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Don Smith A-26 Build

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Old 11-01-2014, 01:44 PM
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Eldher
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Default Don Smith A-26 Build

Hey all. I'm starting a build thread on a 105" Don Smith A-26. Two of us in northern Colorado are building these at the same time. Also, I'm building mine as my first competitive scale build. Just Sportsman class, but still a scale build.

As a scale build, documentation is key. I'm putting together several pieces. Mine will be built as B-26B "Brown Nose" from 1951 in Korea. Originally built in July of 1945 as an A-26 and saw combat in Korea, which received the designation B-26B. To complete the confusion, when the plane was flown in Vietnam, it was designated an A-26A/K. Oh well.

Attached is just a couple of shots of the plane I'm modeling.
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Old 11-01-2014, 02:47 PM
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Get that thing done! We have a Scale masters qualifier in Phoenix to attend the first weekend of March!
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Old 11-02-2014, 07:26 AM
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Researching the kit, I found that it seems to build a little heavy. The examples I found of the 105" version (there's also a 120"/126" version) come out between 32 and 39 lbs. My 95" B-25 weighs 30 lbs and flies well. But I want this plane to come out as light as possible. I ordered a short kit of all the cut parts. Upon opening it I was impressed (aghast even ) at the amount of ply. Attached is a pict of just a few examples of the ply. There are 2 huge bags of these. Every former in the fuse is ply (24 formers). The last 6 of these are only supported on balsa stringers, seems like they could be balsa too. Formers for the 2 HUGE nacelles are just as bad.

Second, as you'd expect, the entire plane is sheeted/planked with balsa. To save weight I will be putting lightening holes in the ply and using contest grade balsa for the sheeting. The entire plane will be fiber-glassed, here I'll use .5 - .7 oz cloth.

Of course the other issue with weight on twins is the obvious fact that you have 2 of everything related to the engines. More on this topic later.
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Old 11-02-2014, 07:57 AM
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Don Smith designs do look and fly well, but are occasionally over "beefed". You could also re-cut a few parts in lite-ply, or like you said, just drill a bunch of holes. Get a set of Forstner bits from Harbor Freight. They will cut the holes clean with less "break-out" on the back side. Spade bits will work well too, but you need to cut 1/2 way thru, and then flip the part for a good clean hole.
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Old 11-02-2014, 08:37 AM
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Or as much as it may be a drag, replace those formers with balsa ones. May be helpful in avoiding any tail heavy situation that could occur as well.

Forstner bits are great, but you do still need to back them up to avoid tear out on the back side. Flipping the parts over may be a good idea regardless of which type of drill you use, if that is the direction you choose to go.

Good thing you did not go with PCK on your kit, as you would have had even more surprises! I have essentially cut half the the kit over for my TA 152 myself, do to improper material that was supplied. Even though you get parts from a kit cutter, I do not consider these builds as from a kit. They are still more of a scratch build from plans. A whole other beast. One of the best things you can do is try to find another build thread, if one exists, to help you avoid any pitfalls others have encountered.
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Old 11-02-2014, 02:42 PM
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TLH101 & Grimmace ... thanks for the suggestions. I've got the Forstner bits, learned their value from other projects.

Sorry to hear that the PCK kit is a POS. My kit was cut by Lasercut USA. Great people to work with, and the parts look great. BUT, I'll hold off any meaningful praise until after I get some parts built during the coming week
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Old 11-07-2014, 05:56 PM
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Construction begins!

rudder is first up. bad news is that Don Smith's rudder is not scale, good profile, but his is sheet-ed, the real one is fabric covered! So, here we go, custom rudder.

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Old 11-07-2014, 06:23 PM
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The wonderful world of scale modeling. The design you choose is always just a rough outline to be manipulated into what it needs to be, to create the impression of the real thing. The challenges are many.
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Old 11-09-2014, 12:22 PM
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Rudder is complete. It seemed as though the TE above the trim tab could be weak/easily damaged. So I fiberglassed it. Tried to get a pict of it, the closeup below, but not sure it comes through.
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Old 11-10-2014, 09:32 PM
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Today's progress, the top half of the right elevator. Again, custom. More complicated scale lines than the rudder as the elevator is 33% sheeted, remainder is open bay. Also, the plans don't agree 100% with the parts. So had to reconcile the differences. Oh well.
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Old 11-11-2014, 07:24 AM
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Originally Posted by Eldher View Post

Second, as you'd expect, the entire plane is sheeted/planked with balsa. To save weight I will be putting lightening holes in the ply and using contest grade balsa for the sheeting. The entire plane will be fiber-glassed, here I'll use .5 - .7 oz cloth.
I built the Don Smith 118" ME-110 and used 1/4" balsa for all the formers except where ply was really necessary and the flying weight is about 35#.

You could cut the insides of the ply formers down so they are just rings about 3/8" wide. It will still be strong once the sheeting is on.

Jim
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Old 11-11-2014, 09:17 PM
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Tmoth4 ... I like the idea of cutting the ply formers to 3/8" wide as I already have them all cut in lite ply. thanks for the suggestion.

