Re the Sapphire

[pylon500]

You may find that once you change gears and get some load on the prop, you'll probably need to drop the needles again...

 

 

[aro]

Pitch sensitivity is a symptom of an aft CG, so it suggests a weight and balance issue with the heavier engine.

 

Aft CG has killed plenty of people, I would suggest not flying it until you confirm the weight and balance. Pitch trim doesn't fix aft CG.

 

 

[kasper]

Pitch sensitivity is a symptom of an aft CG, so it suggests a weight and balance issue with the heavier engine.Aft CG has killed plenty of people, I would suggest not flying it until you confirm the weight and balance. Pitch trim doesn't fix aft CG.

if your wing is not swept ( and I do not think any of the fabric 95.10 wings were) you really should check your cofg and be prepared to put a lot of lead up under the pedals - you getting 10kg heavier is probably still not enough.

 

The 95.10s with fabric wing have no sweep on the wing and were designed for the 22kg KFM107ER engine - to accommodate the heavier glass wing and the 447 the wings were swept on the 95.25 sapphires - if you have a straight leading edge really consider that you have nearly doubled the engine weight over the original with a 503 and A box.

 

 

[microman]

Thanks for the advice - will do a weight & balance tomorrow - if its significantly aft I probably have no alternative but to remove the 503 and replace it with something much lighter - I do have a Kawasaki 440 available which should do the job.

 

 

[pylon500]

I do have a Kawasaki 440 available which should do the job.

For their power output, the 503's are reasonably light, you may find the Kawasaki not a great deal lighter than the 503 when compared to the KFM's, 277's and 337's used originally...

Do you have any pictures of your machine?

 

 

[microman]

Can anyone help me with a simple weight and balance formula f0r the Sapphire? I have been playing around with different formulae but just seem to get tied up in knots. I know there is a simple formula available but cant seem to find it on the interweb.

 

 

[kasper]

Can anyone help me with a simple weight and balance formula f0r the Sapphire? I have been playing around with different formulae but just seem to get tied up in knots. I know there is a simple formula available but cant seem to find it on the interweb.

You are not able to have a SIMPLE formula for the Sapphire as there are two very different wings on the two groups (95.10 and 95.25) and they put the aircraft in different attitudes for level flight and you need to know the stations of the wheels in the flight attitude with reference to the datum.

My method uses a spreadsheet, bathroom scales, 2 bathroom scale height blocks, an orange crate, a petrol dip stick and about 30 minutes ... but that because my spreadsheet already has the stations of the wheels in it, the stations of my buttocks and the stations of the two fuel tanks in it ... and as mine has no manufacturers handbook I elect to fly between 25-40% of chord.

 

If you are a member of RAA you can download their W&B calculator spreasheet, if not PM me with your email and I can send it across.