Custom 1965 Correct Craft Mustang build |
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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It's more so when I have somebody in the front seat, 2 in the front and 2 in the back I can barely break 30. My driveshaft is at a steeper angle than factory, not sure if I ever mentioned that. After I did all the bottom work and stringers whatnot I went to install the driveshaft and strut to find it was binding on the driveshaft housing log. I thought the spacers on the old strut was because it was bent, but I guess either the log was removed/replaced or incorrect angle from the factory. You could see that the old driveshaft was rubbing for years. So I made a little fiberglass shim for the strut and called it good. I order the lenco low clearance kit. It comes with 4x12 tabs which I will either modify to be 12x9 or replace all together. I need the short actuators and it's actually cheaper to buy the kit than the actuators separately. I'm going to mount the actuators so they are completely below the waterline |
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SNobsessed
Grand Poobah Joined: October-21-2007 Location: IA Status: Offline Points: 7102 |
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Would it be possible to reset the prop shaft angle back to OEM spec?
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“Beer is proof that God loves us and wants us to be happy.”
Ben Franklin |
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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Not without cutting out the shaft log and some of my stringer floor supports. |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Going back to the shaft angle that CC used would, in my opinion, be my recommendation. Installing "band aid" trim tabs as mentioned by several members may not work and in fact may create a dangerous handling problem. |
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Eether
Groupie Joined: October-20-2015 Location: Greenville Status: Offline Points: 64 |
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Resetting the shaft log isnt too bad..
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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But I'm guessing all motor mounts need to sit lower, pretty big task.
It will be interesting to hear what the tabs end up doing for you. I also like the idea of trying a different prop, I realize it's a bit limited for the older hulls but if you could find something a lot different you would find if the porpoise changed speeds or went away. |
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'63 American Skier - '98 Sport Nautique
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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Here's why I really don't want to pull the log out, stole this from page 16, makes my stomach hurt when I go back that far and how much work I've done.
I put my specs into a prop calculator, I currently have about 9.5% prop slip which from my research is pretty good at top speed. How can prop dimensions effect porpoiseing? I only get the porpoiseing between 43-48mph but it goes away completely after 48. The trim tabs are only for extra passengers, I will probably leave them fully retracted when it's just me in the boat. Based on my experience with the Chris Craft the tabs will be a perfect solution for a loaded boat |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Props with more aft rake which is typical of a CNC machined prop, produce more of a cone shape aft wash which has been reported to affect the attitude of hulls. Based on my experience tabs are the worst thing you can do to a wood hull under about 26'. |
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peter1234
Grand Poobah Joined: February-03-2008 Location: United States Status: Offline Points: 2756 |
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how many degrees of angle do you think you actually changed it? i bet it was no more than 3 degrees . i cant imagine that give or take a degree could change the hull performance that much?
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former skylark owner now a formula but I cant let this place go
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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I could see it making a pretty significant difference, especially on a 16 foot boat. A few degrees on a 21 foot boat, maybe not so much impact, but on a short boat like this a few degrees change in thrust angle could have a big effect.
Just thinking aloud, because of course I have no experience doing this myself, but I wonder if the largest diameter prop you can fit under there, with a pitch to match your peak rpm, might help. I'm just thinking the most blade area you can have might give the best result, even a 4 blade if that's possible on that boat. Again, just guessing. |
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'63 American Skier - '98 Sport Nautique
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peter1234
Grand Poobah Joined: February-03-2008 Location: United States Status: Offline Points: 2756 |
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Jim what is the center of the shaft to the hull measurement ? maybe you could get some comps from a few similar boats on here providing the parameters are also similar . face of the prop to strut etc.
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former skylark owner now a formula but I cant let this place go
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Jim,
When you did the hull, did you remove any of the hook off the bottom? You measured and found the hull had about a 1/4" hook. Removing any of it can make a big difference. Also, keep in mind previous warnings:
BTW, my comment below was on a wood Chris Craft modified with trim tabs to get the bow down.
Again, I feel you will be modifying hull performance with the tabs that could be very dangerous. Did you ever contact Peter (peter123) regarding his problems with a larger HP in his Mustang? |
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peter1234
Grand Poobah Joined: February-03-2008 Location: United States Status: Offline Points: 2756 |
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I love going fast. I love running something to my fear point. That boat was great fun for a holeshot. I would never go through that project ever again it went so far beyond scary all i could think of was i was either going to die or worse yet i was going to kill someone. mess with hulls that are made for it . or just make yours a launching monster from idle
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former skylark owner now a formula but I cant let this place go
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TRBenj
Grand Poobah Joined: June-29-2005 Location: NWCT Status: Offline Points: 21169 |
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This hull can run fast relatively safely- when set up properly. I do not believe trim tabs are a means to that end.
