Belly Pans for 1/8 Scales

[BobGutsell]

Hi Guys

Will be starting to build one of Mike Luszcz's kits in the next few weeks. I'll be running a CMB greenhead in it and believe I'll need to incoporate a belly plan nothing else to give the engine more clearance under the cowl, as well as lowering the centre of gravity.

I'm aware of the max allowable dimensions for a bellypany, but would like to know if there are any general rules around the clearance I should allow from Sponson bottom to underside of the belly pan?

I suspect that on some boats the bellypan when built to max allowable size based on the rules will hit the water in some conditions? Or am I being paranoid?

Cheers

Bob

 

[Dan Kramer]

it will hit the water sometimes.it will act as a "3rd" sponson, keep it sharp as all riding surfaces should be .

i used impba allowable maximum and lowered, keeping adequate clearance for starting belt.keep engine forward as much as cowl allows .

 

[Hydro Junkie]

NO, you're not being paranoid. There are size limits on the belly pan in length and width, but most importantly in depth. The belly pan MAY NOT project down far enough to be below the running surfaces or used as a running surface. If you plan on racing your boat, you need to verify the actual limits with either the club or with the sanctioning body in your area or for the club you wish to race with. It could be any one of the three, APBA, IMPBA or NAMBA.

 

[BobGutsell]

NO, you're not being paranoid. There are size limits on the belly pan in length and width, but most importantly in depth. The belly pan MAY NOT project down far enough to be below the running surfaces or used as a running surface. If you plan on racing your boat, you need to verify the actual limits with either the club or with the sanctioning body in your area or for the club you wish to race with. It could be any one of the three, APBA, IMPBA or NAMBA.

Thanks HJ, as previously stated I'm aware of those limits, but also aware that sponson depth varies from boat to boat and whilst the belly pan should never go deeper than the sponson depth, I can also see that from a practical perspective there's got to be a minimum distance from bottom of sponson to belly pan base, that may mean you use a belly pan depth less than that legally alowed, you wouldn't want to infringe upon from a performance perspective.

hope that makes sense?

 

[P THOMAS]

it will hit the water sometimes.it will act as a "3rd" sponson, keep it sharp as all riding surfaces should be .

i used impba allowable maximum and lowered, keeping adequate clearance for starting belt.keep engine forward as much as cowl allows .

impba has limits? I know NW scale clubs have a certian size restriction. I have a epoxyglass one that I used on my Atlas van line.

 

[Dan Kramer]

it will hit the water sometimes.it will act as a "3rd" sponson, keep it sharp as all riding surfaces should be .

i used impba allowable maximum and lowered, keeping adequate clearance for starting belt.keep engine forward as much as cowl allows .

impba has limits? I know NW scale clubs have a certian size restriction. I have a epoxyglass one that I used on my Atlas van line.

Belly pans are acceptable to clear engine and/or flywheel

as stated in impba . no size limit stated, (correction)

thanks,dan

 

[Hydro Junkie]

This is copied directly out of the NAMBA afiliated Unlimiteds NW rulebook:

Motor Belly Pan: For motor and flywheel only. If applicable, dimensions will not exceed 3-1/2” in width, 7” in length and ¾” in depth. Under no circumstances will said Belly Pan be located in any position to be construed to have intent for a riding surface or recovery surface purpose

If I remember right, the rule reads about the same in the R/C Unllimited rules as well.

 

[Hydro Junkie]

Here's the whole section on 1/8th scale hulls:

SECTION III: BOAT SPECIFICATIONS, ELIGIBILITY, OWNERSHIP, REGISTRATION, INSPECTION & QUALIFICATION

A.

Hull, Engine & Equipment Requirements

1.

All boats shall be models of past or present American Power Boat Association unlimited hydroplanes that are listed on the U.N.W. Master Hull Roster.

2.

Boats shall be built to a scale of 1-1/2” (model) equals1’ (actual unlimited).

3.

Boats shall measure within the following tolerance of true scale size, excluding appendages:

a.

Overall Length: + or – 5%

b.

Overall Width: + or – 10%

c.

Hull Depth + or – 10%

d.

Afterplane Length (three point design) + or – 10%

e.

Tunnel Width: + or – 10%

The true dimensions of any boat shall be derived from the dimensions listed on the U.N.W. Master Hull Roster.

4.

Boats shall be painted, configured and detailed like the actual unlimited. The acquisition of proof validating a paint scheme, cowling configuration, engine configuration or other scale details shall be the responsibility of the boats owner. Photographs of the boat in the water may constitute proof.

5.

Boats shall enter competition complete with cowling(s) and driver(s).

6.

The boat engine(s) shall be concealed by either an engine cowl or fake engine (modeling an Allison, Rolls, etc.) or both.

7.

A boat bottom shall have the same general appearance and number of propellers as that of the unlimited the hull represents. Exceptions include:

a.

Sponson riding surfaces, which may be modified.

b.

Propeller shafts, which may be articulated.

c.

Rudders and skid fins, which may be configured and located as desired.

d.

Motor Belly Pan: For motor and flywheel only. If applicable, dimensions will not exceed 3-1/2” in width, 7” in length and ¾” in depth. Under no circumstances will said Belly Pan be located in any position to be construed to have intent for a riding surface or recovery surface purpose.

8.

Outdrive units are specifically prohibited and the forward most part of the stock propeller hub shall not lie behind the transom plane.

9.

The engine size shall be a maximum of .67 cu. In. total on-board displacement.

 

[Dan Kramer]

This is copied directly out of the NAMBA afiliated Unlimiteds NW rulebook:

Motor Belly Pan: For motor and flywheel only. If applicable, dimensions will not exceed 3-1/2” in width, 7” in length and ¾” in depth. Under no circumstances will said Belly Pan be located in any position to be construed to have intent for a riding surface or recovery surface purpose

If I remember right, the rule reads about the same in the R/C Unllimited rules as well.

i knew i had dimensions , i just didnt remember where i got them. that is what i made mine like.