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21
General Discussion Tolman Skiffs / Re: My GA build
« Last post by Dave Wright on September 22, 2016, 11:56:57 AM »
Since I run comparatively low HP engines propellers make a difference to me. I'd never used a Yamaha aluminum three blade before. I took the Yamaha 3 X 13.5 X 14 alum prop off my 70 HP Yamaha on my Widebody and measured it as follows, picking three arbitrary radii:


Hub diameter 4 inches at forward end

Pitch at 6 inch diameter = 15.19 inches

Pitch at 10.5 inch diameter = 13.84 inches

Pitch at 12.5 inch diameter = 17.42 inches

The measurements seem to confirm my hunch that one gets a higher average pitch with this series of Yamaha props.  This would explain Chris Collins inability to exceed 4800 RPM with the Yamaha 70HP on his 18 foot Standard, and my inability to exceed 4200 RPM with the same 70 HP engine on my Widebody. By measuring other props I'll know for sure whether I'm right or wrong.  I'll be measuring my new Quicksilver prop when it arrives in the mail.

Measuring props is quick and easy on the bench, it has been done a particular way since the invention of the propeller. Unfortunately, you won't find the method in Gerr's current propeller book. Fortunately, there are many free descriptions of the method on the internet. Here's a good example:

http://www.propellerpages.com/?c=articles&f=2006-03-27_manual_pitch_measurement
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General Discussion Tolman Skiffs / Re: Southern Maryland Jumbo Build
« Last post by david.nolan.940 on September 22, 2016, 10:42:55 AM »
dave    for reference, my cabin is seven feet, my pilot house is six feet to the bulkhead of cuddly     the forward sloped wi shield gives us lots more extra room

we spend lots more time in wheelhouse than cuddly

rod storage is always an issue    pilot house too low for overhead 

cuddly too short for most rods

also   offshore deep water combo trips start 22 oct with season opener    last year vet day  trip was a blast   jumbo sea bass and porgies in170 ft!


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23
General Discussion Tolman Skiffs / Re: My GA build
« Last post by Squeeze on September 22, 2016, 08:14:07 AM »
thats the pitch for running, more cup in the blade will produce more stern lift, so its all a dance to find the optimal size, pitch and cup
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General Discussion Tolman Skiffs / Re: My GA build
« Last post by Cannon on September 22, 2016, 07:59:34 AM »
Dave,
I just reread your last post. Very interesting analogy! The whole prop thing is for most of us end users a hit or miss undertaking. Not something to be taken lightly since the final decision will either make the hull perform better or worse, and if purchasing a SS version at double the money VS aluminum, it can be quite frustrating as well as expensive.
Rather than wing it, which is my normal MO, I am going to go through a local company (yet to be decided ) which will give me the option to try before I buy.
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Introduce Yourself / Re: Hello from Southeast Alaska
« Last post by Cannon on September 22, 2016, 07:42:02 AM »
I used AB marine fir. The only thing I would caution about would be that you glass both sides if you do use fir. It can and will check if you don't. For the cabin, if I were to do it again, I would use MDO, which gives a nicer finish with less work.
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General Discussion Tolman Skiffs / Re: Southern Maryland Jumbo Build
« Last post by cj8mule on September 21, 2016, 12:18:38 PM »
I was always told, It's not how good you are, it's how well you can cover your mistakes.

That is so funny Skipjack....  I was just showing a friend where I messed the bow area up a little bit.  He was looking at the area stressing out a little bit....  It's no big deal though.  A little wood epoxied on the stem (like Dave Nolan did) and I'm off and on to the next screw up.  lol
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General Discussion Tolman Skiffs / Re: Bow stem Shelf to Fairbody measurement?
« Last post by david.nolan.940 on September 21, 2016, 07:47:43 AM »
I inlet the stringers through the transom and had extra stock on stringers     I didn't cut until
way later

I set my bow stem by pushing  down on the shelves until I had what looked good to me, not a beddie but not stock,   

shot in a couple screws to mark it, then glued it up

later I built up the stem with ply and PL and planed it to make flush

it was simple and quick

I like having the bottom assembly, stringers, and stem all movable to get the best fit

I trimmed my excess bottom off later also




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28
we had that on party boats     sometimes customers caught off guard and went Hans first into the Windows     they popped out

I really like lexan silicones in and screwed    its structural too whereas the rubber gasket isn't

I caught hell trying to remove the lexan from the old t top




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29
Introduce Yourself / Re: Hello from Southeast Alaska
« Last post by david.nolan.940 on September 21, 2016, 07:14:25 AM »
elk   my guess is 8-9 kts   I go 5.5  really but the second half throttle only gets us about six

my guess is the extra 15 Hp will get you a couple more kts

i think it's drag from that square stern dragging water behind the boat     


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