Modern Engine Size Equivalent

[builditright]

Hi Guys,

What would be the modern engine size equivalent to an old Forster "29" engine.  ( Simple answer is ? )

Okay since this went a little off direction let me show the reason why I asked the question.

I was in the process of finishing up some plans and one listed some info on older engines of which I am not
familiar with, so I figured I would ask without going into details. 

That said I finished up the plans for a future kit of DMECO's the "BIPE"

[Randy Cuberly]

LA25 with a 10x3 or 10x4 prop!  In my opinion the La15 mentioned earlier is plenty of power but the engine is too light to be considered and equivalent to a forster 29.  I have several old Forster 29's and they can be sufficiently powerful to fly any of the old profiles.  The LA25 is a bit more controllable also in that it can easily be adjusted to compensate for more or less power.  The 15 is a bit more finicky about that!
For instance an LA 25 in a Ringmaster is pure fun and easy to deal with (I've had several set up like this), and makes a pure fun (and competitive Old Time entry)!

Randy Cuberly

[BillLee]

Hi Guys,

What would be the modern engine size equivalent to an old Forster "29" engine.  ( Simple answer is ? )

4.9
 

[Dwayne Donnelly]

4.9
 

No the answer to everything is 42. 

[Craig Beswick]

How many will get that Dwayne? Or should I call you deep thought?

Craig

[Paul Wescott]

How many will get that Dwayne? Or should I call you deep thought?

Craig

42 is not the answer to everything.  It is the answer to Life, the Universe, and Everything.  There’s a difference.
HGTG Trivia: It took the “super” computer Deep Thought 7.5 million years to calculate that answer.

And thanks for all the fish...

Paul

[builditright]

Plan picture added

[Tim Wescott]

LA25 with a 10x3 or 10x4 prop!  In my opinion the La15 mentioned earlier is plenty of power but the engine is too light to be considered and equivalent to a forster 29.  I have several old Forster 29's and they can be sufficiently powerful to fly any of the old profiles.  The LA25 is a bit more controllable also in that it can easily be adjusted to compensate for more or less power.  The 15 is a bit more finicky about that!
For instance an LA 25 in a Ringmaster is pure fun and easy to deal with (I've had several set up like this), and makes a pure fun (and competitive Old Time entry)!

Randy Cuberly

I'd consider a 15LA and a hunk of lead.  I know that a Ringmaster is designed for a Fox 35, and is overpowered by a 20FP.

[Tim Wescott]

Plan picture added

IMHO the CG on that is way too far forward -- the author seems to have located it correctly if the bottom wing is missing, but with as much stagger as that has it should be around the middle of the top wing.  If I built that I'd be doing some serious experimentation with CG which would drive changes in leadout location.

So, 15LA 'cuz that'll move the CG back nicely!

[Dennis Leonhardi]

"Back in the day" ...  OK, the '70s - I flew this profile SE5 with a Forster .29.   It was probably roughly equivalent to a Fox 35 - I could never get it to slow down as well as I would have liked.  I wouldn't underestimate the power of that engine because it's "old".  I'd probably choose an FP .25 myself.  Hal deBolt was known for fast airplanes you'll recall ...


Dennis