TOPIC: Thrust Measurements

Here are a collection of thrust measurements of various Tendera, and eventually, Jetex and Rapier motors. I've been making these with the thrust rig I put together. I hope they are of interest.

Number 1 Tendera L1.

Tendera L2
1.6mm

Tendera L2 1.5mm

And the L2 variants (just different nozzle sizes) on the same page

The 'Jetex/Rapier' (or should that now be the 'Jetex/Tender') community should be very pleased with these data, and thanks to Terry for making them . Terry's 'high-Tech' apparatus is much more efficient than my old fashioned techniques, and I'm pleased I don't have t do them - that is the testing of motors - any more!

As to the results, Terry's and mine are broadly in agreement and the graphs are certainly comparable. In general, I recorded lower thrusts; this might be because the ambient temperature was lower (I did mine in early spring) , so it may be a good idea to record the temperature out there during testing.

What is clear is that these motors are a quality product. The L-1 is a great little motor and I'm so pleased my little Wren will keep flying.

The L-2 responds well to 'boring out' and this can be done to match the model: A large model like Howard's F-4 Phantom can be flown with a 1.5 m nozzle diameter, where as (say) my Drakens or a Skyray will go well if the nozzles are bored out to 1.7, or even 1.8, mm.

There are lots of experiments to do out there on the flying field, and it would be great if we can all share our experiences and results so we have a 'pooled' knowledge base that will give us all confidence in buying kits, making new models and encouraging others in our wonderful hobby.

This will I hope, make rocketeering more popular - Piotr deserves to sell his motors by the lorry load, and, as his production increases, perhaps the costs will come down!

Here's to a resurgence of Smoke Trails at our Free Flight Flying Meetings, of which, hopefully, there will be lots of in 2021!

rogersimmonds wrote: Here's to a resurgence of Smoke Trails at our Free Flight Flying Meetings, of which, hopefully, there will be lots of in 2021!

Thank you Roger. When I get chance I'll try some more L1s at different nozzle sizes, although perhaps there is not too much virtue in reducing the thrust of an L1, what does the team think?

I hope we don't have to wait too long for a meeting. Really, there are open air markets in the UK now, why not flying meetings?

Roger comments: I would keep the new Tender TSP L-1 'as is'. It appears to match the old Rapier L-1 for power, but with a bit more duration. Perfik!