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  1. #11
    Join Date
    May 2007
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    100

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    There is one other boat made kind of like this called a

    www.craigcat.com

    It is my inspiration in general but I hate to admit it but I am winging it otherwise. Got any suggestoins.......

  2. #12
    Join Date
    Aug 2006
    Location
    near rochester NY
    Posts
    9,881

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    how much $$ you figure you will have tied up in it at finish ?? are you planing on painting it ? and what about the pore in foam, good or bad idea ??
    oh also is the bottom flat ???
    thanks for the help
    ......or..........
    hope i helped

    feel free to shoot me an e-mail direct i have time to chat. james@newyorkmetalart.com
    summer is here, plant a tree. if you don't have space or time to plant one sponsor some one else to plant one for you. a tree is an investment in our planet, help it out.
    JAMES

  3. #13
    Join Date
    May 2007
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    I have done a budget and projected $4500.00 with everyyhing except a trailer but the boat I bought for the engine has one I might justify modifing and I haven't allowed anything for that yet. I would like to have a double jetski trailer as they would work out fine. I have kind of been thinking that If I can get it done for close to the cost of buying a new engine that could not be too bad. I scored a crappy doner boat for $2200 but it had an 2003 40hp. Mercury engine in near new condition so that was a huge help. It does have flat bottoms so foam filling would add some stability to the oil canning I might experiance but I don't want to do it right away cause I am sure there will be some modifications before I am done. That stuff is real expensive too.

  4. #14
    Join Date
    Oct 2006
    Location
    DFW area
    Posts
    180

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    Quote Originally Posted by Doug Doty View Post
    foam filling would add some stability to the oil canning .
    That foam is amazingly strong. Poured into the sponsons, it will strengthen them the way the new generation styrofoam surf boards are done. US Composites was where I got mine. They were the cheapest and most pleasant to deal with.

    Saw a picture years ago of a ultra light airplane wing that was styro. covered with one layer of epoxy resin & cloth. The wing was held up on each end with a milk crate, and had 2 adults standing in the middle. There was no noticable deflection or bending of it.

    If you use it, don't try to confine it as it expands. The stuff does generate some pressure, and if you try to trap/confine it as it 'blows', your sponsons will look like footballs when it stops expanding. It has to have a escape route for when you measure too much of a batch at once.

    Something to check on is that you may have to have some form or fashion of foam in there as 'perma-float' before you can get it registered. As I recall; The Coast Guard requires that boats below a certain length have to be 'unsinkable'.


    When I poured my hydroplane full of the 2 part stuff, I also trapped a bunch of 2 litre soda pop bottles in there with it to take up space, and hold down the amount of foam I needed for it. (save a buck where ya can)


    Something else with that thing having so much engine, and the speeds it will be capable of... You're going to have some issues about, and with the center of gravity, pitch, and yaw. If it was me, I'd mount the seats in a braket that can move back & forth. And, you'll need to be able to move the engine up & down on the transom to find where it needs to be also-- or more nearly- how high it has to be to run right.

    .
    Last edited by Winger Ed.; 05-28-2007 at 02:42 PM.
    "Gone are the days of wooden ships, and Iron men.
    I doubt we'll see either of their likes again".

    Circa 1920.
    Author:
    Unknown US Coast Guard unit Commander.

  5. #15
    Join Date
    May 2007
    Posts
    100

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    I appericiate you chiming in. I really like the idea of the 2 liters when the time comes in to foam it. I would not be a big deal to make the motor mount adjustable up and down while building from scratch anyway, Have to do that !!!

    Thanks,

  6. #16
    Join Date
    Oct 2006
    Location
    DFW area
    Posts
    180

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    Glad to help.

    On your engine placement- the lower unit has more drag than the hull. The more of it you can get out of the water the better. Ideally, the cavatation plate above the prop should be even with the bottom of the hull for starters. After you get it running, start moving the engine up a little bit at a time until it cavitates on start off, or won't get on plane due to the prop cavitating.

    Not exactly a fair example, but on the hydro, its worth about 5 mph per 1/2 inch I can raise the engine to that maximum point. On mine, it does have a surface drive propeller and the center of the prop shaft is just a fraction below the bottom of the hull. At speed, only the bottom half of the propeller arc is in the water. Raising the engine from the starting point to where it is took the boat from 65 to almost 90 mph.

    I doubt if that sort of speed is what you're shooting for, but the principles are the same.

    .
    "Gone are the days of wooden ships, and Iron men.
    I doubt we'll see either of their likes again".

    Circa 1920.
    Author:
    Unknown US Coast Guard unit Commander.