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Riley
Grand Poobah Joined: January-19-2004 Location: Portland, ME Status: Offline Points: 7953 |
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But someone still has to be the test pilot to figure out if it's set up properly. |
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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Kind of like the old Mutual of Omaha Wild Kingdom - Marlin stays safely in the tree stand while Jim fights the wildebeest. Only in this case "let's film safely from shore while _______ (fill in Peter, Tim, Joe, Reid, etc.) drives the 16 ft. CC at 60 mph". |
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'63 American Skier - '98 Sport Nautique
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peter1234
Grand Poobah Joined: February-03-2008 Location: United States Status: Offline Points: 2756 |
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you know its bad when your 18 yr old calls you from the lake and says dad can you come over here ? i am never driving this thing again
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former skylark owner now a formula but I cant let this place go
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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I'm using the trim tabs to accommodate more people
The trial and error of changing props, shaft angles ect. MAY solve the issue of having more people in the boat, or it could cause the boat to slow down, flip at high speed, who knows Boat drives great with just me in it, the amount of time effort and money in changing the shaft angle and prop to possibly fix one problem, when I know for a Fact the tabs will solve it, doesn't make much sense to me |
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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Jim, Are you insured especially for liability? |
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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Jim, keep up the good work and let us know how the tabs work out.
Pete, was that question really necessary? When other guys on the site put more HP to their little hulls than they were ever intended to handle, I haven't seen you ask them about their insurance status. |
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'63 American Skier - '98 Sport Nautique
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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David, Absolutely! I feel you are forgetting about the modified shaft angle, all the warnings about the nose down problems that tabs can produce plus the added HP! Have you forgotten the problems peter1234 had with just the added HP?? Would you load your modified boat up with a bunch of people and not have insurance? |
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63 Skier
Grand Poobah Joined: October-06-2006 Location: Concord, NH Status: Offline Points: 4269 |
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I think you are missing some points. Jim sounds like a very experienced driver and someone who has worked on a lot of different hull types - he's not some yahoo slamming the throttle down and seeing what happens. He is trying to correct a porpoise happening at around 30. The idea isn't to put the tabs down at 50, in fact he says in an earlier post that he will warn the Chris Craft owner of the dangers of over-tabbing. I think he'll approach this cautiously.
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'63 American Skier - '98 Sport Nautique
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8122pbrainard
Grand Poobah Joined: September-14-2006 Location: Three Lakes Wi. Status: Offline Points: 41045 |
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This friend like many of us grew up from a very young age behind the helm and had thousands of hours experience before the accident. Chine lock can happen suddenly is certainly unexpected and can happen at low speeds. What I didn't mention is he too had a full boat of passengers, told me he was at about 35 and knowing him was never a "yahoo slamming the throttle down". |
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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Considering just about every inboard from the mid 90's to present was offered trim tabs from the factory it's not crazy to believe that the instances of bow steer and chine lock are relatively low on factory or modified boats. Especially considering I personally know about 80 people with inboards (about 20 with trim tabs) and the only accidents with injuries I've learned of were related to crashing into land (2 instances) or fire (1 instance). To negate trim tabs as a reputable solution is completely absurd and the fact that they do work isn't up for discussion in my thread because I have seen them work flawlessly to solve the exact problem I'm experiencing. I too thought them a poor solution, but only due to the stigma some have to them on this website, I found that my real world first hand experience they are a great solution.
If you feel that strongly against trim tabs, just leave my thread. Now onto the tabs! My kit came in the mail today, some quick measurements assured me that I will be able to mount these below the waterline no problem, which is very important to me as I HATE the black plastic. May even paint all the black Perfection white, but that's much later on. The tabs themselves are 12 wide by 4 long which obviously won't work, still have to decide if I'll cut and weld these tabs or buy 9x12s. It's 10 degrees outside so I'm not sure when I'll start this project. |
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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Just realized I never showed you guys the two motors I got over the summer. The one out of the tan Mastercraft is a standard 351w PCM that was sitting for 12 years in Texas. It would need a total rebuild but is complete. The other is a 351w Holman Moody that kinda runs but needs lots of love, compression OK but fuel and ignition need a lot of work. Hoping to come across a first Gen mastercraft or first Gen nautique hull or barracuda for the Holman Moody someday. Both are in my tent with the boat. Both boats got brand new fully dressed chevys.
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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Hussler
Gold Member Joined: February-04-2012 Location: - Status: Offline Points: 897 |
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74Wind
Grand Poobah Joined: August-02-2011 Location: Georgia Status: Offline Points: 2101 |
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My brother put tabs on his 72 Southwind 20 about 10 years ago which dramatically improved the wake, and has had zero trim tab related problems or issues since. |
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1974 Southwind 18
1975 Century Mark II |
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fanofccfan
Platinum Member Joined: December-13-2009 Location: North Bend NE Status: Offline Points: 1772 |
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Someone along the line added them to my Marauder....they are the manual type that are set with a bolt.......I have never tried setting them different and don't know if they make one bit of difference. I also don't get past 43-45 mph. But with a few people in the back at WOT it hops down the lake like a wild amusement park ride!
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