Thread Tools
Jul 19, 2019, 11:46 PM
Registered User
AntiArf's Avatar
Thread OP
Thanks Meltor

This model is proving to be quite nose heavy and may end up with a smaller battery than envisioned, while accounting for how CGs tend to creep aft with covering/paint weight, and a dummy pilot. Not a surprise, as the last subject where I had to move the battery rearward from the original planned location was a Gee Bee R2. Heavy sheeted cowl and nose sheeting, with a light weight covered stringer rear fuselage. Should have no problem balancing with the aileron and tail servos toward the wing rear, and the aileron E-Z links need to be accessible from the cocpit.

This is yet another build where the covering will be done with the wing panels attached. Seem to have run into a lot of that with jet builds in recent years. Spent a good deal of time making sure the wing incidences, washouts and sculpted wingtips match. The inner wing panels will be sheeted outward to about 1" from the fuselage to the second rib. The LE sheeting was decked down to about 1/2 thickness on the top wing surfaces where it joins to the wing stringers, and tapered caps strips using 1/32" sheeting were added to blend the sheeting into the wing ribs on both the top and bottom surfaces. I used the same LE sheeting scheme with the E205 section on another build, which flew well. Should go together fairly quickly now, with the upper front fuse stringing/sheeting remaining. The servo mounting 1/16" balsa spars attach to top and bottom inner wing stringers, adding some strength as continuous spars. The tail feather pushrods were ran and balsa insert plank exit points were added between the stringers, at the rear fuse. I will be able to cover the model first and attach the tail feathers last, which are test fitted in the mock up photo below.
Sign up now
to remove ads between posts
Jul 20, 2019, 08:50 AM
Big gov never Works
St. Martin's Avatar
Hi Bill, thats a very nice frame. I have, on occasion, built frames too light in the back. Just about the time I think I'm doing good, over do it. I don't recall ever building a P-51 that was tail heavy.

Fuzz
Jul 21, 2019, 10:30 AM
Pro Hoarder
turbonut's Avatar
She looks great..I bet it flys great too
Latest blog entry: In flight
Jul 21, 2019, 11:32 PM
Registered User
AntiArf's Avatar
Thread OP
I'm optimistic about this one flying well Turbo, coming in a lot lighter than the Bristol 72 racer that I'll get around to flying someday. The weight on the Bristol ended up a good few ounces heavier than I would have liked.
Fuzz the Guillow's P51 was the easy one of the 400 series lot to balance, with the battery over the CG. Still seeing maybe a few grams of tail ballast needed on this subject, but the AUW looks good at 14oz as a high end estimate, where some of the forward weight contributes to ballast that would have otherwise been required without the retractable gear and dummy radial. I'd like to think I'll end up closer to 13oz. The span is about the same as the elliptical wing Guillow's Spitfire which flew well at 14oz built in my heavy building days with a brushed/geared 370, while this subject has a deep center chord and a good 10sq-in more wing area than the Spitfire. The way the wings seated against the fuse make the span 27-7/8". Wasn't worth hacking to decrease the span 1/8" for scale, and the fuselage is about 1/16" longer and wider than the plan anyway, where the raised stringers added about 1/16" of fuse width, so the wing span deviation is really off by less than the full 1/8".

Covering will be interesting, being used to covering with panels, building a number of sheeted fuselage subjects in recent years. A few small pieces of sheeting were added at the wing TE to fuse joints, as there needs to be something there to attach the covering to, while still trying to keep the scale spar covered fabric look. There's only one stringer width of balsa along the fuselage under the wing panels to attach covering to. Need to get in there with the tip of the covering iron and fasten it down really well in the corner, where the stringers meet the sheeting, and run a bit along the wing panel bottom sheeting. Could double up the stringers, but it would detract from the scale appearance as it would show through the covering.
Jul 22, 2019, 02:26 PM
Big gov never Works
St. Martin's Avatar
To me, Bill, thats a lot of hard covering work with an iron on. I could never do an acceptable job.
Jul 24, 2019, 11:48 PM
Registered User
AntiArf's Avatar
Thread OP
Thanks Fuzz. Fuse covering went well, with easy parts left to do. Microlite makes it easier, with the high shrink rate. The entire framed rear fuse, running under and up to the wing bottom had to be done with one piece per side. Was very careful not to tear the pieces when trimming and working them around the fuse to wing TE joints. This build wins the prize for using up scrap balsa and covering. The covering pieces shown on the tail parts were scrap left over from the last project, where I made templates to arrange and get the most out of the covering, for the remaining pieces needed. The battery door in the cowl bottom has a dowel pin and spring assisted slide latch, with a securing string to keep it with the model when opened. A short length of aluminum tubing was embedded in the cowl for the 0.032" wire latch pin to engage into, so the pin can't bore out the hole in the balsa. The cowl has a few coats of sanded primer and will be painted, to avoid having to cover the part. Actually found the standard primer to be better than the high build, as the coats dry much faster on wood and can be sanded in an hour, versus a day.
Jul 30, 2019, 12:20 PM
Registered User
AntiArf's Avatar
Thread OP
Painted the Microlite covering with Rusoleum metallic silver, starting with the hair dryer on high heat/low fan to remove a few wrinkles from painting, which takes some time, as once the process is started you pretty much have to work across the entire model. It seems that the wrinkles finally shrink out when the paint is fully cured from the heat, and after the heat is removed from an area. This time I ended up using a heat gun carefully, holding from over 1 foot away. Works well, but the heat has to be removed as soon as the wrinkles start shrinking out, as they hit a critical point and pretty much instantly shrink out. The key is holding the gun as far away as possible while still getting enough heat to shrink out the wrinkles.

