Building Prop E--trials and tribulations

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Building Prop E--trials and tribulations

Postby Fastjeff » Fri Mar 09, 2018 1:28 pm

For 90 % of this build it when incredibly well: The pitch came out around 19 on both blades in only two or three tries--whoppee! The position of the prop blades on the hub (fore and aft on the prop shaft--meaning the hub didn't hit the housing in front, or the blades hit the exhaust snout in the back) was also perfect.  The floating inner hub even lined up dead flush with the outer hub with the blades welded to it to be simply welded together instead of a plug weld.  Eureka!  

Next came a 'heat and beat session' where I heat the blades cherry red with my oxy-acetylene torch to hammer cup and what I call curl' into the blades. The trick here is to get BOTH blades correct AND similar.  Must be getting good at this, for it came out right the first time. Double eureka!

Finally (after dressing and polishing the blades) came balancing.  One blade was heavy, so I back ground the heavier blade a few times, getting nowhere--it was off that much.  The only fix left was to add a bunch of weld inside the hub, which is open for an inch on the inside (the splines stop in about the middle on Mark 55/ Merc 400s).  And there I screwed up BIG time.

Tired (and a bit stupid) I added weld on the heavy side.  Doh and double Doh!  Have you ever tried to remove a 1/4 x 3/4 x 1  inch lump of steel with a freakin' pencil grinder?  Aaargh!  Spent hours grinding away at that sucker before deciding to add an even larger lump of metal on the other side of the hub. No luck there either, for the balance (I learner learned) was off that much.

To make a loooong story shorter, I got a brainstorm while lying in the bath tub--get some of my best ideas there.  I used a whiz wheel with the wheels (old, worn ones--I'm a cheapskate) ground down on a brick from the wife's garden (shhh!) to the point they were almost gone.  That did the trick, for I could sneak in there and grind away.

PRop E now balanced out fine, but JEEPERS, BATMAN, it took almost that much time fixing my screw up as building the fool thing!  And cold?  The compressed air coming off the pencil grinder and whixz wheel could have frozen ice cream!

Jeff
Attachments
Prop E- 2.JPG
Prop E- 1.JPG
Words spoken in two stroke heaven: There's no fuel like an oiled fuel.
Fastjeff
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Re: Building Prop E--trials and tribulations

Postby outboard315 » Fri Mar 09, 2018 11:26 pm

Jeff, I just realized I am an hour from spinelli brothers, do you want me to see if I can hook you up.
Brandon Cocola
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Mark 20, Mark 30H, WA25E, KG7H
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Re: Building Prop E--trials and tribulations

Postby Yellowjacket » Sat Mar 10, 2018 12:25 am

I see a lot of surface area and surface area is drag...

Do you really need that much chord...  The faster you go the less prop area you need, and too much area is just drag.

With this much area it's not going to have much slip, but if you're going fast it's going to have a lot more drag.

If you get the hull working right you shouldn't need that much prop area.

JMHO....
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Re: Building Prop E--trials and tribulations

Postby Fastjeff » Sat Mar 10, 2018 1:03 pm

..."If you get the hull working right you shouldn't need that much prop area."

Right on!  That's the plan.  My whiz wheel is ready to remove what's not needed.  Much easier to remove it than add it.

Who are the Spinelli brothers? Is one of them Don with the Mark 75 I rode in at Lake Hoptacog?

Jeff
Words spoken in two stroke heaven: There's no fuel like an oiled fuel.
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Re: Building Prop E--trials and tribulations

Postby outboard315 » Sat Mar 10, 2018 1:49 pm

Brandon Cocola
Upstate NY
Mark 20, Mark 30H, WA25E, KG7H
14' Texas Maid, 12' Sea King, 12' Sea Nymph
outboard315
 
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Re: Building Prop E--trials and tribulations

Postby Fastjeff » Sat Mar 10, 2018 3:06 pm

Walcott, NY?  That's a zillion miles from Rock Hall, MD.

Are these guys interested in hack builders (like me) or something?

Jeff
Words spoken in two stroke heaven: There's no fuel like an oiled fuel.
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Re: Building Prop E--trials and tribulations

Postby outboard315 » Sat Mar 10, 2018 3:37 pm

Don't know, but maybe they could build you a custom prop.
Brandon Cocola
Upstate NY
Mark 20, Mark 30H, WA25E, KG7H
14' Texas Maid, 12' Sea King, 12' Sea Nymph
outboard315
 
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Re: Building Prop E--trials and tribulations

Postby Fastjeff » Sun Mar 11, 2018 12:38 am

Yeah, but what configuration (diameter, pitch, cupping, etc.)?  That's the problem.  I  haven't the funds to buy a series of props until I find one that works.

First of all, I gotta make my BOAT work, and that's been the problem all along--the damn bow won't come up.  Yellowjacket's solution looks mighty promising...and I might get to try it if the damn weather would break!  Sheesh!  Twenty five degrees again this morning.

Jeff
Words spoken in two stroke heaven: There's no fuel like an oiled fuel.
Fastjeff
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