The JVD 20 Sport Hydro

[Jerry Dunlap]

I decided to try my hand at designing a 20 Sport Hydro. As can be seen from the photos, the design incorporates concepts(Flat Plane Technology) developed by Rod Geraghty and David Hall for the JAE hydroplanes. Rod has been very supportive of my design endeavors.

I built the boat to conform to NAMBA 20 Sport Hydro rules. It does have a transom mounted strut which should be NAMBA legal next year if the strut rule change proposal is approved.

The boat is constructed using WOF methods. The overall length is 30 3/4", the width of the tub is 6", the sponsons are set 10 7/8" apart. The cowling is a Phil Thomas epoxy glass cowl that Phil had laid up for a 40 Sport Hydro. The hardware is Speed Master.

The engine is a 3.5 Nova Rossi PLUS M, an Andy Brown muffled pipe, and I tried two props today - X442 and a Joe Monohan 1445. Grim Racer 50% fuel.

The first two run were made using the X442 and a third and final run with the 1445. The boat launched easily with both props. The speed and cornering were as good as my 8 year old Mini Mutt. After just 3 runs, I'm really pleased with how well the boat runs.

JD

 

[anthony_marquart]

awesome... man would I like to see plans on that!!!

 

[Jerry Dunlap]

awesome... man would I like to see plans on that!!!

That's a possibility.

JD

 

[jeepers]

that's wild looking Jerry, very cool!

 

[Kevin Krogness]

I can't wait to see a video nice work!!!

 

[RodneyPierce]

this wouldnt be legal for IMPBA would it? I think the lack of deck between the sponson and the tub would be an issue. But, its very cool none the less!! I bet it will be a rocket!!

 

[Jerry Dunlap]

this wouldnt be legal for IMPBA would it? I think the lack of deck between the sponson and the tub would be an issue. But, its very cool none the less!! I bet it will be a rocket!!

I designed it to meet the NAMBA 20 Sport rules. There aren't very many specifications: Boat must be 27" long, no more than a 25% pickle-fork, the afterplane cannot exceed 60% of the total length of the boat, the minimum width of the tub is 4", and no riding surfaces back of 50% of the total length.

In NAMBA, transom mounted struts are not allowed. However, there is a rule change proposal in the works to allow struts to be mounted either inside or outside on the transom. District 8 does have a rule allowing transom mounted struts.

.

I am not sure how "lack of deck between the sponson and the tub" appears in the IMPBA 20 Sport Hydro rules. Maybe someone with knowledge of the IMPBA rules can provide some insight.

JD

 

[RodneyPierce]

JD, I understand, and wasnt in any way bashing it. Its a very cool design. Something I have thought on hard myself after seeing the performance of the JAE, but have never brought it to reality. Like said above, it will be a rocket im sure!

 

[dave roach]

The impba rules say it has to be a full deck hydro.

Dave Roach

 

[Lay26]

Its Scratch building u can put a deck on no problem. Very nicely done.

 

[Dasboatman]

Hey Jerry,

Oh, No!!! Here we go again.

You have touched on two topics that have entertained the NAMBA Sport Hydroplane and IMPBA Sportsman20/40 Hydro (Sport 40 Hydro)classes for years:

1. Modified Outrigger hull

2. Transom mounted strut

I have raced sanctioned events under both organizations since 1970 - on and off. My NAMBA Rule Book is up to date, however, the IMPBA Rule Book is still being revised - the hard copy I have is dated March 2006. Every so often the Transom mounted strut raises it's Ugly head, a rule change proposal is submitted, and we vote - over and over again.

To date, the NAMBA Rule Book for struts reads:

B. Boat Specfications 8. The propeller drive dog may be one drive dog length behind the transon of the boat. While this configuration would be legal within District 8, it would not be legal to race at the NAMBA Nationals - it does not comply with B.8.

Under IMPBA Sportsman 20 Hydro (Sport 20 Hydro)

Boat Specifications

2. Hull must be a three (3) point hydroplane configuration and resemble a limited or unlimited hydroplane design of past or present. Hulls not permitted: outrigger, modified outrigger, tunnels, or canard hulls.

