Home made propeller

[Ron Hill]

After You Weld the First Blade: How are you planning on knowing where to weld the next two blades?

[champ20B]

You'll have a tough time getting a grinding wheel in there no matter how you do it. Be sure to leave at least a 1/4 inch radius fillet weld AFTER grinding or the blades could snap off. (In other words, avoid excessive grinding.) A 1/2 inch fillet would be even safer.

Jeff

PS: Nice fitting of the blades to the hub! You might want to bevel that straight edge on both sides of the blade to improve weld penetration.

The wonderful DREMEL tool makes everything like this easy. That's what is needed here for precise work in corners. It will take time though.

[Ron Hill]

Send me your Bondo pitch block and the diameter of your hub, I can cast a few blanks.

Here are some pictures that might help you.

First picture is CNC'd aluminum pitch blocks and fixture to hold them.

We are now printing our pitch blocks from a 3D printer. Your Bondo will work fine and long as we put the blades on slowly and in wax. Welding blades on works, but it is a "HAIRY" deal and I don't weld...But the way we've done it, it tack weld in about three spots on each side of the blade, then check the picture, some of my early gauges were homemade, but they worked to compare blades to blades. I do know that a good weld will want you blades to be "VEED" where they attach to the hub.

Blue Prop Scan is a more modern and the sand paper is "HOMEMADE"...but works pretty good...

[Glenno]

Hi there,
Hi Ron, hope your well. With blade position I have put a centre punch mark on the hub (in picture below, I am pointing a scrap piece of steel at it). I got these three marks by just wrapping a piece of paper around the hub and then deviding the length by three, putting the paper back around then marking.
I also thought last night of welding a little tab to the jig at the very tip of the blades to align the lengths more accurately. I will also just tack it all then place it on a flat surface measure the distance between blade tips and also blade tips back to the flat surface. If it's all out I will bust the blades off and rethink it or adjust where needed. Thanks heaps for the info mate, I really need any help offered.

I am having a lot of fun with this project, for some reason propellers really fascinate me, probably because I love boats, water, speed, outboards, inboards, anything that floats.
Recently also vintage outboards.
Cheers,
Glenno

[Ron Hill]

A small error at the hub is nothing, but by the time it gets to the tip, it could be off a quarter inch. Before you do your finish welds, measure from point to point on the tips.....

What pitch, diameter are trying for? What s the hub size? What motor??? 30 Tohatsu???

I'll be 72 on 4/25/16, I've fooled with propellers all my life. I took the "Rope" tail off my rocking horse, when I was five, and put a Water Witch aluminum prop where the tail was. I also ground it thinner on my dad's grinding stone and filled the stone with aluminum....I only did that maybe 40-50 times more in my life...My dad was so fussy about only using his grind wheel to sharpen cutting tools for the lathe, then, I come along and grind aluminum and plug up the stone.

[Glenno]

Hi there,
I definitely will measure the tip to tip before I weld fully, good point.
The motor is an 8hp Tohatsu (slightly modified) hub size is 60mm od and I am trying to achieve around 13 pitch with low rake, diameter is 9 inch or just under.
I have raced 25hp and 550cc supersport but had a bad accident last year so sold off all my race boats, gear, props etc and happy to be alive.
Just want to make a prop for fun not really for race, unless there is a bathtub race somewhere.

Cheers,
Glenno

[zul8tr]

Hi there,
I definitely will measure the tip to tip before I weld fully, good point.
The motor is an 8hp Tohatsu (slightly modified) hub size is 60mm od and I am trying to achieve around 13 pitch with low rake, diameter is 9 inch or just under.
I have raced 25hp and 550cc supersport but had a bad accident last year so sold off all my race boats, gear, props etc and happy to be alive.
Just want to make a prop for fun not really for race, unless there is a bathtub race somewhere.

Cheers,
Glenno

8hp w/ 9 x 13p?

[sharpeye Mike]

Like Ron said vee out the 2 sides of the blades, this way you will get more penetration, best to get full penetration.

[Glenno]

Hi there,
I will definitely chamfer off both sides of the blades where they are to be welded to the hub to get better weld penetration.
My greatest concern now is controlling the pulling action created when welding stainless.
Cheers,
Glenno

[smittythewelder]

Are you thinking of peening the beads?