Bolt55 1-23H 1:4 Scale Build Log

BUILD LOG - BOLT55 - SGS 1-23 1:4 SCALE BETA

BUILD LOG

This is a build log for the new Tom Martin designed SGS 1-23 1:4 scale sailplane kit.

One of my jobs around the shop is being the asker (yes, asker) of stooopid questions. As a builder I have intermediate build skills - I am no where near the class of a Herbert Eberbach, Fred Guilfoyle or Tom Martin. So in addition to being the official "asker" I am also the official guinea pig designated to beta build our new kits (see if I can build them - then most anybody else can).

The way my beta builds go is I jump in and start building - as I encounter questions or problems I ask Tom - who then guides me through the process. With each beta build we also have a master builder document his beta build - so you can see how a pro does it. For the 1:4 scale 1-23 - Herbert Eberbach will also be doing a beta build which he will begin documenting in August. You can follow Herberts build here when he starts in August.

I will maintain a "trouble" list here on this first post to indicate problems, corrections and  workarounds as they are encountered.

This build log is interactive - directly below each posting is a comment box - please feel free to chime in and ask questions or offer input. Use the RSS feed to stay up to date.

TROUBLE LIST

1. Spar dimension on plans is incorrect - reads 1/4" x 1/2" - should read 3/16" x 1/2".

2. Washout dimension is 3/16" - not called out on plans.

3. 1:4 scale "H" version total wing span is 158" not 126.4" (dimensions indicated where for the 1:5 scale).

4. Detail for wing joiner rod bend to be added.

SGS 1-23 Beta (draft) Building Instructions

We have posted a DRAFT version of the building instructions for the 1-23 1:5 scale for reference. The 1:4 scale builds somewhat similar to the 1:5 scale but there are several significant changes to be aware of called out on the plans. That being said - we think you'll find the draft version to still be helpful click 1-23 Draft Manual (caution large file - 16MB) to download a PDF version of the manual.

Build Order - How I Like To Build...

Unless there is a compelling reason to change I have always built wings first, then empanage parts and finally the fuselage. For me it seems fitting that fuselage is last because it integrates all of the other parts. I know Herbert and Tom both prefer starting with the fuselage but I'm going to start with the wings. So my order of build will be wings, empanage then fuslelage.

Ahhhhh... Clean Bench.

Between all the inventory and stuff for Aerosente my shop is pretty cramped right now. I'm looking for new space for a shop here in NorCal. Until then my building board is a 72" long slab of hardwood upon which I tacked down cork using 3M Super 77. Each wing for the "H" 1:4 scale is 79" so I'll have to rig an extension.

Laying Out The Plans...

I enjoy the whole process of building. Some parts of the process I enjoy more than others. I know this may sound a touch wacky but I visualize new or difficult build procedures. I will stare at a plan in order to understand how something works. Then I visualize how I will build it - then I build it. The reason I do this is because alot of this stuff does not come second nature to me - so I need to figure it out. See a lot of you guys were born knowing how to do a scarf joint - not me. If you were to listen to many of the conversations between Tom and me you'll hear me saying many times to Tom "sloooooow down". What comes second nature to Tom - I need to learn and master. My first study of the plans is always enjoyable for me - I work much better off of plans than I do off of written instructions. So it was with great anticipation that I rolled out all 96" of the 1:4 scale plans for the 1-23.

Starting With The Wings - Scarf Joints Are First

Because of the length of the wings spar caps they will either need to be custom cut and shipped (expensive) or scarfed together out of 36" stock. I'll be scarfing together my spar caps out of douglas fir. Tom wrote up a nice piece on "Flightline" describing how he scarfs a joint. Several important things to remember about scarf joints and spar caps as pointed out in Tom's posting:

First of all, a scarf is a diagonal or sloped joint used to marry two pieces of stock together to make a larger or longer part. In boat building we use them for gunwales and side and bottom planking and in aircraft for stringners and leading or trailing edge stock and spars and spar caps.

Second, its best if possible to make the scarf joint fall on or cross over a structural framing member such as a rib or bulkhead.

