SIG Kougar Refurb and Electric Conversion

[Gary Clark 1]

Thanks John and Ron, both very helpful tips there.

I hadnt had too much thought toward CG yet since it feels like there is so much else to but I'll have a look later and see how she is looking.

I did find that the CG had to be a bit further back than suggested on this to help open up the full flight envelope but didnt bother to note down what worked.......well done me.

Despite feeling like EVERYTHING needs fixed, I'm enjoying this restoration job. It's like building a new plane but with lots of the work already done!

Gary

[Gary Clark 1]

I've managed to get a bit more done, mainly with power selection and setting up the new firewall position. Lot's of measuring and temporarily placing things to check fit nut nothing worth taking photos of to share.

I did have my first go of using peel ply whist fibreglassing. I have glassed a fair bit an am fairly confident with it but fancied a go of peel ply and the hope of less sanding. As far as the peel ply was concerned, it was a total success and when removed, i gave the rudder a very light sand with 200 grit for a minute or so then a coat of primer to see how it came out...

Clearly not perfect yet but considering that it did not require a flow coat or lots of sanding, i was very happy. There a some pin holes and you can see the weave in a couple of small places but those are easy touch ups.

Now the problem. I glassed one side of the rudder, fin and horizontal stab and left to dry overnight. i was excited to peel the peel ply off the next day considering how well the rudder had turned out but i was pretty shocked at what i found. All the part were pretty badly warped and the fin and horizontal stab are total write offs

Those were lovely straight pieces when i started!!!! I'm not sure what has happened but i made those part from two sheets layered as i didn't have any 3/16 available so maybe having two sheets that were different have allowed this to happen as the epoxy cure? i have no idea but what i do know is that i'll be making new ones

I have a wood order going into SLEC to reload my stores so needless to say, i have added some hard sheets of 3/16 to that order! The joys of building!

Gary

[kc]

Were the two layers of balsa laminated with grain parallel or at right angles?

For this job I would have been tempted to laminate with one layer at 45 degrees ( parallel to the top edge of the fin ) rather than 90deg. Normally using 1/4 instead of 3/16 would suffice though.

Peel ply was a new term to me but a Google search answered my questions. Interesting though.

[Gary Clark 1]

I honestly cant remember what the grain direction was KC (which shows I wasnt thinking about it) but one way or another I messed it up as I've never seen that before. I'm thinking it could have been the same direction and different quality of wood as they all came from the same laminate. Good little lesson though.

I fancied trying peel ply since the results look great. Loads of videos on youtube and Danny Fenton ones are particularly useful. My limited advide would be use more epoxy than youd think and the results are great

Gary

[Gary Clark 1]

Post christmas carnage is complete and I e managed to get some work done on the kougar.

First job was to remake the tail parts

Still got the leading edges to shape and re-hinge and bloody hope they stay flat when glassing this time!

The majority of the wing is back to a starting point and ready to fit retracts and ailerons

Replacement leading edge is on now and ready to be drilled for the mounting dowels.

Got bits and Bob's done on the fuse but nothing worth showing yet. If I'm being honest, if these were easier to get hold of now then I'd just have bought a new one as this is more work than I thought initially

Gary

[Ron Gray]

Ah but just think of all the fun you’re having Gary

[Gary Clark 1]

Haha I'd be having more fun if I only had to do things once Ron! It will be worth it when the old lass is back in the air

[Gary Clark 1]

More progress has been made on the kougar.

The wing has 1 retract in and has been tidied up overall. Tail has been remade but I'm not totally happy with the glassing again so might have to start attempt 3

Cowl and nose gear are in as seen below

More work needed to reinforce and tidy up but getting there with it.

I have emailed 4max about a motor as the one i was planning on using needed a 13" prop and i don't have the clearance. i really id like to stay with 4s battery for weight and also i have a few of those around already.

Gary

[Gary Clark 1]

Hi All,

The Kougar has creeped out of the corner and is back on the table! I have far too much going on the build table just now but wanted a break from the larger scale stuff and get back into a sport model for a few nights.

I completed the fitting of the retracts in the wing and got everything lined up. i use a bit or brass tube or piano wire to align the 2 axles

Sorry for it being inverted, i meant to change it but you get the idea from it.

I also bought a motor from George at 4max which means i can swing a 3 blade 11" prop on a 6s LiPo and get the thrust i need. Only issue is that this doesn't come light so she may be a little on the plump side of the scales but will only find out one way. I think i will end up around the 7lb mark which is a whole lb heavier than the expected weight on sig's website but i don't see it being an issue.

Hopefully i can keep up the momentum again.

Gary

[Mark Turner 12]

Hi

What retracts have you used and how have you strengthened the wings structure to take them, I’m considering something similar on a Cambrian fun fighter spitfire

Mark

[Gary Clark 1]

Hi Mark,

I am just using a set of cheap ones from Hobbyking. I can't remember exactly what ones they are but they came as a set of 3 and were about 30 pounds i think but they look great and feel pretty solid.

As far as strengthening the wing, I don't go to far when putting a load of reinforcements in. I believe that if you have a bad landing, ripping the gear out is much easier to repair than bursting a wing because you had the gear so strongly built in. It is clearly a balance between the 2. I either put a couple of spruce spars down the length of the space cut for the oleo or use a ply plate where the mount attaches. Both work well but the ply plate method is more common. The link below has a good example of this:

SIG King Kobra Build

Hope that helps.

Regards,

Gary

[Mark Turner 12]

Hi Gary

Thats a great link, really useful.

Mark

[Gary Clark 1]

No problem Mark.

