Sagitta XC Build

[erich]

Am hoping to document and complete a Sagitta XC glider. Purchased a rib set from DreamCatcher before it was sold. So...except for the ribs, all the parts need to be handmade...... oh boy lucky me. This is one Big plane. Span is about 14' with a root chord of 13". Fuselage is 4" longer than my workbench, which is about 52". The whole plane will be built using only wood. Well maybe a little kevlar around joiner area. Have plan only, no manual or directions, except what's on the 3 page plans. So if anyone wants to wade in with advice, am more than willing to listen.

Will probably make a few minor changes over what the plans show. Intend to make fuselage 1/4" longer. Will be making a full height rudder (no balance) which will be 1/2" higher than plans show. Spar will be kevlar wrapped in area of joiner. Joiner tube will be 5" in each wing as opposed to 3" shown on plans. TE will be 1/2" carbon strip laminated between 1/16" balsa sheets, as opposed to the spruce TE, on plans. The tip / main panel, joiners, are shown as 5/16" steel joiner rod, will probably use carbon rod here, although, will still use a steel one for wing / fuselage mating.

Have redone my work bench to accommodate a 13" chord wing. Pinnable work area was only 12" wide. Purchased some great lumber from a place called, National Balsa Co., (which just happens to be 30 miles from my house) so am pretty much ready to go.

Will start, by building the main panel spar. This is built in total with no break in the ply webs from root to wing tip. That's 48" of a 1 1/4" x 3/8" spar. It has 1/16'" ply shears on front and back of spar, which go the full 48". The spar caps are 1/8" spruce which is doubled for 24" on top cap, and doubled for, 18" on bottom cap. Between caps are 3/8" balsa shears.

Have glued the doubled spar caps for both wings, Used Titebond then let sit under weight for a day or two, to make sure glue doesn't warp the wood.

erich

[oracle_9]

This will be an interesting build..looking forward to it. :)

[tw126a]

This is great Erich, love following your build threads especially since I have so many of these sailplanes in my hangar. Great reference for when its time to build my Gentle Lady, Olympic II and Mirage. I might not have a Sagitta XC but I'm sure my Sagitta 900 will benefit from this. Your ideas and methods, such as scalloped trailing edges, look like they could be used in many applications. Thanks.

Tom

[tw126a]

double post

[terry.cx]

I was just about ready to start mine, when I relized my pinable area wasn't wide enough for the wing cord! Back to Home Depot I go ;^)
Terry

[erich]

Yea, had to cut a 3" wide strip and tape it alongside my "not wide enough 12" wide" ceiling tile area. Had some left over from when I first put down the ceiling tiles. Have built 6 planes on the same tiles. The whole building board is getting pretty ratty looking. Well one more plane, then it'll be time for a new board. Are you building a Sagitta XC or another Windsong? Either one sounds cool to me (can you tell I'm from the sixties).

Made some reductions (40%) of the plans.



erich

[erich]

While waiting for spar caps to fully dry, worked on making some of the parts for fuselage. Had full size copies made of the plans at a Kinkos. Also made a 40% copy of fuselage and wing sheets. The smaller size makes it MUCH more convenient to check out plans. On the full size copy, cut out the fuselage side view. Cut this in half, where break is between front 1/8" birch ply and rear 1/8" lite ply, sides. Taped paper template to ply sheet using one of the straight sides to line up with edge of ply sheet (less cutting that way). Cut out with a small scroll saw. Taped & temporarily glued the two forward fuselage halves together. Planed and sanded till sides were as close as possible to plan, and identical to each other. Drilled out holes for front and rear joiner tubes (while sides were taped together). Using ply root rib as template for the holes.

As to photo 3....please don't ask what that big hole just in front of forward joiner hole, is!!

erich

[balsaaddict]

Looking forward to the build. Are these plans available commercially?
Enjoyed your Challenger build too. Its a great looking airplane with interesting construction methods. Im from the sixties too, but actually started life in the fifties... :cool:

[Ollie]

The stock fuselage is very short! You should increase the tail boom by 6".
See:
http://www.qualityfiberglass.net/
"Quality Fiberglass offers an excellent line of both r/c sailplane kits, and r/c power kits."

I'll bet that they have the better fuselage length with the molding tooling XL Sagitta. Ask them to build a better epoxy-glassfabric fuselage from their old tooling.

Check the small tail moment arm and tail areas. This comes from Dr. Mark Drela.

"Ch = (A_hori/A_wing) * (tail_arm/avg_wing_chord)
Cv = (A_vert/A_wing) * (tail_arm/avg_wing_span )

A well-sized tail will be in the range...
Ch = 0.35 - 0.50
Cv = 0.02 - 0.035
If the Ch and/or Cv are below the minimum values, the handling will suffer."

The Sagittas all have problems with the stab mount to the fin. The problem of small music wire jointer rods have high bearing stress in the fin. Eventually the stabs wobble in the fin mounting. The solution is bigger 1/8" diameter and brass tubing nesting (5/32, 3/16, 7/32, 1/4" brass K&S tubing in epoxy) up to 1/4" diameter brass tubing in the fin mounting. Another way is to change the 1/8" music wire with a 3/16" diameter carbon rod jointer.

[erich]

Ollie

Thanks for the help. And the link to "quality fiberglass" But as to using a fiberglass fuselage...................

One of the main reasons I am building this plane is the wood fuselage. It's my favorite part. Will only work on all fiberglass fuselages if forced to. Have increased the fuselage by a small amount, but not 6 inches. Hey my trunk is only so big. Will be using a bigger dia. stab pivot wire, also longer. May also make stab a little bit thicker. Had a Sagitta 900 which had the wobble in the stabs. Am planning on making fin and rudder 1/2" taller, with a NONE balanced rudder. Appreciate you giving me the proper numbers, but those kinda things just make my head hurt. It's probably wrong most of the time, but I go with the TLAR method. I do however listen to what others have to say. So Ollie, if I do anything too weird, please let me know.

