SeamusG

av8djc - I like the cowl "angles" with respect to the foredeck and the bottom of fuse. Since it doesn't matter what orientation I choose for my engine I'm gonna wait on a source for this cowl before finishing the front end.

<edited> I'm tempted to follow suit an "not" use the headrest.

Em, MA - don't be bribing these guys to hold off on the info until you finish your Hog. [sm=punching.gif]

SeamusG

Fuse Construction

Step 7c & d: Assemble remaining formers, top and bottom laser cut sheets.

Step 8a. & 8b: Align and glue.

Building Note: I followed the guidelines presented in the manual and held everything together with rubber bands. I used balsa blocks pinned to the board to hold the fuse in alignment with the box formed by the fuse sides and F-1 / F-3 because I know that they are square and glued in place. I then start messaging the fuse / formers starting with F-5 and work my way back. I use good old Harbor Freight mini bar clamps rather than tape. They put enough tension on the pieces to accept a bit of pushing and pulling to align the fuse side to the plans. Also, make sure that the sides are vertical as well. Mine looked like street-vendor pretzels before I started. They ended up very straight. The bottom edge of the fuse was spot on the plans. The top edge of the fuse was out by ½ mm at one former. I’ll accept take that.

After making sure all was aligned properly thin CA was used to tack the various pieces and parts together again starting with F-5 and working my way back to the transom. Before applying any glue I rechecked the alignment with the plans. Before gluing the last section under the stab support I removed the stab support so that all gluing would be inside the fuse.

Once all was tacked I went over all joints with thick CA. My eyes are still watering.

Oh, check out the 4x4 blocks covered with foam. These are great when trying to support the plane or wing off the surface. Canopies, former, engine cylinders, exhaust pipes are all held above the surface yet the fuse / wing are very stable and you can put quite a bit of pressure on your work without causing hanger rash.

Also, I'm using Sullivan Gold-n-rod instead of SIG stuff. The Sullivan is 13/32" OD (I think) and much smaller than the SIG. I marked and drilled out some scrap lite ply to provide a tight fit for the control rods.

TTFN,

MasterAlex

Too funny!! At the pace you're on ... let's see ... you'll pass the point I'm at in about 12 days. [:@]

-MA

SeamusG

Building Note: Just because the fuse came out very straight doesn’t mean that it was a good glue-up. I just inspected the fuse and turned it over to look at the bottom. The bottom was not fully seated to the fuse sides when I CA’d the bottom and sides. The result is a gap about 1/16”. Not a big issue because it was easily filled with a finishing resin micro-balloon paste which sands pretty easily. Probably won’t consider any transparent covering though.

TTFN,

av8djc

My Feedback: (4)

I guess we have similar taste I'll be following your great thread and waiting to see who mde that cowl. If I remember right it fit the fuselage sides right off, no need to chop and channel.

My old OS80 2-stroke isn't running like it did pre-crash. I might do another change if I can find a Saito 91 cheap. That should be a perfect engine for me.

Dave

SeamusG

Fabricate a fuel tank hatch using 1/8” dowels positioning the front of the hatch and magnets holding it in place in rear. I used the Somethin’ Extra cockpit / canopy hatch as a model.
• Fabricate copies of F-1A and F-2.
• Add ½ wide lengths of 1/8 lite ply to the insides of the fuse extending the top of the doubler back to the leading edge of FTF.
• Fabricate and glue ½” balsa stock to the front of F-2 extending F-2 to the leading edge of FTF.
• Fabricate the hatch floor from 1/8” lite ply fitting it within the boundary of F-1, the fuse side doublers and the extended F-2. The top of the floor will be flush with the top edge of the fuse sides. It will serve to center the hatch between the fuse sides.
• Notch the hatch floor to accept the tabs of the F-1A and F-2 copies.
• Glue the copies of F-1A and F-2 to the hatch floor.
• Fabricate and glue 5/8 x ½ balsa as hatch side rails that will extend over the fuse sides supporting the hatch and sheeting.
• With the hatch in place, locate and drill 1/8” holes thru F-1 and the hatch’s F-1A.
• Fabricate 1/8” dowels with rounded ends and drive thru F-1 exposing 3/16” into the hatch F-1A.
• Cut dowels flush with front of F-1 and sand.

