Lifting Rails- Chines

[hideout]

Does anyone know the pros and cons about installing lifting rails, chines on a 1978 42 C. ???

Will I get better speed, will it stablize the roll ?
What does it do on a following sea? email nrd0235@aol.com

[Boss Lady]

Pros on lift rails, reduced roll, and roll dampening, some speed increase. Cons, can pound more. I had Starman put some pretty agressive rails on Boss Lady. These are glass over divincel foam. If they turn out to cause too much pounding on the bow section, they will be easy to reshape and reduce their profile. I did a lot of questioning other owners that had installed rails and the slower boats picked up around 2 knots, and the faster boats picked up as much as 4 knots simply by installing the rails.

Click on the link below and see some pictures of the rails.

[Trojan]

About the only style boat that will show any real gains is a boat that is stern heavy. They will help any boat somewhat depending on the lift rail size and length. They will help all boats come out of the hole quicker. On a Hat I don't think you will see much gain in stabilization because we already have a heavy chine. Maybe a little bit, but I don't think they are worth adding for stabilization reasons. They won't help at all in a following sea. They may make things worse If they catch a wave on the corner. I thought about increasing the rail size on my 43, but reconsidered. Just my thoughts.

BILL

[Nonchalant1]

They also have a VERY strong rub rail on them which serves to keep the hull off of lock walls and dock walls. At least the factory lift rails do. I took them off to refinish the paint and I couldn't believe how heavy and strong the one piece solid stainless steel rub rails are.

Yeah, I know, we're all such good pilots that we never touch a lock or dock, but I touched quite a few and the hull never touches.

Doug

[Boss Lady]

that is an excellent point Bill. Like anything there are trade offs. Since the rails are below the waterline unless up on plane, I do believe they will provide some dampening, the effective area is greater than a sheet of plywood so there is a lot of surface area. It remains to be seen how much a following sea will affect it. I took the opportunity to experiment, and if I don't like the way they make the boat react, they will come off quickly with nothing more than a sawsall and a grinder and a repaint below the boot stripe. Most of the 53 Cs I have seen have lift rails added. I can't comment on how they actually perform since Boss Lady has taken a back seat to Paul's new responsibilities getting the marina back in shape. However, it looks like he is getting new staff on board and hopefully get back on her, and we can splash the boat this summer and test out all the new things we added.

[Trojan]

If they increase your planing area your going to get some help. Both in lift out and some speed. Just by increasing the planing area. But if they reach any further forward than the planing area you could get a pounding ride. They need to be in the water at all times to help. Hat's are so wide and the chine is so hard that you won't show much stabilization gain, but they sure can increase the planing area. But how wide will they need be to make it worth while change. Kind of like the carbon fiber prop I think:D. I guess it would be safe to say the lighter the boat the bigger the gain in lift and speed. The heavy boat would require size able larger rails to make the same gains. If it would. I think boat length and weight would determine how much benefit you would gain.

BILL

[Boss Lady]

I am very old school when it comes to engines and controls, but I do believe that some new technologies are worth playing with, especially since some of the propeller technology used by the military is now finding its' way to the recreational market. I almost went to gear reduction and larger blade area props, but the shaft sizes would have required all new struts, shafts, and shaft logs (very expensive). It makes sense for new boats but a refit does not compute for Return On Investment.

And then of course it is a boat and it doesn't have to make sense if it fits in one of the three main categories: 1) I needs it. 2) I wants it. or 3) I just gots to have it! LOL

[MikeP]

My "next door neighbor" (toward the head of the dock) at our marina has a 58MY w/lift/spray rails. When I noticed them last summer I asked him about them and he told me that it was a waste of money. He said they provided NO benefit at all on his 58 - no increased speed or efficiency and no noticeable reduction in spray. He runs his 58 - or did at least through last season- at planing speeds most of the time so if the spray rails were going to do any good, they should have demonstrated it on his boat.

Maybe they would be more effective on a different hull.

[Boss Lady]

Mike look here: http://www.thesmartrail.com/photo_pages/1_before_and_after_photos.htm

[MikeP]

Yes, I've seen that ad. I'm just repeating what Larry (w58MY) told me about his experience with them.

[Boss Lady]

If his rails are installed too low, the bow wave will ride over the top anyway and render them ineffective. I have seen this occur. If you look at some of the pictures you can see how the spray rails redirect the water that follows the hull up towards the deck down and away. I saw these on a Bertram as I followed along beside him and I was so impressed I followed him to the dock to look at them.

The smart rails and fast rails work by cutting down on the wetted area, and this reduces drag.

hard lift rails also decrease wetted hull area, and provide additional hydrodynamic lift.

[Mike36c]

My boat had very large full length lift rails when I purchased it. After the re-power and now 20+kt cruise the ride became terrible, I cut them off. I don't miss them.

[REBrueckner]

How convenient: The "old" picture shows the Hatt moving through wake waves...just when spray is a maximum....note the lower photos..in the smooth, low/no wave portion of the photo boat wake...