Just measured it, the fuselage is going to be 58" overall (not counting rudder). Please let me know if that's within acceptable limits.

erich

[erich]

balsaddict

I got the plans and ribs from DreamCatcher, which went out of business awhile back. RCM or Flying Models might have plans.

Just checked them both, no plans. Sorry

erich

[oracle_9]

Just a remember of the Dreamcatcher line of kits to those just in case do not know, but "Aerosphere" company took over, and they will be reproducing the kits. As to when? No one knows, but they will....especially paying $$$ for the rights... so, if you wait a while, then maybe you can get the plans...and kit too.

[terry.cx]

Are you building a Sagitta XC or another Windsong?
erich

Building a Sagitta XC this time.
It's interesting that the Airtronics building instructions for the Cumic Plus noted the thicker stab in this plane as an improvement over the Sagitta stab. I guess I'll have to do that also.
Quality Fiberglass does make a longer f/g fuse for $125.
Terry

[Ollie]

erich,

There is another way. If you don't want to stretch the fuselage 6", you could increase the tail area about 20%. If you do with a stock design, with small tail areas, it fly but it will handle poorly. With a longer fuselage and more tail area, it will fly groovy and, in gusty thermals, it will return to trim quicker.

Without enough tail moment arm and tail area, in the gusty conditions, the porpoising flight is not groovy. It is hard to control the flight smoothly at long range. It increases the pilot's work load on long flights.

[erich]

Ollie

Thanks a bunch. I will increase tail area. Am assuming you mean BOTH H. stab and V.stab + rudder. To re-cap: I need to figure area of H.stab, then increase that by 20% PLUS do the same for the rudder & fin area? Is that what you mean?


erich

[Ollie]

erich,
I tried to read the plans but couldn't. If you measure the span, wing area, fuselage from spar to pivot stab for arm length and wing chord then I can calculate the tail vert. and horz. areas for you. I would be happy to do the caluclation percent tail areas for you in one minute. I don't make my head sore with calculations if I have the data.

[erich]

Ollie

OK. Got out my somewhat accurate ruler and measured up plans. Here's what I get:

Span (includes the 2 1/2" of fuselage width): 166"
Wing Area: 2054 sq. in.
Distance from spar to H. stab pivot point: 39"
Wing Chord (main panel): 13 1/4"
Avg Chord (tip section): 11 1/2"

Length Main wing panel: 47 1/2"
Length Tip wing panel: 34 1/2"

erich

[Ollie]

erich,

I recomend a large stab area of 292 square inches (13.5% of wing area) because the shortest tail arm (3.15 times the average wing chord). I picked a Ch= 0.45.

I recomend a vert tail (fin plus rudder) area of 164 square inches (8% of wing area) because the shortest tail arm (0.235 times the wing span). I picked a Cv= 0.2.

[Ollie]

There's more.

With the larger stab, you can move the CG more aft. With a large stab you can fly faster while under control.

Even with the larger tail it is with the TLAR method.

[erich]

On the original plans area of stab was: 234 sq. in.
The fin and rudder area was: 104" sq. in.

New stab area: 292 sq. in.
New fin area: 164 sq. in.

Ok. Using your figures here's what I've come up with. Rudder and fin median width...12", median height...13.5". Each stab half: median chord...7.25", span.. 20". What this amounts to is: adding 2" to height + adding 3" to width, of fin. Also, adding 2" to span of each stab, and .75" to median chord.

Using the TLAR I had come up with 280 sq. in. for stab, but only 125 sq. in. for fin and rudder....... ooops.

erich

[rdwoebke]

Hope I am not hijacking your thread.

Also hope you enjoy the build. I'll be reading. I know you have seen these pictures, but here are my Sagitta wings. I looked at them again this weekend. :) or ;) or :(

But then went back to working on that Aegea spar for my 2 meter Aegea project.

Ryan

[erich]

Ryan

Don't be silly. Hijack away. Do enjoy building, especially fuselage, which is the fun part. Been looking at the wing plans. It'll be nice to build something so big, I won't need my glassess. Am saving the photo of your wings, to compare, if I get mine done. Good luck on the Agea, hear it's a real nice plane.

erich

[erich]

Finally got fuselage sides, sanded down, to match plan. This birch ply is some kinda nice wood, BUT hard. Used a little too much CA to tack sides together, for awhile thought I was gonna have a 1/4" thick fuselage. Made up 2 of the 7 formers needed. Used the same 1/8" birch ply. The plans don't give a front view of formers, so used overhead view to get width and side view to get height. Cut them way oversize then used disc sander to get 2 long sides parallel with the right width. Then squared off 3rd side followed by sanding last side to proper height, and parallel to 3rd side. Will make holes in formers for the wiring, later.

erich

[rdwoebke]

Ryan

Don't be silly. Hijack away. Do enjoy building, especially fuselage, which is the fun part. Been looking at the wing plans. It'll be nice to build something so big, I won't need my glassess. Am saving the photo of your wings, to compare, if I get mine done. Good luck on the Agea, hear it's a real nice plane.

erich

Yeah, now that I see your fuselage pictures I don't think it will be too bad. I need to order the ply next time I do a wood order.

After reading what the other guys said about the flutter, I really figured doing a full sheet on the center was a good idea.

The Aegea is my first cloth over foam wing. Seing if I like that building method before going hole hog with a Supra build. It will sit on my Allegro Lite fuselage.