The hatch fits snugly between F-1 and F-2. To remove the hatch the bottom edge of the hatch’s trailing edge will have to swing back towards F-2 on FTF. If F-2 is vertical, the F-2 will interfere with the hatch bottom edge and the hatch cannot be removed. The ½” balsa stock glued to the front of F-2 will need to be tapered back 1/8” at the top. For the hatch to fit well when closed the rear hatch former F-2 will need a 1/8” balsa shim tapered from 0” at the bottom to 1/8” at the top.

For a screw-less installation magnets are inserted into the bottom of the hatch just ahead of the hatch’s F-2 and inserted into the top of tab mounted to the underside of the leading edge of FTF. Just make sure that the magnets are epoxied with the “attracting” sides facing each other.

Computer Note: Microsoft Picture Manager has a real bad tendency to lose pictures! If you happen to rename a picture the same name as an existing picture the existing picture disappears. It does NOT end up in the recycle bin.

It’s back to the instruction manual to start adding stringers …

TTFN,

SeamusG

Thanks to *JCB* for the heads up. Just placed an order for a cowl from Fiberglass Specialties for an SK-26 cowl.

SeamusG

Back to the instruction manual build sequence …

Step 8c: Fit & glue ½” tri-stock to reinforce the firewall.

Note: this was delayed to determine the maximum height of the tri-stock with the tank hatch installed.

Building Note: Don’t forget to adjust the fitment of the tri-stock because the firewall and fuse sides are not at 90 degrees – 1 ½ degrees off. I didn’t – required filling the gap with epoxy. Next time I will get it right. [:@]

Step 8d: install the tank floor. Time for another deviation from the instruction manual.

First, determine the appropriate tank location when mounting an engine rotated 90 degrees. According to un-named sources the tank center should be (best case) at the same level as the spray bar of the carb. According to my research, for both Saito 4-strokes and OS 2-strokes the centerline of the carb is at the thrust line of the engine. When mounted the engine’s thrust line and the fuse’s thrust line are the same. So, I plan to mount the tank so that its mid-line is at the fuse’s thrust line. That’s my story and I’m sticking to it!

The Dubro 12 & 14 oz fuel tank’s center line is 1 1/8” above the tank floor. I transferred the location of the tank floor so that the tank’s center line will be at (or near) the fuse’s thrust line.

I cut 2 lengths of ¼ x ¼ balsa to serve as tank floor supports and CA’d them to the fuse sides. The ¼” stock allows enough width to hold #2 machine screws. To allow the tank floor to rest on the new supports I had to trim 1/8” off each side of the tank floor.

Holes along the sides of the tank floor were located and drilled for #2 screws. I used 4 #2 x 3/8 machine screws to bolt the tank floor to the supports. After test installing the floor the screws were removed and the holes were reinforced with thin CA.

Right or wrong (your call) I went ahead and fuel-proofed the entire fuel tank area with very thin 30-minute epoxy / alcohol mixture as everything is SO easy to access.

Once the epoxy dries, it’s back to step 8d.

<edited> While reading thru the instructions I should have waited until AFTER 9b (LG & reinforcing tri-stock) but BEFORE 9c (fuse bottom front sheet) to seal the inside of the tank compartment. It will add time waiting for stuff to dry.

TTFN,

SeamusG

Because I have a tank hatch I am postponing steps 8d (install & block tank) and 8e (install throttle cable) until I have my hands on the cowl.

Step 9a. Epoxy the LG plate.
Step 9b. Cut and epoxy ½” tri-stock braces above the LG plate.

Deviation: Since I fabricated my own LG plate with 4 holes to match the Dubro LG I noticed that ½” tri-stock braces significantly interfere with the blind nuts. I chose to fabricate my own braces out of 1/8” lite ply from the scrap heap.

Building Note: I used 30-minute epoxy for both the LG plate and braces. When the LG was clamped in place I needed some influence to keep the LG straight – see toothpick – whatever it takes to keep things straight. After gluing up the LG plate and braces I used a cotton swab soaked in alcohol to clean up all errant epoxy.

TTFN,

<edited> Btw, there is no interference between the LG bolts and the 1/4" wing mounting dowels.

SeamusG

Skipping step 9c – fitting of the fuse bottom front lite ply sheet until I get the cowl.

Building Note: Step 51 addresses the mounting of the bottom wing. Part of the procedure includes marking the leading edge of the wing with sharpened ¼” dowels. If you hold off installing the fuse bottom front (FBF) installing the wing will be easier.

Step 10: Fit and glue the front and rear stringers.

