TLJC 1/6th Hyper Scale F105D Kit

#21
The next stage of development is to look into the aerodynamic optimisation of the wings and stabilisers, for this we are using CFD and wind tunnel testing.

The general aerodynamic arrangement of the full size is as follows.

The aircraft planform consists of a 45 degree swept wing at the mean 25% chord line. Both the horizontal stabiliser and vertical stabiliser have a sweep of 45 degrees at the mean 25% chord line. The airfoil sections in the wing are NACA65A005.5 at the root blending to a NACA 65A003.7 at the tip. The NACA 6 series aerofoils are designed for high levels of laminar flow at sustained supersonic speeds of up to Mach 2.0. The aerofoil was designed specifically for high Reynolds number applications and is unsuitable for our applications in 1/6th at low Reynolds numbers.

The wing includes a 7.5 degree droop between the intake outboard section and extends to the inboard edge of the leading edge flaps. The leading edge flaps include a gradual span wise chord increase of 28% and have a maximum extended position of 20 degrees. The span wise chord design increases the wings camber towards the tip on extension.

Trailing edge devices consist of a fowler flap with a maximum extension of 46 degrees. Combined with the LE devices and the large span wise dimensions of the TE flap (65% of the wing) increase the camber of the wing dramatically helping low speed handling.

Roll control is accomplished with ailerons which are augmented with spoilers. The spoilers are only deactivated at high speed. To maintain roll authority spoilers are required to operate with ailerons in the medium to slow speed envelops.

The aircraft presents many aerodynamic challenges in 1/6th scale. The F105 was designed for sustained high supersonic speeds and coupled with its 45 degree sweep represents the worst aerodynamic configuration possible for low reynolds number operations.

The airflow velocity experienced by a swept wing is lower than the actual aircraft velocity. This leads to concerns that our 1/6th scale aircraft will struggle in the slow speed flight envelop unless we make design changes to the original wing. Our prototype will include all the high lift devices of the original. Optimisation of wing within the original plan form using CFD and wind tunnel testing will need to be carried out to achieve the best out of our scale model.
 
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#22
Alex,
Excellent article in JET International magazine! However, I have a comment about the figure of sorties flown by the Thud in Vietnam. The 70% (20,000) figure may represent the most sorties flown in the North, but does not correctly represent the most sorties flown in Vietnam. The F-100 Super Sabre is credited with over 360,000 CAS, Interdiction, Wild Weasel and Misty softies. The Thud pilots did face awesome defenses in the north, incurred heavy losses, and received special recognition for 100 missions.
I'm still watching the progress of the F-105D model with great interest! I understand a lot of effort and hours have gone into this project. However, I'm wondering if you could pass along to those of us interested, anticipated release date and price?
 
#24
Hi Guys,

Thanks for the interest in our 105.

Glad you enjoyed the article Grchud, there were some omissions in that article which wasn't my intention.

Regarding our kit... We have been waiting for wind tunnel time and have started designing the wind tunnel specific models, these will be tested in October so release will probably be in the Autumn of 2020 but I can't be precise as we have so much work left to do. All I can be certain about is that we will release the model. We need to put all the infrastructure in place to support the manufacture and we must get this model right as the philosophy this model is based on will be the same for all our future kits.

Our target price is around £8000 (GBP) this would include composite kit, retracts, wheels, oleos and fuel tank along with bypass ducting. Options like the cockpit, fully functional speed brake petals will be extra. I'm hesitant to even give this as costs can increase and the uncertainty in Europe etc... means its difficult to predict.

If you look at the some of the German manufactures their scale Jet models are a similar price with the same options so we hope to be competitive with what is currently available.

I know it's all very vague but we are working hard to produce something really good and rather different to what we are currently used to.

Kind regards

Alex
 
#25
Thanks Alex,
I certainly won't be holding you to those prices this far out but that's quite encouraging that you are thinking in this sort of price range. Will stay in touch with the project
Bob
 
#27
Alex,
I just discovered your thread on the 105 production. I'm very excited about your project. I've registered and will follow progress so I can get my Thud kit:)
Lenny
 
#28
Hi Lenny, I'm pleased you are interested in the Thud :) We have had some positive news with regard to manufacturing here in the UK so soon we can move onto the next phase of the design.
 
#29
I'm pleased to say that we are working with the University of Cambridge on aerodynamic enhancements using their wind tunnel. We will be able to see how our new wing performs and make further enhancements is required. The wind tunnel model is currently being designed to mount on a Sting Balance enabling us to make a detailed analysis of our wing design.

45% Windtunnel Model v5
by Alex Jones, on Flickr
 
#31
Hi Lenny,

Currently we are busy manufacturing the wind tunnel model. Our tunnel time is slated for the first two weeks of October so we should get a good feel for our wing direction around Christmas.

Concurrently with the wind tunnel work and aerodynamic study we have put the manufacturing out to tender here in the UK. I'm now working with our chosen manufacture to reduce component costs where possible by tweaking the design in some areas. This cost study will be finished in around 4 weeks and should give a better understanding of associated costs. The cockpit is nearly finished and will be a real highlight as I believe it is a step up from what is currently available for our models.

