2023 Agenda A Build Log

[Crist Rigotti]

I cut and epoxied the 2 pound foam to the molds last night.  Today I trimmed the foam and sanded it with 80 grit sandpaper.  Before I glued in the foam, I blackened the edges of the formers with a black Sharpie.  This now acts as a guide when sanding.  When the black starts to disappear, then I've sanded far enough.

I'm now in the process of adding 3 coats Polycrilic  to the moulds to stiffen them and to help waterproof them.

[Crist Rigotti]

Molded the top block skins today.  There are 3/32 thick and 5.6 pound wood.
I use the bed sheet method to wrap the wetted balsa around the mold.  This will leave a nice flat surface as opposed to Ace bandages which leaves "waffle" marks in the balsa.

I then cut out the bulkheads from some 6 pound wood and when the balsa was dry, I glued them in with thin CA.  I then sanded the bottoms flat and trimmed the fore and aft ends.  The total weight of the top blocks is 24 grams.

With them taped on the fuselage, it weighs 151 grams.  59 grams to go for the nose/chin block, the bottom 3/32 sheeting, the upper tail block, canopy, and the battery holder.  I think I'll be close to my budget of 210 grams.

 

[Crist Rigotti]

Oops!  I made an error in molding the front 2 blocks.  I drew some formers wrong, hence the sharp bend in the shape of those blocks.  Back to the drawing board to redraw the formers and redo the blocks.

[Air Ministry .]

Removable Gear Leg , ( not a particularly good illustration, But. )



Mutter , the picture wont go on . Basically vertical ply boxes . If the sping bits aft , there wants to be a packer holding the leg forward , or they spring around on rough surfaces .

looks like a neat plane . 

[Steve Helmick]

Did you find out how PW mounts his LG legs? I'd like to know. I think it would be important to slant the legs a bit, to give some flex, but Paul probably has calculated all that stuff...so do whatever he says!  Steve

[Crist Rigotti]

Did you find out how PW mounts his LG legs? I'd like to know. I think it would be important to slant the legs a bit, to give some flex, but Paul probably has calculated all that stuff...so do whatever he says!  Steve

No I haven't talked to Paul.  I do plan on bending them so they slat outward some.

[Curare]

Hooboy! This is looking good Christ! I've always liked your build threads!

Speaking of landing gear retainers, Bob Hunt has a very elegant way of doing things which I've used on a couple of models (even I beamers)

Have a dig around and see if you can find it, but in a nutshell...

[Ken Culbertson]

Hooboy! This is looking good Christ! I've always liked your build threads!

Speaking of landing gear retainers, Bob Hunt has a very elegant way of doing things which I've used on a couple of models (even I beamers)

Have a dig around and see if you can find it, but in a nutshell...

Been doing them that way since the 60's.  It is to me the best method.  I line the bolt holes with thin wall aluminum tubing and put a thin strip of 1/32 plywood over the blind nuts.  Nothing can ruin your day better than hearing that "clink" as a blind nut falls into the wing.

Ken

[Teodorico Terry]

Crist,

Quick question.  Looking at the fuselage cutout for the wing it appears that you are going to use a "snow cone" airfoil.  Is that right?  I am just curious because I been reading up on some of the old threads related to airfoil section, their thicknesses and how glow vs. electric might enable different airfoils.

Thanks,

Teo

[Crist Rigotti]

Hooboy! This is looking good Christ! I've always liked your build threads!

Speaking of landing gear retainers, Bob Hunt has a very elegant way of doing things which I've used on a couple of models (even I beamers)

Have a dig around and see if you can find it, but in a nutshell...

Greg,
Yes, I used Bob's method over the last 10 years or so.  On this model I wanted to try the titanium removable landing gear from Yatsenko.

[Crist Rigotti]

Crist,

Quick question.  Looking at the fuselage cutout for the wing it appears that you are going to use a "snow cone" airfoil.  Is that right?  I am just curious because I been reading up on some of the old threads related to airfoil section, their thicknesses and how glow vs. electric might enable different airfoils.

Thanks,

Teo

Yes, that's the airfoil that comes with Pat Johnston's Epiphany series of model designs.  He provided the laser cut wing kit.

[Curare]

Greg,
Yes, I used Bob's method over the last 10 years or so.  On this model I wanted to try the titanium removable landing gear from Yatsenko.

Ahh cool, I must have missed that in my drug addled state (at home sick).