[ferincr]

After reading what the other guys said about the flutter, I really figured doing a full sheet on the center was a good idea.
Have you thought about making the spar caps thicker???
3/8" it seems like quite narrow for such a big wing.
I've been told that spar resistance goes up exponencially for every unit of thickness added (chord wise).No idea if this is true though.
My Aquila XL wings (150") have a 5/8" spar.
I know you already have the rib set laser cut (Erich) and won't be worth it to modify that, but does anybody know if there any fundaments for what I've been told???
Fernando

[erich]

Fernando

Am not sure about this, but I think widening spar caps does not give much added strength, since the loads encountered by the spar are in a vertical direction (in the caps 1/8" dimension). From root out to 18" the 1/8" x 3/8" caps are doubled top AND bottom. Giving essentially 1/4" caps. Then out to 24" just the top cap is doubled up. A lot of the spar strength (IMO) comes from the ply webs. On this wing there are two, 1/16" full span, ply webs.

erich

[erich]

Ollie

Thanks a lot for the help, on tail dimensions. May all your thermals go in the right direction.

erich

[rdwoebke]

Have you thought about making the spar caps thicker???
3/8" it seems like quite narrow for such a big wing.
I've been told that spar resistance goes up exponencially for every unit of thickness added (chord wise).No idea if this is true though.
My Aquila XL wings (150") have a 5/8" spar.
I know you already have the rib set laser cut (Erich) and won't be worth it to modify that, but does anybody know if there any fundaments for what I've been told???
Fernando

From what I have heard, the spar is OK in strength. Several have suggested to wrap it though (especially at the joiner). What I was worried about was torsional stiffness (flutter) and I have heard that sheeting the center helps there.

Ryan

[ferincr]

Thanks for the clarification. I would need to check and ask for more info from the person that told me that (next time I'm in Argentina) he is quite knoledgeable and studious of the forces involved in the wings. He gave me the explanation as why this is so but it was too elevated for my simple brain.
I was just wondering if I could get some confirmation about it.
I remember some of the explanation he gave me but once again I don't want to distract a great building thread into something I can't hold any support fundaments for.
I'm looking forward to this model finished since I was thinking about it some time ago.
Someone had a kit for sale but I didn't have the money he was asking for.
I love 4m planes, and since my only histart is for 4m I'm kind of limited there.
I wrote to aerosphere some time ago to see if they were thinking of rekiting this plane but it wasn't on the inmidiate priority list.
I'll be following the thread and drooling over my keyboard.
Fernando

[erich]

Fernando

Ryan makes a good point. I have heard the same. That stiffening the wings in torsion (by adding full span sheeting on inner panels) is more important than strengthening the spar.

erich

[erich]

Enough of this fun stuff, on with the build......

Added top 1/8" x 3/8" spruce longeron. This goes from back of nose cone to front of fin proper. This is over 48" so will be spliced in the area of former #5. Cut angled splice onto front part of longeron and glued this in using Titebond. Clamped well, as it makes a slight bend near the spliced area. Will let sit with clamps till glue is fully cured. Also added 3/8" balsa tri stock to bottom edge, this runs to just in back of former #5 where it will change to the 1/8" x 3/8" spruce, which will be added after rear portion of fuselage side has been spliced to forward fuselage.

erich

[erich]

Both forward sides now have upper longeron and lower tri-stock glued in place. Cut and shaped remainder of formers, 7 in all. Made clearances for the bottom tri stock and for upper longeron. Traced and cut out, rear lite-ply, fuselage sides. Again taped two sides together (used no CA this time) and sanded to plans' outline. Did some sanding on splice area so it would mate well with forward fuselage. That's pretty much it for part making, on the fuselage. Next step splice, fuselage together.

erich

[glderguy]

I have built and flown a stock Sagitta XC back in the 80s. I didnt notice any really bad pitch issues but strongly suggest at minimum you increase the rudder area/per Ollie as it wasnt very effective. I found overall the plane, due to its huge size to be quite impressive but very slug like in handling, even for a RES plane.
Walter

[erich]

Walter

Thanks for the input. Intend to add 60 sq. in. to rudder and fin area, plus 50 sq. in. to stabs. Have also increased length of fuselage by about 1" .

erich

[erich]

Spliced front and rear fuselage sides. Used 5 min epoxy for, angled butt joint. Will add 1/8" ply doubler after longerons are in place. Most of fuselage bottom is a straight line (except for front 10"). To aid in aligning sides, butted bottom of front and rear sides against a 4' straightedge while gluing. Covered with wax paper and added some weights. Next step the longerons.

erich

[oracle_9]

I never have built a large XC type plane before. When you get to the balsa parts, like ribs, sheeting, etc. typically what "pound" balsa you use? like 8 pound ones? or even heavier or lighter?

[erich]

Can't give you actual weight types. But I do weigh the balsa, and put heaviest further inboard and so forth. Would say for sheeting use mostly medium balsa. For the XC the ribs have been pre-cut (got em from DreamCatcher). But the one plane I did make the ribs on, I used heavy balsa for the inboard ribs and medium to light towards tips. Only place I use that ultra light balsa is on the end tips. Don't really have much choice when buying sheet balsa, I get it mail order. It's mostly med stuff, but still varies a lot. So then I use the scale, to distribute the weights, best I can, with what I have on hand.

erich

[Ollie]

Eric,
I admire your craftmanship. Your craftmanship is better than mine. I enjoy your building threads.

I sort balsa, weight it and mark the piece. I use a balsa table of weights, sizes and density. I don't have to caluclate density by using the table. See
http://web.ukonline.co.uk/sssrcsoaring/Articles-tips/Balsa.htm
I use the balsa table as an important tool in my work shop.

[erich]

Ollie

Thanks. Your observation on my building skills holds up, only, IF, you don't get to close to the planes. Pretty much do the same, I can roughly tell by handling the wood which is densest (is that a word), then use scale to fine tune. On long pieces will also check the balance, and put heavier end toward root area, or toward front of fuselage. A lot of the time will even replace spruce (not on spars or longerons) with hard balsa, IMO it glues up better.

Thanks for the link, good stuff, and it only hurts the head, a little.

erich

[erich]

Have added the top and bottom 1/8" x 3/8" longerons using Titebond. With fuselage sides flat on board, used T-pins spaced every 8" or so along edges, to help in aligning longerons. Used a number of small metal clamps to hold spliced area together. Also glued in splice, doubler. Weighted longerons & splice down, and let sit for a day.

erich

[erich]

Did some more work on the formers. Made holes for wiring and finished up notches (for longerons). Somehow managed to get the notches on two of the formers, in the wrong place?? Glued in some spruce and re-notched em.

erich

[erich]

Glued in triangle, former supports, (what do you call those corner triangle things). On one fuselage side... only. Made absolutely sure of their positions, using formers to help locate them. Made small relief holes for control tubes in the tri stocks before gluing em in with Titebond. Also added outer stab control tube.

erich

[cynjon]

Glued in triangle, former supports, (what do you call those corner triangle things).

