Any Hull Experts out there ?????????

[Liberator*21]

I'm thinking of adding some lifting strakes to my hull that would actually form a semi pad. My boat has a radius'd hull (no flat pad to run on). The strakes I have now are pretty much worthless due to there small size. I have some ideas, but need an experts advise................anyone care to help me out ............:confused::confused:

First idea is to make a pad from strake to strake, see pic below.............
What's the pro's and con's of either of theses types, Bass Boat Hull.........

http://i177.photobucket.com/albums/w201/90profx/Boat%20Misc/STRAKE1.jpg

[Cobra1racer]

sounds like a jet boat bottom. I put a pad on a jet boat hull powered with a whacker and it ran like shiat. But that's what he wanted and thats is what he is stuck with.

[Liberator*21]

Bass Boat Hull, added pic above..............:)

[Liberator*21]

Come on, surely somebody has to know something about this????????????
BTTT

[staylor]

...as the 14 inch plus width is awful wide. My Checkmate Pulse 210 had a pad that was about 8 inches wide and with a 225 plus the 1700 pound hull plus about 500 lbs of gas, gear, and driver the boat would come fully up on the pad at about 53 mph. The C-Mate ran a flat pad which seemed to work just fine.
Doug

[Liberator*21]

...as the 14 inch plus width is awful wide. My Checkmate Pulse 210 had a pad that was about 8 inches wide and with a 225 plus the 1700 pound hull plus about 500 lbs of gas, gear, and driver the boat would come fully up on the pad at about 53 mph. The C-Mate ran a flat pad which seemed to work just fine.
Doug


I'm not even close to being an expert here, just looking for somebody who maybe has some in depth knowledge to explain if a 5" pad is good then why isn't a 10" pad better, that sort of thing is what I'm after.
Thanks

[staylor]

The purpose of the pad is to be a high speed planing surface that allows the boat to lift out of the water and run only on the pad surface. This reduces water drag on the hull without compromising the overall ride of the boat over waves. If you make the pad overly wide the drag will go up and the speed increase from running on the pad will be less- and the ride deteriorates. If you went all the way from chine to chine with the flat pad then you'd have a flat bottom boat- with a very rough ride and probably not much faster then your existing hull. If you're having chine walk issues with the current round bottom hull then going to a wide flat pad should cure the chine walk. This may help the top end, but not allow as large a speed increase as going to a pad with just enough area to allow the hull to lift out an run entirely on the pad at about 70% throttle and up. This allows you to be firmly on the pad at top end.
Doug

[Liberator*21]

Doug,
Thanks for the input. I understand the pad concept and yes I have chine walk issues that I'm trying to get out of. As you noticed in the sketch of my hull, the radius bottom is my chine walking problem. Long story short I'd like to put a pad on the bottom to eliminate the walking issue if at all possible. My thoughts were to make the pad out of 3/16" aluminum plate and screw it into the hull as shown in the first available strake from center out. Reason for this is, if that doesn't work, I can remove it, fill the holes and aknowledge I'll have to live with what I've got.

With my boat it's mostly either idling out of a channel or creek then it's WOT to the next spot, hardly ever in between.

Which pad works better.........flat or angled ???????

Thx again

[staylor]

...since at the speeds you're running I'd be concerned about the angled pad packing air near the keel line. This would make the rig harder to drive at speed since she'd want to walk on the pad itself. The flat pad is easier to drive without steering, pad walking or potential kiting issues, IMHO.
Doug

[Liberator*21]

...since at the speeds you're running I'd be concerned about the angled pad packing air near the keel line. This would make the rig harder to drive at speed since she'd want to walk on the pad itself. The flat pad is easier to drive without steering, pad walking or potential kiting issues, IMHO.
Doug

What about just making the lifting strake on each side bigger ? The current strakes are pretty much useless at 5/8" deep x 1" wide. Sketch below is what I'm talk'n about;

http://i177.photobucket.com/albums/w201/90profx/misc/STRAKES.jpg

[Jimboat]

290 Sprint - it sounds like you've got quite a project going on! Regarding your thoughts for a "pad"...the benefits of the modification would depend on what you're actually trying to accomplish, what you're trying to "fix" with your current hull design.

There isn't a "stock" answer to whether a pad would make your hull run better. A properly designed pad needs to consider the entire boat design and setup, in order to effectively perform well and with stability. Since we don't know much about the details of your current hull design and setup, it's tough to make definative suggestions.

Bottom Mods - your variable deadrise ("round") bottom design (is this round section the bottom or the pad?) as it is now is specifically designed for your hull's layout, setup, weight and original performance expectations. If you have some particular performance issues that you're trying to solve, hull modifications can be beneficial, but you should know that such changes will also affect other aspects of your hull's performance.

