RE: GP Extra 300S - Group Winter Build
 

I had labeled the ribs and one on the outside edge was facing the right way so I knew the root side and since I had not cut the top sheeting, I knew which wing it was. The other one, was then easy to deduce.

I probed with pins to double-check.

Yes, they are extended by one bay.

RE: GP Extra 300S - Group Winter Build
 

Finished ailerons.

Dry fit fuse and read ahead to make sure I knew what changes I could make before starting to glue:
1. add doubler to rear firewall and to #7 bulkhead (under where the landing gear rails go) to reinforce (Photo #1,2); just used scrap 1/8" ply. I think it will add strength but also give 1/4" vs 1/8" of gluing surface for the rails.
2. mount rails and servo bracket for both rear-mount elevator servos (photo #3,4). Layout should have top hole of servo arm line up level to the lowest control horn hole. Hopefully this will keep control rod lined up parallel to fuse and level.
3. checked tank height for 16oz tank (no changes needed) (Photo #5); which was good because I should have checked before gluing the firewall parts in case "C" needed to be changed lower the tank floor. It worked fine though.
4. Engine throttle location (changed from their marking)
5. Tank fuel tubing locations (different from their photo) plus one extra hole for fill line.

Started to glue fuse (Photo #6,7). I spent some time with a file to get each "tab" the right depth. Seems the die-cutting usually ends up with a small "mark" into the tab depth which needs to be filed to ensure a flush 1/8" depth for mating.

Not sure if I will use aliphatic or CA for the side of the fuse...depends on how wet I need to get the wood.

RE: GP Extra 300S - Group Winter Build
 

Screwed up when assembling the fuse. My reinforced F7 was supposed to face F6 but I glued in wrong and had it facing F5. I did not notice until the sides were being glued. The problem is that the wing needs the unmodded surface to mate too. So I had to cut out the extra ply piece and re-glue another one and repair the ply facing. So much for careful planning and fore-sight. It would have been easier to just glue in afterwards (but for the firewall, this did need to be done before mounting).

Photo #1 - corrected F7 with reinforcement facing "inwards" to F6
Photo #2 - the repair on the facing of F7 where the wing will mount

For the fuse, I decided on epoxy for the "sides" where they mount to F6 and 7. I mixed the epoxy, applied, and then realized I forgot to wet the wood! I just clamped anyway and it seemed OK. I really do not have enough clamps...only had 2 which were big enough to get around the sides. It ended up that the tops were not fully clamped down so I went back later and re-epoxied with 5 min. and clamped again and it seems "OK". The rest went together without any concerns.

Photo #3 - Fuse


Now I will fit the wing and see how things look....

RE: GP Extra 300S - Group Winter Build
 

OK. Wing is fitted. Photo #1 shows the side and I think this looks OK

Photo #2 shows my concern (F7 is really starting to grate on my nerves). You can see F7 is "bowed", which I assume arose from the clamping. The center of F7 bows towards F6. This leaves a gap.

Should I be concerned?

RE: GP Extra 300S - Group Winter Build
 

I do not think that F7 would need any remedial work, from the photo it could also be the LE of the wing not being straight, if this is the case I would be even less worried as this portion of the wing is inside the Fuz and will not affect flight characteristics at all.

Put a straight edge on the LE to confirm, if you are concerned add some scrap light ply or hard balsa to the bowed portion of F7 and sand flat, not sure that I would bother with it though, unless you were planning to do competition IMAC or similar.

RE: GP Extra 300S - Group Winter Build
 

It is F7 and not the LE of wing. I checked with straight edge and it is flat along the top but bowed in the center of F7. I can "push" F7 into the wing with a fair amount of force.

I know it is "hidden" but not sure about having a flush surface to distrib force from the wing...(although the wing is being pushed away from F7???)
I guess a piece of 1/16" blasa sanded would work...will look to see if it is easy to do or not in terms of access.
Another option is to wait until the tank floor is installed and see if I can force it back and then use the floor to hold it in place without the bow. I will go check this mock up to see if that works.

As an aside, I do not like the idea of threaded plywood so I plan to use these brass inserts in the wing bolt plate instead (epoxy them in). The plastic bolt seems to thread very smoothly into them and they can not strip and I do not think pull out either. The package says 3/8" hole but I tested and that was big (dropped in instead of threading in) so I wil start with 5/16" and expand it slightly while drilling.

RE: GP Extra 300S - Group Winter Build
 

Working on the firewall sides. Looks like F6 is bowed in like F7 (barrelled when I clamped the sides of fuse). Not sure how I could have stopped except not so much clamp pressure?

Anyway, F6 is bowed in and the sides for the firewall do not touch F6 at the "top" (meaning bottom of plane). Thoughts on how to fix?

I can can tip the bottom of the fuse up in the air and force everything tight but that will change the down thrust angle. I can push F6 out and try to glue but I am worried this will just pull the tab (top of the firewall box but facing the building board in the picture) up with the same ultimate impact.

RE: GP Extra 300S - Group Winter Build
 

I did some more thinking, looking, and measuring.

