RE: Skygate Hawk - build (virtual manual)
 

Mick, would you be able to post a drawing on how you would tackle this?

marcs

RE: Skygate Hawk - build (virtual manual)
 

Mick,

Does this not depend on where in its range of movement the servo fails and whether it fails seized or fails but can still easily turn the output shaft.

Not sure there is a 'solution' to the std setup? They'll always be a chance it wouldn't work. Only other real option would be to run 2 pushrods to the elevator but again, if a servo seizes the other servo & pushrod will likely stall??

I know you like the AW Hawk setup but if you have 2 8711s on that setup and one fails solid the other wouldn't move it sufficiently to give you any movement would it?? That too would probably burn the good servo out? Also, they're too close together and attached to too solid a mount for there to even be a chance of generating movement through torsional flex of the control surface as they're may be on a large span aileron being driven by 2 servos??

Rgds,
Mark

RE: Skygate Hawk - build (virtual manual)
 

Has there been a solution to this problem in an easy to use setup - ever? Seems a tricky one to solve in a practical and simple way......

marcs

RE: Skygate Hawk - build (virtual manual)
 

Yes, Stick with what works !
Nothing wrong with that set up on any of the SG hawks that I have flown or that are flying around the world.

RE: Skygate Hawk - build (virtual manual)
 

After a lot of deliberation I kept it as supplied by Skyagte and will do the same on my TomaHawk.

YES, there IS a chance it could cause an issue IF a failure of a particular kind occurred but, as we all know, there are a 100 other things that can go wrong on these models IF a particular scenario occurred.

Mark

RE: Skygate Hawk - build (virtual manual)
 

There is a setup that offers multiple servo capacity with fail-safe in case one servo seizes. You would just need to figure out how to retrofit it in.

http://www.swbmfg.com/images/2X-3XSA.jpg

SWB's new self adjusting servo's trays are not only compact but will never bind while still loading each servo 100% equally. Unlike matching servo's electronically, this system self adjusts across the complete travel of the servo, not just at neutral and full deflection!!! In fact you can have a servo completely lock up in a full deflection and the bellcrank can still be able to get back to center, a great safety feature. This system is available for standard size servo's as well as the popular 1/4 scale size.

Due to the many combinations of servo tray, bellcrank and servo manufacture's I will only be taking phone orders. These kits will include the following.
1-Servo tray w/your choice of bellcrank.
(4",5"straight/3-1/2",4",4-1/4",4-1/2" or 5"offset bellcrank)
4-1/4" = 2.6m Comp-ARF


1-Self adjusting hardware kit (everything you need to mount your servo's and connect the bellcrank).
1-1/4 Full servo arms (quantity needed)
1- Pair Wire Tensioners (For Rudder)
10' #90 Nylon Coated Wire (For Rudder)
DETAILED INSTRUCTIONS!!!

2X Standard Self adjusting Servo Tray kit $140.00 ea.

2X 1/4 Scale Self adjusting Servo Tray Kit $145.00ea.

3X Standard Self adjusting Servo Tray kit $225.00 ea.

4X Standard Self adjusting Servo Tray kit $270.00 ea.

Due to pre introduction popularity Self adjusting hardware NOT sold separately

RE: Skygate Hawk - build (virtual manual)
 

Marc, in the absence of being able to completely redesign it (I prefer the Airworld method) here is what I would do.

With the origininal the only way it will continue to work is if one servo jams. With the new, the restricted movement of the bell crank if one servo fails limp, which in my opinion a servo is more likely to fail that way, the elevator will still work.

This can be made from 2mm G10 board with the original dimensions. The adjusting screws are there to adjust the dwell for lockup.

This device is so simple and easy to make it has to be a useful addition.

m

RE: Skygate Hawk - build (virtual manual)
 

But if the servo doesn't fail limp but locks up you will break your elevator pushrod with the bellcrank, or snap off the adjustment srews, something's gotta give here...

Regards, Bart.