As for chine walking - this problem is typical of vee hulls and vee-pad hulls (should be less on round bottom hulls) and is caused by a dynamic balance issue during the "transition" phase of hull planing ("hump zone"). Adding a pad would not necessarily, by itself, solve a chine-walking problem, however such a modification would definitely change dynamic balance and change the speed at which you experience the chine walk. The chine walk issue might well not go away though!

Check out this thread on chine walk (http://forums.screamandfly.com/forums/showpost.php?p=1148482&postcount=14) and this article on "Chine Walking" (http://www.aeromarineresearch.com/publications/HB_Jan2008.html) for more info.

Vee Pads - the hull modification of adding a "flat" pad would make more efficient lift, but the hull would not have been designed/balanced to properly use the lift. (It was designed for the rounded hull shape). So the added lift can't necessarily be translated into more speed, or better handling, unless the overall hull design is re-balanced to effectively use the lift. (As for the "angled" pad concept, not recommended).

The performance that a pad vee hull design often realizes doesn't mean the pad design is always better, it just illustrates that the design of the hull needs to be done as a whole, and not in pieces. Changes by trial and error often don't work out too well for this reason.
<O:p
Here's some info that may help you out...
<O:p
Check out these threads on vee-pad design...
<O:phttp://forums.screamandfly.com/forums/showpost.php?p=1022478&postcount=23<O:p</O:p
and...
http://forums.screamandfly.com/forums/showpost.php?p=1018833&postcount=4

and...
http://forums.screamandfly.com/forums/showpost.php?p=1332498&postcount=23
<O:p</O:p
If interested in more details see the article on "Vee Hull Pad Design" (http://www.aeromarineresearch.com/publications/F&PB_Sept2005.html)....this may be of some help too.

[Liberator*21]

Thanks Jimboat for your input. I've searched over threads & posts concerning this project and was hoping you'd jump in here. Here's what I've got; 19 ft vee hull bass boat, 10" CMC Hyd. Jack Plate, Merc 225X ProMax. The strakes that are on the hull now near the rear are not really worth much as far as having the ability to provide lift. The chine walking issue is want I'm trying to work out of. The bottom of the hull as you've noticed is a radius and the first strake outward is only 5/8D x 1"W @ approx. 7 3/8" from center, the next strake is 18 1/2" out from center and measures 1"D x 2"W, then it's off to the outside of the hull where there is a strake 1"D x 2 3/4"W, then the hull goes upward. I started out with a Merc 150 XR6, no J/Plate, motor set at 3" below pad and boat chine walked at around 60-62 MPH, added a 6" J/P and tried every motor height combination possible, best MPH before chine walking was 70'ish, so the 6" plate helped. Next time around I picked up a new motor Merc 225X P/Max and went to a 10" Hyd. CMC J/Plate running a 29P Drag 4, again tried every height combination possible, balanced the boat out the best I could (weight distribution) and my best to date speed has been 86.4 MPH/GPS with prop shaft even with pad and that was for a nano second because the chine walking came back once I hit the 80's. There more there if I can just get the darn thing to quit break dance'n at the speed. I'd appreciate your take on the above trials.....................I guess I need to make me a 24" J/Plate.........LMAO...:D:D
Thanks,

[Jimboat]

what make of hull is it? do you have a picture of the aft end of boat? (is this round section the bottom or the pad?) any pics of the boat while running? how wide is your hull at rear? what is total loaded weight? What RPM are you turning to get 86.4mph with your 29" prop?

[Liberator*21]

what make of hull is it? what is total loaded weight?

2000 Sprint 290DC (Bass Boat "no longer made")
Boat/Motor/Gear: 2200-2400 MAX.

Pics on trailer posted below. No pics while running. The round section is the bottom of the boat, it has no flat pad of any sort. It goes from the vee in the front to a progressively large radius at the rear.

Stats:
PowerTech 29P Drag 4, 1.87R SportMaster w/built in torque tab on skeg (Ally Mod), WOT RPM 6400-6500 (7000 Redline).

(Good talk'n to ya over at BBM too)

http://i177.photobucket.com/albums/w201/90profx/Hull/IMG_0576.jpg
http://i177.photobucket.com/albums/w201/90profx/Hull/IMG_0575.jpg
http://i177.photobucket.com/albums/w201/90profx/Hull/IMG_0573.jpg

[Liberator*21]

Jimboat,

I had to paste this together. It's 1/2 the back view, I figure that's all you'd need. Bigger shot just didn't turn out well.

http://i177.photobucket.com/albums/w201/90profx/Hull/HullPic.jpg