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Balsa USA DH-4 build

Old 11-12-2013, 06:56 PM
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a65l
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Default Balsa USA DH-4 build

So I realized at our last Dawn Patrol that there are no 2 seaters around. I've had a bug for one, and since BUSA was there, and had stuff on hand, I bought the DH4. I need to get the winsock datafile, as there are really no good online resources for the DH4. Strange, considering how many of them were used and how many services/nations used them. It will be powered by a 50ish CC engine, if a G62 will fit between the fuse sides with the carb hidden it may be an option as well.
I haven't built a BUSA kit yet. I have owned two of their 1/4 scale D8's, and had plans for both and instructions, so was fairly familiar with the quality of their books and their plans. What I wasn't really prepared for was how nice the die cut parts are. I've started assembling one wing, and the ribs/false ribs/ etc need very little, if any sanding to fit properly. Very well done guys! I was short a couple die cut sheets, but a phone call took care of that right away. There are a few glitches in the book, referencing the lengths of the inner and outer leading edges, but certainly no show stoppers.
So, after a day or two of inventory, and a week or so of cutting what seemed like thousands of ribs and rib parts out of sheets, we're ready to begin. We start with an upper wing panel. The plane uses basswood spars, two foward and two aft. The instructions specify that the spars should be 60" long, but by my measuring tape they're only about 58". The aft lower spar came up about 1/4" too short. After a call to Marinette, I went ahead and spliced a couple inches on to the outboard end.


Ok, I guess no pictures tonight. Maybee tomorrow....
Old 11-12-2013, 07:41 PM
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Thats a BIG ambitious build, will be fun to watch it come along.

I am a big fan of the BUSA kits.. I hope you have a fun time building it.. I have a 1/4 N11 in line for future build.
Old 11-13-2013, 04:35 AM
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A651, I built a BUSA DH-4 from the first batch of kits they produced. The only problem I remember having was that the plans (or prilnting thereof) resulted in the root wing ribs not being perpendicular to the spars. consequently when I fit the three sections of top wing together, there was a gap at the trailing edge.

I built model for one of my clubmates. It has an RCG 55 cc engine.

Chuck
Old 11-14-2013, 05:49 PM
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Well ***. Still can't post pictures. Unpinned the first wing from the board today. Not a lot of sanding to do, I appreciate that after the last build. It appears I didn't get the front spar quite perfectly straight, there's a ltitle bow I can see in the alieron spar, but it's probablly less than 1/16 inch so no worries there. Still have shear webs and cap strips to install, and then lots of shaping of the wingtip.
Old 11-20-2013, 04:19 AM
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Nothing like a new kit... lotsa wood in this one




Lots of sticks... and no inventory list for them




About a week or so to remove all the die cut parts from the sheets. Once again, excellent die cutting, very accurate, every bit as good as laser cutting







The top wing fits my board well, the fuselage is gonna be a stretch...



Here we go!

Not much action the last few days, catching up on some homework and it's been a little chilly out there. Plus I ran out of glue. 1 1/2 ounces of thin CA to get this far. I ordered an 8 ounce bottle, I'll use most of it for this airplane. Hopefully today will be shaping leading edge and wingtip, and hinging alieron. I just realized I need to add some hard points to the top of the alieron in order to run scale cables. My windsock datafile should be on the way today, but it's coming from Merry old England, so I don't expect to see it for a week or so. I need it to plan out rigging hardpoints. The airplane doesn't require rigging, I haven't decided whether to do actual rigging or just elastic cables. Either way, I want to reinforce any places the rigging attaches.
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Old 11-20-2013, 11:57 AM
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Just watching you start this makes me wish I had more STORAGE room ! hahahahaha

I can always get them built, but where to keep them SAFE from hangar rash keeps getting harder. ESPECIALLY when building bigger and BIGGER planes !
have fun, this 1/4 scale is big as most 1/3 scale WW1s :P
Old 12-08-2013, 06:40 AM
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Not much to update here, finished the left hand upper wing and started on the right. Finals are upon me, so I haven't had as much time out in the garage as I wanted, but over the next couple weeks I should be able to dig in and make some real progress.

One thing I didn't catch in the plans. You laminate together the balsa tip bows, and then install them. The plans aren't specific, or perhaps I didn't understand them well enough. I propped up the aft end of the wingtip bow with a 3/32 spacer, just like I did the spars, ribs, etc etc. That's not the way it's supposed to go.. it should sit flat on the table. You cap strip the top and bottom of teh alieron spar, and if you don't let the tip bow hang down, you have a shelf. I fixed it on the r/h uper wing with another piece of 3/32 sheet, not a big deal, but on the second wing I got it right. I also seem to be missing something, the tip bows are a little short to span the entire distance, I had to introduce a filler piece to make it work. Again, not a big deal, but I wonder what I'm missing here...