More progress tonight. Right elevator is complete and the left top half is complete.
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Old 11-13-2014, 09:04 PM
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Finished the left elevator and started work on the H-stab. Until I get to the wing, I will build according to the plans, they are scale ... at least for my goals.
The H-stab gets built in halves, like most parts in this plan. The top right gets built up and sheeted before being removed. 3 of the ribs will get cut to make room for the ply joiner. To make the cutting easier and also the installation of the joiner itself, I put 1/8" balsa crutches between the first 3 ribs. Also put some thin balsa crutches between the ribs near the TE, to keep them aligned while sheeting. you can see these in the first photo. the second photo shows the net result after sheeting and removing the pieces of rib for the ply joiner, there's now a nice box for the joiner. Last photo shows the top right H-stab with the right elevator sitting in place.

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Old 11-15-2014, 12:06 PM
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After lifting the top halves of the H-stab from the plans they each warped up towards the sheeting along the length of the spar. It's slight, but unacceptable. To correct this I wetted the sheeting and spar with some Windex. Then glued the lower half of the spar in place with slow wood glue. Then clamped the assembly to a straight piece of wood. See the picts.
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Old 11-15-2014, 12:33 PM
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With the stabs off the clamps, everything is now straight. added all the bottom half ribs and LE.
For power, I'll use 2 x 30cc engines. With the design of the plane around 2 x .90 glow engines I really don't want to see the H-stab fail. So, I've added 2 lengths of carbon fiber rod (1/32 x 1/8) to the bottom of the spar. These will be under the sheeting. The CF strips will also discourage any future warp.
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Old 11-15-2014, 03:49 PM
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Looking good! This is a good weekend to just hide in the shop. We have certainly entered building season!

Thought you might find this interesting. Firgelli lineal actuator on the canopy of my TA 152. Nice to not have to put an air cylinder on this. Just plug it in like a servo.

https://www.youtube.com/watch?v=QMze_vb7Z9A
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Old 11-15-2014, 03:50 PM
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the elevator control rods are supported only on the balsa ribs (per the plan). Clearly this will never hold for long. So I've added ply doublers as you can see in the photos.
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Old 11-15-2014, 10:25 PM
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Hey VG ... Love the sliding canopy. Now spray some paint on that thing and go fly it!
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Old 11-16-2014, 07:17 AM
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Originally Posted by Eldher View Post
Hey VG ... Love the sliding canopy. Now spray some paint on that thing and go fly it!

Still have a little bit to do before I am slingin' paint, but I am getting closer.

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Old 11-16-2014, 08:29 AM
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That TA-152 is looking great! Gee that cowl sure is short. do you have to build a removable section or hatch below the engine?

BTW ... What thickness of balsa is the fuse sheeted with? I note that your's is sheeted, where my A-26 will be "planked".
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Old 11-16-2014, 09:01 AM
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The sheeting is 1/8" balsa. There are definitely sections where the sheeting needs to be "treated" to bend properly. Wetting one side with your choice of liquid is the key here. Lots of opinions on this. The moisture throws it out of balance making it curl one way. I generally use alcohol.

The cowling is scale, and it is even smaller than it would appear as most of it is cowl flap, which I do plan to make functional. The firewall is set back some, but the engine (DLE 55 R) will require 1" stand offs to get it in the right spot. There will be some engine hanging out, but not much.

Right now I am sheeting the bottom and finishing the bottom of the front end. I am pondering what to do in the way of access hatches and such. I have found it to be a big mistake to not build in access, even though the plans and design do not specify this. The fuel tank slides into a box, and I am pretty much set on just closing up the front end once I get the engine mounted. I may end up using blind nuts on the firewall (backed up by plywood) to bolt up the engine.

I have done my share of planking, and I think you want to use as wide material as the area will allow. I think it is a lot of fun actually, but it takes time and patience.

It looks like we are going to have some cool new planes at the field this next year!

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Old 11-19-2014, 08:16 PM
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Progress from the weekend ...
Here's the 2 H-stab halves glued up and with the control rods in each side. You can see that I fiberglassed the H-stab TE for strength.



Here's the elevator hinging setup. The elevator gets quite thin to the outside, so I used two 1/8" Robart hinges for the outer two locations and two 3/16" Robart hinges for the inner two locations.



and here's the finished H-stab & elevator assembly all together. Still needs some trimming and sanding, but it's all there. Note how extreme the dihedral is in the H-stab!
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Old 11-19-2014, 09:05 PM
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Figured I post the 3-view references I'm using.
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Old 11-22-2014, 03:57 PM
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starting on the V-stab and fuse. These are built together. First the left side then the right. About 80 cut parts, so a lot to organize. Found one of two F14's missing. no big deal, made a new one. However, really glad I looked closely at plans are parts. The left side F2 is cut wrong and need to be adjusted. F2 - F6 will have hardwood rails to support the nose gear. The left side F2's rail cutout is wrong. Here's the picts on how to fix this part. First pict show the problem. Second pict shows the corrected part. Again, not a big deal NOW, would have been less fun to fix once assembled.
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Old 11-26-2014, 07:29 PM
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Well, I am glad my son was building with me last week. We were working on the vertical stab. Planned to build it as part of the fuse. See pict #1 and the note on the plan stating you can build both together. This sounds like a great idea, it will keep the V-Stab set perfectly with the fuse. Back to my son. He noted in the plan that it looked like the main V-stab post (part that the rudder connects to) runs through the H-stab. I said, "Naw, cause the H-stab has to slide through the opening left in the fuse/V-stab. Fortunately for me, he disagreed! We took some measurements and indeed he was right! The V-stab is now complete and removed from the plans. I have opened up the sheeting in the H-stab and cut a slot in the main V-stab post to slide over the center ribs in the H-stab. I all now assembles nicely! See other pictures.
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