I expect to start machining patterns in January once we finalise the design this year.

It's taking time to do right plus we are having to build on existing relationships and start new ones in some areas of manufacture which takes time to bed down.

I believe it will be worth the wait... realistically I expect to have a flying prototype next year and the kits should be released a year later after throughly testing the prototypes.

Thanks for your interest and if you have any other questions please feel free to get in touch.

Kind regards

Alex
 
#33
The construction of our wind tunnel model to evaluate the wing design of our 'Hyper Scale F105 Thunderchielf' kit is well underway. This image shows the early stages of our CAD design.

The sting-balance rig provides full aerodynamic force and moment measurement capability. The loads applied to the balance are characterised in terms of normal force (NF), side force (SF), axial force (AF), pitching moment (PM), yawing moment (YM) and rolling moment (RM).

Two weeks of wind tunnel time should yield plenty of data and allow us to invest in the wing tooling with confidence.

PES_
by Alex Jones, on Flickr
 
#34
Good progress has been made on the wind tunnel work with the first week of running going better than expected. We're ahead of schedule and the model is performing faultlessly. We have all the base line data so we can start to push things a little more in the week 2 run program. Initial analysis shows the wing to be performing better than expected but we will know more once our full data analysis is completed.

Some pictures of the testing.

Image_3_TLJC_F105_Testing_Watermarked
by Alex Jones, on Flickr

Image_6_TLJC_F105_Testing_Watermarked
by Alex Jones, on Flickr

Image_9_TLJC_F105_Testing_Watermarked
by Alex Jones, on Flickr

Image_13_TLJC_F105_Testing_Watermarked
by Alex Jones, on Flickr
 
#35
Work continues on the aerodynamic development of our Hyper Scale F105 Thunderchief. At this stage it's probably worth re-visiting why we're going to the effort of CFD and tunnel testing.

We need to optimise the wing based on a much lower Re number. The full scale aircraft on approach would have a Re of around 23 million. Our scale model in the same configuration will be around 1 million. Clearly a massive change in flow characteristics between the two.

To give the above point context... to achieve the same flow characteristics for the approach as the full scale aircraft on our 1/6th scale model i.e the two aircraft working at the same Reynolds number. The full size aircraft would fly the approach at close to 180kts (Re 23M). For our 1/6th scale model to operate at a Reynolds number of 23M is would have to traveling at over 1000kts! We are of coarse ignoring the obvious problems with the the 1000kts assumption but it illustrates the issues of scaling the aircraft to a smaller size and trying to keep the same wing. It just doesn't work, exasperated by the fact we are dealing with a large supersonic jet with high laminar flow aerofoils.

We did as a matter of interest put the original wing through CFD at 1/6th scale and as predicted it was terrible. We’re building a scale model so want to keep the planform exact but we can change the aerofoil thickness and shape. We have blends of differing aerofoils running along the wing and a small amount of twist running span wise towards the tip. This combined with the high lift devices of the original has improved the low speed flow. It’s a balance restricted by the aesthetics. We could drastically improve the wing performance but it wouldn’t look like the wing of a 105 so we have done as much as we can without detracting from the aesthetics. Still more to do but we do have some good initial results especially considering that no matter how you address the problem we are still stuck with a 45degree swept wing which is not the most conducive shape to produce lift at the critical stages of flight.

You might then wonder why RC jets like the F100 with a 45 degree swept wing look fine to fly but remember the F100 is 25% smaller, 35% lighter but has 4% more wing area than the F105. The original aircraft in this case is operating at a less dramatic Reynolds disparity being a smaller aircraft the model size is a larger scale keeping it within the 3/4 meter length which all means you can be less aggressive aerodynamically with any changes to the wing.

The aircraft scale is also really important and it is looking like our 1/6 scale target might be a touch small for optimum performance. It’s likely a size increase to 1/5.5 or 1/5 will have a dramatic effect on the performance. This is the importance of the tunnel testing at this stage. We hope to not only make a great looking scale jet but also one that performs as good as it looks.

The F105 is a challenging subject to get right and maintain accuracy but we are well on the way to achieving that. Not by guessing but by research led design.
 
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#37
Tufting is a little rudimentary but still valuable as a 'coarse' look at the flow before the oil visualisation work which will give us a more detailed look. Here we can see the effect of the leading edge devices with regard to span-wise flow. This data and all the data collected so far is helping us determine the areas in the wing which can be improved, optimum aircraft scale and the need for aerodynamic devices.

Image_14_TLJC_F105_Testing_Watermarked
by Alex Jones, on Flickr

Image_16_TLJC_F105_Testing_Watermarked
by Alex Jones, on Flickr

Image_17_TLJC_F105_Testing_Watermarked
by Alex Jones, on Flickr
 
#38
A short video showing one of the tufting visualisation tests for our Hyper Scale F105D Thunderchief kit. Note the span wise flow progressing until departure. Aircraft configuration is Leading edge flaps at 17 degrees and trailing edge flaps at 18 degrees. Aircraft angle of attack -6/+16 degrees at 50 m/s.

 
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