Piranha rigger

here's a copy of an image from the inside title page of the Prather Piranha assembly instructions booklet showing a "factory" boat being launched in the water by Al Prather himself (Circa 1980's). That particular boat was owned and built by Norm Teague (Team Prather member). Norm was a very meticulous RC model builder, he paid close attention to every detail. His Piranha model's were the most beautifully constructed I've witnessed up-close, they really stood out. Both were K&B powered (a 7.5cc and 11.00cc), and were finished in a very nice yellow & silver scheme using Dupont Imron paint (the black & white image does it no justice). All hardware was polished.

This was an exciting time in the hobby (mid-1980's), Prather had just released this new model boat kit, and the major manufacturer representatives were present (at District 19 events) to observe the development of these latest products, including- John Brodbeck ("Mr. K&B"); Al & Terry Prather, and others. The K&B 11.00cc Marine was a new release. I will post a few images of Norm's boats once I dig them up.

Note: The "factory" boat shown (white w/red strip) on the assy instructions booklet cover page (posted below by Gil) was constructed by Al & Terry Prather .

Bob its a Piranha for sure and beautifull boat.We also are looking forward to see the boat running and wish to get a video in a few days.I asked the owner about the booklet instructions and he brought it to my workshop yesterday..absolutely original!

Today we finally could send the boat to water and for its maiden I think everything worked good.The Sg turnfin keeps the boat on rails and despite the small prop used for the break in I think this beauty has more to offer so more tests will happen soon.As the owner is very conservative about high percentage of nitro the boat was tested using only 20% nitro fuel and I can say he's happy for the moment.We hope to finish the break in in the next weeks if weather helps and test better props.Gill

https://youtu.be/C1FSOxGtBZA

Gil that was awesome to see that boat run and it ran great

Awesome job thanks for the video

gil sonsino said:

Today we finally could send the boat to water and for its maiden I think everything worked good.The Sg turnfin keeps the boat on rails and despite the small prop used for the break in I think this beauty has more to offer so more tests will happen soon.As the owner is very conservative about high percentage of nitro the boat was tested using only 20% nitro fuel and I can say he's happy for the moment.We hope to finish the break in in the next weeks if weather helps and test better props.Gill

Click to expand...

thanks for posting Gil, that's exciting to see. And it looks like you can definitely get much more out of it post breakin. You guys have a nice lake there

Thanks David yes for the very first tank after 25 years I think my friend is pretty happy to see his toy working.The lake is in a private club good enough for testing but we use to race in another site .

Gill

Andy Brown said:

Very Awesome story Gil. Beautiful work!

Click to expand...

+1... very cool, Gil!... regarding Picco's and RPM rods, we never had to use them- probably just got lucky, I guess.

We opened the clearance a wee bit on the bushing/ crankpin interface, ran a bit more castor and only ran 50% in

the big Picco's and never blew one up... yep, guessin' we were lucky.

Agreed Timwhalen we also were lucky with Picco's rods but the RPM's were nice products and their rods very good. Thanks Gill

gil sonsino said:

The lake is in a private club good enough for testing but we use to race in another site

Click to expand...

in Sao Paulo?

Yep

After the break in of the Picco 80 we tested the boat at our official site despite one of the wrost dry we are facing in years .For the owner its ok and the boat returns to water only for our vintage event that will be held in december..........here the last video.Thanks for watching

Gill

Man what a nice place to test. You are lucky.


Sent from my iPhone using Tapatalk

very cool Gill, thanks! Now I can't wait to get my Piranha finished and running.

The vintage race sounds fun.

Thanks guys and yes Chris this is our place for heat and saw running despite the low water's level but with the begining of spring and summer coming up we will have the necessary rains to raise water. I would like to mention that we decided to swap the rigid motor mount for a flex one with very few mods,the rest remains original.

Gill

gil sonsino said:

 we decided to swap the rigid motor mount for a flex one with very few mods,the rest remains original

Click to expand...

interesting, I'm curious to see how the flex-mount works out for you guys. With this style of outrigger it was not un-common to experience engine crankcase failure. Due to the fact that the aluminum "wing ding" supports transfer stress from the sponsons directly to the engine mount, which in turn flex the engine mount pads (like a "lever"), resulting in potential cracked crankcase. Especially with the torque exhibited on the bigger engine displacement (.67 to .80). Consequently Prather produced aluminum reinforcement plates to prevent motor mount flex (they also produced pre-fabricated aluminum plates welded onto Octura Swift Switch style mounts).

But I'm thinking, using the popular rubber isolated mount (like you show) may allow the sponson supports to flex, but not torque the engine mounting pads.    If this works successfully for you I may switch my rigid mount for a flex mount too.

I think that the sponsons are going to beVibratingto the point of the crankcase fails or the hull will. You need the support and tie the boom together. Maybe a boxed aluminum tube? MO

Brad

Why does everyone think they need to tell everyone how to do there boats I think gil knows what needs to be done that boat is not going to break the sound barrier they are just having fun with a old vintage rigger not trying to be mean but come on guys

All in fun- constructive input. A natural response.

The epoxy-glass construction is noticeably very light weight and, consequently, very pliable (flexible).

brad nichols said:

I think that the sponsons are going to beVibratingto the point of the crankcase fails or the hull will. You need the support and tie the boom together. Maybe a boxed aluminum tube?

Click to expand...

yes, the hull will flex, it may need some form of a bulkhead (plywood or aluminum, etc.,...) 

Guys after replaced the motor mount we did noticed some minor flex (torsion) in the hull but definetely nothing serious to get in trouble,that video is  with the flex motor mount and the boat ran very smooth I can testify that no reinforcements are needed. 

Gill