schroedm

My Feedback: (1)

Marc,

mod looks fine but why??

Show me a SG Hawk where the normal method has failed or become suspect and I'll say 'do the mod'

ta,
M

marc s

Mark with you on that, I'm just not a fan of cutting slots in things where you cannot guarantee getting glue where you want it, its a little hit and miss. Four nuts and bolts leave no doubt.

marcs

tobba

Marc

I agree. I had planned a similar mod for my Tomahawk. I have been using carbon plate successfully on a 1/2 Pitts I am most of the way through. Was looking at making new horns from plate that went through the joiner and were fixed top and bottom.

Like the mod a lot. I am into sight unseen glue joints either. See a few shots custom carbon plate horns on my Pitts. Nice to work with and strength vs weight is amazing.

Nice work.

marc s

1/2 scale Pitts, my my thats one big plane, make sure you let me have some shots of the finished project.
Did you make the carbon horns yourself?

marcs

schroedm

My Feedback: (1)

WOW. That's some might fine workmanship just in those few pics!

So Marc, four bolts or two slots full of aeropoxy? Which way you going?

marc s

Not sure yet, see if anyone else has any thoughts.........

Countryboy

My Feedback: (25)

Marc,

I personally like your modification idea better than the stock setup. My only concern would be what the underlying structure is like. It would have to have something between the top & bottom skin so that when you cinched the bolts down the outer shell does not break/crack. I would assume there is some sort of wood top to bottom inside since the original setup called for gluing the horns in.

tobba

Hey Marc, yep these are custom made. Pretty easy - carbon plate from the composite store, calipers, scriber, dremel, bandsaw, elbow grease and good to go. The Pitts is big - more bulky than anything. The wingspan is 120".

My ten cents worth on the horn fittings... I really like the aluminum horns you've made and feel they would be structurally very sound. Re the fixings for the underside, I have been using some nice mounting nuts available down this way - see the pics attached. They are aluminum, very light and available in M3, 4, 5 and 6. You just over drill the underside exit hole by 1mm to the depth of the nut insert - around 5mm. I then squeeze them in place with a small G clamp. I usually include some hysol and they work very well. They have a nice lip around they edge to soak up the load too.

Pics are not great - camera struggled to focus up close. Shot of the Pitts I'm building too. (not mine)

I'd go for it.

marc s

Update.
Ran the elevator push rod through to the stab and aligned it with the servo deck, sanding and making sure the holes made in the rear formers were clear of binding etc - they needed a little fettling. Once done I took the two elevator rod support towers and assembled the x-posts, then cleaned out the two brass sleeves of burrs, keyed the top surface and glued them in into the ply towers.
I then slide these over the push rod and marked their footprint on the fuselage so this could be scuffed well for glue fixture.
Once happy with the alignment, and with the rear fitted to the stab to hold true, I applied glue to the base of the larger tower near the servo deck, if you rotate it so the base is upwards you can get a good glue bead on it, then by wedging a piece of balsa under the end of the rod nearest the servo deck you can slide the glued tower to the correct position, spin it round and lower into place by removing the balsa support. I let this support dry before doing the smaller one, but used the same method of spinning it upside down, apply glue, hold off fuselage with a balsa shim and drop into place once in the correct position - it will rest in the best position naturally at this point.

marcs.

marc s

Next job was fitting the rudder phenolic tube to the rear former set.
I fitted the wings to act as the reference for horizontal, then trial fitted the fin and tube assembly, once in I set up the laser level and aligned the horizontal with the wings, then checked the vertical on x-wire - the fin required a little tweak to get it vertical which was achieved by sanding the holes in the ply formers, once all the laser lines lined up and the fin was bang on vertical I applied some Aeropoxy to the formers and left overnight to cure up a little. Once this is done I will apply further Aeropoxy to the other areas and also apply the carbon tows.