I've thought about using a yatsenko style LG system myself,  my plan was to machine a nylon or delrin block to accept the LG leg, and then bolt that to a ply rib.

I'll be waiting with bated breath to see what you come up with.

[Crist Rigotti]

I pretty much finished shaping the nose and molding new top blocks.

From the firewall forward I used 9/16 end grain balsa and a 1/8 basswood nose ring.  I cut the hole in the balsa first then glued on the nose ring with medium CA.  This was then epoxied to the fiberglass firewall/mount.  I used the motor mounted to the firewall and a 5mm hole drilled in the nose ring to center everything up.

I then added a 1/2 thick 6 pound chin block.  This was glued into place using Titebond glue.  I then added a 3 inch wide 1/8 5.6 pound balsa for the bottom block.  Then the whole thing was sanded to shape using 80 grit or 120 grit taped to various diameters of PVC tubing.

The molded top blocks were pulled from the molds, formers added using thin CA, and the bottoms were sanded flat.  Then their mating surfaces were sanded to match each other.

With the nose block done and the molded top blocks taped into position, hatch covers it weighs 184 grams.  All that is needed is the canopy (on order), the accelerometer mount, and the top tail block.  My budget is 210 grams.  It's going to be close!

[Ken Culbertson]

Perfect place for a nose scoop with that taper.  Throw some air on the battery.  Sorry I didn't have a more finished picture. Just a thought.
I had too much top fuselage taper at the nose.

Love the rails in the battery box.  Lots of folks forget that you can't just cool one side, but then your batteries don't have sides.

Ken

[Crist Rigotti]

Perfect place for a nose scoop with that taper.  Throw some air on the battery.  Sorry I didn't have a more finished picture. Just a thought.
I had too much top fuselage taper at the nose.

Love the rails in the battery box.  Lots of folks forget that you can't just cool one side, but then your batteries don't have sides.

Ken

I'll think about a scoop.

[Lauri Malila]

Yes, that's the airfoil that comes with Pat Johnston's Epiphany series of model designs.  He provided the laser cut wing kit.

Off topic, but for some reason the original airfoil of Pat Johnston Skywriter kit has been replaced with a similar style icecream cone airfoil, I wonder why.
But nice workmanship, Crist!
L

[Doug Moon]

I'll think about a scoop.

No scoop, that fuse slope looks very nice!!!

[Ken Culbertson]

No scoop, that fuse slope looks very nice!!!

How can you make an Ice-cream cone airfoil if you don't have a scoop?

[Curare]

+1 for no scoop! I'm all for cooling on electric models, but if it ain't broke...

[Crist Rigotti]

Wow, it's been 9 days since I made a post to this thread.  I've been busy with my other hobby and getting the house trim painted along with other family activities.

The weekend of the 17 - 19 I was at out Antique Radio, TV, and Phonograph Convention here is Dallas.  I entered 2 events in the contest.  AC Radio Pre WWII and Television Receivers.

My 1936 Philco 36 B Cathedral Radio won 1st place!

My 1949 Admiral 19A11 7" TV won 1st place too!

Then at our Banquet, I won the Best Restoration of the contest for my Philco radio!

Needless to say I was very happy and had a good time at the Convention.

[Crist Rigotti]

Back to the Agenda.

I decided to make my own canopy.  I used some poplar I got at Home Depot and epoxied it together, then shaped it using the side view and bulkhead view for templates.

I then made up a vacuum box from 1/4 MDF and 1X3 furring strips.  It measures 11 x 14.  The same size as the PETG I got from Amazon.  I still have to make the frame that hold the PETG while I "bake" it in the oven.  I ran out of time.  I'll get to it later this week.

[john e. holliday]

Good to hear you are getting recognition for your other hobby.

[Crist Rigotti]

Thanks Doc.

[Doug Moon]

Congrats on your accomplishments in the radio and TV restoration event!  VERY COOL!!  That radio is immaculate! I can't imagine watching football on that TV. 

[Crist Rigotti]

Congrats on your accomplishments in the radio and TV restoration event!  VERY COOL!!  That radio is immaculate! I can't imagine watching football on that TV. 

Thanks Doug.

[Crist Rigotti]

Well, I'm back on the Agenda after being out of town. 

I tried vacuum forming a canopy this evening.  No go.  I think Amazon sold me acrylic plastic rather than PETG.