Building Note: I took a look at the formers that support the stringers front and rear. Knowing that these will be sheeted with 1/16” balsa sheet it follows that there needs to be 1/16” of leeway between the fuse side and where the former terminates just above the fuse side. Most have this leeway but some don’t. Before I fit & CA’d the stringers I made sure that there was 1/16” leeway for all formers – rear fuse, front fuse, tank hatch and firewall. Take time to get this right or sheeting will be problematic.

I used thick CA for all stringer joints with accelerator where needed. I tried to keep the stringers flush to or above the edge of the formers so as not to have to sand the former “down to” the stringers.

The 22” Great Planes sanding bar was great for ensuring the all of the front stringers were in line and similarly all of the rear stringers were in line. This bar has 80 grit paper on it so before sanding I put several layers of tape over the firewall and F-4 to make darn sure I didn’t sand right thru the former – especially F-4. I used the tape as a scuff coat to tell me when I had sanded everything straight. For the rear stringers I used the “laser burn” as a scuff coat to keep track of what had and had not been sanded.

Building Note 10c: During sanding of the 1/16” sheeting the sheeting may become very thin. Consideration should be given to add 2 or perhaps 4 more stringers between F-5 and F-6. One would be added to each side of the center stringer. An additional 2 could be added above the bottom stringer. These can be added as part of 15b – file and sand the fuse. I added this note after Post 66 as I found that the 1/16" sheeting was pretty thin after sanding.

At the end of the day I’m pretty happy with the results. Sheeting will tell the real story. I would have been more comfortable if the 22” bar had 150 grit paper instead of 80 grit – I got lucky and kept a close eye.

TTFN,

pic 1 shows the tape before sanding
pic 2 shows the tape after sanding
pic 3 shows the 22" bar and how straight the foredeck, hatch and firewall will be
pic 4, 5 & 6 show the 1/16" leeway between the fuse side and the end of the former (firewall)
pic 7 shows the glued up but not finished hatch
pic 8 shows rear stringers before sanding - check the laser burn on the formers
pic 9 & 10 show the front and rear following profile sanding - ready for sheeting
pic 11 - location of optional stringers to provide additional sheeting support

chashint

DUDE !!!
You are a building machine [sm=thumbup.gif] [sm=thumbup.gif] [sm=thumbup.gif]

SeamusG

Step 11: Sheet the top of the fuse

Note: there is a materials typo in the manual. 1/16”x3x24 should read 1/16”x3x30 in all cases. There are 24” sheets but they are for the top and bottom wing leading edge sheeting. But here’s the ruff – the 24” is overkill for the front and rear fuse sheeting – SOOOO – use the 24” pieces for the fuse sheeting and save the 30” stuff just in case SIG pulled an oops.

Step 11a.: Form 4 pieces of sheeting to the front and rear stingers. Because these will ALL butt joint with the sides of the fuse that are straight, make sure that you have a straight side on each of the sheets.

Em, don’t want to cut this stuff with a razor blade. Hey, MasterAlex’s build thread said something about a sanding jig for truing up balsa sheets. So …

I have a 48”x1x1/2” aluminum “L” bracket. I cut pieces of 120 grit paper to ½”x11 ½” pieces (5). I sprayed the backside of the sandpaper with 3M 77 adhesive. The strips were then applied to the ½” edge of the “L” bracket. The bracket is clamped to the building board and you have a 10 minute straight-edge board. A couple of minutes and all of the 1/16” balsa sheets had 1 straight edge. Thanks MasterAlex!

The sheet’s straight-edges were aligned on the fuse sides and taped. They were then shot with water / ammonia solution. In short order they were very flexible. The sheets were then wrapped snuggly to the stringers and set aside to dry.

pic 1 - the 1/2" 120 grit strips
pic 2 - strips glued to back of "L" rail
pic 3 - testing accuracy of clamping to make sure it's straight
pic 4 - showing a pretty sizable bow in the sheeting edge
pic 5 - after a couple of swipes
pic 6 - ready for a bath
pic 7 - ready to dry

TTFN,

SeamusG

Step 11b.: Sheet the top of the fuse, hatch and firewall.

Building Note: I used medium CA to glue the straight edge of the sheeting to the top of the fuse. I glued most of the sheets at one time. I couldn’t glue one because I forgot to cut the sheets down to size before wetting them and there wasn’t enough room to do both sides. I then glued the left front and right rear sheets using a syringe full of Titebond (aliphatic resin) with an extension of fuel tubing on the tip to run a bead of glue over the stringers and formers. The pieces were then taped down to the fuse until dry. After dry the two sheets were trimmed straight on top of the center stringer. I repeated the approach for the right front sheet. The left rear sheet had not been glued down at all due to interference so I decided to glue the sheet at one time. I aligned the edge against the center stringer first and wrapped it down the side and trimmed above the fuse side. It was taped in place to dry.