marcs

digitech

My Feedback: (10)

isnt that overkill on that elevator?
i once build me a 1:1 STOL plane wich had a elevator of 2,5 meters
it was slotted with 3 x m5 nut and bolt to hold the stab
the rudderhorn was made of 3mm thick alluminium , rivetted to a main spar..

marc s

Sandor you are possibly right, but the aluminium plates are no different to the glass plates that were originally supplied, the only difference is I opted to fix with bolts going through the stab rather than slotting the stab and using a ton of Aeropoxy - this method is also slightly more flexible in terms of servicing -

marcs

marc s

With the phenolic tube secured I added Aeropoxy to the bottoms of the two ply tube supports, added triangular x-section wood strips with Aeropoxy down both sides of the phenolic tube and then finally added two bands of carbon tows through the holes I had made in the back ply plate prior to mounting the formers - kicked them with cyano.

Lightened and finished off the elevator horns and back plate, and added studs to the elevator pivot mounts, I found trying to locate the M4 bolts into these plates was a tad tricky, so reversed the situation and loctited studs in - makes assembly much easier.

The angle cover plates that fit to the inner face of each elevator half are supplied made from thin plastic, I have been told that these can bend and deform when the stab assembly is placed on the ground etc and that a stiffer alternative would be better. I used some thin FR4 board and made copies of the two items, stuck the two small plastic 'accessories' to each one with cyano and fitted each to the stab with two small screws so the plates could be removed for painting and general maintenance etc.

marcs

Ali

My Feedback: (5)

Hi Marc
Is that rudder tube attachment standard or something that you have modified?
I like the glass elevator cover plates. Having spent a day trying to make good the set fitted to the Hawk that I have in the work shop I can concur that this is worth while mod. I am sure you will do it, but I can also tell you that its a worthwhile mod to the Ventral fins and wing fences as all of these on mine look to have been through a war... and lost!

marc s

Ali the rudder fitting is slightly modified, I added a thin shaped ply plate to the upper section of the former, effectively closing it in, as I had heard that there were some issues with rudder stability and this would add rigidity to the top section of the former where the phenolic tube was mounted. I added the carbon tows as I have always liked the BVM method to add security by this means.

Ventral fins and wing fences will also be made from FR4.

marcs

Ali

My Feedback: (5)

Hi Marc
Can I order a set of FR4's for me please.

schroedm

My Feedback: (1)

Marc,

Told you it was worth changing them to FR4! The 0.5mm plastic supplied is just too soft and easily knocked/split. Change the wing fences too! It's near impossible to put these wings in the wing bags without knocking them and even when they're in the bags the fences push up tight to the lining and thus the wing still effectively 'rests' on these thin plastic items. []

Also, not sure if it is too late to easily do now but it would have been useful to leave a few holes in that fin supporting former you strengthed to pass wires/cables through. Now you'll need to go underneath it close to the tail pipe.

Cheers,
Mark

schroedm

My Feedback: (1)

Marc,

There should be a very thin glass plate that holds the two elevator pivots in alignment so the M4 bolts are easier to fit.

Cheers,
M

marc s

Ali, I will email you to discuss...

Mark the glass plate is not ideal as the pivots are threaded to accept an M4 bolt, without the bolt in the thread which you cannot do unless the stab is fitted the glass plate is not very useful. With studs fitted the plate will hold the pivots in the right place so works this way round ;-)

I'll pop a few holes through when required, its not thick ply so easily done, cheers for the concern.

marcs

marc s

Fitting the glass horns to the rudder was the next job. Supplied are two tiny glass board horns, which resemble tuning forks, these need to fit into two slots in the rudder in the area marked on the rudder by panel detailing. I mounted the ball clevis to the two horns to get the correct spacing and taped off the area for slotting with some tape. Originally I was going to drill a few small holes but thought to try a blade first, no problem, it cut through the skin fine, I adjusted the holes with a junior hack saw blade to suit the horns. It took a while but then I realised the two slots cut into the horns straddle the rudder retaining pin and plastic snake running up the inside of the rudder, this will provide some additional fixture for the Aeropoxy.

