some photos & information on the original boat for those interested. I find that researching a project can be as much fun, and certainly as interesting, as building & running a boat.
A Canard design in 1952. Love it. But a tragic end to a pioneer in water speed record attempts.

https://www.google.com.au/search?q=John+Cobb+Crusader&rlz=1C1WPZB_enAU728AU728&espv=2&biw=1664&bih=902&source=lnms&tbm=isch&sa=X&ved=0ahUKEwjh3PK92JvSAhWONpQKHTi2BmYQ_AUIBigB

And here's a few pics of the basic frame work. Early days yet, but the shape is there.

[srislash]

Oh yes I see the inlet issue. Should be another fun build though.

[785boats]

Yep. The main thing is the challenge & the fun factor with these boats.

But I've done a few calculations & without ruining the scale features too much, I can increase the inlet areas to about 30% larger than the fan area.The scoops will be a bit larger of course, but the main gain will be by increasing the angle & depth that the concave areas recess into the hull. That makes the area at the rim of the scoop much larger. And then with the extra area of the open cockpit floor added to that, it might just be enough to work. Here's hoping.

[785boats]

Made a bit of progress this afternoon.
Installed the rear blocks to give the stern some strength & the required shape for the skins.
Then the bottom half of the side skins were attached.
The 1/16" ply that I normally skin a hydroplane with, would not conform to the compound curves of this boat, so I decided to use the age old method of balsa planking. That's actually what is shown on the drawings in the smaller scale, with 1/8" balsa.
I used 5mm balsa.
The top will be covered with 5mm x 10mm planks. They will need to be tapered & beveled to fit the curves.
That's the next part of the project. But I'll have to seal the inside with epoxy resin first.
I might even add a bit of fiberglass tape along the joins where the sides meet the bottom of the boat. Just for insurance against cracking as there was a fair bit of pressure on the curves along those joints.

Rear balsa blocks added to form the shape at the rear of the hull

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Starting the side skins.

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Bottom view.

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Side view.

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[785boats]

I cut some sheets of 5mm balsa into 11mm wide strips. & spent a lot of yesterday merrily planking the hull. It's been a long time since I've built a boat in this fashion. Balsa planks on ply frames with good old PVA exterior wood glue. And pins. Lots of pins.

The cowling was already framed up in the hull, so when the glue had set, I cut through the planks at the bulkdead/cowl lines and pried the cowl loose. As I suspected some glue had seeped into the gap between the bulkheads & the cowl frames so it took a fair amount of persuading to get the cowl free. a few chips & dings to patch up, but that's easy.

So now I need to cut the holes for the air intakes & the cockpit. Hopefully the cowl won't spring out of shape with 3 big holes in it.

The final few planks pinned into place.

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The cowl lines cut through

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Cowl off. Plenty of room in there for batteries & ESC etc.

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[Shooter]

That is a true masterpiece.

[785boats]

Thanks Pete.
Not quite yet, but I'll try to do the old boat justice.
Here's something a bit different. The original boat had the rudder mounted on the heel of the front ski.
I wonder how the model will behave with that setup?
It will be interesting to say the least.

[srislash]

Thanks Pete.
Not quite yet, but I'll try to do the old boat justice.
Here's sometjing a bit different. The original.boat had the rudder mounted on the heel of the front ski.
I wonder how the model will behave with that setup?
It will be interesting to say the least.

Oh man, I would be dying to try that, but then I'm peculiar that way. I would not think it would take much travel for it to do its job, for its given purpose. You will likely be playing with the Tx adjustments to get it right.

[785boats]

I too was thinking that it may be sensitive to the controls.
But I did read somewhere that they increased the size of the rudder because he couldn't turn the boat around at the end of a run without assistance.
But if it was on the full size boat, then it's going to be on a scale model too. That's the law isn't it?

Also on my list of world record holders to build, is the Miss Britain III. She also had a rudder at the front of the boat. In front of the main step even. I don't particularly like the look of this boat. But I have to build it at some stage, because I have the plans, and it was such an innovative design for 1933. Here's a couple of pics.

The forward rudder.

MISS-BRITAIN-III-boat-plans.jpg

The rudder linkage across the deck.miss-britain-iii-power-boat-national-maritime-museum-greenwich-london-B086P1.jpg

A sketch of the whole boat. It was designed & built in just 10 weeks.

missbritain.jpg

[785boats]

I hacked into the hull last night and cut out the recessed inlets and lined the resulting hole with some 0.4mm aircraft ply. Looks pretty cool. As stated previously, I made them slightly bigger and deeper into the hull where the rim of the external scoop will be. That created a larger intake area in total.
I shaped a foam block to make the scoops from fiberglass to get a more scale like shape for the final product. A bent piece of ply just won't make the right shape.

The cutouts with the 0.4mm ply added to the hull section.

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A view into the EDF location.

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The cowl removed.

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The foam plug for the air scoops.

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[785boats]

Slowly getting a bit more done.
The scoops have been made.
I made the front Ski today.
A bit of 1/16" ply for the sides. Some foam block for the main shape & some 1/16"ply for the bottom skin.
The heel of the ski was laminated from 2 pieces of 1/8" ply because the rudder post will need to be attached to that part of the ski.
The original boat had a flat Ski, but I added a bit of dihedral into the last part of the ski to try and eliminate the bounce that canards can get with a flat ski.

I also received the pilot that will become John Cobb.
Amazing detail. Almost the same pose as the last photo of John Cobb before his fateful run.

One of the scoops.
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The sides with the foam infill.
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Bottom skin fitted, showing the added dihedral.
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The pilot John Cobb.
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The last photo of Cobb.
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[785boats]

A bit more progress during the week.The bottom halves of the sponsons were made from some 1/16" ply & epoxied to the spars.
As it was St Patrick's day, a few pints of Guinness seemed appropriate at the time.
I also glassed the main hull. Another coat of resin & then the cowls & headrest can be attached.

The basic sponsons.
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Epoxied to the spars.
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Bottom skins added.
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The three forward panels epoxied together. A few pints of Guinness to celebrate St Patrick's Day.
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Glass-work on the main hull ready for trimming.
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[Beaux]

Very cool.

[785boats]

Thanks Beaux.

[boredom.is.me]

Back at it again!