I repeated this process for the hatch using Titebond exclusively. I applied two pieces of sheeting to the top of the firewall using medium CA.

After everything was dry the tape was removed and the pieces were sanded straight with 80-grit, then 150-grit both using sanding bars. I then finished sanded everything with 320-grit on a foam-backed sanding block.

Everything appears to have worked well but I left out all of the profanity and self abuse. I had not used aliphatic resin for a while. I didn’t have everything on the table to glue things up and then clean up. Too much Titebond makes a mess, but a relatively easy to clean up mess. Because of the small spaces between the stringers glue application was hit or miss so I error on the side of overkill. I needed a piece of bent brass tubing to extend syringe to get into tight places. There is a good reason for doing this step. I used medium CA to ensure that the sheeting was even with the fuse sides. CA doesn’t sand well. Several joints puckered out from the Titebond being wet. Subsequent sanding made the sheeting very thin, maybe too thin.

After all said and done I guess that it’s a fair job – not a good job.

Oh yea, removing the blue painter’s tape pulls slivers from the lite plywood fuse sides. Need to go back and fill these divots.

Step 11c: Mark and cut out the cockpit opening.

Building Note: I used a new #11 blade and made several passes inside the edge of the cockpit pattern. I used a piece of covering “tubing” cut to 6” length as a hand held sanding drum. I taped 320-grit paper to the cylinder. This worked very well to extend the cockpit hole to the pattern edge. I noticed that the sheeting below the sides of the cockpit felt pretty floppy. I cut a couple of 1/16” balsa doubles and CA’d them on the inside of the cockpit. I also extended the rear of the cockpit to the former because the center seam of the sheeting was sanded too thin and it wouldn’t hold up to (ab)use.

pic 1 - one side glued and taped
pic 2 - hatch glued and taped
pic 3 - remainder of sheeting glued and taped
pic 4 - firewall sheeted
pic 5 - firewall sanded
pic 6 - I forgot to glue the center seam on the front sheet - oops
pic 7 - rear sheeting ready to go - note the tape marks
pic 8 - sanded with the hatch installed
pic 9 - hatch seams are pretty good
pic 10 - cockpit cut out with sanding block
pic 11 - cockpit finish sanded
pic 12 - reinforcing side rails added to the cockpit

TTFN,

Minnreefer

Looks good,

You are a building machine[X(]

Jon

SeamusG

OK peanut gallery - Anybody have a wee bit of a challenge getting the cabane struts to line up in their little ole' holes? My front sheeting now has a very nice #3 screwdriver hole that needs repaired. Sheesh ... [:@]

chashint

Mine fit pretty good.
I did have to trim about 1/32 off the bottom of one of the legs.
Don't know if it was to long or if I had glue in that little bracket that you build.

MasterAlex

I seem to recall mine fit just fine too ... This area is very fragile however and I took WAY more time cutting and trimming those holes than I had anticipated.

-MA

av8djc

My Feedback: (4)

What I remember about fitting the cabanes is that I didn't need to adjust anything. It all just lined up when I put the Robart incidence meter on it!! That's when I discovered how great laser cut kits really are.

Do the new kits have a canopy or still the old windshield deal? I had problems keeping the windshield on until this last install. I carefully (and Quickly) put it into boiling water then pulled it out and quickly draped it over a coffee mug. You should also heat the mug first. Most likely my problems were in using the .030" plastic stock. Anyway, I think a canopy would be nicer and would keep the pilot cleaner if you have a verticle engine. I still like the looks better without the headrest.

Dave

SeamusG

Step 12 was skipped because a cowl is being installed

Step 13a – c.: Assemble the cabane plate assembly.

Building Note: The center plate is 4” and the outer plates are 5 1/8”. I marked the location on of the center piece on both the top and bottom plates. I also marked top and bottom so I could remember which was which during assembly. I used 30-minute epoxy and 2 13/64 drill bits to keep things centered. When buttering the pieces with epoxy I left 1/8” at the ends of the center plate clear of glue so that when clamping no epoxy would ooze into the gap where the cabane strut would sit. I noticed that the barbs on the blind nuts were longer than the bottom plate was thick. When installing the blind nuts there would be interference between the barbs and the cabane struts. I used a Dremel sanding drum to shorten the barbs so they wouldn’t hit the aluminum of the struts. The cabane struts were inserted, the blind nuts were glued using 30-minute and then whacked into place with a tack hammer capturing the cabane struts in the assembly.