Gussets?

Keep the build coming...nice change of pace with the scratch build. I've never had the motivation to completely scratch build a model--having a rib kit available would definitely make a difference. I could see myself doing everything but the ribs...does anyone make a Sagitta 900 rib kit and plans? If I was going to scratch build anything, the 900 would be it...

[rdwoebke]

Gussets?

Keep the build coming...nice change of pace with the scratch build. I've never had the motivation to completely scratch build a model--having a rib kit available would definitely make a difference. I could see myself doing everything but the ribs...does anyone make a Sagitta 900 rib kit and plans? If I was going to scratch build anything, the 900 would be it...

Dreamcatcher did. That is where the thread starter and I got our XC rib kits from. But DC is out of buisness. I don't know if the company that bought thier stuff is yet up and running.

I bet if you posted a few times on groups you might find somebody that bought a 900 rib kit and just has it sitting around that might sell it to you.

Ryan

[erich]

Ryan, cynjon


Ryan, your're right, someone did. Me, bought the XC and 900 rib sets before he went out. Will probably never build the 900 though (had one, great plane, only plane I ever had that flew better was a Dodgson, Windsong).

Gussetts! Duh, on me. Guess their sorta stretched out gussets..

Oh, cynjon, I did a total scratch built years ago, the ribs aren't that bad, made all the ribs for a 112" span canard in 2 days (12 hrs work).

erich

[cynjon]

Dreamcatcher did. That is where the thread starter and I got our XC rib kits from. But DC is out of buisness. I don't know if the company that bought thier stuff is yet up and running.

I bet if you posted a few times on groups you might find somebody that bought a 900 rib kit and just has it sitting around that might sell it to you.

Ryan

As far as I know, the company that bought out Dream Catcher is not producing kits yet...unfortunately.

In hindsight, I should have done a scratch-build during this deployment. I didn't want to build a kit because of having to ship it back to my home once it was built, but I definitely could have had the balsa/ply shipped to me here and gotten all the necessary pieces cut and shaped, ready for assembly once I return home. Oh well, live and learn. I stay pretty busy anyhow, probably the last thing I need here is a hobby.

I'll definitely keep my eyes open for a S900 rib kit, though. I'd love to build one, and the kits just keep going up in price...especially the ones with FG fuses.

[erich]

This ship has one beautifully tapered fuselage. So now, as opposed to the bottom which has a long flat section, the sides have no real flat sections. Taper starts at former #3 and goes to just in front of fin. From former 3 to tip, fuselage is even more heavily tapered. So the only place any former is square to the sides is: you guessed it, at former #3. Sooo glued in #3 first (making sure it was square to side of course). Used 5 min epoxy to glue to side, which, has the gussets. This and the placement of next former or 2, are the most critical, to keeping fuselage straight and true. Pinned and blocked fuselage side with the glued in former, over the plans. Making sure to accurately locate former and sides, in area of former. Squeezed tail end together with a clamp, and aligned sides (to plan) from former 3 all the way back to tail end. Slid both rear and front joiner tubes through fuselage, to make sure of fore and aft alignment. Made sure when other side butted up against former #3 both sides were also 90 deg. to board. THEN and only then glued right side to former #3 with 30 min epoxy.

erich

[erich]

Former #4 and #1 were next to be glued in. Since it is easier to clamp in these formers, used Titebond. Upper portion of #4 is flush with the vertical extension on fuselage sides. While waiting for this to dry, wetted down forward fuselage sides, then used clamp to squeeze sides together a little more than will be necessary later. The sides are a pretty heavy ply so wanted to pre-bend them. It's not so much the abruptness of bend but the short side area forward of bend, which will want to pull sides apart with quite a bit of force, unless sides are pre-bent.

erich

[erich]

While waiting for formers to dry. Cut out and pre-shaped a piece of hard balsa for nose block. Made sure I got the sides angled exactly right so as to get a good glue bond between sides and block, as this area will be sanded quite heavily later.

erich

[cynjon]

erich, I was curious if the rib kit/plans from Dream Catcher included a list of required materials for the scratch build. It would definitely make a project like this easier if you knew up front what materials were required and could procure them before starting. Not all of us have huge stockpiles of balsa ;)

I PM'd you, as well.

[rdwoebke]

erich, I was curious if the rib kit/plans from Dream Catcher included a list of required materials for the scratch build. It would definitely make a project like this easier if you knew up front what materials were required and could procure them before starting. Not all of us have huge stockpiles of balsa ;)

I PM'd you, as well.

I don't think it does. At least mine did not. The instructions are basicaly a photocopy of the Airtronics kit instructions.

OK, so get this. Here is where my XC "came from". A client of mine at a company I used to work for decided to get me a little gift for a bunch of extra hours I put into thier project. They found out from some people at work I liked planes, and went to hobby-lobby's website via a google search. They then thought "cool, I can get a gift card for this guy at the Hobby Lobby down the street"... Well, as we all know, that is not the same thing! :-) So I had like a $200 gift card at a craft store. Good thing is they have lots of wood, and if you have one down the street like I did at the time you can just swing by there on grocery store trips and pick out the good stuff. :-) So all my sheeting, etc. for this project has been bought at Hobby Lobby.

Ryan

[cynjon]

Ryan, thanks for the info--It hadn't occurred to me to check Hobby Lobby for balsa...I'll check it out when I get back to the States. It amazes me that a city the size of Wichita has so few decent LHS's...I guess the best bet is to study the plans carefully and make a "best guess" list of the unique sizes of stock needed and have a stockpile of the more common sizes. Still, a "materials needed" list would have been a nice touch, since the rib kits were designed for scratch builders...

[erich]

cynjon

There were no instructions of any kind, and no list of materials (BOM). All I got from DreamCatcher were the plans and ribs. Tower has balsa too. There is a place here in Mass. that does mail order or web orders. I get most of my stuff from them, it's better quality, overall then the big stores. It's called National Balsa. http://www.nationalbalsa.com/products.htm

erich

[oracle_9]

http://www.lonestar-models.com has balsa too.