That said, spray rails CAN of course help keep spray down UNTIL waves break above the rail,,say wakes, wind driven,etc...then the spray pretty much will rise as it always has...

I don't belive a gain of two to four knots is possible from lift rails alone...I'd even be surprised with a half knot, but would believe it might be possible.

Let's say the half hull width, keel to chine, is 7 feet; then an additional four inches (for example) width for a rail is another 1/3 foot....an increase in area of about 1/21...call it 5%....I can't see how that would change speed much;but maybe stability a bit since that extra bottom area is at the extreme leverage point (biggest moment) for lateral stability...would it even be noticeable??

[Boss Lady]

I agree that the pictures shown could have been done better trying to replicate the same conditions. I did see them work in person out in the Atlantic and was impressed. I did not buy these rails, I had them fabricated instead, since I don't care for plastic do dads, that will wind up with ageing problems down the road. If you look at a Hatt hull there is very little horizontal lift surface. We added 6" wide lift rails which provides roughly 25 square feet of horizontal lifting surface to the hull that will remain in contact with the water. Hydrodynamic lift increases with the square of the velocity. I have done extensive research on this, along with interviews of owners with lift rails installed. I am convinced. However, my objective was not intended to provoke discord. If your cursory opinion is that lift rails do not offer anything then leave them off your list of things to do. For those interested there is real science available. Here is a handy website that has an extensive collection of NACA data: http://naca.larc.nasa.gov/search.jsp?R=970925&id=10&qs=Ntt%3Dhydrodynamic%26Ntk%3Dall%26Ntx%3Dmode%252 0matchall%26N%3D17%26Ns%3DHarvestDate%257c1
We do have a few bonafide engineers aboard that my indulge us with some analysis of this topic. I for one do not see any real science being applied in the recreational boat industry. The normal answer is usually more power. However for a boat that has some real engineering applied look at this example of what can be done. Then you be the judge if the manufacturers really spend any time improving the breed, or more on marketing. http://www.amsgrant.com/files/ams17.html
This is a 67 foot boat that cruises at 36 knots with 1000 hp total power and top speed is 47 knots. I have had numerous conversations with this naval architect on this topic and many others. My next boat will be one of his designs. In the mean time I will maximize what I have.

[mopester]

I will throw my un edjumacated opinion in as well.

I read a lot of old threads here before and after i joined. I walked around many yards up here to find boats with any form of rail. i even found two of the same boats docked next to each other, one with and one without, and they both agreed it was night and day. Most of the people i talked to spoke posative. the only one out of about ten was this huge 70 ft trawler type thing? after reading about the variuos hull types, drag, wetted surface and go fasts i was more confused....

I decided to use a 3 1/2 wide plastic type from a popular company in maine. I drilled the holes and then threaded the holes in the hull. I used 5200 and s/s screws every 8 or 10? inches to fasten it to the hull. out of all of the screws i put in i only found one that went through the hull. i then filled the screw holes with a soft milky colored plastic plug material that was cut off proud then sanded flush. I dont yet have any test results as my boat is not complete yet.

If you want some pics go to me link in my signature and look through my pics.

Chris, I have seen yours up close and talked to paul at great lenght about them. I think yours will be better than mine!!
The marina is looking great!!

[mopester]

Paul, thats a nice boat in that link. I like the double step puting in all that air underneath.

Here is a picture of a boat with a different twist on the rail. The picture makes it tough to see, look under the orange part near were the word coast starts. it is actually square shape with the bottom cut off. these boats drive like its on a rail.

http://www.safeboats.com/default/boats.html?boat=rbs

Here is one with a video of the sharp turns, click on the yellow boat video.

http://www.safeboats.com/default/video.html

[Boss Lady]

Mopester, the new paint is looking good! What paint did you use?

[Reelin]

How convenient: The "old" picture shows the Hatt moving through wake waves...just when spray is a maximum....note the lower photos..in the smooth, low/no wave portion of the photo boat wake...

That said, spray rails CAN of course help keep spray down UNTIL waves break above the rail,,say wakes, wind driven,etc...then the spray pretty much will rise as it always has...



The pictures on the Smart Rail site are my boat.

The intention of the Smart Rail installation was to make the boat a little less wet, not necessarily gain speed. I will tell you the installation of the rails on my boat have done exactly that. There is a noticable difference in the amount of spary thrown up at the wheelhouse. If the seas are big enough, I still throw spray up on to the bridge, but under normal conditions, they do lessen the amount of spray.

On the Reelin we have 1 eight foot rail installed from the bow right on the chine. They do work.

[REBrueckner]

Chris, Wow...I now recall a prior thread post where you mentioned 6 inches addtional spray/lift rail width.... I can understand some change in stability and perhaps noticeable speed/lift...did you gain some speed??

I skimmed the NASA article but I wish the author would have summarized results...I did not see any result thast jumped right out at me...

Reelin...My experience with PVC spray rails, about three inch width, on my 48 YF, at the bow is similar to yours...Even though I installed them above the top of my waterline, they could have been raised an additional 3 to 5 inches to catch additional wave action.