7. A strut width no greater than 9/16 inch wide may be mounted either under the hull or on the transom with the farthest end of the drive dog, as measured from the transom not extending out more than 3 inches.

The description of Hull configuration makes the hull illegal in IMPBA, looks like the strut will fly once be sort through the "Sea Lawyer" paragraph 7.

I personnaly preferred the look of you Mini Mutt hull - much better looking than Jim's "Thingy". I believe it was premature of you to put the strut on the transom prior to a revision of current rules. Kind of like counting chickens before they hatch. Yes, I do realize that hull design has changed over the years.

Attached are pics of Scott Liddycoat's 1 liter boat. Very similar to Jim's hull but I can't see where his strut is mounted.

Looks like the IMPBA strut position is OK for your hull, but it appears they could use an update to hydroplane configuration.

I'm not trying to push any agenda here, Jerry - just trying to point out to the new boaters why, specifically, your hull would not be legal under Rules of either Sanctioning activity except if run Under NAMBA aand ONLY in District 8.

I have believed the Drive dog not extendining more than one drive dog length aft of the transom within NAMBA is concise and to the point for years.

Yes, I do understand the performance benefit of hanging struts off the transom as I'm quite sure you do.

I can't tell you how many years we FLAILED about whether the drive dog "Ears" are part of the drive dog or not. CHEERS !!! Bob

 

[Jerry Dunlap]

Hey Jerry,

Oh, No!!! Here we go again.

You have touched on two topics that have entertained the NAMBA Sport Hydroplane and IMPBA Sportsman20/40 Hydro (Sport 40 Hydro)classes for years:

1. Modified Outrigger hull

2. Transom mounted strut

I have raced sanctioned events under both organizations since 1970 - on and off. My NAMBA Rule Book is up to date, however, the IMPBA Rule Book is still being revised - the hard copy I have is dated March 2006. Every so often the Transom mounted strut raises it's Ugly head, a rule change proposal is submitted, and we vote - over and over again.

To date, the NAMBA Rule Book for struts reads:

B. Boat Specfications 8. The propeller drive dog may be one drive dog length behind the transon of the boat. While this configuration would be legal within District 8, it would not be legal to race at the NAMBA Nationals - it does not comply with B.8.

Under IMPBA Sportsman 20 Hydro (Sport 20 Hydro)

Boat Specifications

2. Hull must be a three (3) point hydroplane configuration and resemble a limited or unlimited hydroplane design of past or present. Hulls not permitted: outrigger, modified outrigger, tunnels, or canard hulls.

7. A strut width no greater than 9/16 inch wide may be mounted either under the hull or on the transom with the farthest end of the drive dog, as measured from the transom not extending out more than 3 inches.

The description of Hull configuration makes the hull illegal in IMPBA, looks like the strut will fly once be sort through the "Sea Lawyer" paragraph 7.

I personnaly preferred the look of you Mini Mutt hull - much better looking than Jim's "Thingy". I believe it was premature of you to put the strut on the transom prior to a revision of current rules. Kind of like counting chickens before they hatch. Yes, I do realize that hull design has changed over the years.

Attached are pics of Scott Liddycoat's 1 liter boat. Very similar to Jim's hull but I can't see where his strut is mounted.

Looks like the IMPBA strut position is OK for your hull, but it appears they could use an update to hydroplane configuration.

I'm not trying to push any agenda here, Jerry - just trying to point out to the new boaters why, specifically, your hull would not be legal under Rules of either Sanctioning activity except if run Under NAMBA aand ONLY in District 8.

I have believed the Drive dog not extendining more than one drive dog length aft of the transom within NAMBA is concise and to the point for years.

Yes, I do understand the performance benefit of hanging struts off the transom as I'm quite sure you do.

I can't tell you how many years we FLAILED about whether the drive dog "Ears" are part of the drive dog or not. CHEERS !!! Bob

Bob,

Great comments and observations.

JD

 

[Tim leyde]

I believe NAMBA should get with the times and change the location to the transom. How many full size boats run that way today.