One down. Three to go.



Second one framed up. That's the easy part done..





Wingtip bows aren't quite long enough. I don't know if I'm just not fitting them right, or what. Not a big deal, because they do overlap, and filler pieces are easy to install.



The wingtip bow should sit below the aft spar as shown. I built the other wing first, and didn't realize that the side elevation drawings were on the other plan.



Bows appear to be short. Next wing I'l lay them over the plans and compare sizes.

That's all for now, hopefully more to follow soon.
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Old 12-08-2013, 08:37 AM
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Nice big project, keep up the good work, please post several pictures of your progress.

Thanks, Merry Christmas
Rich
Old 12-12-2013, 09:47 AM
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Houston, we have... well, an issue. After finishing the second wing, I built up the center section and prepared to join Just for fun, I stood the two wing panels up next to each other, and lo and behold, things were not as they should be. There were numerous misalignments with the ribs,and the two wing panels were different in length by about 3/8 inch or so. Now, I'm no master builder, so I laid the two top wing plans over each other to check, and lo and behold, they were off, just like the wings. I don't see this as being a serious problem at this point, as long as I remember to make sure the lower wing's ribs line up with the corresponding top wing's. Well, specifically, the ribs for the inboard edges of the alierons, and teh ribs that support the interplane struts.

Second panel done... ready to make the monster



Center section ready to go



Pretty obvious that there's something wrong... the root ribs are lined up at this point as are the leading edges. The LE's and TE's line up well, so no issues there, but the rib spacing... There is no linear progression, some ribs are closer than others. Very strange... almost rates a call to Marionette...
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Old 12-12-2013, 03:18 PM
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I have heard that same comment on other large builds. I know plans can shrink so it is best to get out the measuring tape and check each wing left & right. I have built several giant scale airplanes and I never checked the wing panels together. I will from now on.

Good build

Thank
Rich
Old 12-18-2013, 04:41 AM
  #11  
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Thanks Rich.

Not much to show, all four wings are essentially the same thing. I finished up the other top wing panel and the center section and got them joined up. That's a bit of a job, because you set the diehedral with 1" blocks (included!) at the last W1 rib, and then join the outer wing panels to the center panel by gluing the root ribs and the wing tube receiver box to the shear webs. I sanded and fit and fit and sanded and got the outer panels fairly close to the center section, but not a perfect fit. I made some small shims to correct a little unevenness, installed the anti rotation dowel and drilled for the retention bolts. I was thinking about moving the bolts outboard on the wing so you wouldn't see them, but decided against it, there are enough other challenges on this build. First lower wing is in process, and the process does seem to go quicker every time. Score one for building true biplanes...

I hate to do this again, but I found another shortage in the kit. While counting up false ribs, I discovered I'm 8 shiort to finish the last wing. The kit inventory calls for 13 sheets of 10 ribs, making 130 total. By my count the wings require 138 total.

I did create one issue with the lower alieron, the leading edge shifted while I was gluing ribs, and I didn't notice untill well into the process. It's just a little shift, so I made an end piece and scabbed it onto a rib. Problem fixed.



It's all one piece for the first time. I'll get a couple pics for size hopefully today.



Whoops.