[Boss Lady]

The boat is not in the water yet.

The science end of this will make your head hurt, unless you are an engineer. The point I was making is that these types of issues are not readily apparent to the layman. Hydrodynamic lift and drag coefficients are much larger than for air. This is why very small foils can lift very large boats out of the water. Just think of a 747 trying to fly with 2 foot wings, but that is good comparison for what can be done in the water. Look at this site for some interesting reading. http://www.foils.org/gallery/usn.htm

I have said before that I have not seen much being done in the recreational market.

I like Krush because he does not automatically accept the status quo', neither do I, hopefully he will figure some things out at an earlier age than I did and be able to take advantage of that knowledge. Krush you are right age and position do not automatically make one smarter or superior. However, those who pay attention do obtain wisdom. That is the only thing one might learn from us old farts.

[ThirdHatt]

http://www.amsgrant.com/files/ams17.html
This is a 67 foot boat that cruises at 36 knots with 1000 hp total power and top speed is 47 knots. I have had numerous conversations with this naval architect on this topic and many others. My next boat will be one of his designs. In the mean time I will maximize what I have.



That looks like a very fast hull that reminds me of a Fountain stepped hull. Their website says twin 1,000hp Cat's so actually it's 2,000hp total power though. Big difference but still very impressive speed from relatively "small" engines. Cool boat!

[Boss Lady]

My bad, i forgot to add them up, but just look at how much power Jarret Bay, Tribute, Rybovich, or Hatteras puts in to go SLOWER, and then you can appreciate what Grant has accomplished with this design.

The Hatteras 68C with twin 1,800 HP, total 3,600 HP only runs 36 MPH at WOT. This is their latest hull design. The Speed Merchant was built in 1995, and has 2000 HP, cruises at 41 MPH, and tops out at 54 MPH, with roughly half the HP.

Yes it looks like a Fountain hull. It also looks like a stepped hull from the 1930s used on airplane floats. My point being that I don't see much technology being used even today.

[REBrueckner]

You have a really good point with the HP speed comparison....I wonder what the tradoffs are with their design...there are usually some...I see Trinity commissioned them to design a new exterior....not hull, I wonder why??

Yet speed with modest HP is not entirely new, but those 40 knot speeds may be...Huckins has long achieved a hi speed/HP configuration with its Fairform Flyer hulls. And believe it or not in 1973 Matthews (of Port Clinton, Ohio) offered a Ford gas turbine in their 57 foot fiberglass hull as an option...none were ever ordered....

I would have thought the really weak link is props rather than hulls... now I begin to wonder....

[REBrueckner]

Lift force is related to speed....more speed, more force from the water and hence more lift...you can feel the difference with a hand in the water...water ski principle....and it would seem a somewhat light weight boat is required...the lift strakes introduced by Dick Bertram ( in conjunction with deep vee design) and widely copied, I think Sea Rays likely use them, and of course many high speed race hulls all provide lift, but usually in hulls a lot lighter than our older Hatts...

[Boss Lady]

The theoretical drag reduction using air entrainment (stepped hull) is 80 percent. The only place this technology is being used is by Fountain, Regal, and Donzi for production boats.

[NAN-PO 41]

If I remember correctly didn't Rybovich offer an outboard powered center console years ago that had a stepped hull that the steps flooded when at rest to give stability to the boat when it was stopped. I remember seeing it at the Miami show ( had to be 30+ years ago ) and it was scary fast for it's time with the power available.
Fred

[Trojan]

I was under the impression that the original question pertained to a Hatteras designed hull. You all have valid good points. The examples are good. I prefer the step hull for the faster hulls. I still think the money spent to put them on most Hatteras boats is money lost. You would really need to look at all the parameters before going ahead, There are many factors that change with the particular style boat. Like length, width, speed, HP, deep V, keel, weight, hard or soft chine, DC, MY or SF are just a few. I think each boat must be evaluated on its own, even if two boats appear to be or look the same. This is a good topic. I don't know when I can join in again they limit my time in intensive care. Going on 10 days. Looks like launch will be delayed a while.


BILL

[Boss Lady]

Get well Bill, I didn't know you were back in thehospital. God speed my friend.

Chris

[mopester]

Mopester, the new paint is looking good! What paint did you use?


I was going to use strait awlgrip but let them paint rep talk me into awlcraft due to its repairability..

thanks for noticing!

mike

[Boss Lady]

Paul has convinced me to go with Awlcraft this time for the topsides. It is close enough to Imron, and can be buffed down the road.

[old41]

Well, after taxing my 56 year old brain and finally correctly linking 2 pictures to my photobucket account, which I've never used, I put the cursor over the said links and no highlghts!

The top of page informs me I need 15 posts to connect to a link.

To top it all off, I'm late for happy hour!

4:46 Monday

Have a good evening guys!
Bobby

[mopester]

old 41, what were you going to show us?

Plus yachtsman bill is asking questions about his rails in the "cant take the strain thread if any one has any info for him.