RE: Skygate Hawk - build (virtual manual)
 

The way it is set up as standard allows that arm to flex when either the servo is not set up correctly or when the servo fails. ( Ask me how I know :eek:)
Most of the failures that I have seen with high power digital servos has been due to two servos on one surface fighting each other. This burns the servo and always causes it to lock solid. I saw an air wolrd hawk lost in spectacular fashion last summer due to this.
Marc. Please leave the elevator linkage on this model as standard. Thankyou.
Regards Al

RE: Skygate Hawk - build (virtual manual)
 

OK.

m

RE: Skygate Hawk - build (virtual manual)
 

Ali, I was not planning on changing this system so no worries there, for me it was curiosity over this topic which as raised its head on many occasions and I'm interested to see what options if any are available for the 'twin servo' dilemma ;)

marcs

RE: Skygate Hawk - build (virtual manual)
 

Good, good.
Understood and thanks.

RE: Skygate Hawk - build (virtual manual)
 

Marc,

The answer to your question in post 199 is that Tomahawk-design uses the same principle, but with some modifications. The double board is replaced by a lightweight aluminium part with integrated ball bearings for servo arm mounting. The rod is stainless steel 0.3 mm wall thickness. I was not able to test the 'play' (tolerances).

I agree that this system will have a very limited if not zero throw if one servo fails limp.
I haven't started to build my Tommy-hawk yet, but during the pick-up in Germany we've discussed this with Andreas. He agreed but hasn't found a solution yet, so he's sticking to the original concept for the time being. I'm not sure what I will do...

Remco45

RE: Skygate Hawk - build (virtual manual)
 

Remco,

Is that your model or Tomahawk's??

2 x 8411s on that enormous flying stab seems a little risky??

Rgds
Mark

RE: Skygate Hawk - build (virtual manual)
 

I think Skygate has the better setup with the bellcrank not attached onto the servo-arms. No risk of servos fighting eachother!

RE: Skygate Hawk - build (virtual manual)
 

Mark,

This picture was made when I picked up my Hawk kit in Germany; it's someone elses Hawk.
Because the stab is not balanced, there's a considerable pull on the servo's.
As said before, I'm not sure what setup I'm going to use, but it will be with stronger servo's.
When the 8511 and the 8811 came on the market, the 8411's have been modified and an extensive test in FMT after 4 maximum power movements gave as result 206/174/113 Ncm for the 8811/8511/8411 respectively.
The 8511 and the 8811 weigh only 6 gramms more, but are slightly larger.

@ Rufter: although i did not test it in Germany, I think the Tomahawk set-up does not pose too great a risk of servo's fighting eachother because the aluminium bracket is wide enough, has ball bearings and first support point for the rod is quite far down into the fuselage. Depending on available servo arm angle, servo arm radius, and the position where one servo would freeze, there's an optimum bracket width that results in the smallest delta of that bracket width...that should be an interesting formula :)

Improvements are welcome.

Remco

RE: Skygate Hawk - build (virtual manual)
 

Still here - promise!

I have not had a chance to update the thread recently, not because the build has stopped but simply because the jobs underway are not exciting to describe or photo. Anyway here is a little update....

The landing gear is at a friends machine shop where next week it will be cut and re-welded in the correct position so it matches the gear leg that fits in the wing.

My friend Rich has glassed the finished inlet duct moulds, so tomorrow afternoon once the resin has cured we will see how they fit. In the background a lot of planning has been going on to work out the best way to make the ducts removable, and this is how we plan to tackle this.
The two inlet mouldings are fitted to the fuselage with stainless location pins in several places, some builders glue these permanently to the fuselage as they do not increase the rear fuselage section by much and saves a job of fitting at the flying site. We have decided to make these removable. The ducting will be permanently glued to the inside lip of the intakes once the alignment has been double checked, these can then be filled and blended to give a smooth appearance. The mounting face of the inlet duct mouldings will have a former made to sit inside the rim of these mouldings (see pic of prototype) this will carry blind nuts in the locations where the alignment pins are, as the pins are hollow an M3 bolt will be passed through from inside the fuselage into the blind nuts allowing fixture of the intake moulding. Access to the bolts can be made from inside the main gear opening when the gear is down. This former will also be shaped to support the duct, its shape being transferred to the former and then glued in place. Hopefully this will mean the inlet ducting is fixed at the intake lip and the back of the intake moulding creating a strong support for the big ducts.
Hopefully it will become clearer as the former takes shape.