Looks like F6, although glued to the base square per instructions, was not square at the top. It must have been pulled over while clamping the fuse sides. Close inspection showed the fuse sides actually over-hung a small amount (1mm) over F6 but only on the top. I think the problem arose because I could not get a square in to F6 when clamping the fuse side and it looks like it tipped a bit on the top. So it was bowed and not square. (Note, when I say top, I mean as it is on the board versus the plane top and bottom...too confusing when building upside down but hopefully you know what I mean).

In hindsight, I think they should actually have you glue "S" and "L" in place before putting the fuse sides on as a way to ensure F6 stays square.

Anyway, I figured better to fix it than try to patch so I cut the epoxy bond between the fuse sides and F6. I hope I gain more strength through alignment than I loose by cutting through the ply (hard to just cut the epoxy). I cut the top half of the glue joint (see photo). This allowed me to move the fuse sides back; I had S and L in place to ensure F6 was square along the full length.

I re-glued with 5 min epoxy, clamped, and put a good fillet on the inside. Now the firewall sides are square to F6.

I also cut in same place on F7 but I still can not get that to come up straight. Plus, I already have the belly pan built tight against F7 so I can not move it much anyway.

RE: GP Extra 300S - Group Winter Build
 

Repair/Reset of F6 seemed to work well.
I dry assembled everything including the landing gear rails and marked the landing gear hole locations. I then drilled and epoxied in #8 blind nut on rails (Photo #1/2).
(This had to be done before gluing as there is no access to the bottom of the rails once mounted.) Between the ply doublers on F7 and the back firewall, and the blind nuts, this should beef up the landing gear.

I then expoxied the heck out of the firewall, rails, and "top" wall and clamped. Added gussets to firewall (wish I had put them in while epoxy was still wet as it was hard to get at 90 deg. due to seapage of epoxy from the firewall.

I am pleased with how it turned out (Photo #3) (especially given all the grief I had with F6 and F7).

I followed the lead from Andrew and built some posts to mount the rudder servo rails at the correct height for about level pull-pull wires (photo #4,5).

Finally, I took the opportunity to mount the tank floor as I have big hands and it seemed easier to do before building the canopy.

RE: GP Extra 300S - Group Winter Build
 

some nice build tips here for mods to the tail surfaces. i have one of these kits sat waiting for building and im real tempted to start it. but i have other projects that need tending to and finishing.

RE: GP Extra 300S - Group Winter Build
 

Dont wait any longer you are missing out on a great flying machine.
Alan

RE: GP Extra 300S - Group Winter Build
 

the problem i have is i start a kit and lose intrest, the extra 300 is a kit iv always dreamed of having, now i have it i dont want the same to happen to that, i doubt i would let it sit half built but i dont want to take no chances, im waiting to get the real heavy cravings to build it then il knock on with the build. i already have a kit on the bench a flair at6 texan, oh yeah and a dave smith merlin and 10 - 12 other half finished rebuilds and scracth builds. so im sitting back watching you guys build them and in the proccess picking up on what you guys are having problems with so i can watch out for the same problems when i build mine.

RE: GP Extra 300S - Group Winter Build
 

As builds go, this one seems fairly involved; lots of fitting and sanding and of course, lots of sticks. My first build was a SSE and the laser cut and building was a dream. This one definitely takes "wanting to do it"...
So you want the list of "problems"? OK. For the fins and wing, things went well. For the fuse, several "oopps"

1. The whole F6 and F7 thing described above. Instead of expoy and clamps, maybe using CA and "hold with your hands" and slowly glueing the fuse sides to F6 and F7 would have been better (can keep them 90 deg and not barreled). Also, the F7 mixup after adding my ply doubler but mounting backwards.
2. I put the blind nuts on the FRONT of the firewall and only noticed after expoxied. Had to pull them off, repair the firewall, and re-glue to the back. (That was a big dumb moment but glad I caught it.
3. For the belly pan, I lined up former #11 and the aft belly pan former #22 to be even at the top. This meant that the belly pan sides did not "key" into the #22 properly but I thought they should line up as priority. After, when I actually looked at the blue-prints, I realized I should have had #22 flush on the bottom of the wing instead and sanded #11 down. Oh well.
4. The brass threads worked great for the wing nuts but when I screwed them into the ply, they went in at an angle (but I did not notice). This meant the screws going in at an angle which meant I had to relocate the holes for the paper tubes and then fill the old holes. No big deal but lots of work.

All in all, added about 5 hours times two nights earlier this week to fix everything.

5. Of course, my big question is if the rear servos will mess up CG; this is not a screw up yet but will be if I have to move them back to the middle of the plane.

The good news is that none of the above can be noticed by anyone other than the builder :0)

RE: GP Extra 300S - Group Winter Build
 

Hi Chemie, what engine do you intend to use?, I have just moved the elevator servos on mine to the rear to counter some of the nose weight from the saito 120.

Either way the battery can be used to fine tune the CG, I do not think you should have to add lead, front or back.

