Quote:
Originally Posted by Bushwacker
Good idea on minimizing setback and making a wide tub!
On the width of swim platform, you might want to consider extending it far enough past flotation tub to be able to mount a swim ladder underneath platform! Regarding angling bottom of swim platform, you're losing some flotation doing that. Looks like you're planning to mount it a bit lower than mine to gain flotation (good), so understand desire to prevent dragging in water, but might want to send a PM to Don Herman about that. The Hermco bracket is straight on bottom and longer (30"), but it doesn't drag in water when on plane, even at 12 mph. Even if it did drag temporarily coming on plane, it would act like a trim tab and provide more stern lift to help boat get up on plane, so I don't think that's a bad thing! Might look at making bottom straight with no slope but mount about 4" up from bottom, and see which design has more flotation.
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Thanks for the insight, I can make the swim platform wider for the ladder to fit under and that might be a nice addition for the kid getting in and out of the boat (this will be out family boat). How wide of a space is needed for a telescopic ladder like you have? I was going with the 72" wide unit due to that is what my last one was on the 20' hull and I already have the top half mold built. I wanted to make it 84" wide but after looking at the rear of the boat the 72" would give me clearance for the rams for the trim tabs or the K planes that I will probably use. I have the tub so wide and the swim platform so low it doesn't leave much room for the tabs rams. I want the platform low to the water as possible and even with the low clearance model tabs I don't think I have enough vertical room to mount the top of the ram. The narrower platform will let the rams mount beside the edges and clear the platform. I don't want to cut holes in them and run them threw the swim platform or I don't want to use the Volvo tabs (they are nice but not good for my application). I have a sketch of a custom trim tab I will build if I do not get the expensive K planes that is similar to Mr BlueHerons tabs. It looks like I go with have to go with the more narrow platform and have room for the rams or I will have to make some kind of low mounting custom rams for the tabs that will mount low enough to clear if I make the platform wider. I don't mind making a new mold for the top half, but just need to figure out the details so the ladder and tabs will all fit correctly or it will not be worth doing and then it will make more since to use the 72" mold I already have.
Now about the taper on the tub, I may be worried about something that will not be a problem. I figured it may need the extra room due to me mounting the tub so low. I didn't realize the Hermco is straight outward on the vee part of his, Every bracket that I have seen other than his has had a taper up wards on the vee and more than the 2" that I used. Most taper is like 4-5" up wards. I don't want to loose the volume and had it sketched out as a straight leg but after pulling strings and taking measurements I figured it would drag unless the boat is riding very flat, level or have the tabs buried to keep the nose down. Even with the 2" up wards angle it will only allow for a minimal attack angle before it drags. I changed this last minute after reading about another guy who made one without the taper on the vee and it caused his to porpoise back and forth he clames. He said it would hit the vee and then it would make the nose dive like a tab would but then it would lift back on it and start proposing. He said the boat did not do it before the bracket but only after installing. It was mounted low also. His may of just been a balance issue mainly but it got me worried and that is my basis for adding it.
Far as what would have more flotation volume (not a math wiz) but the 2" taper vs no taper at a 2" higher mounting height would cause me to loose more volume if mounted higher even with the straight leg? The lower 2" mounting would allow the larger part of the tub to sit in the water more vs only a 1/2 of the 2" slice I am cutting off. Correct me and I may be wrong but wouldn't the lower mounting with the 2" taper yeld more volume? You got me curious now because the main thing I wanted was the most volume as possible with out any negative effects. Looking at other pics of 25' seafari's they seem to ride bow proud with the hulls planning at an angle upwards and this would greatly effect the outcome of needing the angle cut on the tub or not I am thinking? I figured to start with the water rising off the transom will rise at 1" per foot back, so that will leave little clearance at 22" back due to the water should of rise around 2" at this point letting it just scrape by with out any addition room for error and that is assuming the boat is level in the water at plane. Factor in the angle of attack the boat will ride at and that will cause the tub vee to angle down into the rise of the water leaving the transom. I might be over thinking all this but that has been on of the blind factors I have been trying to figure out. Any more incite on this would be greatly appreciated.