Now came the problem of getting glue into the correct areas, for this I cut a hole in the base of the rudder, then a hole through the foam former so that access to the cavity where the horns were was visible (a torch helps here). I will fix once the final alignment is done.

To fit the servo in the fin requires routing the servo cable back on itself, and extending it a little as well. To route the cable I used the bath chain method - never fails me, wiggled it through the desired holes and then attached the servo lead and pulled it through, the JR8711 fits the slot made in the fin former fine, the hole registration however is not quite right for this servo, but angled in slightly the screws found the pilot holes and everything tightened up good and solid.

Linkages are all supplied. The fin requires a cut-out around the linkage exit, which currently is a work in progress and will be completed once the horns are fitted.

marcs

tobba

Hey Marc.

Love your mods. Just been on another thread of yours - the PC-21. Are HT now doing this Kit full composite? Still seeing ref to the built up wing etc on their website.

Thanks

marc s

Fully composite I understand now, the one I did was very good, the only slight issue with the wings was the servo trays are pre-moulded so only certain servos fit, I think originally Hitec's were used, JR's were a pain to get in.... speaking to HT at Jetpower this year said that mods were going to be done in this area.

I'm back on the SG Hawk now, been away for a fews days relaxing so will post some updates as they happen.

marcs.

tobba

Thanks Marc. Nothing on the website. Will contact them.

Cheers.

marc s

Back from a fews days away, so stuck back in.

Fitted the two rudder horns in and set with Aeropoxy fed from the hole in the base of the rudder, adjusted the control linkage hole in the fin to allow full movement without binding.
Connected up the servo to the linkage via a clevis and security silicone tube, locktited the ball clevis end so adjustment could be made. Temporarily fitted M2 nut and bolt to secure linkage to rudder.
The front of the fin requires a security fixing, so drilled an M3 hole through it at a point that would miss the internally fitted elevator control linkage support, scuffed this area. Removed rudder greased up the M3 bolt, made a small ply plate to accept an M3 captive nut, refitted the fin and slide M3 bolt through. Added some epoxy to the ply plate and located the M3 bolt (you need long arms!) tightened up the bolt pulling the ply plate onto the fuselage and left to set up.

marcs

marc s

The rear hatch cover required fitting and securing. After a little trimming to tidy up edges and inside flanges I opted to instal two carbon locating pins in the forward section, rather than fit them to the hatch I fitted them into the fuselage. I made two holes in the cover in the desired location and mounted the hatch to the fuselage.
I was able to get a pencil through each stab hole to mark the hole locations on the fuselage mating face, after removing I drilled through the fuselage faces and through the ply former which sits a few millimeters behind it, this provides a good fixing. Once these holes were drilled I cut some carbon rod of a suitable diameter, rounded one end, scuffed it up, inserted into the holes prepared and then to make sure they were perpendicular to the face slipped over a collet of suitable hole size, once this was flat on the face I tacked each in with some cyano from behind.
I then opened up the holes in the hatch so there was enough room to allow a brass tube to slide over the carbon pins and locate in the hatch, this will provide a strong sleeve for the carbon pins to locate in for security. Again I was able to slide on the brass tubes then the cover onto these and tack the brass tubes to the hatch with some 10 min thixo epoxy, once set I removed and finished off with Aeropoxy.
The rear of the cover requires a simple bolt fixing, I wanted this to finish below the surface so after making a hole in the desired position I fitted an M3 bolt to a small piece of ply and glued this in place so the bolt head was just below the rear surface of the hatch. I added a ply plate to the rear fuselage section complete with M3 blind nut fitted the hatch, taped it down flush all round, screwed the ply plate that was going to be fitted to the inside of the fuselage tight onto the plate fitted to the hatch and applied some epoxy to this through the rear pipe exit hole.
The hatch required a small internal light ply former to be added to pinch the sides in a little to conform with the fuselage contour.
Once all was done and dried I applied some grey primer to finish off the inside surfaces.

marcs