SailNet Community - Reply to Topic

   Search Sailnet:

 forums  store  


Quick Menu
Forums           
Articles          
Galleries        
Boat Reviews  
Classifieds     
Search SailNet 
Boat Search (new)

Shop the
SailNet Store
Anchor Locker
Boatbuilding & Repair
Charts
Clothing
Electrical
Electronics
Engine
Hatches and Portlights
Interior And Galley
Maintenance
Marine Electronics
Navigation
Other Items
Plumbing and Pumps
Rigging
Safety
Sailing Hardware
Trailer & Watersports
Clearance Items

Advertise Here






Go Back   SailNet Community > General Interest > General Discussion (sailing related) > Prop size for 4-107
 Not a Member? 


Thread: Prop size for 4-107 Reply to Thread
Title:
  

By choosing to post the reply below you agree to the rules you agreed to when joining Sailnet.
Click Here to view those rules.

Message:
Trackback:
Send Trackbacks to (Separate multiple URLs with spaces) :
Post Icons
You may choose an icon for your message from the following list:
 

Register Now

In order to be able to post messages on the SailNet Community forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
Please note: After entering 3 characters a list of Usernames already in use will appear and the list will disappear once a valid Username is entered.
User Name:
Password
Please enter a password for your user account. Note that passwords are case-sensitive.
Password:
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:

Log-in

Human Verification

In order to verify that you are a human and not a spam bot, please enter the answer into the following box below based on the instructions contained in the graphic.



Click here to view the posting rules you are bound to when clicking the
'Submit Reply' button below


Additional Options
Miscellaneous Options

Click here to view the posting rules you are bound to when clicking the
'Submit Reply' button below


Topic Review (Newest First)
05-20-2013 10:18 AM
lancelot9898
Re: Prop size for 4-107

I've been using a hard bottom paint such as tridad on my max prop for over 20 years with pretty good results. However, it's important to prep the prop properly before application. Besides removing all the prior paint from the prop and getting it nice and shiney again, I etch it prior to putting the underwater metal primer(thin coats) and then two thin coats of the bottom paint. It takes me almost a full day doing this although I'm also taking the prop apart and repacking with grease as part this ordeal. I'm able to keep the boat in the water 2 to 3 years between haul outs and maybe dive once on the boat during that time to remove a few barnicles from the prop. Good Luck in getting the right prop.
05-20-2013 09:41 AM
PorFin
Re: Prop size for 4-107

P,

FWIW, it's generally considered a bad idea to use bottom paint on your underwater running gear (i.e., prop & shaft.) It may seem a little counter intuitive, but you'd be much better off leaving the metal bare than coating it with anti-fouling paint.

Why? The copper in the paint doesn't play well with the bronze and stainless. Underwater -- particularly saltwater -- you are establishing a small galvanic cell that will leech the zinc out of your bronze and accelerate corrosion of your stainless. Take a little time to read up on galvanic corrosion; it's well worth your time.

There are products specifically designed for props and shafts, but they can be pretty spendy. PropSpeed gets lots of great reviews, but get ready for sticker shock. Do some internet window shopping for underwater metal paint to get a better idea of the alternatives.

Personally, I'd recommend just leaving the stuff bare. If you use the boat often, just running the engine does a pretty good job of keeping the metals relatively clean. If you don't use it often, then giving the prop a coat of anhydrous lanolin before you splash will help some.
05-20-2013 02:01 AM
bobperry
Re: Prop size for 4-107

Pye:
Sounds like a safe plan to me. Please let us know how the prop works out.

Maybe a nice snatch block for your wife?
05-19-2013 10:20 PM
pyewackette
Re: Prop size for 4-107

Quote:
Originally Posted by bobperry View Post
Ok we know a few things:
I figured a 2.57 to 1 reduct gear and you have a 2.51 to 1, close enough.
Your prop is either a 16 by 16 or a 16 by 12.
16 by 12 is much close to my recommended 15 by 10 than 16 by 16.
But while it is clearly still too much prop I'm not sure that it is big enough to cause the problem that you are experiencing. But it is obvious by your symptoms that you are over propped.

Find a reputable prop shop. They can measure and tell you excatly what the dia and pitch are of your existing prop. Ask them if they can resize the prop to 15 by 10. Try that. Or buy a new three blade.

If you really love your boat and you have a birthday coming up, or better yet, your wife has a birthday coming up, giver her a new Max-Prop for her birthday. It's a lot like jewelry. She'll love it. Max-Prop will send you the new prop, already adjusted for what they know to be right for your engine and gearbox. You will love it and you will have far better performance in reverse due to the syrmetrical blade design of the Max-Prop.