[rdwoebke]

http://www.lonestar-models.com has balsa too.

And much cheaper too! I normally order all my wood from them than the hobby shops or hobby lobby.

But, since I had the gift cert from HL, I figured the XC was about as good as any project to use up that certificate.

Ryan

[erich]

Ryan or oracle_9

Speaking of wood. Do you ever use basswood instead of spruce. I checked out Lonestar,
and they don't seem to have spruce, but do have basswood. Just curious.

erich

[erich]

Added formers #5, & #2 with Titebond. When clamping, made sure formers made contact with sides, top to bottom, (one clamp high, one low). Also glued in nose block with Titebond. Left clamped for a day.

erich

[rdwoebke]

Ryan or oracle_9

Speaking of wood. Do you ever use basswood instead of spruce. I checked out Lonestar,
and they don't seem to have spruce, but do have basswood. Just curious.

erich

Probably. I am not sure what I used as the spars on the Sagitta wing I built. Whatever was at Hobby Lobby. :-) I figure with a plane of this size, the wood was not super critical (as opposed to say a HLG or something that is smaller and needs to work low lift). Just as long as I did not make some mistake and the wing ends up failing... That would be bad. I'll probably start on the fuselage for it sometime this summer after I finish the Aegea wing. Will be something to piddle away at in the shop after dark.

I know that the basswood from Lone Star is good quality. I ordered some 3/4 inch thick for the joiners on my Aegea.

Ryan

[erich]

Ryan

Have been using basswood instead of spruce in some places. Seems to have a more consistant grain. Thanks again for the XC manual. Got all of it just fine.

OK....Got the rest of the directions, looks to be 14 pages in all.

erich

[erich]

Glued formers #1 & #6 in place. Added gussets to formers as they were installed. Gussets near front needed to be angled somewhat, to seat flat against formers and fuselage sides. Before adding gussets on right fuselage side, made clearance holes for rudder control rod. Lot easier to do that before they're glued in (did the same to formers). Will also put in former #7 shortly.

erich

[erich]

After all formers were in place left clamps on for 24 hours to insure good glue joints. Have taken clamps off and gotten a good look at the XC fuselage. It's basically an overgrown Sagitta 900. Somewhat taller, a lot longer, and just a little wider. The front 1' or so seems to taper more on the XC than in the 900 fuselage. Glued together bottom longerons on the last 10" or so on tail end of fuselage. Did this over plans to maintain alignment. Also had an upright clamped to back of fuselage to keep back of fuselage as close to vertical as possible (checked against joiner tube and rod).

erich

[Whorges]

Erich,
Since you're working on the fuse, does that mean that the wings are done?
Did you decide to extend the top sheeting?
I finished the right wing on my sagitta 600. The left wing is going together about 5x faster than the right side did b/c I'm familiar with the construction and the stock. I extended the top sheeting on the airfoil to the point where the top of the airfoil was pretty close to a straight line. This was maybe the 60 - 70 % cord.
The trailing edge tapers and then ends at approxamately 1/16". Do you sand this to a point or leave it thick for strength? At that point the flow is turbulent so i don't know if it matters much.
As usual you're industriusness is amazing. Nice building.

[erich]

Whorges

NO. Had started on wings by doubling up spar caps. Then got sidetracked onto fuselage while cutting out the parts, for it. So all I've done on wing is make the doubled up spar caps. As to TE, what I did on the Sagitta 900 was to add a 1/16" x 1/4" spruce piece to TE. This was then sanded down to a knife edge. This is shown in plans (also for XC). I believe the knife edge really helps to lower drag (at any rate my 900 flew very fast). What I intend to do for XC's TE is make a sandwich of 2 pieces of 1/16" x 1" balsa sheets with a thin 1/4" carbon strip glued between them. Then that will be sanded to a knife edge. The carbon strip method needs less sanding and planing than the spruce edge and is less prone to be wavy.

Will NOT be extending top sheeting. Although from what I've heard, it probably is a good idea. I like the look of open structured wings. Am not looking to get the ultimate of performance out of this design. Looks and a plane that controls well are more important to me. Hope to enhance performance by flying plane, well. AND as we all know, a good looking ship flies much better than a, not so good looking ship. Believe it's the 7th law of aerodynamics. May be wrong but you can check me out on this.

Good luck with plane. And let's see some pics of it, finished or not. You could post them here in this build. Would love to see them.

green air

erich

[erich]

Made a servo mounting tray from the same 1/8" ply used on forward fuselage. Plans show a fourth servo for tow release. Prefer to use just an old fashioned hook. Had the airtronics tow release on a Sagitta 900, found I could live without it. So tray will hold 2 servos, and a third one (for spoilers) will be just behind main joiner tube.

Had intended to make wings first. But once I got to cutting out the parts for fuselage, just couldn't resist putting them together. So now, will probably get to wings last. Am anxious to see what the fuselage will look like with the much larger, rudder/fin and somewhat larger stabs.

erich

[erich]

Need a little advice about the stab control rod, actuator pin coupler. Plans call for what looks like an electrical wire type connector. My question to anyone who has this plane (glderguy). Are the typical eyelet type, wiring connectors good enough to use? Have included photos of the ones that I have on hand. Also the coupler shown on plans.

erich

[erich]

After adding servo tray, glued on the bottom sheets. From former 6 forward bottom is sheeted with 1/8" birch ply, from there to tail 1/8" balsa. Before gluing in bottoms, did some sanding on fuselage bottom to get formers, gussets, and sides as flush as possible. Pre-bent forward part of ply bottom. Used Titebond for gluing ply and balsa bottoms, then clamped and taped, will let sit for 24 hrs.

erich

[erich]

Made rear hatch. Used 1/8" x 3/8" basswood for framework and 1/16" ply for top. Will use monokote as hinge, angled front will be held down by angle on canopy. Marked fuselage curve onto the 1/8 x 3/8 side pieces, sanded to marks in order to match fuselage. Then glued up with Titebond.

erich

[gliderlee]

good jobs erich... thank

[erich]

Thanks gliderlee. Next step; planing and sanding, followed by more planing and sanding.