fixt.
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Old 01-11-2014, 08:23 AM
  #12  
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Not much action for a while, but it's because building the lower wings is a carbon copy of the top wings. I did run into a small problem. I inventoried the die cut parts when I first started the airplane. There were a few shortages according to the inventory and BUSA took care of them with their usual excellent customer service. I also ran into a small issue with not having enough basswood stock to build the wing center section, but that again was handled superbly.
According to the kit instructions you should have 13 sheets of die cut false ribs, with 10 ribs per sheet, for a total of 130. By my count you need 138 false ribs to build the wings. I saw references on another build thread to not having enough false ribs, but figured it would be fixed by now. I didn't realize I would come up short untill I divvied up the ribs for the two bottom wings and saw the shortage. But once again, a call to Marionette and the parts were on the way, around Christmas, no less, and received right on time. Again, excellent customer service all the way.
So the top wings were finished, joined, and set aside. The way the kit builds you have two exposed bolt heads on the top wing for the retention bolts. I thhought about moving the bolts outboard on the wing and recessing them below the top covering, but decided it wasn't worth it. I'm going for a few new things with this airplane and am aimingn to keep it as simple as possible.
No issues with the bottom wings, by the time I build the last one it was going fairly quickly and almost routine. I guess I'm well prepared for my next busa kit whenever that happens.
Building the tail is straightfoward and goes fairly quickly. Do pay attention to the instructions, you use a different size cap strip for the leading and trailing edges of the stab. I don't think there will be an issue, but that side will be designated the bottom anyway to no worries. I am going to engineer a way to make the stab bolt on, to that end I did not sheet the center section of the top of the stab. I'll wait untill I get the fuse built and get to the stage of joining the stab to the fuse. I don't think it will be a big deal to engineer anyway, it adds minimal weight if done right and havign the stab removable has paid dividends for me on other airplanes. I will be hinging with piano wire, instead of the split pins included with the hinge, so should be able to very easily remove the tail if necessary. One other thing I may have to re-engineer, I am planning on using external flight control wires as per the original, instead of pushrods. That may require some local reinforcement of the LE of the stab where the pulleys mount, and will require different control horn locations, but that shouldn't be an issue. I did not drill holes for the flying wires yet, I think I may try and "sleeve" those holes with small diameter carbon fiber tube. I did this on my D-8 and it makes for a harder surface to tighten a bolt and nut down on, plus it makes finding the hole easier under covering.
Fuse plans about cover my whole table. I was trying to compile a time lapse of my building one of the fuse halves but it didn't work out quite the way I wanted. I was a little doubtfull about using balsa for the main stringers, but it's obviously strong enough and most of the fuse is either sheeted or has cap strips, so I think no worries there. The frames build fairly quickly, the only trick is making sure you overlap all your joints. The fwd fuse balsa sheet parts are a little oversize, which is very nice, I built a little differently from the plans because I couldn't find the basswood stock for the radiator mount in the kit. I've got one frame complete and the other is nearly so, so hopefully when I pull it off the table they'll be mirror images...


Cap strips. Fun fun fun.



Obligitory "now that's a wing" picture



More of the same for the bottom wings...



Even the stab is big... all balsa



Looks like a tail to me



Building table to capacity.

More pics of the fuse to follow shortly...
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Old 01-13-2014, 07:05 AM
  #13  
a65l
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On to fuse building. BUSA has you lay up the stringers from 1/8" balsa strips, two of them. They are spliced, and of course you stagger the splices when you lay them down. I deviated from the instructions just a little bit, I laid down the 1/4" fwd fuse parts first, and adjusted the stringers to them. Seemed to work out fine, I got two mostly matching fuselage frames. When I say mostly matching there may be a 1/16" deviation here and there, but they sure matched up better than the wings did! You then prepare the formers by gluing a 1/8 x 1/2 inch stiffener to them, and two of the formers are "U" shaped and need to have a stiffener applied across the open end. The drawn plans were a little off here, I wound up doing some measuring and squaring before I glued. My fuse halves seem to have a slight bow, from top to bottom, but shouldn't be a problem once they're glued to the formers. Haven't joined them yet, I did make a little mistake. Some of the formers have 1/2" tabs that stick out, those tabs are where the stiffeners go, and shouldn't be sanded off. I got my formers confused and sanded off the tabs on one, but it'll be short work to fix it. Hopefully I can get some homework done this morning and get out into the garage in the afternoon for some squaring fun...

Fuse frames laid up for some matching up... I used the wing receiver box to help line them up The wing receiver box, the top of the fwd doubler and the stab saddle are the critical alignment points....



That's gonnna be one big fuse.


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Old 05-22-2014, 02:46 PM
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So it has been a little while since the last post. Blame school, in particular calculus. Had a week, did some constructing. Fuse is 3d, and wht a fuse it is. I had to get a large soldering iron to be able to build the cabane struts. I got an 80 watt weller off amazon and it did the trick with some to spare. Nothing tricky about mounting the wing, just measure measure and drill, and measure again.




This is the jig you build to solder up the cabanes. Fairly straightforward, but the 80 watter is a necessity as you solder the lugs in situ. Getting the cross wires right is a little tough, I wound up tack soldering them and then wrapping them. It's fairly clean and near, I did take their advice and wash it thoroughly in soap and water when I was done to ensure I had all the acid flux gone.