And it all ended happily ever after.
Here is what I plan to do; the bottom paint I use works really well, except for the prop and shaft. I assume it is because I don't change the zincs soon enough, the bottom paint wears off quicker on the metal than the hull. So, I have always wanted a second prop so that I could switch them off mid way through the year. Grind and paint the second one and have it put on. So, switch props as they get more difficult to keep clean.

If I buy a second used prop, 15x10, I will have one to switch on and off to clean and repaint. There is a local boat yard that has lots of used props for sale.

Besides, I can tell you right now, the prop as jewelry idea, it ain't going to fly with my wife. So, this is the best I can come up with for now. But, now that you mention it, she wants a Electro Scan waste system, so I can used that and claim it's like jewelery. Works for me.
05-19-2013 01:59 PM
bobperry
Re: Prop size for 4-107

JonB;
I never really thought about it. I design the rig prportions by eye with a target SA/D in mind. General rig proportions will be a fucntion of the type of boat I am after and the position of the keel.

So,,,I pulled out my own book and went through it looking at th sloop rigs I have designed. In almost every case of a masthead rig the fore triangle is much bigger than mainsail area. The closest I found to a "square rig" was, MOBISLE, LOON and WHITE EAGLE. They are not strictly square but they are close.
05-19-2013 01:43 PM
SloopJonB
Re: Prop size for 4-107

Quote:
Originally Posted by bobperry View Post
JonB:
I don't know about "square" sail plans. I'm not sure I would go along with that theory.
Interesting. It was something I read years ago and it was not explained, just one of those "That's just the way it is, nobody knows why" kind of comments.

Just out of curiosity, have you ever designed a "square" sail plan?
05-19-2013 12:56 PM
bobperry
Re: Prop size for 4-107

Ok we know a few things:
I figured a 2.57 to 1 reduct gear and you have a 2.51 to 1, close enough.
Your prop is either a 16 by 16 or a 16 by 12.
16 by 12 is much close to my recommended 15 by 10 than 16 by 16.
But while it is clearly still too much prop I'm not sure that it is big enough to cause the problem that you are experiencing. But it is obvious by your symptoms that you are over propped.

Find a reputable prop shop. They can measure and tell you excatly what the dia and pitch are of your existing prop. Ask them if they can resize the prop to 15 by 10. Try that. Or buy a new three blade.

If you really love your boat and you have a birthday coming up, or better yet, your wife has a birthday coming up, giver her a new Max-Prop for her birthday. It's a lot like jewelry. She'll love it. Max-Prop will send you the new prop, already adjusted for what they know to be right for your engine and gearbox. You will love it and you will have far better performance in reverse due to the syrmetrical blade design of the Max-Prop.

And it all ended happily ever after.
05-19-2013 11:26 AM
pyewackette
Re: Prop size for 4-107

Interesting new development since the subject of resizing a prop came up. When I originally looked at the prop it had 16x16 stamped on the outer hub, but the inner hub had a 16x16 stamped but the last 6 was vague. It was still a 6 but it had scratch marks. Wen the subject of resizing came up I went to look again, still hard to make out, so I went to an old survey and there I found that the surveyor indicated a 16x12 prop. I went back the prop and took a wire brush to it and I can now see a faint stamp of 2 over the last six.

So, I am now assuming that the prop is a 16x16 re-sized to a 16x12. Have any idea how that effects things?
05-19-2013 01:50 AM
bobperry
Re: Prop size for 4-107

JonB:
I don't know about "square" sail plans. I'm not sure I would go along with that theory.
But for props diameter is the more important number so it figures you should give up pitch for more diameter. You size or diameter first then pick the pitch.

The way I size a prop is a method I have used very succesfully for many years. I pick up he phone and I dial:425-355-3669

This is the phone number for Max-Prop. I ask for Fred or Fredrique. They both know props well. Then I do exactly what they tell me. It never fails.
05-19-2013 12:12 AM
SloopJonB
Re: Prop size for 4-107

Quote:
Originally Posted by bobperry View Post
What you have now is what we call a "square prop" i.e. diameter and pitch the same and they seldom work well.
There's an interesting point. The same thing applies to engine bore & stroke ratios - when they are the same it is also called a "square" engine and it seldom works well either.

I understand that sail plans where the area is equally split between main & jib ("square"?) also don't generally work well.

Any math wizards here who can explain this curiosity?
This thread has more than 10 replies. Click here to review the whole thread.

 
Posting Rules
You may post new threads
You may post replies
You may post attachments
You may edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is On


All times are GMT -4. The time now is 11:18 AM.

Add to My Yahoo!         
Powered by vBulletin® Version 3.8.7
Copyright ©2000 - 2014, vBulletin Solutions, Inc.
SEO by vBSEO 3.6.1
(c) Marine.com LLC 2000-2012

The SailNet.com store is owned and operated by a company independent of the SailNet.com forum. You are now leaving the SailNet forum. Click OK to continue or Cancel to return to the SailNet forum.