So I ordered some real stuff from eBay.  It'll be here in a week.  In the meantime, I used a Pepsi bottle and a heat gun to see if it would work.  It did, but the PETG is only about .015".  Too thin, but it did produce a canopy to prove the mold.

[Crist Rigotti]

Today I messed with mounting the Fiorotti timer.  I cut 2 holes in the fuselage side and lined them with aluminum tubing.  For the switch I used 5/32 OD and for the LED I used 7/32 OD.

I then worked on the accelerometer mount.  It is supported by some 1/2 x 1/4 balsa and the mount is made from 1/16 PCB material.  Then the crossbars are made from 1/8 Birch ply.  I'm using 2-56 socket head screws and blind nuts.  I cut some rubber "isolators" from some black Du-Bro fuel line cut to about 1/8 high.

I'm pretty much done building the fuselage for now except for the canopy and bottom sheeting.  The fuselage weighs 193 grams and still needs the bottom sheeting (I estimate 10 grams) and the canopy.  I think the canopy could weight 20 grams.  So as of right now it looks like I'm going to be about 20 grams over budget.  Not bad seeing I've made this fuselage a bit more bullet proof than the previous ones. 

I'm 47 grams under budget before the fuselage and let's say I'm 20 grams over on the fuselage, that leaves me 27 grams (@ 1.0 oz) under budget with the wing left to build.

[Ken Culbertson]

Today I messed with mounting the Fiorotti timer.  I cut 2 holes in the fuselage side and lined them with aluminum tubing.  For the switch I used 5/32 OD and for the LED I used 7/32 OD.

I then worked on the accelerometer mount.  It is supported by some 1/2 x 1/4 balsa and the mount is made from 1/16 PCB material.  Then the crossbars are made from 1/8 Birch ply.  I'm using 2-56 socket head screws and blind nuts.  I cut some rubber "isolators" from some black Du-Bro fuel line cut to about 1/8 high.

I'm pretty much done building the fuselage for now except for the canopy and bottom sheeting.  The fuselage weighs 193 grams and still needs the bottom sheeting (I estimate 10 grams) and the canopy.  I think the canopy could weight 20 grams.  So as of right now it looks like I'm going to be about 20 grams over budget.  Not bad seeing I've made this fuselage a bit more bullet proof than the previous ones. 

I'm 47 grams under budget before the fuselage and let's say I'm 20 grams over on the fuselage, that leaves me 27 grams (@ 1.0 oz) under budget with the wing left to build.

Love the tubes!  Use them everywhere.  wonder if using a clear hard plastic tube might make the light appear bigger?  The light is my only, and I do mean only, thing I don't like about the Fiorotti timer.

Ken

[Crist Rigotti]

Just a quick look at what I'm shooting for.

[Dennis Nunes]

Today I messed with mounting the Fiorotti timer.  I cut 2 holes in the fuselage side and lined them with aluminum tubing.  For the switch I used 5/32 OD and for the LED I used 7/32 OD.

Crist, how do you actually mount the Fiorotti timer to the fuselage? Inquiring minds need to know! 

Dennis

[Crist Rigotti]

Crist, how do you actually mount the Fiorotti timer to the fuselage? Inquiring minds need to know! 

Dennis

I'm using a 4-40 screw and 1/2" dowel about 5/8 long, with the hole drilled off center.  I have a blind nut in the LE plywood bulkhead.  The screw goes into the blind nut and the 1/2" dowel acts as a cam, pinching the timer to the fuselage side.  Then the screw is tightened.

[Crist Rigotti]

I pulled the canopy today.  I used some .030 PETG I got off eBay.

I worked a little on the bottom sheeting and I'm calling the fuselage at 225 grams.  15 grams over budget.

This leaves me at 32 grams under budget with the wing left to build.

[Crist Rigotti]

I started the wing today.  Remember that this is a Pat Johnston Epiphany 617 wing that I clipped the tips and added 1 1/4 inches to the root of each wing panel to come up with 56 inch wing span and 628 square inches.  Pat supplied the laser cut ribs and such.  But due to my modification, I couldn't use the flap material, spars, and trailing edge sheeting that he provided.  BTW, when assembling the wing, the spar slots were dead on and the accuracy of his laser cut ribs is outstanding. I also decided to go with a fuselage mounted landing gear.

Besides the mods listed above I also went with a 1/4 thick TE instead of the 1/8 on the plans.  I'll also mount the bell crank just forward of the spar using 1/8 basswood doublers like the lost foam method does. And will use the eyelet method for the lead out guides.  I had to come up with a tip rib but that was very easy because of the "ice cream cone" airfoil.

