hey everybody, i'm planning on building a couple of daddy rabbits for competition this next year and had a couple of questions. first off, after reading the directions on the spa site it looks like i can use an os 91 4 stroke. my question is, can i use the fuel pump version that is offered by os. basically its the same engine as the 91 4s but with a pump. i'm planning on building the wings from foam with my cnc foam cutter so if anyone is interested in a set let me know. thanks toby....

Toby,

That engine is legal for SPA.. Also Dennis Hunt already produces the DR and has cores for the same..

Scott Anderson spa239

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Yep, the OS .91 Surpass II pumper is SPA legal. I just bought two of them. Now to get the Intruders ready to fly. <G>


Ed Cregger

Do pattern ships of that era fly about the same on a .91 4-stroke as a .61 2-stroke? Is there ever a problem with propeller ground clearance? I assume the 4-stroke swings a larger prop.

Tom

No

Yes

Yes


Mark

lol, thanks guys. starting building my daddy rabbits this coming weekend. wish we had a few spa contests up north! i'm going to try my best to get to the tn contest this year. toby

Sorry, Toby. That was just too easy to resist... In answer to your questions:

1) No, they fly slower with a more constant speed presentation with the 4 stroke than the screaming 60's. If you search this forum on "Deception" there is a thread with a new Deception built with the OS 91 (I think) and the builder gives a good description of how it flies compared to the old ones.

2) You may need longer LG to get enough clearance for even a 12" prop, a 13" is pretty much out of the question. The old planes were never expected to fly with more than an 11", so that is what the designers planned for. You do get a bit of a "stork" look to them with long enough gear for the big props.

3) The 4 stroke will swing a much bigger prop, but you need to compromise with a smaller diameter, higher pitch prop to keep the load up where the engine wants it. The extra pitch also helps recover some of the speed these planes like.


Mark

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That’s what I think too!

Thanks Mark. Your comments are making me like 2-strokes better.

Tom

raindave, Did you have something to say? Let's hear it. I like your build thread, by the way. [sm=teeth_smile.gif]

Tom

I was going to tell tobytorkn that a new SPA chapter has been started in New Jersey since he said:

"...wish we had a few spa contests up north!"

But, then I saw that he lives in Ohio. That's not really close to NJ so I figured my post would be of no help to him.

At any rate, a gentleman named James Hamilton has gotten his new SPA chapter approved, so for those of you "up north" you will probably have some SPA contests in your area this year.

I love 2 strokes (don't own a 4 stroke, in fact), but keep in mind that the OS91 is the dominant engine for good reason under the current SPA rules structure. If you fly a 2 stroke, you will be at a competitive disadvantage in SPA. Since I live several thousand miles from the nearest SPA contest, this is not a concern for me and I would use a ST90 to get the power in a 60 sized 2 stroke. It depends on how competitive you want to be. If winning is your goal, use the 4 stroke. If you simply want to compete with a classic aircraft you enjoy, then a 2 stroke will be fine and you can buy a bunch of extra fuel (cheap fuel, too - no 30% heli mix required) to practice with using the savings from the cheaper engine.


Mark

rainedave, I used to live in New Jersey. Would you happen to know where the new SPA chapter is? I used to go to Tony Bonetti's home field to watch people fly. Tony once took off my Tri-Squire for me and then handed me the transmitter. He was the fellow you went to, to get your Kraft radio worked on. I was hard on nicads back in those days.



Thanks Mark. To me, much of the appeal is the look of those '70s pattern ships. Lengthening the landing gear would not be an option.

Tom

OK, Ohio guys, we have two members in Columbus. Eric and John Nessler both live on the nortwest side of town a little below Dublin. I think they've got a practice site out toward Marysville and have been known to fly with the club that flies near the Alum Creek Dam. We've also had enquiries from some guys in the Cincinnati area.

Trisquire, make it a tail dragger and make the legs longer. That's become the standard configuration. Tail dragger helps offset the weight of an OS. You could also use a Saito 91 which is a bit lighter than the OS. If you choose a non-pumped engine, mount it on its side to keep the carb in line with the tank.

guys, i have my own flying field in peebles, ohio. i have 4 runways ranging from 750' to 1100'. i have put several imac contests on and i also put the heart of ohio huckfest on last year. (83pilots). if there is enough interest, i would be willing to put on an event. let me know. toby....

Sounds good, just over 4 hrs from KnoxvilleTN.. Count me in if it's my off weekend... shoot you should also do a AMA meet

Scott Anderson
SPA 239
Team Tanicpacks.com
Team Castle Creations

The problem with prop clearance is not as bad as it first sounds. I fly a trike gear King Altair from a sometimes bumpy grass field, and have used 14 inch props without problem, and even a 15inch. The tips DO turn green, but there is no problem getting off the ground. A lot depends on the size wheels you use. I use 3inch wheels on the mains and 2.75 on the nosewheel.

The plane will fly slower and more constant speed witn the 4-stroke, and you should get better vertical performance.

I would seriously consider the drive from Asheville, NC. With at least 3 current SPA members in the Ohio, and further interest in the Cinci area, it would be great to get someting going up there in "Buckeye Country"---isn't that right Steve, (Buckeye) Byrum?.

.

Thanks spbyrum, It sounds almost like a classic/F3A hybrid. I can see the advantage however. They would have used 4-strokes in the '70s if they had been available. The pumped OS .91 looks pretty sweet, although it's $100 more. A fuel injected one for $850? That's a little over the top.

I stop at the Alum Creek field now and then. If I'm lucky, the next time I'm there, the Nesslers will be flying their pattern ships.

Tom

From what I have seen it only really mattered in Master class. Most fly novice and I don't think it really makes much of a differance there.

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We have to find something to worry about, you know?

I had a Deception in 82. I forget the weight of the model when completed, but it was within the typical range for a kit built model in those days. Mine was powered by an OS .61FSR with OPS pipe (running down the right fuselage side) and was equipped with Rhom-Air tricycle retracts. I flew from a grass field in Salem County, New Jersey. While our grass field accommodated most kinds of models with ease, flying the Deception from that field was pure misery because the field was simply too small and rough. Every landing, no matter how gentle and slow, resulted in a session of restraightening the 5/32" landing gear legs. I was working in a machine shop at the time and made up a special tool to grab the aluminum landing gear blocks and let me bend the wire gear back to a straight position so that they would retract cleanly on the next flight.

The OS was a good engine for sport flying, but it was not strong enough to haul the Deception well vertically. At that particular time, Rossi and YS engines were sold before they even entered the country. Just having money was not enough to buy one. You had to be someone of note in the pattern community in order to qualify for purchase. That wasn't me.

Realizing that I did not have the resources (flying field and money) to compete effectively, I dropped out of pattern competition. I won or placed in the few contests in which I did compete. But I couldn't compete with the wallets of those with more money. Some things never change.

Now that I have the money to compete successfully, I no longer have the vision or the energy to do so. Life is weird like that.


Ed Cregger

It probably makes the most sense for the sponsored pilots, because they're...........well............sponsored.

Tom