tobba

Thanks Remco,

Away in Europe for another week. Will share a few images and info when I return.

Regards

tobba

Back on deck...

Beginning with the elevator servo tray - added some carbon plate and a little more length to have more surface area on the glue joints. Planning some fuse doublers to strengthen the joints also.

Glued in and ready to do the continue.

tobba

Elevator tray/fuse doublers in place to give more glue surface area - 1/4 lite ply.

Also former doublers at the fin post support. Again 1/4 lite ply. Carbon tow wraps around phenolic tube through formers to come.

tobba

Made new thrust tube supports the attach the bellmouth to the turbine mount frame. Wasn't 100% happy with the bent 2mm aluminum sheet supports as supplied.

Laser cut from 6mm aluminum sheet. Fixed to the bellmouth with 3 x M3 cap screws.

I made 10 extras - 3 sets free if anyone is interested.

roydefiant

Tobba, Joe Grice and I are both finishing up Tomahawks Hawks. We would be happy to get ahold of your thrust tube mounts. We would need 2 sets, one for each of our hawks. We are more than happy to pay shipping. Regards Roy Maynard, Minnesota USA

tobba

Will do guys - and that's the last off them I'm afraid. PM me your address and I'll mail them to you.

Some work on slightly stronger carbon plate horns. A 4mm carbon locking dowel for a bit of added safety through the bottom tabs. About to glue in with hysol.

roydefiant

Will do thanks Roy

tobba

FItted the rudder to the fin - did a little extra work on the hinge pivots. Decided to remake them from marine ply with 2 x 1/16 carbon plates laminates either side.

Also installed carbon locking plates for some extra strength at each hinge point.

marc s

Tobba nice work as usual.
In addition to the mods you have made on the hinge points for the rudder, you may also need to check the area around the point where the linkage exits the fin, this seems to be an area where fatigue and failure occurred on some SG Hawks - I added a carbon plate in this area to spread the loads in this area. It may be the larger hawk has this addressed but worth checking.

Pic of the mod I did, and also the elevator horns changes done too - made removable.

marcs

tobba

Hi Marc,

Hmmm, yes I saw a SG Hawk virtually destroy its fin on its second flight here in NZ. I agree the rudder pushrod exit is definitely a weak point. This was the next job on my list and something i noted from your thread many months ago.

The shot attached is a little bit of a give away don't you think...

All your reference has been absolutely priceless mate - thanks!

T

tobba

A few things completed. All fin hinge supports done included strengthening plate through the push rod exit area. Elevator horns glued in.

Turbine fitted to engine mount structure and tail pipe mount complete. 2.5mm carbon support plates pick up the turbine mounting points and support the tail pipe. New pipe mounts trued up nice. NB: Complete turbine mount was lowered 2.5mm to maintain engine thrust line.

Using Marc's upgraded engine mount/tank but no full bypass at this stage. Thanks - parts fit in perfect.

roydefiant

The risk of flutter damage to the vertical fin may well be due to a short moment on the servo arm fighting the rudder. We are extending the servo arm thru the vertical skin and using 1 1/2 inch servo arms as well as using a thick piece of G-10 glued into the rudder for the linkage to fit to. Although one may argue the unsightly appearance of external control pieces this will give the servo much more authority on the rudder. If you notice on the skygate hawk the tear is very uneven. Reinforcing the trailing edge may help but also may be worth laying carbon fiber cord inside the vertical fin along the leading edge. Roy

tobba

Thanks for the input. This is very valid in my opinion and something I had thought of very early on.

I am using a ball link setup on the internals vs the standard setup. There is a zero slop in the linkage and I hope this will improve the setup. See image attached and link below.

http://www.flugmodellbau-shop.eu/pro...-Graupner.html

I am keen to keep the linkage within the skin if I possibly can, but you have made me second guess and I'll be reviewing it when I have all together.

Thanks,

sskianpour

My Feedback: (2)

WOW! What is the minimum powerplant requirement for a bird this size? I am guessing 160+ Newtons at the minimum?

Shaz

schroedm

My Feedback: (1)

Shaz,

Yes 160 is the minimum. 180/200 is perfect.