The canopy on this plane is pretty long. Had to extend the longest piece of balsa, was able to find at the local hobby shop, with a shorter block. Glued in a 1/8" thick ply insert to reinforce joint. Used medium grade balsa for canopy pieces. Usually hollow out canopy, but since this is going to be a fairly heavy plane, won't bother, cause it probably will need the extra weight in front. The traditional Sagittas used a countersunk wood screw, set into the front underside of canopy, which then slid into a narrowing slot in a piece of ply, while the rear of canopy sat between the upper fuselage sides. And was locked into place with a dowel set in rear of canopy which then slid into a hole in front of hatch, holding both canopy and hatch in place. A clever arrangement. Won't be doing it that way. My way isn't as cool, but IMO it makes for a better looking canopy. Besides I've gotten reasonably good at this kinda of hold down, since I use it in most of my planes. Will be using dowel in front of canopy and screw / blind nut in rear, with a downward angled back edge which will mate with upward angled edge on hatch, so holding it down also. Sorta of a backward version of the traditional. Could of built a whole other plane with the chips and sawdust from shaping this canopy.

erich

[rdwoebke]

Wow, you are a big time craftsman! That fuselage does look nice. I am not such a pretty builder, but it does inspire me to work on the XC after I finish this Aegea wing. BTW, wrapped and bagged the center section spar this weekend.

Ryan

[erich]

Ryan

Yea... been checking out your build. Love the pink foam, to bad it's gotta be covered up.
What did you wrap your spar with, looks like aluminum foil?? Must be strong.

erich

[rdwoebke]

Ryan

Yea... been checking out your build. Love the pink foam, to bad it's gotta be covered up.
What did you wrap your spar with, looks like aluminum foil?? Must be strong.

erich

Aluminum foil? Hmm... I have got to get a better camera! :-)

That is 2 ounce bias cut glass wrapped around it. In the last picture, it is not yet wetted out with epoxy. The picture was taken just before it was wetted out and bagged.

Ryan

[erich]

With main part of fuselage done, time to work on the fin / rudder. Will increase fin/rudder area from about 90 sq/in to about 160 sq/in, as suggested by Ollie, and glderguy. So, have extended fin 1 1/2" toward front, plus 1 1/2" in height. Rudder is the same 1 1/2" taller, plus 1" wider (obviously toward the rear). This, plus the fact I made fuselage 1" longer should help to correct the planes slow response. Redrew the three lines on plan: forward line of fin, top line of fin/rudder, and TE line of rudder. Just adding the 1 1/2" has made fin quite a bit bigger. Takes up entire width of mounting board. In fact had to pin plan down, diagonally, to fit on board. Will also not be using the balanced rudder thingee. To make enlarged fin am using a total height 1/8" x 3/8" basswood LE and for TE...2 - (laminated together) 1/8" x 3/8" basswood pieces. Bottom half of fin is, as per plans, top portion is sheeted with 1/16" balsa. Before gluing up, tapered TE basswood pieces, quite a bit. Used shims to prop up tapered pieces when pinning to board. Am using a 3/16" brass pivot tube instead of the 5/32" shown on plans. Used 2-1/8" thick ply pieces laminated, for stab pivot. Drilled the stab pivot hole slightly oversized.

erich

[erich]

Ryan

Might want to hang onto that camera a little longer. It's more likely my eyes and not your camera. I probably need to get a larger monitor.

erich

[raeme]

This is good reading and I congratulte you for all the construction article. I built the Airtronics kit of the XC many years ago now and it is still flying today. I must have had over 1000 flights and minor damage along the way. The kit was built out of the box with no modifications and covered with silk and it is as strong as steel. The only major problem that I had was with age the stabiliser mount started to get a bit of play in the pivot point. I modified it to 1/8 music wire and also added a piece of 3/8 sq spruce to each side of the vertical fin, sanded it to match the shape of the stabiliser, inserted a brass tube and the unit is now rock steady. It gives a larger pivot point because it is now a lot wider.
I hope that you get as much enjoyment out of flying your XC as I have had with mine. I also have the 600 plus the 900 Airtronics Sagittas and they are the best
raeme

[rdwoebke]

Ryan

Might want to hang onto that camera a little longer. It's more likely my eyes and not your camera. I probably need to get a larger monitor.

erich

It is only a 1.3 mp camera. My wife got a 5 mp for Christmas, but I have not started using it yet. The old camera is nice to bring to contests and what not because I don't worry about it getting damaged any longer. :-)

Your fin looks nice.

[erich]

Ryan

Hope to see some pics with your new camera. Saw your last post, spar looks more normal in that photo. Wait till you see the fin and rudder together, they may look nice, BUT they are BIG, almost make the fuselage look small.

erich

[erich]

Raeme

Just saw your post. Thanks for posting. Thousand flights, she had to be built pretty well, to last that long. As to loosness of stab. Had same problem with a 900. Have increased dia of pivot music wire to 5/32" and depth of penetration in each stab from 1 1/2" to 2 1/2" will also extend fin tube 1/4" on each side of fin. This will give about 1" of tube support. Tubes in stabs will then be recessed by the same (1/4"). Will add a 1/4" (3/16" balsa & 1/16" ply) root rib to accomplish this. In fact am working on stab pivot tubes at the moment.

green air
erich

[erich]

Rudder time. What the heck does that mean?? Made rudder hinge post first, by laminating a 1/2" x 1/8" basswood stick to a 1/2" x 3/8" balsa stick. Balsa side will be the LE of rudder. Planed a shallow V into LE to serve as clearance for hinge line. Then tapered this piece from 1/2" on bottom to 1/8" at top. Drilled out 4 holes for Robart hinge points. Pinned this piece over plan propping up the taper as needed. TE edge is two 3/32" x 1" balsa sheets with 1/4" wide carbon strip epoxied between them. Used hard balsa for top cap instead of the spruce shown on plans. Did laminate a square piece of basswood, on bottom curved section. That's the area that will get the most abuse, on landing. A lot of sanding later (went from 1.2 oz before sanding to .7 after), had a rudder tapered from front to back and bottom to top.

