Help with blow over issues

[rogerdavis]

Getting ready to build a Dumas Pay an Pack hull. A fellow member on here has told me that they are good hulls to run but they have a bad habbit of blowing over. Looking for any comments from boater that have built this hull to maybe fix or reduce this problem. pic's would help of the under side of hull. Thanks, Roger.

 

[Scott Schneider]

Getting ready to build a Dumas Pay an Pack hull. A fellow member on here has told me that they are good hulls to run but they have a bad habbit of blowing over. Looking for any comments from boater that have built this hull to maybe fix or reduce this problem. pic's would help of the under side of hull. Thanks, Roger.

Old school hull from a time where the engines made less than 1/2 the power we see today.

Deep air trap is one BIG issue causing far too much air to go under the hull for lift.

If you can find a way to bring the level of the belly skin forward at the same depth and eliminate most of the ramped portion hull won't fly as easy.

It is a built in design that does not really have an easy fix other than a redesign of the entire air trap and leading edges / nose portion of center tub.

Most of the newer design hydros have a pretty flat belly skin to nose profile and minimal air trap strakes beyond the trailing edges of sponsons.

JMO

 

[Don Ferrette]

Getting ready to build a Dumas Pay an Pack hull. A fellow member on here has told me that they are good hulls to run but they have a bad habbit of blowing over. Looking for any comments from boater that have built this hull to maybe fix or reduce this problem. pic's would help of the under side of hull. Thanks, Roger.

Actually that hull can be helped big time by cutting off the air traps that extend off of each sponson end on the underside. With the more powerful motors we run today you do not need to trap that much air. I helped a guy cut them off of his Dumas Pak sport 40 and it went from blowing off constantly to a reasonably competitve hull with a few other more tweaks.

 

[glenng]

Getting ready to build a Dumas Pay an Pack hull. A fellow member on here has told me that they are good hulls to run but they have a bad habbit of blowing over. Looking for any comments from boater that have built this hull to maybe fix or reduce this problem. pic's would help of the under side of hull. Thanks, Roger.

Buit one last winter, Cut almost 3/4" off the bottom of the sponsons and cut the air traps off. Bill Gibson is building a much nicer one now perhaps he would send you a few pictures. Good luck,

Glenn

 

[Hydro Junkie]

another way to help the blowover problem is to move the radio box out of the back. Move it into the nose and put the fuel tank under the deck. The added nose weight will help prevent the blow overs that have been a hallmark of these boats

 

[RaceCraftBearings]

I ran this one with Picco Power in the late 90's and won with it often. The hull had a tendacy to warn you when blow off was near and at that point all you had to do to settle the boat was a slight blip of the the throttle and continue on everytime. I think I blew it off once before I was in tune with the warning sign.

Pay n Pak

 

[Dasboatman]

"I ran this one with Picco Power in the late 90's and won with it often."

Hey Ron,

Good to see you back on here. Hope all is going well for you. CHEERS !!! Bob Johnson

 

[RaceCraftBearings]

"I ran this one with Picco Power in the late 90's and won with it often."Hey Ron,

Good to see you back on here. Hope all is going well for you. CHEERS !!! Bob Johnson

Hey Bob you still in that god forsaken state of Tejas LOL.......Good to hear from you!

 

[Hydro Junkie]

One thing you didn't tell us Roger is what size boat kit you're building. Depending on the size, different changes may be needed

 

[rogerdavis]

This is the 30 inch hull. Going with a CMD .21. Ive received a lot of great info so far. Just like to say thanks. Roger.

 

[Hydro Junkie]

Okay, that was my first boat, so I know exaclty what you're dealing with. I can see several changes to the boat to make it better:

1) REPLACE ALL THE FRAMING WITH 1/16 AIRCRAFT PLY. This will cut almost a third of the weight out of the hull. The exception is the transoms, the rear being made out of 1/4 aircraft ply and the sponson transom with 1/8 aircraft ply DO NOT USE LITE PLY. Also, when you get the framing together, cut lightening holes in all the under deck frames for a further weight reduction

2) Change the bottom angle in the front so that it has the bottom break at the back of the radio box instead of at the back of the engine bay. This will lower the drag of the hull up front

3) Don't hard mount the engine using the supplied blocks as they add weight and transmit vibration to the hull. Use soft mounts instead

4) Widen the tunnel an inch or so, preferably in the engine bay when you set up the framing

5) Move the radio box up into the front and move the fuel tank under the deck, makes exhaust and driveline routing easier and lightens the rear of the boat

That should get you started

 

[rogerdavis]

WOW, great info! thank you. Roger.

 

[Scott Schneider]

Just to give you an idea of just how little of an air trap and minimal amount of air we want under these faster .21 sport hulls, here are a few shots showing a **** good running hull.

BTW, this being one of 3 RHT sport .21 hulls I have built over the past 10-12 years.

 

[Dasboatman]

"Hey Bob you still in that god forsaken state of Tejas LOL.......Good to hear from you!"

Hey Ron,

Yep, still here in the Grande and Glorious State of Texas. Wife likes it - need I say more?? Har, Har !!!

Have only seen one race of Scale boats and Sport 40s in the 6 years we've lived here, so I'm building a couple Classic Thunderboats to play with. Running with Rick Lamb these days and we have no problem making a speed run to Florida for a Nitro fix. We made the Winter Nats this year and will be back soon.

I still have a few Scale boats and a couple Sport 40s around the shop ready to go - - just need to see, and smell something other than oil based pollution generators every once in a while. I think they should add some burning Castor smell to these stinkin' ass petro-chemical plants & toxic waste around here. Maybe pipe in a Shorty's BBQ scent also - Har, Har !!!

Good to see you still have a couple Scale boats in the wings. CHEERS !!! Bob

 

[Bill Gibson]

another way to help the blowover problem is to move the radio box out of the back. Move it into the nose and put the fuel tank under the deck. The added nose weight will help prevent the blow overs that have been a hallmark of these boats

Thats exactly what ive done to my 1/8 scale PAK.....cant wait till i finish the darn thing someday to see how it all works......Oh and Glenn, if you read this....thank you for the compliment...still got to build the nose and rear cowl for the boat......Bill

 

[Hydro Junkie]

That's how most of the scale boats in the Northwest have been set up, radio box in the nose, fuel tank under the deck someplace. It all depends on the balance of the boat or available room as to where the tanks are located