The aileron torque rods were fitted to clear the pilots arms, but I ended up padding the insides of his arms with small plates of 1/32" balsa, as the arms were rubbing against the linkage. Basically just sanded away the plastic thickness down to the balsa padding to cure the problem. The pilot slides on a 1/32" balsa fabricated base, with a small RE magnet in his back that grabs against a washer glued to the cocpit rear. The pilot is a Parkflyer Plastics Tuskeegee pilot. Not exactly correct, but the scale is close and isn't yet another WB pilot that requires adding a torso. Added fuselage detail for what appears to be a fuel cap shown on the plan, which can be seen in full scale photos if you look carefully.
Jul 30, 2019, 04:02 PM
Big gov never Works
St. Martin's Avatar
WOW! look at all that linkage! I have often been called a masochist for building Guillows, but I bow to the master. Very nice, Bill. That Microlite, is that a polyester?

Fuzz
Jul 30, 2019, 04:13 PM
Registered User
AntiArf's Avatar
Thread OP
Thanks Fuzz, not sure what the Microlite material is, likely mylar though This is the plastic version of their covering and not the polyester tissue. The polyester tissue will probably be around for some time though. I gave some away preferring the plastic, and the LHS still has a bunch of the tissue in stock.
Jul 30, 2019, 04:40 PM
Big gov never Works
St. Martin's Avatar
Who makes it, Bill
Jul 30, 2019, 10:51 PM
Registered User
AntiArf's Avatar
Thread OP
The UK Coverite company recently closed doors, so the product is discontinued. I'll probably be looking at some type of laminating film soon. The brand Bare posted about seems decent.
Jul 31, 2019, 11:43 AM
Big gov never Works
St. Martin's Avatar
Ok, Bill, thanx. I recall something about that.
Aug 01, 2019, 12:43 AM
Registered User
AntiArf's Avatar
Thread OP
Finished with an AUW of 12.8oz with a TP3s-480. Added 9.7gms of tail ballast in a slot previously cut behind rudder in the rear fuse for a CG at 23% center chord. With the elliptical wing, the CG should be a bit more forward than models with straighter wings. Given that I've flown models like the Guillow's FW190 with retracts and Sterling P26 at 11oz on the same small battery, I'll keep the weight as low as possible since the power level should be fine with the greater wing area, and actually quite pleased with the final AUW with over 1 sq-ft of wing area. The larger than necessary battery box was foamed in at the front to move the battery as far rearward as possible, with large lightening holes cut in the foam to not add any additional nose weight.

Experimenting with the DX6 I managed to get the retracts working as desired. They need to move fairly slowly, so that the winch servo does not keep rotating much after the limit switches shut it off. There is only about 1.5mm of clearance between the landing gear mounting block (slides up and down) and the top and bottom fuselage keels when fully retracted or deployed, so the block will continue to move, stop against the keels, and stretch the cable if the servo doesn't stop quickly enough. The full scale gear is hand cranked, so it should also move slowly for scale appearance. The 3 position switch B is used to operate the retractable gear, where the center position fully depowers the system, so that it's not depending on the limit switches to disable the winch servo when in the center position. The gear channel was mixed to switch B, which operates the master direction control servo mounted on the firewall. Next the AUX channel was reassigned to the gear channel, which operates the winch servo, providing direction and speed control for the winch servo. In the servo setup menu, the two servos are listed individually as gear channels, while you have independent control over them as if they were two separate channels. Also added a bit of an ail-rudder mix to ensure good turning.
Aug 01, 2019, 10:33 AM
Big gov never Works
St. Martin's Avatar
That is nice, Bill. Are you going to fly it? I wouldn't!

I think I figured it out, that your a tinkerer! I have known a few modelers, like yourself.
Aug 01, 2019, 10:44 AM
Pro Hoarder
turbonut's Avatar
Dude! that looks outstanding.....very nice ..scratch building at its best...I think I am with Fuzz..just hang it on a string in the living room and fly it in circles
Latest blog entry: In flight


Quick Reply
Message:

Thread Tools

Similar Threads
Category Thread Thread Starter Forum Replies Last Post
Build Log Scale Build-Off 5 (DNF) Scratch built 64.5" span Gloster Sea Gladiator Guy Fawcett Scale Kit/Scratch Built 133 Sep 09, 2019 01:38 PM
Build Log Peter Rake Scale Build-Off 27" span Sopwith Camel jeffh22037 Scale Kit/Scratch Built 35 Feb 25, 2019 11:25 AM
Careful! Bristol 72 Racer 30" span (1/10 scale) AntiArf Scale Kit/Scratch Built 94 Jun 11, 2017 11:26 PM
Build Log 1200 mm Span Sailplane/Glider (Now a Slipso 400 inspired pylon racer) Toomb Raider Foamies (Scratchbuilt) 2 Jul 16, 2016 07:34 PM
Idea Requesting Cessna 152 or Other Cessna Plan (1M Wing Span) FlyingBaby Australia 7 Feb 24, 2010 03:11 PM