erich

[raeme]

Raeme

Just saw your post. Thanks for posting. Thousand flights, she had to be built pretty well, to last that long. As to loosness of stab. Had same problem with a 900. Have increased dia of pivot music wire to 5/32" and depth of penetration in each stab from 1 1/2" to 2 1/2" will also extend fin tube 1/4" on each side of fin. This will give about 1" of tube support. Tubes in stabs will then be recessed by the same (1/4"). Will add a 1/4" (3/16" balsa & 1/16" ply) root rib to accomplish this. In fact am working on stab pivot tubes at the moment.

green air
erich
Erich
I have done this modification on my three Sagittas and that is about all that is not out of the box on my planes. It took all of the play out of the stab and they are a lot better for it. I have had the usual minor landing damage but the reason that they have lasted is the amount of care taken while building and the silk covering. Silk is not as easy as monocote but it adds a lot of strength to the wing.
raeme

[erich]

Raeme

Have been curious about silk. What do you use to apply the silk? I have a box of something called "Genuine Silkspan" Model airplane covering by K&S. Have had this since 1986. It's kinda of a translucent, off white color, the box it comes in is about 24" long and the stuff comes in 3' long sheets . Could this be, what you used?

Have just finished spot gluing brass tubes in place. That's one big stabalizer....

erich

[erich]

Have started work on stabs. Have extended LE by 1/4" and TE by 1/4". Length has been made 1" longer on each end. Overall it'll be: 2" longer and 1/2" wider. Rear pivot tube will be 1/32" bigger in dia. and 1" longer in each stab half. Actuator tube will be same as plans. On plans thickness of stab at spar is 3/8". Will change that to 9/16". Using 3/32" balsa for Upper and lower LE sheeting; also using 1/8" x 1/2" basswood for LE and 1/2" x 3/8" basswood, laminated to 3/32" x 3/8" balsa, for spar. TE edge will be same as rudder, carbon strips between 1" balsa strips. Tips will be hard balsa.

At this point have pinned down bottom LE sheet and glued laminated spar to TE of bottom sheet. Have also added basswood LE piece.

erich

[erich]

Had to see what plane will look like with fin and rudder in place. May be a little biased, but it looks pretty good to me. Although a little out of proportion with the large fin/rudder combo. Clever the way fin fits between fuselage sides, makes it almost impossible to miss-align it. That is, as long as fuselage is straight, and sides are vertical. If there is a small error, it can still be straightened out when adding rear top decking. Can't wait to see what that, wing sized stabilizer is gonna look like, when plugged into fin. It's so huge, might not even need the wing, although balance may be a problem.

erich

[rogerflies]

Silkspan is paper. It's applied wet (with water, so it shrinks tight) over surfaces that have been sealed with nitrate dope. It gives an excellent finish with a lot of work, but it's easy to damage and difficult to repair. It's advantages are good looks and light weight.

I see you're using a push-pull cable to drive the stabilator. I opted for a bellcrank on the XC I built. I could never get push-pull cables with bends to work without excessive friction or excessive slop. Usually wound up with both.

Roger

[erich]

Roger

I would have rather used a bellcrank, but couldn't find one with an arm long enough to reach control rod. Thought of making one, but wasn't sure what material to use, that would be able to handle the stessess involved. Used the same push-pull cable on a 900, which had an even smaller radius curve than the XC. Never had any problems with the 900 setup. I can understand the excess friction, but what caused the excess slop?

Yea, the silkspan I have, has the consistancy of paper. Does one paint the silkspan after it's applied?

Thanks for the silkspan reply, at the moment am leaning more towards the monokote type coverings.

erich

[may fly]

I used silkspan a lot when I was a kid. It came in three weights plus tissue for really light stuff and I think there was something called bambo paper that was heaver. To apply it, first seal the wood with dope. Cut a section of paper to cover a pannel. Get a cookie sheet and fill it with water. Dip the paper and blot on some newspapers. Apply to wing with dope. Sand off excess when dry and do same process on the rest of the wing. It will dry drum tight. Seal with several coats of dope. Makes a nice looking finish, but I would not use it on a big glider- too fragile. You can put a double layer of it on and that is much stronger and way more work, like covering twice!
Silk was put on the same way and was a little stronger. Tissue paper was put on dry and sprayed with water to shrink it. Silkspan or silk would look just great on an old glider like a Super Sinbad.

[rogerflies]

I used silkspan on models when I was a youngster. I always painted it with butyrate dope to fuel-proof it. Once it's sealed, you could probably use anything that's got a little flexibility as a topcoat.

IIRC, I made my bellcrank from 1/8 aircraft plywood. It was triangular with a large cutout to reduce the weight. The guide for the alignment pin provided additional support to keep the stab horizontal.

There's always some clearance, so the flexible cable inside the plastic tube snakes into shallow S-bends when it's being pushed, and straightens out when pulled. On a long plane (mine had an extra 6" in the tail) it would have been noticeable.

Since you fly these type planes quite far away, judging airspeed accurately is iffy. The last thing I wanted was a little slop in the control system which could lead to flutter.

I covered the wooden areas of my XC with 0.5-ounce glass cloth and thinned epoxy. The fuselage forward of the TE got two or three layers. After a light sanding, I brushed on a coat of butyrate dope to keep it from picking up dirt. I left it the natural color, which is a pleasing gold tone. I covered the open areas with transparent red and yellow Monokote, with 1/2" overlap onto the wood. Seeing the plane was never a problem.

Some test panels I did showed epoxy/glass was slightly lighter than covering with film, and it's not that much harder to do. You don't have to worry about wrinkles, bubbles, or the film coming loose. The e/g is easy to fix, but I never had to make any repairs.

