So, I noticed that several [link=http://www.rcuniverse.com/forum/fb.asp?m=9136707]folks[/link] had mentioned they were planning on building the GP Extra 300S this winter so here is yet another build thread for this kit. Yes, there have been a few as recently as a few weeks ago but they are nearing the completion and I am just about to start!

This will start tomorrow once the wrapping is removed and I am allowed to break into the box. I will detail my build, along with mods, but welcome others who are doing this build over the holidays and into the New Year to join. I know I have lots of questions that were not answered in the many threads.

Planned mods:

1. Tail control surfaces mod per [link=http://www.rcuniverse.com/forum/m_1062376/anchors_1062376/mpage_1/key_extra+300/anchor/tm.htm#1062376]Adrian[/link]. However, I do plan some changes beyond what he did on the elevator so stay tuned for that portion later.
2. Dual, rear mounted elevators per photos from [link=http://www.rcuniverse.com/forum/fb.asp?m=9037736]Deadeye[/link] . However, I might move them a little forward (not under the elevator).
3. Extend Ailerons one bay.
4. 4-40 hardware on surfaces
5. Pull-Pull ([link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXEVW5]Dubro 4-40[/link]) and larger [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXD936]horns[/link] on the rudder.
6. Minor tweaks to landing gear structure and mount them with bolts and blind nuts vs wood screws
7. Add blind nut to wind mounts
8. 16 oz [link=http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXFU54]tank.[/link] (I sure hope I can get it to fit).

Planned Equipment:
1. Futaba S3004 for everything but rudder will be Futaba S3305
2. ST 90 with Pitts muffler (this is a really old engine (Italy version) I got at a swap meet...seems to run fine ....
3. Prop = 14x6 as starting point for prop (maybe 15x4??)
4. 1100 mAh 6V battery pack from [link=http://www.radicalrc.com/shop/index.php?rec=24&shop=1&cart=3361970&cat=19&keywor ds=&match_criteria=&searchCat=]Radicalrc.[/link]
5. External charge port for field charging also from [link=http://www.radicalrc.com/shop/?shop=1&cart=3361970&cat=196]radical.[/link] (half down page "Standard Duty Switch with charge jack").
6. Cover in MK Forest green and Gold. (This will be my first cowl painting job)

This is my second built (First was a SSE which I did minor mods to) and it left me wanting to do more customizations next time.

So, will start by opening and sorting the wood; will post tail control surfaces in next few days.

Hey Chemie,
Good luck with your build. I have flown mine now about 10 times. The last two with out such good luck on the landing. I have pulled out the LG twice now, but no other damage.
Merry Christmas
Alan

Just finished mounting the cowl on mine and will check the balance (CG and lateral) in a day or so (after the xmas rush).

Andrew

This plane can be a bear on landing. It can drop wing tips, either side. Gets mushy on landing. All of this happens if you slow up too much. Land it a bit faster, come in a bit lower and under more power keep extra air flowing over the surfaces and she will and like a dream. Stay off of the ailerons on landing. Once yer over the runway stick with the rudder, use the throttle, not the elevator. With this plane if u use the elevator on landing it can stall it out very easily causing you to just suddenly drop.

If yer having floating issues when trying to land with power add a bit of downthrust...

I love mine!!! I will be making this plane my float plane!!

I'll dig up the pics I took of mine when I built mine and post em if any 1 wants...

Got started today with unpacking and inventory.

Some of the ply sheets were more "die embossed" (vs die cut) because I had to do the "cut" part; only cut about half through. I ended up with a broken utility knife through my finger nail and into the finger during that part! Also several pieces of ply had a layer or two break from the smaller jut-outs and these were glued back too.

Also, some of the balsa sheet for the wing ribs were hard to get the temporary "stub break-aways" out without them "breaking away" all to soon; I had to glue several back on and I hope this will not distort the placement/angle of these.

I guess I was spoiled by the last kit; SIG laser cut was a dream compared to all the cutting and time required to get these parts out. And I still have to sand them yet also.

I had a problem with one inventory balsa stick (EXT6W15); parts list showed it as 3/16" x 9/16" x 24" but there is no mention of this in the plans. They do have a 3/32" x 9/16" x 24" and this was in the Sticks #1 bundle so I will go with the error being on the inventory and not the shipped stick.

Tomorrow I will draw out the elevator mods and finalize my plans for that; hope to get some glue flowing too (will be using Titebond II for most of this; regular titebond for larger laminations and CA only when necessary).

OK. Another inventory issue.

Been reading ahead and see Step 1 of "Build the Stab" refers to 3/16" x 3/16" x 14" basswood "front stab spar". The only basswood in the inventory was the wing spars. The inventory lists the 3/16" x 3/16" 30" BALSA HSTAB spar (EXT6S05).

