Lifting Strakes Have Hole At End/ Weld Gaps: Why?

[Karasu]

Hi All, Boat is a new to me 2008 SunTracker pontoon boat with inboard and outboard lifting strakes. (I think these were referred to in the olden days as "NV Logs", not sure.)

The strakes are essentially long flattened triangles that are welded to the pontoons. They present about a 6" wide area each facing the water. The outboard ones are shorter than the inboard ones.

The front facing parts are nicely tapered and totally welded shut and one entire length along the pontoons is entirely welded shut.

BUT the other side of each strake is only 'dash' welded ( a few inches welded, a few inches not, repeat) AND the end of each strake has a clean circular hole in the end. SO, water clearly gets into the strakes as designed and installed.

? WHY? The extra weight and drag and buoyancy cancellation of all that water in the strakes would seem to offset any benefit of the strakes. Should I leave them that way and just drive the boat? Should I get some plugs and close up the 2" round holes on the end and epoxy seal the gaps in the welds? Or? Any suggestions/comments are welcome!

 

[Silvertip]

Pictures are worth a thousand words! Stress relief to prevent fracture is one reason for holes in certain locations.

 

[HotTommy]

If the strakes were completely sealed, you'd have to deal with pressure changes caused by hot days, cold water, etc. You'd also have the potential for freezing damage if water ever did get inside. By leaving them open that is not an issue. My guess is that your boat cruises slightly nose up so any water inside drains out the holes in the back. The slight additional weight of the water inside the strakes is likely imperceptible and starts to leave as soon as you start accelerating forward. I wouldn't change it.

 

[Karasu]

Attempted pic posting:

 

[ahicks]

So they don't hold salt water would be my guess....

 

[Scott Danforth]

Hi All, Boat is a new to me 2008 SunTracker pontoon boat with inboard and outboard lifting strakes. (I think these were referred to in the olden days as "NV Logs", not sure.)

The strakes are essentially long flattened triangles that are welded to the pontoons. They present about a 6" wide area each facing the water. The outboard ones are shorter than the inboard ones.

The front facing parts are nicely tapered and totally welded shut and one entire length along the pontoons is entirely welded shut.

BUT the other side of each strake is only 'dash' welded ( a few inches welded, a few inches not, repeat) AND the end of each strake has a clean circular hole in the end. SO, water clearly gets into the strakes as designed and installed.

? WHY? The extra weight and drag and buoyancy cancellation of all that water in the strakes would seem to offset any benefit of the strakes. Should I leave them that way and just drive the boat? Should I get some plugs and close up the 2" round holes on the end and epoxy seal the gaps in the welds? Or? Any suggestions/comments are welcome!

no, dont get plugs and seal them. they are there to drain the water that WILL get in there if you did seal it. not to mention, sealing is a sure way to oil-canning the log tube and cause a crack

the strakes are self draining.

technically only the first 3' of the strakes needs to be solid welded. after that, skip welding is all that is needed and preferred (less distortion of the log tubes)

 

[Karasu]

Thanks for all the feedback and info! I appreciate it. I hear the concerns and I'll leave them as is for now, though it still seems less than optimal to want to maximize buoyancy and lift for the boat and still elect to lug around an extra X number of gallons of water weight in the strakes. Haven't done the math but the 4 strakes in total have quite a bit of volume in them.

New proposal: What's your opinion of maybe getting some pvc pipe of whatever the maximum diameter and length that will fit into the triangular lifting strakes, thoroughly sealing both ends of the pipe, and inserting it into the strakes? Goal would be to reduce volume of water that could get into the strakes, replace some of that potential volume and weight with air (air + the weight of the pvc pipe ;-) and still allow drainage via the "corners" of the triangle profile. ?

 

[GA_Boater]

You are trying to fix a nonexistent problem. If you want to save a couple of pounds, toss the wife overboard or let her drive and you stay ashore.

For cryin' out loud, it's a pontoon, not a racing boat.

 

[Scott Danforth]

Thanks for all the feedback and info! I appreciate it. I hear the concerns and I'll leave them as is for now, though it still seems less than optimal to want to maximize buoyancy and lift for the boat and still elect to lug around an extra X number of gallons of water weight in the strakes. Haven't done the math but the 4 strakes in total have quite a bit of volume in them.