Third, if possible and without making the scarf too long, have the ends of the joint pass over at least two structural members.

Fourth, its best not to have the upper and lower spar caps scarf-jointed at the same location so the lower cap can be scarfed on the inner panel. I would chose this method, greater distance to the first scarf on the upper, shorter distance to the first scarf on the bottom with good reason - most failures occur in compression and in the case of the wing, this would be the upper surface. Also, the greatest shear loads on a wing panel occur in the first 10% of the span and diminish geometrically further away from the junction of the wing with the fuselage.

In the case of Mike's 1-23, the rib spacing is less than three inches and the stock he is working with is 3/16" x 1/2" douglas fir. With the 36" long parts, Mike can make the first scarf between ribs 5 and 6 which are the second and third ribs of the outer tapered wing panel. Using a slope of about 5 degrees for the joint will enable him to pass by both of these ribs by about 3/4" to 1" which will yield the highest strength.

By arranging the scarf joints as pointed out above, this will yield the highest margin of safety. In addition, make the joints on upper and lower surfaces fall at least three of four rib bays away from each other so loads can be distributed well away from any inherent weakness in the spar caps caused by scarfing.

So With Tom's advice in mind - the first thing I did was to locate the scarf joints. Each wing will have 4 scarf joints - 2 for the upper spar and 2 for the lower spar. Locate your scarf joints on your plans:

Next I selected the wood:

Now I layout the pieces for rough fit.

Setting up to cut the scarf joints. I did it a touch different from Tom's method. I taped the stacked parts together then used a mitre back saw to do the cut. Worked fine.

Rough cuts before sanding and final fitting:

Joint clamped and glued - I used Titebond III:

Rough scarf joint - repeat 3 more times for a set of upper and lower spar caps.

 

Final product two straight 96" spar caps:

Seaming together the wing skins.

I will be building on top of the bottom skins. Some prefer to build on top of the spar (bones vs. skins) first - I've done it both ways. I think for a model this size I like having the bottom sheeting in place. I cut the plans apart and used the wing plans as a template to build the bottom sheeting. I used 3/32" balsa sheet - a combination of 48" and 36" lengths and 4" and 6" widths which I had around the shop.

Gluing down the spar.

After drawing the location of the ribs, spars, dive brakes, ailerons etc., on the bottom sheeting I then glued the spar in place using Titebond III. Yes those are bricks I use when I need a little bit of PRESSURE.

Laying out the ribs and joiner box.

Use ribs W2 to locate the proper orientation for the brass wing joiner sleeve. Tom designed a simple joiner box assembly that orients the wing joiner horizontal to the spar so that you're not creating dihedral in the box itself. The dihedral with Tom's design is created by putting a bend into the AU wing rod. I used 30 minute epoxy to glue the sleeve in place. Also this kit does not come with ply or balsa web shears which you need to cut yourself. 

 

Cutting and gluing doors, ribs and webs...

Now it is time to glue in the rest of the ribs and webs. You'll need to cut your own webs using 1/8" vertical grain balsa.But first I wanted to cut out the bottom dive brake hatch.

Cutting the shear webs...

Cutting and gluing the vertical shear webs

Suggestions for building the fuselage...

Starting the fuselage... Tom put together a set of suggestions for building out the fuselage. I've reprinted them below and basically followed his suggestions.

1. Place all fuselage formers F1 through F13 on lower center crutch and place that assembly unglued on the stantchions.

2. Lower the upper fuselage center crutch into place and make sure all upper/lower keel to bulkhead notches fully seat with the balsa doublers in place.
NOTE: Balsa doublers to four station points must be placed forward of their ply counterparts.

3. Mark any notches with a fine felt pen where adustments in notches must be made and then disasemble and adjust the notches.

4. Repeat step 3 if neccessary and then repeat steps 1 and 2, this time cementing the lower center crutch to all bulkheads F1 through F13, placing the stantchions on the key flat on the table top.