After the epoxy dried I sprayed the 2” fiberglass tape with 3M 77 adhesive. I cut the piece down to 4” and then applied it to the top of the assembly then around the sides and bottom. I used thin CA to fill all of the fiberglass tape. After it dried it was sanded smooth.

Note from instructions: Correct any problems of alignment now.

I grabbed a piece of graph paper and placed the 4 feet of the cabane strut assembly on the paper. Align? You’re kidding, right? NOT EVEN CLOSE. One foot was ¼” off the paper. Check the pic of the paper to see where the feet hit.

pic 1 - marked pieces just to keep me in line
pic 2 - glue w/ 30-min epoxy - if you have 2 drill bits use 'em
pic 3 - the hammered blind nuts w/ smaller barbs
pic 4 - covered in glass
pic 5 - ditto
pic 6 - graph paper was very useful in getting things straight
pic 7 - only good thing about 1/16" balsa - easy to cut
pic 8 - itty bitty sanding bar
pic 9 - it fits
pic 10 - now it's screwed!

TTFN,

SeamusG

Skipped to step 74: trim the headrest

It’s not real obvious how to mount the headrest to the fuse. The fuse in balsa. The headrest is ABS. I figured that if there was a balsa ballast plate inside the headrest then it would be balsa to balsa. That’s my story …

I sanded the base perimeter of the headrest until it fit flush on the turtle deck. I took some ¼” balsa stock and fabricated an insert for the headrest. I doubled the front to accommodate the front radius opening. The inside of the headrest was scuffed with 80-grit paper. 30-min. epoxy was used. The assembly taped. When it dries I will tape sand paper on the turtle deck and “wear” the headrest’s insert to match the profile of the turtle deck. After covering the headrest will be glued to the turtle deck.

After the glue cured the headrest base was sanded to shape using the fuse with 80-grit paper wrapped over the fuse. The final weight of the headrest is 1.1 oz. I didn’t weigh it before adding the base.

pic 1 - shaped headrest front
pic 2 - shaped headrest side (duh)
pic 3 - rough insert
pic 4 - shaped insert
pic 5 - fitted insert
pic 6 - pre-glue fitting
pic 7 - glued side view
pic 8 - glued front view
pic 9 - using the fuse as a sanding block
pic 10 - finished headrest

TTFN,

SeamusG

Fixing the cockpit coaming – I have 3/32 balsa hands that aren’t comfortable around 1/16” balsa!

I put a knuckle thru the side of the cockpit. I decided to reinforce the entire cockpit sheeting with 1/16” balsa.

pic 1 - the damage
pic 2 - the fix

Should have done this during the initial sheeting step - next time.

TTFN,

SeamusG

Food for thought (or what I think about in the library) ...

What do you guys feel about the following approach before sheeting the top of the fuse?

Fabricate & glue 3/16 x 3/16 balsa stock to the fuse top sheets between the formers positioned 1/16" inset from the fuse side? These will provide a backing for the 1/16" sheeting where it butt joints with the fuse sides.

r2champion

Looks like a great idea, go for it!

SeamusG

I'll GO4IT on my next Hog Bipe

Step 15a: Fit and glue rudder and elevator pushrod tubes.

I’m using Sullivan Gold-n-rod blue/yellow rods. I inserted them into the appropriate exit slot at the rear of the fuse. Depending on which way installed F-7 the rudder is either left of right. I installed it backwards relative to the planes so don’t follow me too closely. I pushed the tubes up to the front of the area where the servos will be mounted. I marked where they passed F-5 (for gluing to the to-be-installed F-5B bracket), where they passed thru F-7 and where they passed thru the fuse slots. The tubes were removed and scuffed with 80-grit paper to improve glue adhesion. Back they went.

I mixed micro-balloons and 30-minute epoxy into a paste and glued both tubes at the fuse & F-7. I’ll wait until the goo gets the consistency of chilled cookie dough and then flush cut the glue with a razor blade. After the glue cures I will flush-cut the tubes to the side of the fuse.

Fuse is finished until I get the cowl.

pic 1 - scuffed tube inserted thru fuse
pic 2 - tubus terminus
pic 3 - buttered tube @ fuse
pic 4 - buttered tube @ F-7

TTFN,

av8djc

My Feedback: (4)

Not needed. Adds weight. But other than that ok[:@]