Top wing mounted for the first time. It's about spot on at the wingtips. It's a milestone, but there's still a but ton of work to be done. I'm trying to be finished for the Mid Atlantic Dawn patrol, but we'll see. Summer classes... ugh.
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Old 07-05-2014, 04:16 PM
  #15  
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Progress, in spite of Calc 2 and Physics over the summer. Not many pics, sorry about that, and will be some more to come.

Big milestone was mounting and getting the incidence set on the bottom wing. Then it was on to building the interplanes. The way BUSA has you do it seems kind of redundant when you read it, but when you start doing it you realize it's exactally the way you would do it if you had done it before. On a plus note, in spite of all my measuring and checking, the opposite struts (outboard and inboard) were close enough to stick a bolt thru both ends without any trouble. So I guess the dihedral matches on both sides, and the incidence (right or wrong!) is the same on both sides. So plus one there. I did forget to clean off the bracing wires, and got a little corrosion when I had soldered. Not a big issue as they're going to get painted down the road. The real trouble is keeping track of where each strut and bracing wire goes, especially as they still need lots of sanding and finishing. I'll come up with something, I'm sure.


Change one from the plans, and I don't have any pics right now, is making scale control connections. The full size plane has external elevator and rudder wires, and it's a fairly noticeable visual detail so it must be done. Plus it will make rigging the controls very easy. I need to see a buddy of mine and pick up a piece of carbon fiber sheet, I'll use it to make the thru bar for the rudder. The elevators are Du-Bro heavy duty control horns, drilled out to fit over a 3/8" carbon fiber tube. The whole assembly pivots in some plywood trunions, and so far it seems like it's going to work out very well. Now I just need to send BUSA some more dollars for guns, covering, I'm sure some other stuff I'm not thinking of right now.

I need to come up with a way to make some different exhaust manifolds from what's in the kit. I'm going to do mine as an Eagle engine plane, but not modify the cowling. But the exhaust manifolds are very different, and very noticeable. Probablly just carve up some pink foam and cover it with .5 oz glass cloth.
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Old 07-05-2014, 04:18 PM
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Forgot. Scheme:

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Old 07-05-2014, 06:42 PM
  #17  
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Takes up a lot of space in my garage....


Struts inwork...



Must have done something right, as the opposite side struts all matched up...



Elevator control linkage. Trying to get it scale. I'll slave two servos to that single torque tube to ensure I have enough oomph on the elevator.
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Old 07-06-2014, 04:32 AM
  #18  
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Pretty ambitious build with school and all!
I read another thread on the busa dh4 but he got disillusioned with the plan inaccuracies and abandoned the project. Glad you soldered on!
It is a huge airplane! Your pic standing next to the wing put it in perspective. All I can saw is - wow!

I'm following along. Wish you all the best with your classes and the build.

Brett
Old 07-06-2014, 01:15 PM
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Thanks for your kind words... I'm trying to not get overextended, especially when it comes to modifying the kit. The

I read that thread and his comments, and noted some inconsistencies myself. But as was pointed out to me, this is not a pattern airplane, nor an precision aerobatic airplane. The interplanes lined up, the wings are fairly perpendicular to the fuselage, and I can get the wings on and off without undue exertion. So as far as I'm concerned, its plenty straight. The real ones weren't all that straight to start with, and prob. got worse the more they were flown and stressed.
Old 07-06-2014, 07:31 PM
  #20  
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Originally Posted by a65l View Post
Thanks for your kind words... I'm trying to not get overextended, especially when it comes to modifying the kit. The

I read that thread and his comments, and noted some inconsistencies myself. But as was pointed out to me, this is not a pattern airplane, nor an precision aerobatic airplane. The interplanes lined up, the wings are fairly perpendicular to the fuselage, and I can get the wings on and off without undue exertion. So as far as I'm concerned, its plenty straight. The real ones weren't all that straight to start with, and prob. got worse the more they were flown and stressed.
Agreed. Still is a HUGE kit and I also agree there is nothing like it at any rc field. 2 seater, ww1 aircraft are just not modeled often, so it will be a real treat for anyone to see it fly!
This plane interests me because I would like to build one and model it after a U.S. Mail plane, but my god its big... and where in heaven do you store the beast!!

I fly mostly ww1 - 1/4 scale & 1/5 standoff scale Fokker's and some of the historical reading I have done of bad workmanship and poor materials/improper building techniques in his own factory was horrible. Albatross built Fokker's were a much better aircraft, so they say.