Managed to get a whole afternoon spent in the garage today and go loads of work done on the Kougar. I got the motor mounted (forgot to take a photo but will add some later), nose wheel roughly fitted, wing mounted and a new (3rd time lucky) tail set cut and shaped.

The only issue i have is that the nose wheel only gives about 1" of clearance, maybe even slightly less for the prop. I don't think this is enough. Also, with the wing mounted i fitted the main gear and i'm worried the ear is too close together so potentially poor ground handling. Hmmmm thoughts?

Gary

[Denis Watkins]

On similar landing gear Gary

There can be no taxiing, other than take off and landing, as the model tips easily as you point out

And there is an argument to fit a 3 blade prop in your case.

Your work so far looks great, very tidy.

[Gary Clark 1]

Thanks Dennis, it's pretty much going to be a new model when it's done since most parts have been replaced!

I'm going to leave the gear as it is and see how she handles. If it is awful then I will sort it later but I'll soon see.

I got out to the garage again tonight and have the ailerons cut and shaped and the wing has been filled where required so that is ready to be glassed tomorrow hopefully.

The canopy isn't in good enough shape to use again so I have started setting it up to fill with plaster to allow me to mould a new one. Getting any SIG parts is near impossible in the UK so this my best option. I'll will get photos of the process and share as I go.

Gary

[Gary Clark 1]

Momentum on the Kougar has continued. I have poured the plaster into the old canopy to make a mould for a new one. I have never made a canopy this way so learning as I go. I made a small frame/box for the canopy to sit it for when I fill it with plaster

This should mean it keeps its shape whilst the plaster sets. Plaster in and fingers crossed

I gave it a good shoogle (great scottish word there) to get any air bubbles out and put it aside to set.

My wife is feeling a bit poorly today so decided to go for a nap when our little boy was napping so I took full advantage and used the dinning room table to do this and glass the wing and tail parts.....I'm am definitely in the bad books wen she gets up but it is much warmer than the garage today!

Wing and tail parts glassed on one side using the peel ply method which has worked well for my moth minor build.

Hopefully get the other sides glassed over the weekend then primed. I also need to build a vac forming box for the canopy and a smaller one for making things like wing tip light covers and similar parts. Again, I am new to vac forming so any tips welcome!

Gary

[Gary Clark 1]

Look what came out of the mould! Really chuffed with this. Need to fill a few little imperfections but generally it is perfectly smooth.

Just need to build the vac form box now and give it a go.

Gary

[Gary Clark 1]

It has been a busy few weeks but i managed to get the vac form box made and had my first ever go of making a canopy. It took a few efforts and a few failures but finally got something useable i think

I managed to break the end of my mould on the last pull so it better work!

The canopy frame transferred over well but i am going to use aluminium tape to build it up more. I also got the hatch cut on top for battery access

I am going to use magnets to keep it in place but i can't really sort out the placement and the other internal workings until i put the wing on, the tail parts, motor and the cowl so that i can get a rough CG then i will put a floor in for the battery to sit on and work out where everything else will go.

I will need to get the wing on to check the join is tidy enough and then i will glass the fuse. Starting to feel like i am getting somewhere.

Gary

[Gary Clark 1]

I've been priming and sanding the wing and tail parts and have them almost at a good enough standard so got the primer on again to fill the low spots. This isn't the most enjoyable part for me but I do love the end results. Meanwhile I shaped the wing to fuse fillet

Before sanding

And after. Filler is still wet but will get that sanded tomorrow then I'll glass over that and add the strengthening glass strip underneath before blending that all in. I still need to sheet the forward fuselage so I'm currently curling a bit of 1/8 so that it's ready to go on. It all needs a tidy up sand but definitely getting there.

Gary

[Gary Clark 1]

I got the fuselage glassed and attached the wing so I could sort some gaps on the join between the two. My much less experienced self didnt do a great job of this so the easiest way is to put some packing tape on the wing and then mix wood glue with micro balloons. The packing tape means the 2 parts will separate and leave a perfect join between them. A little filler can be used if needed later to tidy up the wood glue mix but it's an easy solution to shoddy workmanship!!

[Gary Clark 1]

One thing to add if using the above technique, you can use epoxy instead of wood glue. I just prefer working with wood glue to epoxy and it is easier to sand when tidying up around the area after (or just be more accurate than me bit this is quicker).

I also wait until the fuse and wing are glasses before doing this. It keeps everything easier to clean up and less chance off accidentally sanding and area when tidying up the joint.

Probably teaching alot of you to suck eggs but hopefully someone will get some use from the thread

Gary

[Gary Clark 1]

And this is the result of the above technique, a perfect join

Fuselage has had a coat of primer and will get sanded tonight and decide if it needs another coat before starting to assemble the tail. As soon as the tail is on, I can get the turtle deck and canopy fitted and she is almost there!

Gary

[Gary Clark 1]

I have managed to get the tail and turtle deck mounted and got the canopy on for a look. The canopy still needs a bit of work to get fitted properly but it is looking good and i'm pleased so far

The hatch opens at the back of the canopy so i will put in a former at the back to keep its shape. I'm also going to 3d print an ejection seat and instrument panel and get the canopy painted. Almost on the home straight.

Gary

[Gary Clark 1]

Also, apologies for the messy bench! clean up day is tomorrow!

[Gary Clark 1]

I've pretty much decided on the Thunderbirds display team for the paint scheme but i have a niggle that makes me want to go Blue Angels again as this was the first scheme i used on this plane and the next one will defo be the last!!

I am going to experiment with an emulsion base layer of white if i go with thunderbirds but anyone sprayed emulsion on here? It is pretty popular in America but not seen much recently.

What's the thoughts out there?

Gary