flyingbells

Hi,

I'm wondering if you guys can give me some recommendation, needed a lot more power on a funfly which currently has an OS 46FX with a ton of nose weight. Just wondering what's the largest displacement / power of say a Saito or an OS I can go for.

The catch is I'd like to have the same mounting bolt pattern on the new engine

thanks!

Will.

XJet

The Saito 82 is the largest .46-replacement engine you could probably squeeze in there without affecting your CG too much.

One thing to watch however, are that you still have enough prop clearance. The 82 will want a 14-inch prop to do it justice

On 30% nitro the .82 will happily spin a 14x6 to give you obscenely good power and even on 10% nitro it'll perform very nicely on a 14x4W.

Not too sure about the mounting holes but I did have one profile that I regularly swapped between a TT46Pro and a Saito 82. I can't recall if I had to drill extra holes but certainly the width between the mounting beams was pretty similar if not identical.

asmund

If you can`t fit a 91 (or 100) then the only two sensible options are the one mentioned by Xjet or the YS 63

DarZeelon

Will,


A 'thumper' is used to describe a large-displacement, single-cylinder, four-stroke engine (mostly in motorcycles).

Would you say a '4 thumper' is a large, single-cylinder, four-stroke, four-stroke engine?


I agree with Bruce and Asmund on what they wrote.

You could probably obtain a Saito 72, in good condition (not is the junk sites), that will do very nicely with a 13x6 prop.


If it is used in good condition (that you can actually check before you buy), the cost will be significantly lower than that of a new Saito .82.

RCVFR

My Feedback: (7)

That's right up there with misusing "4 banger" to denote a four stroke. Last time I looked, 4 banger means 4 cylinders!

42etus

My Feedback: (2)

Get a Saito 82 and don't look back. You may need to fab a taller landing, gear since you'll be swinging a larger prop.
Paul

Hobbsy

My Feedback: (102)

He can always use a 12x8 three blade.

DarZeelon

Quote:

ORIGINAL: Hobbsy

He can always use a 12x8 three blade.

Dave,


Since Will's goal is to have better thrust for 3D flying, I have my doubts whether an 8" pitch prop will be very useful...

Full-size aerobatic flight is achieved with props that have large pitch numbers (compared to the diameter), but in model flight props which are akin to rotors are the only ones that are popular...


Also, How many such props are available and at what cost? Will will be forced to fly off very soft grass...

Hobbsy

My Feedback: (102)

Dar, my thinking is always toward practical props not, "go nowhere props" the 12x8 3b would approximate the load of a 2b 14x6.

XJet

But in the case of 3D, a larger fine-pitched prop *is* the practical one.

3D aircraft are not built for high airspeeds (often they'll just fly to pieces if you ignore that fact) so what is needed is a prop that moves a *lot* of air at a relatively low speed.

A larger-diameter low-pitched prop ensures that at least some of the propwash hits the ailerons (giving you roll-control at zero airspeed) and it also ensures that the entire elevator and rudder are also operating in the propwash.

It makes no sense to try and fly a 3D model with a small-diameter coarsely pitched prop it's the wrong tool for the job.

I run 12x4 props on my .46-sized 3D planes, 14x4 on my 4-stroke .82 and a 15x6 on my 100-sized 3D ship.

Even my 50cc gas plane only has a 23x8 prop.

XJet

And as for "go nowhere props" I trust you've seen this video which shows how a 12x4 prop is far from a go-nowhere proposition...

http://nz.youtube.com/watch?v=gck69lc2HoE

We regularly race these planes and a 12x4 pulls that airframe at exactly the same speed as a 10x7. However, the 12x4 gives unlimited vertical and *much* faster pull-out from a sharp turn.

djlyon

Go here and get a tuned muffler for your engine. A lot cheaper than a 4 stroke and lots of power and you can keep your bolt pattern.

http://www.pspec.com/details.asp?ProdID=61&category=8

Denis

XJet

Go where?

