Double Eagle -need to tweak prop pitch or settle with pretty good

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Bill Edmundson
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby Bill Edmundson » Sat Sep 10, 2016 3:22 pm

North

Check for growth on the prop also. A slick prop runs much better than a rough one.

Bill
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North
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby North » Sat Sep 10, 2016 5:03 pm

Thanks Bill. I have been meaning to take a look under it, but don't have any goggles here. Water is also a bit murky / brackish at my dock - on a tidal river. Swimming is great buit water usually pretty dark. I can go beach it softly nearby on an island with great sand and clear water to have alook I may be surprised... sailboat only get slime but that's with antifoul. It's prop stays pretty clean.

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kens
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby kens » Sat Sep 10, 2016 5:18 pm

North wrote:Just verified #s today - top speed was off by a Knot - was a bit windy and I am getting some good growth n the bottom edges of hull, and perhaps under hull....been in the water a couple of months now with epoxy primer only - no bottom paint... will pressure was off when I take it out in a month or so, if not sooner.

Also, i'll correct a previous statement - the hull bottom / hull extension is of course riding on the water on plane - top is dry but water is coming off the bottom, straight back so it is NOT "out of the water" as I thought previously.



That is good to know, I couldn't imagine how the hull could ride with the transom coming out of the water.
Looking at pictures, it is hard to see,. Does your chine spray rails run all the way to the transom? In pictures they look like they stop before the transom?
Is your transom corners wetted when on plane?
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

North
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby North » Sun Sep 11, 2016 4:41 am

Per the aluminum plans, the spray rails fade out / stop but, yes the chines aft still stay on top of the water. There is a nice flow from chines and spray rails forward which make a recessed or lower water area next to the aft chines as well.

North
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby North » Fri Mar 03, 2017 2:24 pm

Hi All - Ken - we have discussed alot of things, pitch, slip, etc.

A bit of new info, i finally removed my current prop (marked 15" x 14") and used a template and software off youtube to measure it - seems to actually come out to 15" x 15".

How does that change your slip calculations - in general I mean... I assume it makes them even worse......?

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kens
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby kens » Fri Mar 03, 2017 7:15 pm

How a prop is stamped doesn't really mean as much as 'how does it run'
If I remember, you were under-propped?
I was suggesting adding cupping? or, adding pitch.

My experience with Double Eagle is that it responds to cupping in a big way. A small amount of cup yields a big result.
Can you go to youtube and find a way to measure your cupping??
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:

North
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby North » Sat Mar 04, 2017 4:38 am

I don't think there is any cupping on current one.
I have found a closer guy who should be able to add cupping, and pitch, if required. Just haven't got in contact with him yet.
Last edited by North on Sat Mar 04, 2017 1:59 pm, edited 1 time in total.

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hoodman
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby hoodman » Sat Mar 04, 2017 7:53 am

Loser? Is that what they call prop technicians? :lol:

North
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby North » Sat Mar 04, 2017 2:03 pm

Hi Matt - thanks for pointing out my typos....

My other prop shop was a 3 hour + drive each way, or start having shipping costs add up if multiple "tweaks" were needed.
just found a guy close to our boat/ shop with prop / machining experience. But, he is retired, with no shop so I have to ask if he is able/ equipped to add cupping and / or pitch in our shop, or make other arrangements.

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hoodman
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby hoodman » Sat Mar 04, 2017 4:17 pm

Ah "closer" makes a lot more sense!

North
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby North » Sun Mar 05, 2017 7:07 am

Unfortunately, the closer guy is not equipped to do it. I will likely ship my current prop to have cupping and about 2" of pitch added, as I need to reduce WOT rpms by about 500rpms. With an aluminum hull, ideally I will eventually find a SS or aluminum prop, as bronze or nibral increase chances of robbing aluminum from the hull. But, I am not in a marina, or close to other boats, nor plugged into shore AC power - so I will make do and keep an eye on things for now, and keep/ watch anodes on hull and prop shaft.

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chugalug
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby chugalug » Sun Mar 05, 2017 7:52 am

:D One of these might be handy to keep eye on things(depending on water clarity)This is cheapie black and white with 60 ft cable.
IMG_0906[1].JPG
it also has Infared setting to see in dark.
Working on regular-sized Bo-Jest


"If it's not crooked,It's not mine

North
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby North » Sun Mar 05, 2017 10:59 am

Those would be neat to have - but my wife will shoot me if \i buy anything else "'for the boat".
I will just snorkel once in a while and also dry out on trailer, or on my launchway/ slip as we have about 5 ft tides and the slipway is grassy. I haven't tried it yet, but with the full keel, I am assuming it will lay ok with some weight on the keel and the rest on the port or starboard chine. The keel and skeg are fairly rugged, but I didn't build it specifically to hold all of the boats weight -I would worry a bit about the prop strut is it were holding most of the weight I could also put a drum or jackstand aft under each side of transom. \had toyed with idea of welding in a short piece of vertical pipe, on each side of transom, so I could then insert a small diameter pipe and use as temporary "legs".

North
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby North » Thu Aug 03, 2017 6:01 am

Hi Folks,

quick update after having prop reworked.

old numbers:
4.5 kts at idle 800 rpms
14.5 kts at 2200 which is where it hits peak torque
About 17 kts at 2500rpms which is max rated rpm for continuous use
About 19 or 20 kts at around 2800 rpms which is max rated rpm intermittent use.
23 kts full out which is I think around 3100 or 3200 rpms - have not been out again since cleaning sensor.


new numbers after adding cupping and 2`of pitch to prop.
5.2 kts at idle 800 rpms
17 kts at 2200 which is where it hits peak torque
About 20 kts at 2500rpms which is max rated rpm for continuous use
max out at About 21 kts at around 2600 rpms which is 200 rpms less than max intermittent use rating due to load on engine.

hindsight is 20-20 - i am happy with results as I reach a cruise speed at a lower, more efficient rpm range- however, if I had it do to over again - I should have listened to Ken, and only added the cupping, or perhaps cupping and only 1 inch of pitch, as I am now slightly overpropped, where previously I was underpropped.
One thing I did not consider, but now I assume would have made a difference- when going by rules of thumb - like 200 rpms for every inch of pitch - most guys run 1.5:1 or 2:1 gears where I have a 1:1 gear - I assume than my pitch change would therefore have more impact as it will turn more times per minute....but that`s an uneducated guess.

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kens
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Re: Double Eagle -need to tweak prop pitch or settle with pretty good

Postby kens » Thu Aug 03, 2017 4:59 pm

Are you saying you lost 2 kts at wide open??

Sounds like a good sea trial, and good fuel efficiency numbers.
Oak is over rated, everything about it takes extra time; then it warps, splits or checks !!! :roll:


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