5. Immediately cement the notches for the top center crutch and jig it into all notches in the fuselage formers and if necessary place rubber bands or tape over the top keel next to several bulkheads to prevent distorting the crutches to hold the assmebly tight and flat on the workbench.

6. If needed, place rubber bands configured with a bead or dowel at one end around the upper and lower crutches where needed to pull the lower crutch up tight into the notches in the bulkheads lower sides. Small spring clamps may be used for this as well at all positions.

7. Drop in the cockpit floor loosely but in position to use as a squaring device as the next steps proceed.

8. Be sure to have all clamping devices prepared and ready in sufficient numbers before proceeding with this assembly.

9. Before cement can fully cure and immediately after clamping, sight along upper and lower keels to make sure everything is in line.

10. While cement on crutches is curing for at least two hours, prepare and cement together the two halves of F17 using a 5-10 minute epoxy.

11. Follow the same procedure of testing, aligning and cementing in the two cockpit side/nose stringers F20

12. After cement has cured for at least four hours, test fit and cement in the side formers F17 using clamps as above to make sure these parts are fully and tightly seated for best adhesive joints.

13. Again sight down structure longitudinally to make sure that no distortion such as twisting or bending is introduced into the fuselage.

14. Now remove the cockpit floor and rout openings for the servos you will be using or mark out their positions and provide the necessary framing.

NOTE: If you keep the servos as far back as possible it will leave space for a scale seat and pilot figure. You may even mount the servos in transverse orientation to allow even more space for scale cockpit details.

15. Cement the cockpit floor into place.

16. Test fit and cement into position all stringers beginning with the aft fuselage and always working in symmetrical pairs to prevent distortion of the fusleage while clamped or curing. Less attention to cementing and clamping is required with these as they are provided soley for glueing surfaces for the sheeting to be applied later.

NOTE: Lower stringers may be applied after removing the structure from the building table and cutting off the stantchions, working in the hand. Do use rubber band clamps as required while cement is curing on stringers.

Laying Down The Key...

Tom has designed this kit with stanchions ("stands" that allow you to "stand" the fuselage up for an easier build). The stanchions are added to the bottom of each bulkhead former. When done building the fuselage you break off the stanchions. Each stanchion has an 1/8" gap at the bottom that you can place over a rail or "key" that will allow you to keep the bulkheads lined up perfectly during the build. This is how I set down my key...

Building on the key...

Dry Fitting Fuselage Parts...

I think most of us who model rarely read the directions - assuming there are directions. We tend to spread out the plans, lay out the parts and start building. When we have questions or are stuck on a problem we ask friends or look for build logs to see how somebody else did it. So with this in mind I lay out the fuselage parts and start fiddling around...

 

Cementing The Fuselage Parts

With a beta kit it is not unusual to encounter missing notches, misfits, missing parts, etc... which is why the dry fit session is so important. The 1-23 1:4 scale kit so far has been quite manageable relative to beta build problems. The only major issue I have encountered so far was the placement of top crutch and stringer notches on the F6 F7 F8 bulk heads. I had to cut or file out the notches in order to get a relatively straight run on the stringers. It's critical to make sure the top and bottom crutch are straight and true.

Prepping to cement - I used a system of of clamps, rubberbands and tape to truss everything togther prior to cementing. In the photo below I'm using mini-clamps to hold the bottom crutch in place against the top of each bulkhead.

Rubberbands used as tensioners... I cut the strings long so I had something to grab.

First Look At The Scale

Ok, with both wings and fuselage roughed in I coerced my shop mates to help with a static display. I was anxious to get a sense for the overall scale and in person I have to say it is quite majestic. Here's a shot:

 

Assembling The Fin, Rudder, Stab and Elevator...

The tail section fell together fairly quickly - no major issues. Couple of minor ones including the notches for the rudder ribs being too small to fit the ply trailing edge. Also - when you're building a surface that has a taper do you build flat on the plans and shim the outboard parts - or do you build vertically stacking the ribs on the inboard spar? Just wondering...

 

More Stabilizer, Elevator, Fin, Rudder...