kmp b25
04-26-2008, 11:19 PM
#2
RE: kmp b25
For the new 95" KMP B-25? Yeah it should be, but a multi-cylinder glow 4 stroke motor does not put out the same power as a single cylinder of the same displacement. Single saito .91 puts out 1.6HP. The saito 90 radial puts out roughly 1.4HP. You should be fine though. Just dont over do it no weight if you can help it. Instead of using say a 13x8x3(is using 3 blade props), you'd probably be spinning a 12x8x3. If using 2 blade you could get a 13x8 or a 14x6. I have a saito .91 that spins a 14x6 easily
The original 85" B-25 could easily fly on saito 62's, but the recommended motors were 70+ 4-stroke.
The original 85" B-25 could easily fly on saito 62's, but the recommended motors were 70+ 4-stroke.
04-28-2008, 03:45 PM
#4
RE: kmp b25
Use an onboard glow system for 3 cyl's and you'll be fine. Just set the off point for the onboard glow well above 1/4 throttle and make sure both motors are broken in well. I had a saito 90TS in an extra 300 awile ago. The power was only a little less then the single 91, and if one cylder does drop, the momentum of the prop along with the other cyl still firing will reignite the dropped cylinder as long as you have onboard glow. I would suggets you use a user set off point type like the SonicTronics Mcdaniels line. You can set the off point anywhere along the throttle curve. On a multi-cyl engine, Id put it above 1/2 so you dont lose too much speed trying to reignite a cylinder if one does happen to drop off. In fact...would be a good idea to have it set at around 3/4 IMO.
05-02-2008, 06:38 AM
#6
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RE: kmp b25
Hi!
Are you joking...??? it is of vital importance in any airplane ,and especially so in a multi engined airplane that the weight is kept as low as possible. Those tripple Saitios arnt suitable at all.
For a 85" span twin I would say .90 four strokes is way ,way too much power. It will only fly like a pattern plane with thoose engines.
If you want to fly scale like...On the wing...use .40-.70 four strokes and remove weight wherever possible.
...Then people who favorite bigger engines will say..."-It is always possible to throttle down"...Yes! But the weight will still be there.
Are you joking...??? it is of vital importance in any airplane ,and especially so in a multi engined airplane that the weight is kept as low as possible. Those tripple Saitios arnt suitable at all.
For a 85" span twin I would say .90 four strokes is way ,way too much power. It will only fly like a pattern plane with thoose engines.
If you want to fly scale like...On the wing...use .40-.70 four strokes and remove weight wherever possible.
...Then people who favorite bigger engines will say..."-It is always possible to throttle down"...Yes! But the weight will still be there.
05-02-2008, 04:41 PM
#7
RE: kmp b25
Jaka is free to have his opinion, although I think he's wrong to some degree. The multi-cylinder engines are fine. Many ppl have put gas motors on these planes and they are heavier then normal glow motors. If you use heavier motors, you'll simply be using more flaps more often when landing. Also, a heavier plane setup is a lot more scale then an 85" b-25 running .70 motors thats light. No bomber was light(except the Mosquito).
If you do use the radial motors, make sure you reinforce the firewalls as well as the retract rails pretty good.
I would suggest though, that if you havent gotten the plane already....get the bigger 95" KMP B-25 thats just around the corner. inf act, I think the first shipments have been sent out. This 95" one would fit the radial motors a little better and would not be effected by an increase in weight for motors.
I have the 85" version of the KMP B-25 and its being fitted with saito 91's.
Some will think this is overpowered, but, not when adding in a host of scale details, bomb doors, bombs, rivit details, etc.
AS an added bonus for using the multicylinder engines, you usually end up saving yourself the hassle of adding dead lead in the nose to get correct CG.
Most B-25 kits come out a little tail heavy if the plane is even close to scale....so you end up adding several ounces or more of weight in the nose. You wont have that problem using 90 radial's.
Its also a little apparent that Jaka doesnt realize that a 90 size glow radial doesnt put out the same power as a single cylinder of the same basic displacement....so in no way would you be "overpowered" even on the 85" size. Again, the weight is not an issue since you need nose weight.
Magnum, if you do use the radials, please do a build thread as I would love to see the plane take shape. It would be just that much more scale having multicylinder motors.
Now, as far as onboard glow, yes its a necessity on multicylinder engines and those units dont weigh much anyhow.
If you do use the radial motors, make sure you reinforce the firewalls as well as the retract rails pretty good.
I would suggest though, that if you havent gotten the plane already....get the bigger 95" KMP B-25 thats just around the corner. inf act, I think the first shipments have been sent out. This 95" one would fit the radial motors a little better and would not be effected by an increase in weight for motors.
I have the 85" version of the KMP B-25 and its being fitted with saito 91's.
Some will think this is overpowered, but, not when adding in a host of scale details, bomb doors, bombs, rivit details, etc.
AS an added bonus for using the multicylinder engines, you usually end up saving yourself the hassle of adding dead lead in the nose to get correct CG.
Most B-25 kits come out a little tail heavy if the plane is even close to scale....so you end up adding several ounces or more of weight in the nose. You wont have that problem using 90 radial's.
Its also a little apparent that Jaka doesnt realize that a 90 size glow radial doesnt put out the same power as a single cylinder of the same basic displacement....so in no way would you be "overpowered" even on the 85" size. Again, the weight is not an issue since you need nose weight.
Magnum, if you do use the radials, please do a build thread as I would love to see the plane take shape. It would be just that much more scale having multicylinder motors.
Now, as far as onboard glow, yes its a necessity on multicylinder engines and those units dont weigh much anyhow.