RE: GP Extra 300S - Group Winter Build
 

For engine, I have a ST-90 which is actually lighter than I thought (same as a 75). What is the weight of your engine+muffler?

Since I am using a pull-pull, I set a spacer with the width equal to the outer holes on the "extra long" Futaba control arm. This is a bit wider than both the exit holes and the max distance on the horns but at least 75% of the run will be at constant spacing. I only ran tubes from fuse exit to this guide (saves on weight but keeps a nice exit hole). Photo #1-4

I changed the instruction order again. Instead of building the top forward canopy, I moved to the mounting of the stab. The reason is that instead of having to set a pin "in the middle of the middle stringer" and under sheeting, I took advantage of the nice "V" grove already sitting on the fuse top (photo #5).

Since my wife is out, I took advantage of the granite in the kitchen again and should be gone b4 she returns!

The Stab had a bow (both length and width wise) so I mounted with bow cupped down, wet the under side, and clamped which seemed to straighten it out (Photo #6+7).

I will need to add a little 5/16" tab at the back of the stab to fill in the 1/2" cut out of the stab.

RE: GP Extra 300S - Group Winter Build
 

I could not find any specs on a Saito 120 but did find a FA-115 which is exactly the same weight as the ST-90 (engine only). I have an old Pitts muffler so I am unsure of its weight but it is pretty big. Sounds like I will be OK for balance!

RE: GP Extra 300S - Group Winter Build
 

Ahhhh, the joy's of kitchen table building, I built my TF P-47 on the kitchen table, let's say that was the last time I ever was allowed to build something on the table. Later on, durring my moves around the country, from ct to colorada to cali to ct and Ri and finally back to CT, I look for places to rent where I can build in my own space. Are you running 1 or 2 elevator servos? And if they are in the tail, I can PM you the way to reverse the opposite servo without using any programing or a reverser.

RE: GP Extra 300S - Group Winter Build
 

Yes, two servos rear mounted. My 7C can handle it without any problem or significant programming.

(I did cover the granite where I was glueing and like I said, she was not home :D)

RE: GP Extra 300S - Group Winter Build
 

Just don't let her see the build thread here on RCU, it might mean many nights sleeping on the couch and the planes being banished from being inside! I got a comment today from my girl, she said I could use her office if I needed to store my paperwork, I said really, I can use your office? The next words from her mouth were no building, just hanging the planes, I guess she's finally warming up to the fact that I like the hobby and it's never going away.

RE: GP Extra 300S - Group Winter Build
 

She saw some saw dust (I need to clean up better) and I claimed to not know where it came from.

RE: GP Extra 300S - Group Winter Build
 

well by the looks of things here with the building scenario il never have problems with my girlfriend because shes building her first kit. she just comented as to she now knows why im always in the model room and thats because its enjoyable building planes. im sat here looking at the extra kit and im dying to start her. arghh the temptation is a pain in the ass. so what engines are you all using in this model?

RE: GP Extra 300S - Group Winter Build
 

Saito 120 for me. Turning a Vess 16X6 prop. Looks and flies great.
Alan

RE: GP Extra 300S - Group Winter Build
 

A few of questions:

1. Do you bondo the joining line on the cowl like the wheel pants?
2. I do not want to buy a big bucket of bondo; what are other options (from Big Box store)?
3. On Page 42 top right corner, there is a photo of the pilot and cockpit area. There looks to be a stringer or lip along the length (on the top of the fuse). I do not see anything in instructions that would lead to that lip. Am I missing something? I think I like the look and might add a strip in there but wanted to first make sure I was not missing anything.
4. Has anyone Rit-dyed the canopy? I am thinking a slight darkening tint...How long in the bucket?

RE: GP Extra 300S - Group Winter Build
 

I used tamiya plastic putty for cowl. About $5 for a tube this was enough for the wheel pants and the cowl and still half a tube left over.

I haven't noticed the lip at the canopy I will hava a look now.

Sir Crashalot - have you started your build yet? No Pressure:D

RE: GP Extra 300S - Group Winter Build
 

Glueing the fin. I did not like their instructions. Basically, they have you ensure the fin is parallel to the center line but not centered.

In my case, if I followed their instructions, the center of the fin was almost 1/8" off center. The reason is the TE of the fin was not on the center line (even though the fin is straight, flat and true). I assume this was because of rear fuse tabs are fairly flexible and are "floating" and when the rear top/bottom fuse formers were installed, it moved slightly to one side.

To explain what I mean, look at Photo #1 where the fin is centered but then Photo 2 when it is parallel (sorry it is blurred but you can see the two center lines marked and offset between fin and fuse).
Photo 3 shows the center line and the fuse sides. It looks like the bottom (left side) is closer. Therefore, the TE fin post was pushing the fin off center line.

To fix, I had to sand 1/16" off the TE left-side fin post and about the same from the left fuse side ply. This centered the fin. (photo 4)

Then I could have the center of the LE on the center line (my addition to instructions) AND have the entire fin parallel to the center line (per the original instructions using a ruler).