Lil' Swamp Buggy Propeller

NEW222 Sat Jan 02, 2016 8:06 pm

Hi there. I am in process of building a lightweight foam version of the Dumas Lil' Swamp Buggy and am having engine decision troubles. First problem is the engine. I am not yet sure if I will use a Bee style engine, or a Product engine with horseshoe backplate. I am really leaning on the side of the horseshoe version as I can add a fuel tank and get some decent run time. Secondly, and mainly why I am here is how to mount the assembly. It is designed for the use of an engine in the 'pusher' configuration. I do not have a 'pusher' propeller and am not sure if I can get one locally. Being a reedy, could I even mount the engine in the 'pusher' configuration and run it so the prop still spins clockwise when viewed from the rear? I would also like to have it in the standard 'tractor' configuration for the ease of starting and the like, without the rudder in the way. Has anybody here built one of these, or similar, in a standard 'tractor' configuration and how did it do? I am not looking for it to be all out wild, but just something I can play with in the evenings at the lake in the springtime, and quite possibly in the snow this winter. Thank you.

I know what a standard r/h prop is. Is a pusher propeller a l/h prop?

NEW222 Sat Jan 02, 2016 8:07 pm

This whole pusher thing is making my mind do tricks....

happydad Sat Jan 02, 2016 8:17 pm

here is a pusher prop from coxengines.ca

cox pusher prop for CCW engine

link:
http://www.ebay.com/itm/Cox-049-051-Left-Hand-Pusher-Prop-5x3-5-Propeller-5-x-3-5-3-Blade-049-051-/370565487119?hash=item56476c9a0f:g:6bcAAOSwVFlUHLar

happydad RC Plane

cox24711 Sat Jan 02, 2016 8:24 pm

NEW222 wrote:Hi there. I am in process of building a lightweight foam version of the Dumas Lil' Swamp Buggy and am having engine decision troubles. First problem is the engine. I am not yet sure if I will use a Bee style engine, or a Product engine with horseshoe backplate. I am really leaning on the side of the horseshoe version as I can add a fuel tank and get some decent run time. Secondly, and mainly why I am here is how to mount the assembly. It is designed for the use of an engine in the 'pusher' configuration. I do not have a 'pusher' propeller and am not sure if I can get one locally. Being a reedy, could I even mount the engine in the 'pusher' configuration and run it so the prop still spins clockwise when viewed from the rear? I would also like to have it in the standard 'tractor' configuration for the ease of starting and the like, without the rudder in the way. Has anybody here built one of these, or similar, in a standard 'tractor' configuration and how did it do? I am not looking for it to be all out wild, but just something I can play with in the evenings at the lake in the springtime, and quite possibly in the snow this winter. Thank you.

I know what a standard r/h prop is. Is a pusher propeller a l/h prop?

just run the engine backwards!

NEW222 Sat Jan 02, 2016 8:31 pm

And one more quick question. Is there such thing as a center of gravity or balance point on this thing as it does not mention it on the instruction sheet, nor where to mount the engine pylon.

1/2A Nut Sat Jan 02, 2016 8:37 pm

If pusher you would need a thrust washer ..all the same the extra drag adds more heat. 1 Oz tank behind the engine / clunk style to insure good fuel flow. Keep the prop tips rotating no more or less than 1/2" off the deck.

1/2A Nut Sat Jan 02, 2016 8:42 pm

Yes 65% from the transom to start will help it track and laterally balance the hull.

NEW222 Sat Jan 02, 2016 8:47 pm

1/2A Nut wrote:Yes 65% from the transom to start will help it track and laterally balance the hull.

Thank you. I have done a bit more reading and have pretty much concluded that I will install it in tractor configuration, unless someone can tell me why it would be a bad idea. And as for balancing, balance it at 65% forward from the rear of the airboat? I am actually getting a bit worried as This boat will be very light it seems for a Cox engine, and am thinking it will literally fly. I am ready to add a deflector up front already, or at least make it ready to accept one. Smile

1/2A Nut Sat Jan 02, 2016 9:34 pm

Simple but effective with a slight angle on the deck to help hold the nose down.
Angles on the side to avoid catching an edge and flipping while sliding into the turns
View is at full throttle and planing on top. You will need about 3 to 4 deg down thrust.
You can also put in a few degs. for right thrust offset due to prop torque. Dynamic
CG will move rearward at speed hence 65% from the transom or rear of the boat.
Once you ride trim it you may wish to move the CG back and evaluate the result.
Will improve its turning, but further back better chance of a blow over in a head wind..
1oz round tank shown and 5x4 2blade prop better top end should add a throttle sleeve
you will enjoy the advantages.

NEW222 Sat Jan 02, 2016 9:54 pm

Wow, thank you. Nice picture you drew for me. This one does not have angled sides, as it was traced off the original wood model. It is just the bottom sheeting I have yet to work on, then the 3 stringers.

1/2A Nut Sat Jan 02, 2016 10:05 pm

Yes Dumas Swamp Boat is not a very good design.

Here is one of my designs very progressive nimble and fast out rigger 3 point hydro
Stable in the turns and rides on the prop hub in the back, hence 3 point hydro.