Pay n Pak sport 20

[Ed.R]

Thinking about building a pay n pak Sport 20 Dumas boat . I have been told that some serious mods have to be done to make the hull competitive . Was wondering if anyone may have some insight on what areas need to be modified . Maybe some set-up info also

Thanks Ed

 

[Hydro Junkie]

Oh boy, where do I start?

1) replace all the framing with good quality aircraft ply

2) cut lightening holes into all underdeck framing

3) rework the radio box

4) widen the tunnel, I'd do this in the engine bay for the most part

5) forget the ply wing, make one that is built up or lighter in some way

6) forget the hard engine mounts, I'd go with rubber mounts through the hull bottom

7) use good quality hardware, but then you already knew that one <_<

 

[davetheacguy]

Thinking about building a pay n pak Sport 20 Dumas boat . I have been told that some serious mods have to be done to make the hull competitive . Was wondering if anyone may have some insight on what areas need to be modified . Maybe some set-up info also
Thanks Ed

I just finished a Pay N pak, the only thing left Dumas about it is the box it came in. I widened the boat to 9 1/4 inches between sponsons, I left the length alone. I also redesigned the running surface of the sponsons. I increased the angle of attack and put steps in. I also lowered the hull, to where the boat is about 3/4 of an inch off the water. The last thing I did was to get rid of the brake under the boat, at least thats what I call it, others may call it a dam, any way I made it flat from end to end. It took longer to redesign than to build. Think hard on all the changes you make be fore you start, I did not and it caused many problems. Good luck, I have not put mine in the water yet but its the 10th or so wood boat I have built, all the rest ran well, only time will tell. One more thing the wood needs replacing when you build new bulk heads, the only wood I used from the kit was the ply. the cowling was also changed i used a cowling off a Dumas Eagle sport 40,

 

[Bill Gibson]

Thinking about building a pay n pak Sport 20 Dumas boat . I have been told that some serious mods have to be done to make the hull competitive . Was wondering if anyone may have some insight on what areas need to be modified . Maybe some set-up info also
Thanks Ed

I just finished a Pay N pak, the only thing left Dumas about it is the box it came in. I widened the boat to 9 1/4 inches between sponsons, I left the length alone. I also redesigned the running surface of the sponsons. I increased the angle of attack and put steps in. I also lowered the hull, to where the boat is about 3/4 of an inch off the water. The last thing I did was to get rid of the brake under the boat, at least thats what I call it, others may call it a dam, any way I made it flat from end to end. It took longer to redesign than to build. Think hard on all the changes you make be fore you start, I did not and it caused many problems. Good luck, I have not put mine in the water yet but its the 10th or so wood boat I have built, all the rest ran well, only time will tell. One more thing the wood needs replacing when you build new bulk heads, the only wood I used from the kit was the ply. the cowling was also changed i used a cowling off a Dumas Eagle sport 40,

sounds to me like youve got the right idea on your mods...ive built a coupla 20 paks and while they are fine for fun running, they dont like to get thier rear ends out of the water...im building an 1/8th scale dumas pak and have made the same type of changes to the hull that you have...especially getting rid of the ramp and lowering the hull....im a long way from finishing mine but i also hope that the changes that i made will result in a better running boat!! Bill

 

[Ed.R]

Thanks for the help . I'll think things over a decide what to do . Exactly how do you lower a hydro hull?

Ed

 

[Bill Gibson]

Thanks for the help . I'll think things over a decide what to do . Exactly how do you lower a hydro hull?
Ed

Ed, another way to put it is your trying to lessen the tunnel depth so that you dont need so much strut depth to get the transom of the boat out of the water when the boat is at at level running attitude. Im no expert on hydrodynamics, but i Think it changes the angle of attack to where the boat runs flatter on the water and is more stable on the water at high speeds due to the more powerful engines that we use today....I know that it is a huge deal with 1/8th scale boats...I know that someone like Phil Thomas or Joe W could do a better job of explaining this than i can...Oh, you can lower a hydro by changing the entire shape of the cener of the boat, in particular the bottom and/or merely shallowing up the bottom of the sponsons. Have Fun, Bill

 

[Hydro Junkie]

I wouldn't do much to the sponsons, I would change the ride pads. I know that on similar sized electric scales, the boats perform the best at 6* AOA, but they also run hard shafts.

I would reverse the bottom design, leaving the aft 25-30% flat, not sloped the whole length. The boat is very shallow to begin with, so why make it shallower in the back where Dumas put the radio box? Like all the rest of the Dumas hydros, this boat is overweight and poorly balanced so lightening up the back end will make a huge difference

 

[norm j]

gentelmen, i have a p&p 20 dumas boat i'd like to get rid of, it has a new,c&b 21gp, motor in it,and a brand new, ko-pro radio,with built in failsafe,it has been made up to be as the p&p hull,but it is painted in a blue color with black stripes on it,i'd like to get $200 or obo for it,pics avail. on request

thanks your consideration

norm j

fmbc

 

[Bill Gibson]

I wouldn't do much to the sponsons, I would change the ride pads. I know that on similar sized electric scales, the boats perform the best at 6* AOA, but they also run hard shafts.I would reverse the bottom design, leaving the aft 25-30% flat, not sloped the whole length. The boat is very shallow to begin with, so why make it shallower in the back where Dumas put the radio box? Like all the rest of the Dumas hydros, this boat is overweight and poorly balanced so lightening up the back end will make a huge difference

On my 1/8th scale pak im sticking the fuel tanks in the sponsons and will run a radio box in the front of the boat just to get as much weight to the front of the boat as possible...the 1/8th scale pak is just a blown up version of the 20 boat and i completly agree that it is a poorly balanced hull!!

 

[Hydro Junkie]

I would'nt put them in the sponsons, but under the deck instead. You would have to pretty much destroy the sponsons to get the tanks out if you have a problem while under the deck you can take off part or all of the bottom without hurting any of the riding surfaces

 

[Bill Gibson]

I would'nt put them in the sponsons, but under the deck instead. You would have to pretty much destroy the sponsons to get the tanks out if you have a problem while under the deck you can take off part or all of the bottom without hurting any of the riding surfaces

I made openings in the cockpit sides to allow the tanks to slide in and out of the sponsons, im gonna have Walt Barney make up the tanks... will hold about 20-21 ounces full... years ago i built a dumas Eagle sport 40 and the plans called for the tanks to be sealed up in the boat.....I thought to myself....are you guys CRAZY?? needless to say, I did NOT go that route!!! Many Thanks, Bill