Dumas Atlas Van Lines

Guys:

Have an old Dumas Atlas kit laying around and I was wondering if it were to be built, what would make it a better, more stable running boat. I've run this hull in the past as another boat but still the same hull. The boat always ran like it was running uphill. In other words, it dragged its tail. I suspect this has something to do w/ the sponson angle being fairly steep. I exchanged emails w/ Don Mock and he said that he had widened the boat to the allowable 10% and also did sponson mods. I would like to build this at some point as sort of a nostalgic project but I will use better wood, or perhaps composites or a combo of the two. What would you guys do to make this boat ride flatter? I would be interested in any specific experience people have had w/ the boat along these lines.

Thanks!

Rich

Rich Jones said:

Guys:
Have an old Dumas Atlas kit laying around and I was wondering if it were to be built, what would make it a better, more stable running boat. I've run this hull in the past as another boat but still the same hull. The boat always ran like it was running uphill. In other words, it dragged its tail. I suspect this has something to do w/ the sponson angle being fairly steep. I exchanged emails w/ Don Mock and he said that he had widened the boat to the allowable 10% and also did sponson mods. I would like to build this at some point as sort of a nostalgic project but I will use better wood, or perhaps composites or a combo of the two. What would you guys do to make this boat ride flatter? I would be interested in any specific experience people have had w/ the boat along these lines.

Thanks!

Rich

Click to expand...

3 things to get you started.

re-make all the parts that are "luan" out of 3 or 5 ply aircraft grade plywood

dont put the relief in the rear (bottom) of the boat like the plans show

dont add all the sticks and extra riding pad on the bottom of the sponsons, just skin the frames, true them up and go.

(the extra parts they add on, make the sponsons too deep)

This should get you in trouble................

One thing you never said was which Atlas you have. Is this the big 1/8th scale, the 1312 Sport 40 blue Atlas or the 1314 white Atlas? These recommendations will work with all the kits, but the scale boat is the only one to have the recess in the bottom at the stern.

To add to Joe and Don's recommendations here is what I would do:

1) Widen the boat to 22" and the tunnel to as close to12" as possible. Both of those will keep you within scale limits

2) Replace all the cross frames with 1/16th ply except the transoms, which I would replace with 1/4 inch. For the stern, use the inner transom part from the kit as a pattern and cut the slots all the way through. Make sure the transom bottom is flat

3) Replace all the lengthwise frames with 1/8th ply, adding 1/8th" to the back of the parts to cover the extra depth in the transom slots

4) Do as Don says on the sponsons. Most scale boats run an approximately 3* sponson rise fron back to front

5) Be sure to cut lightening holes in all underdeck frames. Between the new ply and cutting these holes, you can lose probably in the ballpark of 50% in weight over the stock kit

6) I would move the radio box to in front of the engine. You want as little weight on the prop as you can get, TO A POINT

7) Scrap the tails and wing. Fiberglass parts are available that are lighter and look better than the built up ply parts supplied.

8) DO NOT USE DUMAS RUNNING GEAR OR A TRANSOM MOUNTED STRUT!!!!!!!!!!!!!!!!! Dumas running gear is the bargain basement of running gear. Go with a minimum of Octura, or if you can afford it, Speedmaster. If you plan on racing, the strut MUST go through the bottom of the hull and the drive dog cannot extend past the transom. For more specific information, you can check with the local clubs or rules from IMPBA, NAMBA or APBA, whichever covers your area.

9) Throw away any engine mounting blocks that are glued to the engine bay walls and bottom. They transmit engine vibrations right to the hull and radio gear. Use rubber isolated mounts and mount as directed, through either the hull bottom or engine bay walls. If through the walls, be sure to add a doubler to the back side

These changes may sound extreme, but you will end up with a better running boat that you will be much happier with. Good luck and happy building

Hello Rick,

Looks like some great info above. I would follow it closley. The sponson are way to deep as Joe eluded to. One inch and a quater at the sponson transom is deep enough. Thats wy they run tail heavy. Check around with some other scale hulls for there depth. Balance at 88% from the transom to the sponson transom . .

I wish i had all this info when I built my first Atlas

Bob

You and me both, Bob. My first two boats were the Dumas Pay N' Pak Sport 20 and the Atlas Sport 40. Both were built and weighed about as much as a tank. Too bad I never got them to run right

Rich Jones said:

Guys:
Have an old Dumas Atlas kit laying around and I was wondering if it were to be built, what would make it a better, more stable running boat. I've run this hull in the past as another boat but still the same hull. The boat always ran like it was running uphill. In other words, it dragged its tail. I suspect this has something to do w/ the sponson angle being fairly steep. I exchanged emails w/ Don Mock and he said that he had widened the boat to the allowable 10% and also did sponson mods. I would like to build this at some point as sort of a nostalgic project but I will use better wood, or perhaps composites or a combo of the two. What would you guys do to make this boat ride flatter? I would be interested in any specific experience people have had w/ the boat along these lines.

Thanks!

Rich

Click to expand...

Listen to everything these guy's told you. My first wood boat was a Dumas 1/8 AVL and was built too heavy . I kept as much weight as far forward as possiable and the boat did not drag it's tail with a Octura X 457/2. Weak areas were where the rudder mounts to the transom. Epoxy carbon fibre doublers-about .050 thick inside and outside. Another weak area was the turn fin mount. Epoxy an aluminum doubler inside the sponson before installing the deck and drill & tap for larger 8-32 screws. Do not glass the hull-two thin coats of west system epoxy will keep it lighter.

glenng said:

Rich Jones said:

Guys:
Have an old Dumas Atlas kit laying around and I was wondering if it were to be built, what would make it a better, more stable running boat. I've run this hull in the past as another boat but still the same hull. The boat always ran like it was running uphill. In other words, it dragged its tail. I suspect this has something to do w/ the sponson angle being fairly steep. I exchanged emails w/ Don Mock and he said that he had widened the boat to the allowable 10% and also did sponson mods. I would like to build this at some point as sort of a nostalgic project but I will use better wood, or perhaps composites or a combo of the two. What would you guys do to make this boat ride flatter? I would be interested in any specific experience people have had w/ the boat along these lines.

Thanks!

Rich

Click to expand...

Listen to everything these guy's told you. My first wood boat was a Dumas 1/8 AVL and was built too heavy . I kept as much weight as far forward as possiable and the boat did not drag it's tail with a Octura X 457/2. Weak areas were where the rudder mounts to the transom. Epoxy carbon fibre doublers-about .050 thick inside and outside. Another weak area was the turn fin mount. Epoxy an aluminum doubler inside the sponson before installing the deck and drill & tap for larger 8-32 screws. Do not glass the hull-two thin coats of west system epoxy will keep it lighter.

Click to expand...

Rich, Forgot to add motor bay is around 4.5 inches wide- had to make my own rubber mount's I'll put a pic in my gallery. Glenn

I have to agree with glenng, but I would go with 8/32 blind nuts, but that's just my choise. Which ever way you do decide to go, DO NOT USE WOOD SCREWS TO ATTACH ANY OF THE HARDWARE. Wood screws will rip out while the blind nuts and aluminum plates won't. I would recommend, if you decide to use the aluminum plate, to use short wood screws to attach the plate to the inside of the transoms along with the epoxy

Thanks for the info guys! Plan on making it a project to work on when I have the time and do some experiments w/ materials, etc...

Excellent info gents i found the Dumas Atlas sponsons (ride pad add ons) also make the boat ride to high and i'm in the process of shaving them down before final paint. My hull is the 77 highly modified from an 82 Dumas Atlas kit.