While the ducting, bypass and new larger fuel tank are being made, I started the smoke tank. Its a strange shape but is designed to sit in between the two rearward running formers that support the gear door hinges etc, the 'L' shape is to allow the ducts to swing in past the tank sides to align with the turbine bypass, all is a snug fit but a fit nevertheless. The capacity is around 2.25L. I have made a plug using lite ply, I added a radius to the edges to prevent stress points and am now in the process of adding a layer of glass cloth and resin to seal the surface. Once sanded my friend Rich will apply some high build primer and finish the surface ready for waxing. A mould will then be made and a tank formed in two pieces and joined.

I was always concerned with the strength of the turbine mounting formers, especially running a P200, so I decided to use some carbon cloth faced ply, kindly made by Rich with some pre-preg and an autoclav. The resulting formers will carry a new one piece rail panel which will extend forward of the front former and follow the inner duct contour, this hopefully will give a platform to mount the UAT and pump on on one side, and the solenoid valves and other items on the other. It will also extend back from the bypass edge to the fuselage wall where it will be glued along its length adding around 12' of addition gluing surface contact.

There are a few pics attached of the formers and smoke tank progress, tomorrow I will post pics of the ducts assuming they come out OK ;-)

marcs

RE: Skygate Hawk - build (virtual manual)
 

Any pics of thenew inlet or new tank?
Scott

RE: Skygate Hawk - build (virtual manual)
 

The first set of intakes should be off the plugs tomorrow, the tank is about a week or so away.
The tank should be ribbed for additional strength with around 6.5L capacity.

marcs

RE: Skygate Hawk - build (virtual manual)
 

Got the first prototype of the inlet duct off the plug today, the result fits great but the resin had a partial likening to the release wax so the plug sustained a little damage on removal, next version will be better and the front of the ducting will have a lip moulded onto it to attach to the intake moulding.

The smoke tank is almost ready for preping and have been able now to shape the equipment deck that is part of the main turbine former, this is being cut tomorrow from carbon faced ply.

I have assembled the duct, equipment (template) panel and smoke tank in for reference, and included a picture of the plug made for the new main tank (note strengthening rebates ;-)

marcs

RE: Skygate Hawk - build (virtual manual)
 

Marc,

Do you have plans of making your upgrades, ie the intakes, tanks etc, available for purchase as a kit to add to one's own Hawk?

David S

RE: Skygate Hawk - build (virtual manual)
 

David,

The straight answer is YES, Ali asked me initially to undertake this project for that reason, as he felt the Skygate Hawk, and the new Tomahawk Hawk would benefit from a fully ducted system, and a new tank option/location to allow the ducting to work.
To retro-fit these items is possible, removing the supplied tank will allow the ducting to fit onto the existing formers, it would be best to have left the intake mouldings removable for ease of assembly etc but this is not 100% necessary. The new tank and formers will then fit above the ducts.

Once everything has been made and test fitted Ali will have these for sale, I hope also to do the same upgrade for the T Hawk, using the same tank with different formers to suit the larger fuselage and a different set of ducts.

marcs

RE: Skygate Hawk - build (virtual manual)
 

The longer ducts are a really nice looking design, but it seams that their cross section along the lenght is kept constant. This will definitelly have an effect on the turbine efficency, which is directly related to air pressure just before the compressor. Furthermore, the longer the duct, the higher the friction on the flow, consequently the lower the pressure in front of the compressor. It would be much more beneficial to increase gradually the duct's cross section along the duct's lenght in order to decrease the air velocity, consequently to decrease the frictions (not negligible parameter for a P-200!!) and to increase the pressure. A diffuser in the last 4 inches would be more than enough. I believe that this design is a good starting point for a fully ducted turbine, but it needs some basic optimization. This is the reason because the inlet cross section is much smaller as compared to the end cross section in the original Skygate's ducts (and in the original BAe Hawk's ducts). I hope i did not confuse anyone, but a little bit of theory in our nice hobby might help us to transform our great projects in perfect projects.

MarcS, nice job!! My SG Hawk is not as clean as yours.

Regards

RE: Skygate Hawk - build (virtual manual)
 

Appreciate the feedback.
Could you explain and give an idea as to what the design of the diffuser would/could look like given the ducting you see.

marcs

RE: Skygate Hawk - build (virtual manual)
 

For all those who have expressed an interest and those that might it is important to confirm that this ducting and modified tank arrangement is a project conducted by Als Hobbies, the resulting modifications and parts associated will ONLY be available from Ali once the system has been fully tested and undergone flight evaluation.

marcs