Here is a list of all the postings John A H has made in our forums. Click on a thread name to jump to the thread.
|Thread: John A's Sabre build|
The lack of larger horns for the HS85 is why I ended up using a HS65 on the A4 Skyhawk. With my Sabre needing even more travel, due to the two stage/inner outer munitions drop, non of the standard servo horns were big enough. Also a custom horn means you can line up the holes for the best “straight pull” without been stuck with the standard horn geometry.
Hi Phil, yes I was going to bolt a oversize fibreglass plate to the servo horn (on the HS85 perhaps use the circular horn so you can have 4 attachment screws). Test out the position required for the wire attachment and drill holes in fibreglass plate then you can shape/cut down the plate around the attachment holes (if that makes sense).
|Thread: Jet Provost 1.5metre Andy Blackburn PSS Plan|
Launch party approaching the slope …...
|Thread: PSSA Gliding Events|
I few photo's of Pete's Jet Provost from today on the Orme. The light was very poor and the wind was blowing 60mph on the edge so my launch shots ended up as just a blur with the JP duplicating it's smaller scale brother's typical takeoff by ballooning upwards and backwards. I attempted to break pete's elevator trim switch while dialling in what seemed like 1,000 clicks of down for him. Once trimmed with a little more weight in the nose it flew well - I it had three of four flight before we were rained off.
The flying shots that we attempted were black silhouettes.
Launch party and pilot approaches the slope in determined mood.
About to commit aviation
Leaning into the wind
Bob captures the action.
|Thread: Phil's F-86 Sabre build thread|
You can tack glue the aileron to the wing using 4 - 5 small blobs of thick superglue (CA) at intervals along the trailing edge. Once finished with the shaping just slide a sharp blade between the trailing edge and the aileron to cut through the blobs and release it. If you are bending/shaping the ailerons with this method I would also clamp the two ends of the aileron (root trailing edge and the wing tip) between some scrap balsa.
You might be able to get away with treating the aileron with water or ammonia and then putting the "twist" in by hand and then checking it against the wing, keep easing more bend in until it matches the correct root/tip profile. It maybe possible to accomplish by just brushing water onto the underside of the aileron and then twisting and clamping into place until the water dries off.
Best to do all this before you put any bevel of hinge cutouts in.
|Thread: QFI May 2009|
When I ordered the SRA-1 plans from Traplet (probably back in 2014) they came with a photo copy of the article and also Chris G's step by step instructions that Stu mentions above. There are 24 pages of detailed instructions and I believe they will come with the plans you ordered.
Edited By John A H on 31/12/2019 23:52:25
|Thread: John A's Sabre build|
Peter, both lots of munitions can be dropped at the same time if required. On the A4 Skyhawk I used a Hitec MG65 for the release and on this model have a Savox servo of similar power. The Sabre release drop has a bit more "work" to do as it is pulling against the spring, otherwise it just needs to overcome the friction of the wire in the slots/pylons.
22. Position and glue in the rest of the outboard ribs and R1.
23. After putting on the spar shear webs remove the wing from the wing jig and cut out and open up the slots in the lower wing skin.
Finally you can slot in the pylons and see if it all work. If the release wire is tight when the pylons are in open out the holes in the pylons a little at a time until it slides freely and spring is able to close it. If the pylons end up a little loose it is not an issue as this can be sorted when the weapon load is built onto them.
The next step is to make up a custom servo horn. If you don't install the "2 stage" release option then a standard horn will do the trick (as on the A4 Skyhawk).
If you managed to read all that then I hope it makes sense and is useful to someone. Hopefully haven't put anybody off adding drop tanks, it looks more complicated than it is when written down and only using drop tanks will reduce much of the "fiddly" steps.
18. The release spring is now attached to the release wire. The hole in R6 needs to be opened out to allow the spring to have enough movement, as it is a large hole I put ply doublers both sides.
19. After this next step the release wire cannot be removed from the wing so the ribs need to be in the correct order on the wire (but not glued yet). Slide R4, R3 and R2 onto the wire. Slide the wire through R5 and inner slot riblets. Slide wire through R6 (do not glue R6). Slide wire through the MIDDLE of the spring along with R7, R8 and outer slot riblets.
20. The spring anchor on the wire is a balance between just enough tension to hold the mechanism closed while not too strong for the servo when pulled open. The anchor is just a piano wire hook soldered to the release wire.
21. R2, R3, R4 and R6 can now be glued in position ...... check wires are free running still.
15. Now you can trim the release wires to length, I put a slight point on the end to help it them centre/feed through the holes in the ply slot doublers. The inner release wire is just long enough to pass fully through the inner release riblets slot when the Z bend is against the carbon guide rod. The outer release wire is long enough that when the inner release wire clears the inner slot the outer is still fully through the outer release slot. This allows the outer drop tanks to be retained while dropping the inner munitions (If you only want to be able to drop all munitions at once you will only need half as much servo travel which might help with servo horn geometry).
16. Mark and drill holes in R4 and R2. The hole in R4 needs opening out into a slot so that the solder join between the inner and out release wires can pass through it.
17. On each of the release slots prick through the bottom wing skin with a pin in each corner of the slot to mark it for cutting out later. Make the holes obvious (wobble the pin about a bit to enlarge them) so they are not confused with the various pin holes created when pinning ribs/skins down earlier !
13. Once the carbon rod joint has dried mark, drill and glue in R5. Now put the second bend to make a large Z bend) in the inner release wire so that it sits on top of the main release wire and cut it to length at the join. Do not make the length of the solder join too long as it should allow the required movement for release of inboard and outboard munitions before the joined wires strike R3.