Maybe it is basswood? Any way to tell? I want to make sure I have the right piece if it is basswood vs balsa (although I do not see any other other duplicate parts with the same dimensions.

My kit definitely had two bass wood spars for the hstab. Much harder than balsa although some of the balsa in my kit was pretty hard too. i seem to recall identifying the basswood spars from the size rather than the appearance - also seem to recall them being 18" long before cutting to size. Maybe the photo can help.

Regarding the die cutting...I also broke off one or two wing rib tabs, stuck them back with CA. Even from sheet to sheet I found same part no's with slightly different dimensions, lots of sanding during assembly, especially with the fuselage.

Thanks Andrew. I took a closer look at the stick and it is basswood so chaulk up another typo on the inventory list.

Now, the elevator mod. I want to mostly follow what Adrian did except for one thing. The photo is from his post and you can see by extending the elevator up by 1/2", the gap between the two halves has been reduced from 7/8" to 3/8". I want to keep the 7/8" gap. (No one has indicated that the fuse interferes with this reduced gap but I am still worried). One advantage to my approach is that the current config has a 34 deg. opening for the rudder throw. If I extend the gap back to 7/8", this will give me 39 deg. The only down side is that I will have slightly less area in the prop wash region.

Now, by shifting the in-bound side out by 1/4", I lose 1 sq. inch of control area so I will also extend the TE by 1/8".

So to recap, shift hinge line by 1/2", move inbound edge by 1/4", extend TE by 1/8" and add the CB using the existing Hstab vertical brace as the location marker.

That's the plan...now I will build and pst pics when done so hopefully it makes sense.

Chemie,
Your horizontal stab and elevator looks very close to what mine does. I narrowed the stab and made the elevators wider from front to back. This gave me bigger elevators, but was the same overall size.
Keep up the good work
Alan

Actually, the photo above is from Adrian's post.

Stab: Moved hinge line 1/2" and extended basswood front stab spar all the way across per Adrian's suggestion. Of course, this used up that material so I had to use some shop balsa for the rear stab spar. Since it is sheeted, I do not think there is a strength penalty to using balsa instead of basswood. (Photos #1 and #2)

Elevator: I was not able to extend the TE by 1/8" because of the availability of wood for the 5/16" x 1" x 12" piece. This is used for the elevator root ends and also the bottom of the rudder. With extending the root ends by 1/2" each (1" total) and adding 1" to length of the bottom rudder, there is nothing to spar; I had to cut very carefully to ensure enough material to go around.

Also, I wanted to use some 1/4" triable stock for the hinge lines (saves sanding down the "V" into the LE). So, I built the elevator using the plans, except for the tips and CB (Photo #3 and #4). I removed the stab, added the 1/4" triangle stock, and then re-attached the stab to allow fitting the CB. I used pins to keep a small gap around the CB. Finished unit Photo #5 and #6. Photo #7 shows the triangle stock.

Photo #8 shows the gap restored to the original 7/8", although adding the triangle stock reduced this 1/8" since I had not accounted for when drawing the locations so I ended up in between the original and Adrian's distances.

Photo #9 shows the current gap on the CB...what is the right gap prior to covering? I assume 1/16". Also, do you need to remove any edges from the CB to allow it to swing? (i.e. similar to the "V" like a hinge line)???

Still sheeting the stab so that photo to follow. Working on the rudder right now.
(Sorry about the photo size, I did it the same way as before (which worked) but now they are big!)

Are you supposed to sheet over the "key" in the vertical fin part? The instructions do not say but the photo looks like they do not sheet the key (very bottom 3/16" x 3/16" piece; along the bottom of the fin)

I had the same concerns relating to the fin key. I sheeted mine and tehis seems to work for the assembley with the fuselage later.

Thanks Andrew. The photo is what got me questioning this....

Will sheet and then post pics of rudder assembly.

Getting ready for the wings. They have you glue the top and bottom spars prior to fitting the shear webs. I think I will dry fit the bottom spar and measure/cut all the webs first; this will make measuring much easier. After they have been cut, I will glue the spar ensuring final rib alignment then a quick sand to tight fit the webs.

With the planned increase in the aileron, I will cut end piece of R4 prior to assembly.

Question: Step 9 says "Make marks on the ribs 3/8" forward of the rear spar". Where do I measure from? The fore or aft side of the spar (i.e does this include the width of the spar or do you measure starting from the edge of the spar?

Question: Is G1 supposed to be 90 deg? Mine looks like about 85-87 deg and I would rather use a square to set at 90 if this is the correct angle. I am not sure the die-cut piece is going to be that accurate but I know a square is.

[link]http://www.rcuniverse.com/forum/fb.asp?m=9043744[/link]

Hi Chemie - I had the same issues with G1 (see the above link). I would suggest using your square for all the ribs except the root ribs and for that use G1 so the the upper spar is shorter than the lower spar so when the wing is being joined the correct dihedral can be acheived without a gap between the root ribs.

