Testing the waters and a rather pitiful, amateurish, first attempt at linking videos from my helmet cam; don't yet know how to edit them either. Camera separates the entire vid into sections - did not bother to upload middle of flight... If it doesn't work, you missed lethargic upwind passes and a speck at times. I'll keep tryin'.

https://youtu.be/_J2bLbLDISs
https://youtu.be/Ui3KqXAJ6A0

Hi Dave well done ya did it thank for sharing and with practice you will be doing great passes right by the cam.

The first vid

In the hand right at launch 17.1k static
In the air best pass 22.87k if with a 5x4 prop 87 mph potential with slip at least 76 mph.
If it was a 5x3 prop 65 mph with slip perhaps 56 mph.

17K static - that seems pitiful; may have said it before but I remember a modeler years ago telling me "if the Tee Dee doesn't turn 18K out of the box, you throw it away and buy a new one..."

I have a tach - just lazy about using it I guess.

It was a 5X4 prop - being human and favoring exaggeration would like to think its going faster than 70 mph but with a realistic attitude, find it hard to believe.

I haven't researched your entries in-depth in this sub-forum recently but I remember you're somehow able to use Doppler Effect to acquire groundspeeds - is this correct?

What is slip?

Do you use any particular telephoto setting (zoom) beyond default on your hat cam?

I can preset zoom in but it would record the entire flight that way. I have tried it and decided to
just fly inside a better box more suited for the camera on regular settings. I found have two of
the sport type cameras the first one was a 8MP photo and 5MP video then bought another like
a year ago does 12MP photo and 8MP vid so can hold good focus further out.
Today's tech prices have finally reduced those once high dollar 4K sports cams around 100 bucks,
able to focus so much better on the smaller planes. I will be moving to that at some point soon.
Of course flying small planes still forces you to stay close on the back stretch.


The readings where best rpm not the average of course majority was in the 60's down wind
as I recall. If the plane is not too heavy perhaps a 4.5x4 would be good way to get some extra
punch as it climbs out you are seeing/ hearing the engine struggle the 4.5D will keep the rpms
up.

The rule may be sound but you need to add one main variable - prop.

18k on a 6-3 is a benchmark for TD .049's. Cox says 18.5k is typical, and 23k on a 5-3. 4" pitch is 33% more pitch than a 5-3 and I don't have any typical numbers around for those. I'd >estimate< it should run in the 18k range static mebbe a hair more, one data set shows 5.5x4 on a TD static as 17k. Someone here must have some static TD numbers on a 5-4.

The 1962 Aeromodeller review - now there's some current info but it does relate to proper TD's - shows this:

6x4 TF nylon 14,500
6x3 TF nylon 18,400
5-1/4x3 TF nylon 21,000 (my old fav C/L prop)
5-1/4 x 4 TF nylon 18,200

Correlating between TF nylons and APC or Cox props may be inexact, this is more a relative picture. What is significant here to note the big rpm difference (3k static) by a single 1" step in pitch - it's a big relative change, like 10-6 to 10-8. Lugging a TD down on a 6-4 is sacrilege.. :(