[bbbair]

OK Guys;
Here’s a question for the gassers out there…

I have an Extra 300 that flys – but not well, I just weighed it and it is 11 lbs .

I find that it is under powered with a Saito 120, so I was looking at a CRRC 26cc Engine to get some more power.

BUT!

I looked at the Specifications of both engines and got a real surprise;

Saito FA 120 Weight 900 grams, (1.99 lbs), rated O/P 2.2 HP
CRRC 26cc Weight 1.165 Kgs (2.56 lbs), rated O/P 2.4 HP

So basically if I bought the CRRC I’d be increasing the engine weight by half a pound and increasing the power by 10% - and I have gained NOTHING… unless I missed something.

[Lash]

How about a Saito 150? 1.87 lbs and 2.5 hp
http://www.greathobbies.com/producti...od_id=SAIFA150

Or DL 30 at 2.4 lbs and 3.7 hp
http://www.azurehobbies.com/product_...roducts_id=174

[RAMJET]

how big is the plane ,will it ballance with a bigger motor .I think the DL 30 will be the best power for it's weight ,don't forget to calculate the weight of the ignition batteries /switch harness/ignition/opti kill/means to choke/mounting hardware/bigger prop/.I think by the time your finnished there will be a full pound differance.Roger

[hellyeh]

I have just installed a CRRC 26 on a CMP Extra 300S with a 73" wingspan . It's dry weight is 13lbs. 4oz. . I was a little concerned with the weight and wingloading before i flew it , but all that concern was for naught . The engine only has about a gallon and a half through it so far and is spinning a SY 16x8 prop at 9,000 rpm on the ground . It has good power and will pull the airplane vertical for quite a ways before it runs out of steam . Every flight seems to get better and better powerwise . The landing speed is quite manageable despite the wingloading . I need to try some different props , but i'm pretty happy with it so far . If you have the clearance for up to a 20" prop , and want to buy a new engine , i would go with the DL 30 , but the CRRC 26 seems to work pretty good for my application .

[g-manz35]

I've been looking at a lot of Saitos lately trying to find one to go on my 8 lb Cap. What I noticed is that the 120 is really heavy. in fact I think a 180 is just as light. Or close to it.
http://www.greathobbies.com/producti...od_id=SAIFA180

Also the HP ratings need to be taken with a grain of salt. I find it best to ask around and get some good numbers from a fellow modeller who owns the engine you wish to buy. Once you know the prop and RPM the engine will turn it at, then you can punch that into a thrust calculator. Compare that to the performance of your present engine and PRESTO! you got some good info to make your decision. I've got engines that do not put out anywhere near the HP they are rated for. I think that many manufacturures use "Brake Horse Power" as their rating. I find that depending on the manufacturer this rating is a bit exagerated. That's just my opinion.

George

[chuebner]

George.... a Saito 180 in that little Cap would tear it apart.

That is the same motor I am running in my AgWagon and LOVE IT!!!

I suppose you could always use throttle management!!


Cheers
Curt

[bbbair]

Well Guys;

I have to admit to a bit of stupidity here... I bought this AC from a fellow modeller and I never checked the weight specifications.

This bird has a 64" wing, is rated for a 60-91 2S or a 120 4S - flying weight should be 7.5 pounds...

The builder converted to a Foam Wing and I added the Saito... Current weight is 11 pounds ... 3.5 pounds over weight - no wonder it flys poorly!

I have got to start looking for ways to trim weight off this plane!
My first idea is to hollow out the wing without loosing any strength.
After that I may have to get 'Creative'!

I'm Open for suggestions..

[chuebner]

Hi bb.... just a few questions to help us get started....
Is it kit built or an arf??
What make?? (can you post a link to the manufacturer)
Has it been crashed, reinforced or repaired??

From 7.5 to 11 lbs flying weight is grossly overweight. Pretty high wing loading on that one for sure. Maybe someone can chime in here also.... I did'nt think foam core wings added any weight at all over balsa!

Cheers
Curt

[bbbair]

Hi Curt;
This is a Great Planes Kit - about 10 years old, never been crashed and All I did was cover the plane and add the engine.

I too did not think that the Foam wing would add a great deal of weight... that's why I just covered it and kept on going.

ONE THEORY that I have - is the Saito engine... It is about 1 Kg vs a 60-90 2S that would weigh 6-750 gms (1 pound difference) then there is the added weight to balance the plane (perhaps a pound in the tail to compensate?) and a bit for the foam wing (perhaps half a pound) and it all adds up.

I am going to be looking at the plane VERY Closely this weekend - I may be able to shed some more light on this by Sunday


Thanks for the input,
(and Merry Christmas!)

[g-manz35]

It takes very little weight in the tail to compensate for a nose heavy plane. Usually the weight is placed very near the back. so even if you have a motor that is 400 grams over weight it would probably only take 100 g in the tail to compensate for it. I guess you'll figure it out when you start looking into it. I had purchased a small 25 size plane that was kit built and it would hardly fly. It was about a pound over weight. Realisticly there was nothing I could do with it. there was no added weight that I could remove.

Is this your plane?
http://www.greathobbies.com/producti...od_id=GPMA0236
I know a guy who is building one right now. I could probably get him to weigh it just to compare. I find it hard to hit the weight that they list on the specs. I think if I buit it I would be happy if it came out to 8 1/2 lbs. 11 lbs does seem pretty heavy for that wing area.


Good luck. George