Some of the cheaper trainer foamy planes at my local rc field are much the same - no where near square, lined up, chunks missing, etc. and yet they fly on.
On occasion, we fly these aberrations to intentionally provide much needed hysterical laughter as they lose parts in flight and crash. Then epoxy/ca them back together for another go.

Anyways - I hope you can get her all done up nice and to the field this summer for some flying fun!

Cheers
Old 07-15-2014, 02:49 PM
  #21  
a65l
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Small updates, I finished the control linkages and bellcranks. The Elevator will have two servos driving a single torque tube, with control horns outside the airplane connecting to the elevator thru cables. The rudder is the same sort of setup, with a large carbon fiber horn driven by a single servo. Nothing too complicated. The rudder is not in the correct scale location, but it's a small point and getting it to the correct location wasn't gonna happen without considerable engineering.
I've decided to glass and paint the sheeted portion of the fuselage, it was varnished plywood on the full size. I'll cover the aft portion of the fuselage that was fabric on the full size, and the wings will be fabric as well.

I need to come up with an exhaust system for the engine. Busa used a canister and header arrangement that extended back into the fuselage. I'd rather not do that if I dont' have to. The problem is limited clearance between the engine and the side of the fuselage. There's enough room to fit a Bennett diverter, probably, but I'd rather not chance having the outside fuselage get hot and bubble the paint. I see one fix was to rotate the engine from vertical, giving clearance, and another solution is to mount the engine inverted.

I also need to come up with a tailskid, I'm not going to make it steerable like the full sized but would like it to be a little more scale shaped, and it will have to be sprung. Details details. I also need to make a new upper cowling, will do it with aluminum, but need to get better at making louvers.

anyway, a few pics...

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Old 07-17-2014, 08:00 AM
  #22  
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Have an issue. The following pictures show the engine mounted in the airplane. I need to figure out an exhaust, that will hopefully not:
1. Intrude on the space behind the engine
2. Require me to mount the engine upside down
3. cause the walls of the fuselage to get terribly hot...

Busa used a header and can, that mounted inside the fuselage. This meant that they couldn't mount the fuel tank right behind the engine. This is a gas airplane, so the fuel tank can sit further back on the CG and not be an issue. I'm not doing a full cockpit, at least for the pilot, so that space is available (somewhat). I'm also on something of a budget, but I'll spend what I have to to make it work...



There's about 1 1/2 inch clearance there, but the standoff for the engine mount sticks out around 1/4 of an inch. So the muffler needs to stand off a little bit. Also, when the cowl is installed, that reduces the clearance by 1/16 of an inch, or so...




The cowl reduces the clearance by just a little bit...
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Old 07-26-2014, 04:06 PM
  #23  
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Muffler problem solved, Bennett's exhaust is narrow enough to give me clearance.

Landing gear mostly done, I still need to glass the fairings and all but it's done enough to stand on it's own feet. I used their suggestion, and soldered brass tubing to the wire, and drilled the tube for a cotter pin. Looks pretty good if I do say so myself. Built the tail skid, a little different from the plans, and it's together enough to stand on its own two feet.

Started on the control horns for the empennage. Rudder gets a carbon fiber sheet horn, fairly long, built with a little bit of reinforcement for the rib. I applied a balsa triangle reinforcement over the horn to kinda stiffen things up, probably didn't need it but what the hell, the tail looked light.

I am still working on whether I'm going to epoxy the tail on or bolt it. Bolting raises some issues, technical one that can probably be solved fairly easily. No easy place to put four bolts, so perhaps two and a hook in the rear? I don't know.. will sort that out in the coming week.

One decision that was fairly easy, the fwd portion of the fuselage, that is plywood on the full size, is going to get glassed and painted. The rear half will be covered with solartex, and partially painted.

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Old 08-07-2014, 05:35 AM
  #24  
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Lots of work, but not much apparent progress. Fuse is glassed and painted. All the rest of the control linkages are made. exhaust manifolds mounted. Plane is gonna be sort of a mutt, a mix of U.S. liberty engine and early british plane, but that's all right. Perhaps it was an early prototype.... or a british plane with a liberty engine. Either way.


Just enough clearance between the muffler and the engine mount...




Fwd fuselage is getting glassed and painted to simulate varnished plywood:



Ready for paint



Filling in the weave of the f/g... got tired of waiting for the filler primer to dry


Gray... how exciting....



Starting to look like something

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Old 08-13-2014, 04:06 AM
  #25  
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Mostly together... starting to cover and put on rib tapes. Too lazy to do stitching, though.. and I'm running out of time...




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