lnl1950

Hi Guys,

I just inherited a Daddy Rabbit, no plans or specs, anyone have a recommended CG and Engine? The wing span is 68" and it looks like the original Jim Whitley 1966 model on the Trenton RC website, the plans that are with the article show the CG at about the landing gear block, is this correct?

Thinking about putting my O.S. FS 120 pumped on it for power, weights look like they will come out around 8.5 pounds, is that fat?

Thanks,

Larry

J Strong

My Feedback: (18)

4stroke 91 is a good fit. That's what we're all using in SPA
Check us out at seniorpattern.com

Jamie

bem

My Feedback: (1)

Hi,

You will probably get problem with center of gravity (CG)the OS 120 4-stroke that weight about 35oz /1000 gram. Daddy Rabit was designed for an engine about half of that weight. I suppose You can compensate some with placing standard servos for rudder and elevator in the tail near the control surfaces and maybe a larger then neccessary battery back in the fuselage. But it is always better to have the mass gathered close to CG and not spread out in various directions.
Another problem You will have is the larger prop diameter you need with OS 120 4-stroke compared to a .60/.61 2-stroke - prop clearance to the ground if you make it original trigear will be a problem but You could make main gear/taildragger and that will solve the problem OK.
You will also have it overpowered in my opinion but it will probably fly OK anyway.
It will probably work but it will not be good really. There are so many good 2-stroke, 4-stroke and electric motors out there that will fit a Daddy Rabbit better and make the planefly as intended.
Daddy Rabbitwas enhanced in many versions during the years Jim Whitley flew it both at top US level (NATS etc) and at World Champoinships like in 1969 (10th place),1971 (6th place) and 1973 (8th place). As far as I know Daddy Rabit (I) was in 1966 and then up to version X that was the last version (I do not know the exact year but probably 1973 since at 1973 WC he had verion X).
In 1966 version of Daddy Rabbithe had a Veco (Lee Custom) .61 according to the article in Model Airplane News May 1967.
In 1971 WC he had Daddy Rabbit VII with wingspan 1638 mm (64.5 inch), weight 3714 gram (8.2 lb), Webra 61 (Black Head) with Silence Air silencer, Top Flite 11 x 7 3/4prop and Pro Line radio.
A Veco 61 from that era should not be impossible to find but may take a while.
A Webra 61 Black Head is not that hard to find today even new in box if you have some patience (just check the big auction site and sooner or later it will be one there).
On the other hand a modern engine like OS 55AX or OS 65AX will work fine also.

Weight: In the MAN May 1967 article it is mentioned 8 pounds dry weight and 9 pound take off weight with fuel.

Good luck and please make a build/assembly thread here regardless what engine You decide to use.

/Bo

lnl1950

Bo, you are correct, the 120 is not the answer. The plane was originally set up with the O.S. 55AX and it looks as if that is going to be the largest engine that will fit into the plane without drastically modifying the nose area, but I think the plane will be somewhat underpowered at the 8-8.5 weight range.

The 60 size engines are all wider at the mounting flanges and will require substantial removal of wood to accommodate the engine mount, this also rules out the .91 Jamie referenced in his response.

I could probably get something like a Jett 50 or other hi-power 2 stroke to fit but will probably go with the 55AX due to cost considerations,

Thank you guys for your response,

Larry

J Strong

My Feedback: (18)

The Satio 82 4 stroke is also an option. 17 oz's motor weight, and not as large as a OS, and swings a 13 x 8 pretty well, and should perform as well as most really good 61 two strokers. I had one on a 40 tower Kaos, that wasn't fats but pulled like crazy .
All just a matter of choice.

bem

My Feedback: (1)

Hi,

An OS 55AX should be OK since it is after all rather powerful engine with 1.68 hp at 16000 rpm. That is morehpthen an old Veco 61 and Webra 61 Black Head that was used by Jim Withley in the early Daddy Rabbit versions (I think he used Ross 61 in latest version X and maybe it was close to an OS 55AX in power).

http://www.osengines.com/engines/osmg0556.html


Then You have Jett SJ60 LX high performance engine that is seize of OS.46 engine - that should take care of seize and power.

http://www.jettengineering.com/


/Bo

lfinney

My Feedback: (44)

adding the jett engineering exhaust pipe would really wake up the .55 AX and would be the simplest solution

stuntflyr

The Jett muffler and finding the right propeller will make that 55AX run with plenty of power.
I've found three props I can use with a stock muffler for different styles of flying. It seems to be a very flexible engine.
Chris...

bem

My Feedback: (1)

This is Jim Withley's original Daddy Rabbit version X (the last version) that has been restored - see image below, found in some of the SPA's Newsletter.

/Bo

stuntflyr

Looks like it is equipped with a Jett engine.
Chris...

rv7driver

My Feedback: (105)

have a DR1, with a Silver head os 70 4 stroke, it flys it really well. it is SPA Antique legal with the 70. mine is the red and white DR1,Dan doughertys DR1 on left. Pete