I measured the 3/8" from the end of the ribs and used a piece of balsa stock to mark against. This is to set a line against which to set the TE sheeting, not really a big deal.

Thanks Andrew. I need to re-read your post I guess ;-)

Actually, your link points to a good question. Which side to measure on.

The instructions show them measuring from the left-hand side (with left wing and root rib on the left; i.e. on the root rib side of each rib). On my G1, this will mean the top of the root rib will tilt to the left while on the board (up-side down); I think this makes sense since this is the bottom of the wing and having the bottom longer than the top will allow you to move the tips up to set the dihedral. (Looking at your photo on the first page of your build, it looks like you started with right wing and had R-10 on the left but had G1 on the tip rib side...maybe that is it since G1 does need to be on the correct side; whatever that is; I will go with the root rib side).

I did as you said and used a square to set the R-3 to R-10 on the first spar (using G1 did not change the setting since there is some give on the top of the ribs with only one spar in). I will decide what to do when I set the second spar in and see what looks right. Either way, I agree the key is the root rib.

Some more pics. Photo #1 is finished elevator.

For the rudder, the main issue I had was running out of the 5/16" sq stock. The CB on the elevator used up about 12" extra and I was about 18" short given the additional requirements for the larger CB. I did not have any in the shop so I used 3/8" sq stock instead; you can see the rather beefy ribs; I planed and sanded it down to 5/16" after it was framed and glued. Again, I used 1/4 triangle stock along the hinge line of the rudder.

Photo #2 = bottom of rudder started; Photo #3 CB close up. Photo #4 finished before sheeting and Photo #5 is finished unit.

Started the wing. Photo #1 shows the R-2 being placed with G1. Root rib on left and G1 on left of rib. There sure was not much "meat" to glue those little tabs on to the spars! Had to give in and use CA. (As a side note, the instructions are not the best...for example, they do not even mention using G-1 to set R-1, R-2 and R2A and I would have thought that a special mention would be made for the root rib which is the one that really matters)

For the shear webs, I come from the school that says mechanical reenforcement is better than adhesive so I wanted to put the webs between the spars. For a tapered wing, this even made me question my resolve but with a bit of sanding and testing fitting, I am pleased with the outcome (Photos #2 and #3). What I did was rough-cut, and then sand the length with the second spar removed. I then glued the spar in, setting all angles. I then sanded down the top of each side to get the height.

Question: I have been reading ahead and have a question on the glueing of the root rib. They have you glue the dihedral to the spars and CA the TE spars but they do not mention glueing in between the root ribs? They have you put wax paper underneath but no mention of glueing the root ribs while glueing the braces. This does not make sense to me. Can someone comment on the wing joining procedure?

The dihedral brace assembly is fairly substantial - euphamistically speaking! Glueing the TE with CA keeps them together but glueing the ribs is somewhat redundant compared with the dihedral and spar assembly.

However I glued the whole lot together with 30min epoxy, after sanding to get a good match to the required dihedral.

Left and right wing completed (for the first part anyway) and ready to join. Took out my 30 min Epoxy (less than 1 year old) only to find the resin was gone bad...it should have more shelf life than that. Oh well, ordered from TH as Lowe's was more expensive even after the $5 TH shipping rate and Lowes only had 5 or 60 min.

I will borrow the kitchen granite to ensure flat surface for the dihedral brace glueing.

Photo #1 close-up of TE
Photo #2,3,4 - Various left wing shots. Right looks the same (which is good).

I have the wing portion done now. Despite my wife's protests, I decided the kitchen granite slab was the best, long, flat surface in the house so I used that for the joining on the jigs. The left wing panel at the LE was raised about 1/2" above the middle jig but a few sand bags when sheeting seemed to lock it back to the right place.

Photo 1: Kitchen expoxy session
Photo 2: Close-up of of sheeting
Photo 3/4: Finished Wing
Photo 5/6: Starting on the ailerons.

For the ailerons, since I added a bay, I needed some 36" 3/8" sq. stock as the kit only came with 24 and you need 25"!

I have to do my kitchen granite work when the wife i out of the house or sleeping

Does ensure a true setup though. (Can't remember what the hammer was for

The hammer was for final fine adjustment (and on a side note, I think we have the same granite too!)

I have a problem. I sheeted the two ailerons at the same time and now I do not remember which one is which !!! (and it matters because of the horn doubler inside).

Any ideas on how to ID each one?

Mmmm. Did you extend the ailerons an extra bay? Otherwise I think the ailerons are the same...wait I know...the construction method was such that the bottom sheet was sanded to a feather edge and the top sheet was laid on top. see picture. Match up with the edges on your ailerons to the plans (bearing in mind that initially the top was bottom etc.)