Building the fuselage sequence ?

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MadProfessor8138

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My question pertains to the building sequence of the fuselage for my RW19 Stork.
I'm at the point that both stick built fuselage sides are built and laying in the jig,stacked on top of each other.
My jig was designed to allow both sides to be built together so they would be identical.
The construction sequence that is called for next in the plans is to sheet the sides with plywood and then stand them up to start adding the bulkheads,cross members,spar carrythroughs,etc.
Realistically,I'm still a few months away from ordering the plywood but I would like to continue the build until that time.
I've seen pics of builders that have stood their fuse sides up before sheeting with ply,on various planes,and added everything then sheeted with ply afterwards......like this :
fusebig.jpg

But the plans call for the sides to be sheeted before being stood up.....like this :
100_0015+-+Copy.jpg

I really want to continue my build and I see the pros & cons of both ways....so I thought I would ask for opinions.
Should I continue the build and sheet with ply later.......or wait until I sheet with ply and then continue the build ?

Kevin
 

wsimpso1

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Madprofessor8138,

I am in agreement with the others. Two big reasons for sheeting the sides prior to stand up: Straight flat sides that will stay that way; Good bond strength everywhere between sheet and balance of structures. Another good reason is that you can do the sheeting with the sides flat on the table where clamping is more reliable. Then there is the issue that it was presumably done this way by the designer and then demonstrated to be sturdy - deviating from the known good way of building is adding extra unknown risks to all of the other risks we take with a homebuilt airplane. Who needs more risks?

Stand them up, build the 3D structure, and you are likely to have no flat sides when you go to bond the sheets on. Why? Wood moves as it sits, then the horizontal and diagonal pieces will never be perfect in their sizes, etc. So then you will either have to fill gaps or force the plywood to conform to the undulating surface or a little of both. While epoxy adhesives are good at filling gaps without strength issues, this may exceed its limits and will build in plenty of residual stresses in the fuselage. Much better to start the job of load carrying without using up some of your strength...

My always advice on plans built airplanes has been consistent. Stick to the plans unless you have a known deficiency and a known good fix for that deficiency, then stick to the plans for the known good fix.

You are proposing to deviate from the plans. I believe it is a bad thing for several known reasons, plus adds to the unknowns you have.

Billski
 

cdlwingnut

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I put the plywood on my ragwings sides first then built the boat stage. some don't so they can get to the insides better, but i never had any problems getting to the insides of mine.
 

don january

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As the builder of a extremely curved Taylor -mono I wish I could have applied the ply sheeting before joining the fuselage sides to form the boat. That being said it is in my opinion that the ply should be added "after" the tail and firewall are joined because there is a amount of growth of width and a difference in length and height once joined and waiting would in my opinion lessen the stress on glue joints of ply. It does state on the prints that the bay between front and rear spars can be left un-covered with ply and I believe this is for easement of mounting root spars among other cockpit items. With today's ratchet straps and clamp types getting a good bound to the boat is not a bad project to do.
 

Pops

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When I built the KR-2 back in the 1970's I put the plywood on the sides flat then put the sides up and glued the firewall and cabin cross pieces in place. Took a huge amont of pressure to pull the tail in to the tail post. I didn't like locking in all of the pressure. After that I always build the wooden framework first and then put the plywood on, a lot easier. The plywood just lays down to the curve going back to the tail post with no problem.
 

Victor Bravo

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Others have made potentially valid points about putting shear and pre-loads into the structure later. So perhaps there is a middle ground.

Maybe use a bunch of furring strips and thin sticks to shim up the tail end of the fuselage sides, and shim up the plywood at the rear of the sheeted section, to match the slight curve that you will put in later when you pull the sides together??? Any of you experienced woodworkers see problems with this?

It will take a little more effort, because you are putting in a bunch of shims under the plywood (in order to ensure the plywood is flat and straight except the controlled single plane curve you are creating).

But in return for this effort you will get the best result. Guaranteed good glue joints (because you could use weights and clamps), and you didn't put shear loads on the glue joints when you pull the tail together.
 

MadProfessor8138

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All good points and good advice...I thank you for the input.
With reading the responses I'm still seeing the pros and cons to either sequence for the fuselage construction...it seems that different builders prefer one method over the other for their own reasons.
Just for discussion I'm going to list my observations of each method and would appreciate comments.
From the already posted pic you can see where the ply goes from 1 full sheet to scarfed 3" wide sections that continue to the tail.
Here is a snapshot of the plans......
Screenshot_20200326-200402_Drive.jpg

Sheeting before......
Pro :
1. Good glue joint due it being flat and weighted down.
2. Once sheeted the sides will not move when stood up.

Con :
1. To keep both sides identical they will need to be stapled together along the perimeter to ensure that they do not move from each other....lay the stacked sides on the ply and glue...then once cured,flip the whole assembly over and glue the other side to the ply....once cured remove the staples and separate the 2 sides from each other....theoretically,they should be identical.
Will the ply being on the bottom while gluing there should be no risk of glying the 2 sides together.
2. When pulling the tail together you will be fighting the glue and plywood.

Sheeting after.....
Pro :
1. I can continue my build
2. Setting the spar carrythroughs,firewall,cross members,seats,etc....would have great access to them.
3. I don't think the fuselage ply would have the stress built into it because the tail has already been pulled into position when it is applied.

Con :
1. The 2 sides are identical as they lay in the jig now.....but care would need to be taken to make sure they stay that way when stood up....exact measurements and locking everything stationary so nothing moved as everything is added would be mandatory.
2. The ply would be bonded to a vertical structure so a little thickening of the T88 would be in order and a bunch of staples for the needed pressure would be necessary.

I can't say which method is right and which is wrong because I've seen it done both ways on aircraft.....
If I have missed any points please point them out to me....

Kevin
 

don january

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One point to consider is during final assembly such as wing and Horz. stab incidence set to thrust line you can have a 1/4" twist in over all fuselage shape (Hope not) but you should not depend on any thing other then water level or Laser beam to set your incidence to thrust line. Dihedral of wing and HZ if any to me is what is most important. In other words you can build the Fus. in the shape of a twisted piece of licorice but as long as the CG is with in its range and your surfaces plains are not +/- to each other then the bird should fly with out doing a snap roll on take off. o_O I know I scratched my head also just to try and pass the thoughts along
 

Pops

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The plywood sides are NOT bonded to a vertical structure.
Fuselage is rolled over on it side and the plywood is bonded horizontally. I do the sides first and use C-clamps around the outside along with the nailing strips with the staples and weights. When using C-clamps, I use strips of scrap wood under the clamps to distribute pressure evenly. Then I do the bottom last and have the fuselage upside down and use nailing strips and staples and weights.
 

MadProfessor8138

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Pops.........I hadn't considered rolling the fuselage on its sides to apply the ply.
I thought the fuse would flex too much for that so I figured on applying the ply while the fuse was vertical.
Have you experienced flexing issues doing it that way ?

Kevin
 

MadProfessor8138

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don.....I understand the message you are trying to convey.
And I agree that being precise with location/placement of designated points on the fuselage will be of the utmost importance to keep the structure true.
Laser,levels,plumb bob and only 1 chosen tape measure will be used to keep everything in alignment.

Kevin
 

MadProfessor8138

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A "Safty" note is a point of interest and is used to draw "A-10tion" to a particular item on the plan.
Lol......sorry,couldn't resist that one.

I'm assuming Roger went to college,he use to be a Crew Chief on F4 Phantoms in the military.
In his defense.....he designed the dozen or so aircraft in his stable...but he didn't draw the plans....I believe a gentleman named Chris did.

Kevin
 
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