I also believe IMPBA rules should read from past and leave out present. The newer full size unlimited hydros have little shoes on a lot of them. IMPBA does not allow that. I understand and don't want moded riggers in this class. However both organisations need to change the wording and rules a bit.

TL

 

[Geraghty]

I decided to try my hand at designing a 20 Sport Hydro. As can be seen from the photos, the design incorporates concepts(Flat Plane Technology) developed by Rod Geraghty and David Hall for the JAE hydroplanes. Rod has been very supportive of my design endeavors.

I built the boat to conform to NAMBA 20 Sport Hydro rules. It does have a transom mounted strut which should be NAMBA legal next year if the strut rule change proposal is approved.

The boat is constructed using WOF methods. The overall length is 30 3/4", the width of the tub is 6", the sponsons are set 10 7/8" apart. The cowling is a Phil Thomas epoxy glass cowl that Phil had laid up for a 40 Sport Hydro. The hardware is Speed Master.

The engine is a 3.5 Nova Rossi PLUS M, an Andy Brown muffled pipe, and I tried two props today - X442 and a Joe Monohan 1445. Grim Racer 50% fuel.

The first two run were made using the X442 and a third and final run with the 1445. The boat launched easily with both props. The speed and cornering were as good as my 8 year old Mini Mutt. After just 3 runs, I'm really pleased with how well the boat runs.

JD

Dunny,

Way to go......... .........

I can already hear the screams of desent banging louder than a screen door in a hurricane......

I suspect the Sport.20 boating panties are in the process of knotting up big time........

Rod

 

[Doug Smock]

Rod that looks similiar to MLs P Sport we were talking about a couple of months ago doesn't it?

Great minds think alike! Cool ride Mr. Dunlap!!

 

[Dasboatman]

"........Sport.20 boating panties are in the process of knotting up big time........ "

Hey Rod,

Amen to that!!! I think it's great that Dunny has come out with something diferent and original. Every once in a while we have to "TWEAK the Establishment" Har, Har !!! I still can't believe I lived way past 30 - - Guess the "Trust no one over 30" turned out to be a false premise.

I don't race Sport 20, but I was sure getting tired of seeing PT, and Whiplash hulls here in IW. I miss the days of more custom builds.

"Flat Plane Technology" - - first I have heard this. I still get a charge out of the meaning of JAE - Beautiful, Rod !!! Har, Har !!!

I figured adding pics of Liddycoats 1 Liter would add heat to the fire. It has been over a year since the Mod Rigger/Transom mounted strut debacle has been thrashed about. The first run of the new Staudacher hull style I saw from Ocoee didn't fare as well. Hauled fanny to the first turn, threw the rudder over and rolled. At least they now have capsules when the hulls fall apart around the driver. Cause and result pics added.

Limit the flowery Prose Guys and submit a change request through the proper channels. Gripping about "A" and or "B" on IW is a waste of time and space. CHEERS !!! Bob

 

[Lennard Cuenco]

nice ride jerry

i sometimes wonder why you don't see more ppl running the winston lobster boat in scale

 

[Mike Luszcz]

Rod that looks similiar to MLs P Sport we were talking about a couple of months ago doesn't it?

Great minds think alike! Cool ride Mr. Dunlap!!

Doug, You talking about this one?

Mike

 

[Dasboatman]

"... sometimes wonder why you don't see more ppl running the winston lobster boat in scale ..."

Hey Len,

And you're telling me how bored you get looking at MHR 8255 hulls all over District 8 !!! I haven't seen a decent 8910 Lobster at a 1/8th Nitro race in years. The same hull with maybe a fresh water cowl or a Salt water cowl would get really old quickly. That's why Olde Fartes like myself and Roy build Liberties and Peps IV. None of that: " There are all made of ticky tacky, and they all look just the same" nonsense for us.

Now, quit goofin' around on here and get that U-50 finished - Jan. is coming quickly !!! CHEERS !!! Bob

 

[Grimracer]

Its just a matter of time...........

Grim