Roger

[ferincr]

I would have rather used a bellcrank, but couldn't find one with an arm long enough to reach control rod. Thought of making one, but wasn't sure what material to use, that would be able to handle the stessess involved.
erich
It was triangular with a large cutout to reduce the weightMine is the same
Erich,
My Aquila XL short kit called for a bellcrank made of 1/16" fiberglass.
It's around 2"x3" (roughly)
What I did is to buy the material for making electronic boards and got rid of the copper layer with the acid (you cannot get the ones without the copper here).
Another material I'm looking forward to find an use for (like control horns or something like that)is the disks from bursted hard drives, I have a few of them and is extremely light and quite hard aluminum (the problem here is that it couldn't be soldered).
I normally open them because they also have a couple of very strong magnets inside. Sorry did I said strong??? no I meant STRONG!!!
Fernando

[rogerflies]

Here's some pics of the plane assembled, and in the carrier I made for carrying it around.

Roger

[erich]

Fernando

The size bellcrank needed for the XC would be 3" x 4.5". Am pretty sure I can get pc board, without the copper. May give that a try. Need to make some rudder control horns anyway. Chances are, will go with the direct cable hook up. Would have to rebuilt fin, to go with a bellcrank. The ply pivot block is a solid block of wood. So would have to replace that, plus the pivot point is pretty close to TE of fin, so finpost may be in the way of full bellcrank movement. Thanks for the PC board idea. I got plenty of old PC boards. Will probably use them to make some control horns. Hate the white plastic ones with the 2 screws.

erich

[erich]

Roger

Thought the stabs were mighty big. But now, seeing your stabs next to the wings makes them look small. Nice bird. Looks like transparent purple, and tra. yellow, with white trim. Did you use Monokote?

erich

[rogerflies]

The assembled view is a bad photo made with a cheap camera. It's regular transparent red and transparent yellow Monokote. There's no white on the plane at all. That's just a reflection off the fiberglass/epoxy covering on the wood. The colors show up a little better in the other photo.

Roger

[ferincr]

Erich, another thing I really love and everytime I see it on hardware stores in the US I try to sneak one or two down here is something called High Strength Plastic Welder and it's made by DEVCON it works great with any type of plastic especially with PC board, it's kind of epoxie mix hardens like rock and it smells even stronger (like those acrilic temporary filling sometimes dentists use).
May be you are already familiar with it.
I'm just a glue junkie (that actually doesn't sound quite right)
My girlfriend always laugh at me when we go to hardware stores in different countries ( I just dart to the glue department).
By the way, you owe me a new keyboard this one is getting useless with all the drooling.
Fernando

[rdwoebke]

Here's some pics of the plane assembled, and in the carrier I made for carrying it around.

Roger

Roger,

Nice looking model.

I see that you added what appears to be flaps. At least it looks that way from the picture in the box. That is what they are, right? I don't yet have any landing devices installed on my 80% complete wings, but was leaning towards flaps. Either flaps like you have (although I had planned larger in size) or split flaps kind of barn door hinging from the bottom.

Care to comment on what you did and why?

Thanks!

Ryan

[rogerflies]

I had several Sagitta 900s. My favorite was a straight-wing version with flaps. In fact, I even started building a set of tip panels with ailerons to go on the XC.

The flaps on the smaller plane were much more effective than spoilers, and they seemed to work pretty well on the XC. Being able to use the flaps during a launch was definitely an advantage. I always put the flaps up just before the plane touched down to keep from dragging them.

I flew the plane enough to get to where I could really enjoy it, but I couldn't fly it with complete abandon like I can my Lovesong. It's just soooo big.

Roger

[ferincr]

The flaps on the smaller plane were much more effective than spoilers, and they seemed to work pretty well on the XC. Roger

Roger, just out of curiosity which are the dimensions you made the flaps for the XC.
I've been working in a set of wings for an Aquila XL (similar wingspan as the Saggita XC) and I'm a bit concern about the size, servo power and functionality.
Fernando

[erich]

Love to hear Sagitta and Aquila talk. The Sagittas probably fly better, but the Aquila is the better looking glider (IMO), and hopefully my next plane. Fernando, if you got some recent photos of your Aquila wing, please post them. And stop buying up all the glue....I might need some.

erich

[erich]

According to plans, stab spar, is made from 1/8" x 3/8" spruce with a 1/8" sq balsa piece laminated to middle of spruce. Spar is placed over plans on edge. Bottom and top LE sheets then fit into the 1/8" gaps on either side of 1/8" sq balsa piece. This gives a maximum thickness of 3/8" for the stabs. Instead of the 1/8" sq. balsa piece, am using a 1/8" x 3/8" balsa piece (mainly to give sheets a larger glue area) laminated to the 1/8" x 3/8" spruce. The top and bottom sheets will then go over top of spar ending at rear of spar. Am using 3/32" sheet material making maximum thickness 9/16" for the stabs. Whew...! Before starting this project, had made a list of modifications. Making stabs a little thicker is on the list. However due to daily loss of brain cells have forgotten exactly why I had wanted to make this change. Not 100% sure of this, but believe a thicker stab airfoil will make handling better, at the expense of a slight increase in drag. Anyway that's the way it's being built.

To keep pivot tube centered on spar, have added 3/16" bottom sheet of balsa to serve as seat for brass tube. A 3/16" thick spruce wedge has been glued to back of spar using Titebond. which will serve as the front part of joiner box.

erich

[rogerflies]

I think they were about 30" long and 1.25" wide. The size was determined by a thorough TLAR analysis.

They were driven with a standard size ball bearing servo, but I can't remember if it was a S3004 or S9001. They would come down almost 90 degrees, IIRC. I always slowed the plane down to a reasonable speed before using full flaps.

Roger

[ferincr]

Love to hear Sagitta and Aquila talk. The Sagittas probably fly better, but the Aquila is the better looking glider (IMO), and hopefully my next plane. Fernando, if you got some recent photos of your Aquila wing, please post them. And stop buying up all the glue....I might need some.

erich
Funny, as they say the grass is always greener on the other side of the fence.
I'm not a legendary RCer I just built the AG 20+ years ago (and I rebuilt the same last year) and the AXL, appart from that a few power planes but that is about it, so my repertoire is very limited but the very first time I saw the Sagitta (few months ago) I fell in love with her, I think it's much better looking that the Aquilas. And I assume a much better performer too.
Fernando