New proposal: What's your opinion of maybe getting some pvc pipe of whatever the maximum diameter and length that will fit into the triangular lifting strakes, thoroughly sealing both ends of the pipe, and inserting it into the strakes? Goal would be to reduce volume of water that could get into the strakes, replace some of that potential volume and weight with air (air + the weight of the pvc pipe ;-) and still allow drainage via the "corners" of the triangle profile. ?

first, never confuse a lifting strake with buoyancy. think of it as a glorified trim tab. it pushes against the water, creating a lifting effect. the lifting strakes do not have enough volume to even lift themselves, much less add any significant buoyancy. the only two reasons they are triangular in shape - first, a flat bar would fold over from the hydrodynamic forces, tearing the toon log, second, a piece of angle is cheaper than any other shape other than flat bar.

second, you're perseverating over a non-existant problem since your pontoon sits tail down, they are not filled with water. you should be more concerned about the engine pod falling off of your suntracker pontoon as that is a real problem with older trackers

 

[Karasu]

Geez, some of you folks are hostile and probably no fun on a boat I'm not attempting any speed records, just want to make whatever small changes to the boat that will optimize cruising efficiency and handling.
I did the math. The total volume of all 4 strakes is 9072 cubic inches. 1 gallon of water is 231 cubic inches and 8.35lbs. So at 39.27 gallons x 8.35lbs, that means that (between wakeless speed and whatever speed you get up on the strakes at least, )you're lugging around an extra 328 lbs. Seems silly to me. "ok" but silly. btw, my wife's MMA class wants to see you try to toss her overboard ;-)

 

[HotTommy]

My bottom line is still - leave it alone. But in the interest of persuading you that is the right choice consider this. There is little friction between the water inside the strakes and the strakes themselves. So as soon as you apply power, the strakes move forward and inertia makes the water want to stay where it was. The holes in the back allow that to happen. At any intermediate speed where the rear of the strakes are even slightly lower than the fronts, the water will drain out. .... You're only carrying that water when the boat is stationary. I'd wager a well designed scientific test would not reveal any difference in performance with or without the holes. ..... If you're determined to do something to play with your boat (and there's nothing wrong with that), consider packing styrofoam balls into the strakes and then cover the holes with a screen to keep them from sliding out the back each time you accelerate.

 

[NYBo]

They will never, ever be completely full after you start moving, and will quickly be almost totally empty very quickly.

 

[Karasu]

Good input, thanks. I'll probably do nothing or maybe try the PVC pipe option just for fun. The Styrofoam balls sound like they'd get pretty funky pretty fast and would be tough to remove. Thanks again

 

[ahicks]

Agree with NYBo. That rear hole is designed that size to allow the strake to empty quickly as soon as you start accelerating.

 

[NYBo]

Agree with NYBo. That rear hole is designed that size to allow the strake to empty quickly as soon as you start accelerating.

To quote Montgomery Scott, "Captain, I can't change the laws of physics!"

 

[clemsonfor]

Yes it will empty fast. When your not going fast the resistance of the water is more a problem than any water in there. It also with water I would think would make the boat more stable at rest. Think balast tanks. This is not that big a deal though. I agree with the others. Spend your time on the stereo or putting in something else cool on the boat?

 

[5150abf]

They are not intended to supply additional flotation, they present additional surface area and help get the tubes out of the water at speed, less tube in the water means higher top speed, they also help with turning.

The smaller ones on the outside are splash rails, made to limit the splash from the tubes.

The only way to seal these would be to weld the entire circumference of the chine as water will get in between the welds, simple filling the hole in the back will only keep them from draining quickly and you will be dragging around all the weight of the water in them.

 

[#Lakelife1982]

Hello I'm very interested in the performance of your boat! I have read many articles with the setup you have. I only hope it's true! I currently own a 2020 Godfrey Sweetwater 2086C. It has a yamaha 90hp SHO with currently run 28mph with just one person. I'm looking to add under penning and lifting streaks to my boat to get better performance. What's your boats top speed? Any info would be appreciated! I have attached a pic of my boat