I'm building the wing on a sheet of plate glass that has been shimmed to somewhat even and level.  I sprayed a light coat of glue on the plans and stuck them down to the glass.  I then determined where the jig blocks will go and cut the plans away from that area.  I then glued the blocks to the glass using 3 small drops of medium CA.  Talking to Pat, the wing is usually built in 2 panels and then joined.  I decided to build a 1 piece wing.  After aligning the blocks and shimming where the 5/16 aluminum tubes will go using masking tape I was finally ready to start the wing.

I first filled in the ribs where the Landing gear blocks would have gone and notched the ribs for the 1/8 basswood bell crank mount.  I marked the rib locations on both top and bottom spars, the trailing edge, and leading edge.  I slid the ribs onto the rods and placed them into position.  I then added the top and bottom spars, and pinned on the trailing edges. It then glued the spars, TE, and LE.  This wing is strong!

Tomorrow I'll fair the LE and TE's, and begin sheeting the wing.

[Steve Berry]

Great work, as usual. Just a couple of questions/suggestions:

1. I would recommend radiusing all the internal corners for the rib cutouts to eliminate possible stress risers.

2. On the ribs near the tips...how are you going to address the "bubbles" created by the jig tubes? Remove tubes, fill in, and sand down flush? How will that affect the trailing edge sheeting? Hopefully it won't induce any warps.

Steve

edit: had to modify slightly on a different laptop as the battery for keyboard died in the middle of typing.

[Crist Rigotti]

Great work, as usual. Just a couple of questions/suggestions:

1. I would recommend radiusing all the internal corners for the rib cutouts to eliminate possible stress risers.

2. On the ribs near the tips...how are you going to address the "bubbles" created by the jig tubes? Remove tubes, fill in, and sand down flush? How will that affect the trailing edge sheeting? Hopefully it won't induce any warps.

Steve

edit: had to modify slightly on a different laptop as the battery for keyboard died in the middle of typing.

The bubbles will be cut down when the wing is off the jig tubes.

[Ken Culbertson]

Just a suggestion.  When you slide out the jig tubes, slide in 2 same diameter 12" or so CF tubes to the center and glue them in.  I use 2 arrow shafts joined in the center by a short length of all-thread into the arrowhead ports.  When I do the center section I unscrew them and slide one out halfway and the other all the way out.  Then I slide the center tube in and put the rest of the shafts back in.  Clamp it back down and proceed with sheeting the center section. If the BC is in the way, just do the back one.  Really stiffens the center section.  I use the same jig you do (only yours is better).  Ice cream cone airfoils are really easy to fully sheet too.  You give that any thought?

Looking forward to videoing its first flight - ken

[Crist Rigotti]

Just a suggestion.  When you slide out the jig tubes, slide in 2 same diameter 12" or so CF tubes to the center and glue them in.  I use 2 arrow shafts joined in the center by a short length of all-thread into the arrowhead ports.  When I do the center section I unscrew them and slide one out halfway and the other all the way out.  Then I slide the center tube in and put the rest of the shafts back in.  Clamp it back down and proceed with sheeting the center section. If the BC is in the way, just do the back one.  Really stiffens the center section.  I use the same jig you do (only yours is better).  Ice cream cone airfoils are really easy to fully sheet too.  You give that any thought?

Looking forward to videoing its first flight - ken

Ken,
Thanks for the suggestions.
I'm going with the open bay look.

[Crist Rigotti]

The wing build continued with using 1/8 Liteply for the bell crank mount.  I didn't have enough 1/8 basswood.  The top mount was glued into place using 20 minute epoxy.  Then the TE was planed and sanded down to the top of the ribs, the spars and ribs were also sanded down to ready the wing for sheeting.  All 1/16 sheeting was 6.2 to 6.8 pound wood.  I used Titebond glue thinned about 20%.  The trailing edge, leading edge, center section, and cap strips were then glued on.  I used pins and weights till the glue was dry.

The wing was then turned over and placed back into the jig blocks.  Here I should have done something a little different.  The jig blocks were notched to clear the spars but I failed to move the wing forward then back instead I just let the spar sit on top of the jig blocks!  Duh!  this then caused me to shim the spar in several locations.  Getting old I guess.  In any case the wing came off the jig straight.