Tobba - I wouldn't worry too much. The mods you have made should make the internal linkage absolutely fine. There are dozens of Skygate and TomaHawk Hawks flying around the world with internal linkages without problems. When I see something like that failed fin vs the number of models working fine I always put it down to user error or a one-off issue. If there was a weakpoint then I think you have more than addressed it so, please, keep that linkage inside the fin

Rgds,
Mark

tobba

Thanks Mark,

Yep I'm feeling pretty comfortable with where I'm at with the rudder and keen to keep it inside.

A little more progress...
- Test fitted the tail pipe / mount assembly. New mounts worked great, all is significantly stronger and every lines up... no doubt overboard but it will last the distance for bugger all additional weight.
- Tank support/mounts are all in and made 30mm 1/4 lite ply discs for the end points to help share the load... thinking 6 litres of kero swinging around up there has to be pretty hard work on that structure.
- Rear hatch is fitted at that front end - I'm waiting on parts from details4scale including a chute system so will leave the back end until this arrives and I can review the mods required.
- Setup the elevator just for fun and a little motivation. Seems I have mounted the elevator servo tray 5mm further forward than I should so it may mean a new pushrod... or removing the threaded rods (silver soldered) and fitting new ones. Bit of a pain in the butt and may look at a carbon version yet which would add a little more rigidity.
- Tailpipe is looking sweet at the rear end and I even managed to get in up the right way which was an added bonus...!!

Mark... or anyone, I'm looking for a source for the fiberglass sheet people are using replace much of the sheet plastic in the SG and TH kits. My carbon guys stock glass sheet but it comes with a rough surface both sides for gluing. Anyone know where I can purchase the smooth stuff a differing thicknesses?

cheers,

schroedm

My Feedback: (1)

Tobba,

I get all my FR4 off of Marc Scully (marc_s on RCU).

You could try mailing him at GBRJets or PM here to see if he can send you some.

Once you start to use it you just can't seem to stop. Really nice to work with although a little heavy but not an issue on something like the Tommy Hawk.

Cheers,
Mark

David Gladwin

Tobba, I binned all the plastic from my AW and SG Hawk kits and replaced it with glass board. This is all available from Mick Reeves Models in UK . Its known as Pro_Skin, comes in quite large sheets, can be rolled to fit in a tube for shipping and is very cheap. Its available in three thicknesses and for even thicker parts, such as Hawk ventrals I simply laminated two sheets of appropriate size using Hysol spread very thinly and the sheets weighted down on a sheet of glass. This stuff has numerous applications all over these and other models.

Regards,

David.

tobba

Hi David,

Thanks for the info. Yes I have a pile of Proskin at different thicknesses in my shed. Ive used it 'as is' on my 1/2 scale Pitts a lot and its been great. I've not had good results when laminating though to be honest. Laminated it with Hysol, Cyno and laminating resin, scuffing up all along the way. Some results better than others but all begin to delaminate after a bit of machining and hand work I find.

I have organised some sheet from GBR Jet at the perfect thicknesses which will be great!

Appreciate the information.

tobba

Anyone have any intelligent ideas to help me flatten out some slightly warped flap surfaces? Not twisted, just a slight bow upward. I have them weighted and bent in a slight reverse bow for the night on a glass sheet. Have applied some heat with a hot iron through a tea towel to see it will have an effect... Hopefully OK in the morning...!

tobba

And another question - any thought of balancing the elevator surface? ie: maybe some lead buried in the root at the leading edge ?

Thanks.

Peter A

My Feedback: (34)

The Flaps on mine are a little warped as well but it is not an issue, not much you can do about that anyway, even if you twist it, it will come back to where it was. Flies great with no issue at all. Actually when Itest flewmine Ineeded absolutely no trim at all on any surface.

As far as balancing the stab, NOTneeded at all.

tobba

Thanks Peter - good to hear you are in the air.

Cheers

Peter A

My Feedback: (34)

Yup amazing plane, flies great and lite, slows down to a crawl for landing.
I am no finished yet, have cockpit kit to install as well as all the decals to apply.

tobba

Roy - no sign of you address... I may have deleted it.

Drop me a PM and I'll send the mounts.

Cheers.