14. Solder the wires together while they are in position. At this point because R4 is not glued in you can still remove the release wire.
9. Pushing the wire from the tip end mark up and drill the hole position on R6. DO NOT GLUE IN R6 AT THIS POINT.
10. Mark and drill hole position into the inboard slot riblets using the pillar drill. Also drill a second hole in the slot riblets about 20mm to from the first. While drilling the holes have the bomb pylon inserted with the 1/16th shim.
11. with the guide wire inserted glue in the slot riblets.
12. Now comes the tricky bit - the picture explains it better. Make up the short "inner release" wire with initially the one bend in it, thread carbon guide rod onto it and using pins/balsa jig it in place to run parallel to the main release wire. Glue the carbon rod to the riblet..........check the wires run smooth. Both the inner and outer release wires are still over length at this point to allow for trimming.
6.Once the epoxy has dried and the carbon rod is held firm drill R5 to fit over the carbon rod, make the hole oversize so there is no chance that it effects the rods position and glue it in, using epoxy around the rod.
7. Position R7 and by feeding the wire through the slot riblets and carbon rod from the tip and mark the hole position and drill it. Glue in R7.
8. The release spring is anchored on R7. Make up a 1/32nd ply doubler for R7, drill hole and glue it in place (keep checking that the wire runs freely when threaded through the installed ribs and R3. Bodge up the spring anchor by gluing a short piece of piano wire that passes through the spring to the doubler - photo shows what I mean. The release wire runs through the middle of the spring.
1. Mark the path of the main release wire onto the wing skin (as I already had the release servo in the other wing I could put both wings into the wing jig and check the servo horn position).
2. Mark the position of the wire in the outer release slot riblets, measure the angle between the riblets and wire, set the angle on the pillar drill and drill through the riblets with 1/16th shim and drop tank pylon inserted.
3. Mark the position of the wire onto rib 4 and use pillar drill still set at an angle to put the hole in it. This will be used as a guide for the release wire as we build up the wing so should be as accurate as possible.
4. Pin the outer release slot (riblets) and R3 onto the wing skin (while it is pinned to the wing jig) and feed the wire through both along with a carbon guide rod. Check it is free running and then use SuperPhatic glue to glue the slot riblets into position. DO NOT GLUE R3 AT THIS POINT - LEAVE IT PINNED IN POSITION.
5. Use Epoxy mixed with Micro Balloons to "pot" the carbon rod into place (I actually use Fibreglass flocking because it adds a lot more strength to the join). Before it sets check that the wire is free running and does not baulk when pulled out/pushed into the slot.
Note:- in the picture you can see I initially accidentally used R4 instead of R3 !
Edited By John A H on 10/12/2019 17:33:53
Slightly more than a days work in the wing build due to the convoluted release mechanism
While building up the release mechanism in the port wing I took pictures of each step I used to attempt to make the action as smooth as possible.
Warning reading this might put you to sleep as it's a bit long winded - much like myself. I actually wrote out the steps before I started so that I could glue things in the right order.
To make it easy to mark holes in the ribs for the release wire run I add them individually, by pushing the wire through from the tip end you can mark the hole positions on each one in return. It does increase the wing build time by a factor of 4 but means you don't have to slot the ribs to drop the wire in after the ribs are glued.
Edited By John A H on 10/12/2019 17:36:46
|Thread: Help Needed for Kids Xmas Bike Modification|
Geoff was talking about the bottom bracket shells not the pedals.
Both the bottom bracket and pedals have one LH thread and one RH thread - that is unless the bottom bracket is "Italian" in which case both bottom bracket sides have a RH thread, my Colnago's have "Italian" bottom brackets and over tens of thousands of miles the bottom brackets have never come loose. These days there a lots of different types of bottom bracket/crank systems each with different tool to remove.
For the pedals …. if you put a spanner/allen key on/in them and the chainset freewheels then it means you are trying to unscrew, if the bike tries to move forward then you are tightening them. Righthand side pedal is RH thread and left side is LH thread.
It's slightly confusing because for some pedals you use a spanner around the base of the pedal axle so you are turning it as you would expect for that thread but some use an allen key inserted into the axle from the "rear" of the crank so it seems like you are turning it the opposite way - if that makes sense.
|Thread: John A's Sabre build|
I forgot to say at the start ….. when I build my wing jig I realised that the R1 level did not line up with the rest of the rib jigs, I think Harry mentioned this on his wing build. I glued a 1/16th balsa shim to the plasterboard under the R1 positions before glueing the jig down and it then lined up perfectly.
Here's how it looks from the wing underside with the release mechanism slots :
and with the pylons in ready to have the drop tanks and bombs attached to them once they are built :
Here is the release slot positioned on the wing skin
And how it looks when setup. The inner release wire stops the main wire been able to rotate so if the servo was connected directly to it the arc of the servo horn would cause it to bind or put stress on the servo. To solve this the servo is connected to the release by a ball link and short pull cable. There is then a spring between ribs 6-7 that pulls the release closed. This also has the advantage that when closed there is no load in the servo.
The wires are setup so that with the servo in the mid (neutral position) the bomb release is "open" but drop tanks still attached :
and on full travel both releases are open - so with half travel you just release the bombs and full travel will release both bombs and drop tanks. Releasing one set at a time might make them easier to find in the all consuming gorse bushes !
I will make up a custom servo horn out of glass fibre so that the opposite wing release has as straight a pull as possible.
The inner pylons need to have a slot cut out so that the release wire for the drop tanks can pass through it without stopping it releasing. The inner release is done using a short wire soldered to the main release wire going through the second hole
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