And tuned mufflers are fine (the Tower or GMS47 muffler does offer a useful increase in RPMs) but you can't effectively use anything more tuned than that because it stuffs up the mid-range/transition so important for 3D flying.

djlyon

Not this one I just edited it in. I use them on 3D planes and they don't stuff up anything

DarZeelon

Quote:

ORIGINAL: XJet

Quote:

ORIGINAL: Hobbsy

Dar, my thinking is always toward practical props not, "go nowhere props" the 12x8 3B would approximate the load of a 2B 14x6.

But in the case of 3D, a larger fine-pitched prop *is* the practical one.

3D aircraft are not built for high airspeeds (often they'll just fly to pieces if you ignore that fact) so what is needed is a prop that moves a *lot* of air at a relatively low speed.

A larger-diameter low-pitched prop ensures that at least some of the propwash hits the ailerons (giving you roll-control at zero airspeed) and it also ensures that the entire elevator and rudder are also operating in the propwash.

It makes no sense to try and fly a 3D model with a small-diameter coarsely pitched prop it's the wrong tool for the job.

What he just said!

DarZeelon

Will,


Dave Shadel used to offer another version of the UltraThrust, intended for 3D and higher torque at lower RPM...

...But they seem to not be on the site any more...


Maybe you should try contacting him [link=http://www.pspec.com/contact.asp]here[/link].

Maybe he still has some left, or can make one for you.

XJet

They're virtually identical to the Tower/GMS mufflers but more than three times the price!

I'd just save myself $55 and buy the Tower/GMS. I use them extensively on my 2-stroke .46-sized engines with profile 3D planes.

DarZeelon

Quote:

ORIGINAL: XJet

They're virtually identical to the Tower/GMS mufflers but more than three times the price!

I'd just save myself $55 and buy the Tower/GMS.

Bruce,


They are about four times as expensive, but as to being virtually identical!?

Not only am I certain they are not, but the performance output from the UT muffler is ~700 RPM higher than the best Tower muffler I have ever seen.

The JettStream is very similar in all respects to the UT.


Is it worthwhile paying the extra $55, to make a gain of that magnitude? I guess the number of different answers you will hear for this 'yes/no' question will be quite large...

I am sure, however, that these premium high-performance mufflers can be produced at a cost that will allow them to sell for close to the Tower/GMS price...

Hobbsy

My Feedback: (102)

Picture #1 is a 2.20 cu. in. thumper and picture #2 is a 30 cu. in. thumper.

djlyon

The performance specialties and Jett tuned mufflers are a very different design than tower mufflers. They utilize an internal pipe among other things achieve more power. I suggested them because you seemed to want lots more power with the same mounting. They will get you that at a lot lower cost than a new 4 stroke engine. However if you are just looking for a rational to go buy a 4 stroke just go do it. They are great and great fun. But if you want to put a smile on your face because of performance and throttle response get one of those mufflers.

Denis

flyingbells

Thanks for the responses and the education on "Thumper"

The plane is "Xtreme 3D" by Balsacraft. Here's a few pics of the front with OS 46FX installed, obviously there's no a lot of space here.

It has a wing span of 57.5", and its a built up, which have been kitted on the heavy side

[img][/img]

DarZeelon

FlyingBells,


If room is of the essence, maybe you should with Bruce's recommendations...

If you put a 12x4 (or a 12.25x3.75W) prop on this model, it will fly like no 10x6 - 11x7 will ever allow it.


This includes good 3D capability!

And then, you will not need to invest in another engine just yet...

ChrisAttebery

My Feedback: (15)

Try the APC 11.5x4W on the FX. It will give you great pull and spool up.

Fuelman

My Feedback: (6)

I'm with the Saito gang. Being a 57" wingspan, that is 60 size two stroke teritory for 3D. I would fit a Saito 82 or 91 in there.
Since you are somewhere that high nitro fuel is extremely expensive, I would go with the larger displacement of the Saito 91 and run 10% or 15% fuel in it. That way, you'll have more power than the 82 on the same fuel and very little weight penalty.

XJet

Can you still even buy the Satio 91?

A Saito 100 would be a better option (lighter and more powerful) than the 91.

Remember that this plane won't last forever and when it's "all worn out" you'll want an engine that gives you a good range of choices for your next model. The Saito 82 will power any .46-.55 sized model with great results and the Saito 100 will power any .60-.90 sized model in a similar fashion.