I then again tapered the trailing edge and sanded down the spars and planed and sanded the leading edge too in preparation to sheeting.  I then glued in the other bell crank mount using epoxy.  Then the bottom was sheeted and cap strips were added.  I also added the training edge and spar shear webs.  I'm including extra photos I took during this process.

Next up are the tips, lead out guide and tip weight box.

[Crist Rigotti]

More photos.

[Crist Rigotti]

For the tips I created an extra rib which is the tip rib.  I call it R13.  The wing thickness is an even taper from root to tip, so it was easy to extend the spars out to the tip rib.  this gave me the height.  From the spar to the trailing edge was also straight so that was easy too.  I then continues the leading edge the same way so that gave the the height there.  Then I just added a curve to connect the leading edge then aft to the spar.  It took longer to describe it than to do it!

I then cut off the humps from R12 and added a piece to double up that rib.  This also gave me a "shelf" for the tip sheeting to rest on.  I then glued on R13 to the spars making sure the trailing edge was inline with R12.  I then cut out the tip sheeting from 1/16 and glued them on using thinned Titebond glue.

[Crist Rigotti]

Next up was the tip weight box.  I had an old Hobby Fasteners box and used it.  I surrounded it with 1/164 ply with the ply being 1/4 higher than the box.  I then glued it in place.  I made the cover from 1/16 ply and 1/4 balsa with a 7/32 aluminum tube that will go around the 4-40 socket head screw.  This was screwed into place and the aft and inboard sides were surrounded by 1/4 balsa so the covering would have a place to adhere to.  Then the whole thing was sanded down to match the airfoil.

Then I started on the leading edge.  I use some 6.5 pound 1/8 balsa.  After trimming the leading edge sheeting and sanding the front smooth and flat I traced out each leading edge.  After cutting them out a little oversize I glued then in place using thinned Titebond glue and masking tape.

When the glue was dry I shaped the leading edge using a sanding block to get the rough shape and the use some 120 grit sandpaper like I was shinning shoes to finish shaping the leading edge into a nice round shape.  I followed this up with some 320 grit in the same manner.

[Crist Rigotti]

On the outboard tip I added a 1/16 basswood plate using medium CA.  And sanded it down to match the airfoil.

For the lead out guide I used 2 pieces of 3/32 basswood and 1/16 basswood as the tip plate.  The 3/32 basswood was glued together with their grain 90 degrees to each other using medium CA.  This was then glued to the 1/16 basswood tip plate.  I then laid out the 1/8 holes, drilled them, then I used a hacksaw blade to cut out the "slot" between them.  I then sanded it and added some thin CA to stiffen the holes and slot.

Then the assembly was glue to the tip rib using medium CA.  It was then sanded down to match the airfoil. 

I then terminated the leadouts using annealed 1/16 brass tubing and wrapped them and covered the wraps with 1/8 clear heat shrink.

The wing training edge where the flaps go was rounded as my usual practice.  The wing was then given a light sanding and all that's left is the detail sanding just before covering.

The wing weighs 192 grams.  6.8 ounces.  25 grams under budget!  That puts me at 57 grams under budget.

[Crist Rigotti]

I took care of some last minute details and did the final and detail sanding.  I'm ready to cover the wing, flaps, stabilizer, and elevators with Monokote.

The weights of each piece as pictured in grams:

Wing - 191
Fuselage - 168
Flaps - 50
Stabilizer - 37
Elevators - 38
Fin - 16
Rudder - 4
Top Blocks - 27
Bottom Sheeting - 10
Canopy 15
Flap and Elevator horns and push rods - 47
Landing Gear and wheels - 36

With the carbon fiber Landing gear, I'm 82 grams (2.9 oz) under budget for a 56 ounce airplane.

[john e. holliday]

That is awesome.

[Crist Rigotti]

I just had to do it!  Gotta fit the fin yet.

[Crist Rigotti]

Should I clip the stab tips?

[john e. holliday]

The old DOC says NO.

[Ken Culbertson]

Should I clip the stab tips?

I would rather you round the wingtips but if that is not in the cards then perhaps.  Take a top view picture and put it into MS Paint and edit the Pix.  It will tell you what to do.
 It first has to please you and this plane is really looking good.

Ken

[wwwarbird]

Should I clip the stab tips?

 No, add "real" wingtips. 

[Crist Rigotti]

No, add "real" wingtips. 

LOL!

Merry Christmas Wayne.