  7. #17
    Join Date
    May 2007
    Posts
    100

    Default

    That is neat information. I have been designing an adjustable engine mount as I worked on the tubing today. I think I have a general plan. I am only working with a 40 hp merc two stroke so speed will likely be in the 30 - 40 range. Weight will be between 550 and 650 pounds solo. What would you guess for speed ??? Pontoons are flat bottom and 24" wide each. I have seen v-hulls go 30 at higher weights with a 40 so I am hoping for 35 - 40.

  8. #18
    Join Date
    Oct 2006
    Location
    DFW area
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    180

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    Quote Originally Posted by Doug Doty View Post
    What would you guess for speed ??? Pontoons are flat bottom and 24" wide each. .
    Its hard to guess, but 30-40 is quite realistic. A drawback of flat sponsons is the area in the water, but then again, you'll be running over the top of it, not so much plowing through and pushing it out of the way.

    Something that will help is when you deck it, seal over the tops of the sponsons. You'll sort of approach the effect of a tunnel hull. Tunnel hulls trap & compress air under them***, helping to lift the boat up out of the water--- reducing drag. Water drag is something like 1,200 times more resistant to (forward) motion than air drag.

    ***
    This is the 'ground effect'. Remember the sensation a airplane has just before it lands? That's the ground effect compressing air under the wings and trying to push it back up instead of a continuing a uninterupted glide slope onto the ground/runway. When the pilot feels the ground effect taking place, he has to literally push the plane down onto the runway or it'll ride along a few feet over the ground on the ground effect forever.
    ***

    Using the ground effect is how/why a 'pad bottomed' tunnel hull, or the most extreme case of a hydroplane, can go faster for the same horsepower & weight than a V bottom or common rounded bottom boat.

    The decks of a hydroplane are airfoils. The top of the deck generates lift like a airplane wing, while the bottom of the hull traps air to push it up also.

    The idea is to get as much boat up out of the water as you can, and reduce any drag in the water as much as possible.
    (this is also why properly locating your center of gravity is so important)


    Hey,, how wide is this thing?
    The 90 degree angle on those sponsons will REALLY grip the water in a turn, rather than 'squish' through it like a regular boat. If its not pretty wide, and your body weight sitting fairly low,,,,,,,,, it'll be super easy to turn over.

    .

    .
    Last edited by Winger Ed.; 05-28-2007 at 11:34 PM.
    "Gone are the days of wooden ships, and Iron men.
    I doubt we'll see either of their likes again".

    Circa 1920.
    Author:
    Unknown US Coast Guard unit Commander.

  9. #19
    Join Date
    May 2007
    Posts
    100

    Default

    Beam is 76" and the seats will be low, about 3" above the top of the pontoons. Will this design corner like a typical boat and lean into a turn or want to dig in on the outer edge and lift on the inner edge ??? I have considered making the pontoon mounts adjustable so I can rock the pontoons down in the middle to create a little v-hull effect if cornering is objectionable.

  10. #20
    Join Date
    Oct 2006
    Location
    DFW area
    Posts
    180

    Default

    Quote Originally Posted by Doug Doty View Post
    Beam is 76" and the seats will be low, about 3" above the top of the pontoons. Will this design corner like a typical boat and lean into a turn or want to dig in on the outer edge and lift on the inner edge ??? I have considered making the pontoon mounts adjustable so I can rock the pontoons down in the middle to create a little v-hull effect if cornering is objectionable.
    What the heck you doing up so late?
    don't you young guys ever sleep?


    Your width is great.
    Much wider and you'd have to build a sideways tilting trailer like they carry the 30-odd foot long unlimited hydros on. (that's why you see hydros going down the road carried on trailers at a 40-something degree angle.

    My 16 footer is 84 inches wide at the outside edges of the sponsons. Whenever I'm going down the road and see a State Trooper,,,,,,,,,, I hug the shoulder, and pretend not to see all the gravel and rocks being kicked up .... LOL..

    To answer your question,,,,,,,
    With the sponsons having all those sharp/90degree angels---

    Yeah.........
    Your boat will corner like a (choo-choo)train if you're going above about 20mph.


    For example--------
    In a HARD/HI-SPEED Lt hand turn:
    the hull will (try to) tilt to the right.
    That causes the outboard edge of the stb. sponson to dig in,,,,,,, anchoring itself in the water as it tilts. And yes,,, the inboard edge of the Port side sponson will try to help as much as it can.........

    This effect will do two things--- 'put on the brakes' & stop the boat, and----If you're a Baseball fan--- try to throw you into Center Field.


    .
    Last edited by Winger Ed.; 05-29-2007 at 03:35 AM.
    "Gone are the days of wooden ships, and Iron men.
    I doubt we'll see either of their likes again".

    Circa 1920.
    Author:
    Unknown US Coast Guard unit Commander.

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