HPA

Well, if George okays the initial trim settings, you should do fine at the IIFI!

Many thanks Jeremy,

However, the gym we are currently using is rather narrow/tight and would not endager any flight there.

George also said it's better to try it in IIFI. The airplane is balanced to the proposed balance point, so I'll take my chances!

Quote from: Spiros on Oct 01, 2026, 08:05 AMThank you so much!

First flights will be in IIFI 2026, hopefully!

Spiros

You have a month or so until the IIFI.  It might be a good idea to start trimming it before then

Thanks George for oofle dusting the upload!

Link to the book:
https://hpa.aeromodelling.gr/plans/details.php?image_id=2204

Quote from: Squirrelnet on Sep 30, 2026, 02:34 PMSurely though if you are winding a 10 x 1/8 motor to full turns or presumably 80% of breaking turns then a smaller motor even if wound to breaking turns will not produce as much power and therefore not climb as much ? I wondered if you needed more power ...11 strands ?

If you look at the turns/torque curves (eg on page 24 of the JOD collection soon too be available in the Plans Gallery), the high torque part of the curve doesn't come until at least 90% of the break turns are applied. At 80% you are just in the early part of the cruise part of the torque curve.  Duration models are always wound to 90% or more - that's why you only get 2 or 3 competition flights from a motor.

I think it was looking at the reluctance of scale modellers to wind into the high torque part of the curve that led JOD to say that the motors were under-wound.

Of course, there is another side of the equation that can be looked at. That is whether the prop is correctly dimensioned for the motor.

In the current situation, where you don't seem to be getting quite enough climb from the high torque beginning of the motor run, I suppose there are three prop variables that can be considered:

• reduce the weight of the prop blades  - I've had very little luck are doing this.
• reduce the pitch of the prop - this is the basis of the variable pitch mechanisms used in rubber duration. Finer pitch is used at the beginning to help the climb and during the cruise section, the pitch is increased so that, even though the prop is turning relatively slowly, it is still taking a decent "bite" out of the air with each revolution.
• reduce the blade area - in effect, this makes the proper easier for the motor to turn. It also means that you can make adjustments to an existing prop rather than having to make a new one. You can either slim the prop down by thinning it at both leading edge and trailing edge, or cut an equal amount of each tip or do a combination of both. It will rather depend on how brave you are.

Some flyers that I have met actually have a test prop system which they use when first trimming the model to determine the best prop geometry before making the prop they actually want to use. In essence, it is a hub into which different sets of  blades (with differing diameters and chords) can be inserted and which also allows the pitch of the blades to be adjusted . After a few years, the number of sets of blades can become large enough to allow a pretty good estimate of what the "best" performing prop will be and that prop can then be carved.

One other thought I had is that the lighter motor, if more than 50% of the motor is behind the CG, will bring the CG forward and some of the nose weight may need to be removed to get the CG back to the correct position. You might find that just that reduction in overall weight is sufficient to enable the model to climb better.

As always, there are plenty of things that can be tried to get the desired result!

Thank you so much!

First flights will be in IIFI 2026, hopefully!

Peter, thanks for that. I certainly would appreciate you keeping a lookout  when you're next browsing through Le MRA library.

cvasec, that was a valuable comment. And yes, Dave Hipperson's plan shown in the article, was the same as the one in AeroModeller Annual. However, the mention of FFQ sent me to the bookshelves, and my copy of the Coupe D'Híver Survey, 2006. There are two plans shown .

The first is on page 32, and is headed Champion de France 1968, and centre stage on the plan, the name Yves Sargentini. I'm afraid I don't know who he was.
 
The second is on page 54. It is dated 1975, and the model is now called Les Trumeaux, and is by Georges Matherat. It appears identical to the original plan, apart from rectangular wing and tail in plan view. The original had slightly rounded tips at the trailing edge.

There is a bit more to come. Mike

Jeremy

Thanks for your work in compiling all that valuable material and persistence in making it available to all the members here. Many thanks again.

Julio

Thanks for this Jeremy.Now off and trim your new model.

John