This guy who is requesting my help to build a PT-40, as I have built two of them, e-mailed me this:
(quote) “Can’t use the two 2.5” washout jigs because of bench size. What I am going to do is double the washout jig size leave half of one wing flat and hanging over one end of the bench and place the modified 5” washout jig on the other wing tip. I will then sheet the wing with the washout jig then move the jig to the other wing half and sheet that one (filled some sox with sand to hold everything in place).”

My e-mailed response back to him.
(quote) “Please do not do that with the washout jig until I write to rcuniverse and see if it will ruin your wing. They are more professional about washout than I am, I do not really know about it at all.

Isn't there a level floor you can use somewhere for a few hours that no one will bother it? It would be much better to use the jigs as they are. I do not believe that just raising one wing panel up off the bench will put in any needed washout. I hope it is not too late to persuade you, and you didn't already cut up the jigs.”

Can I please get some response to this situation that I can email back to him. Thank you.

Dose your friend have a vision problem, drop the CAPS!

No vision prob. Just figured that the caps will get a quicker reponse before he ruins his wing.

I had to read his post three times before it sunk in what he was preposing. In theory, it will work, assuming the root ribs are equally zeroed on the bench. I seems to me that the jib is for dhideral as much as wash out. I would really like to see the jigs and instructions for this though.

My build table is just over 60" long, but when I'm doing 4*60 wings at 72" or other large wings, you can only work one half at a time. This is basicly what he is proposing I'm guessing. An 80" or 96" table would be nice, but you can get by with smaller.

Don

Hey Campgems you can borrow my table. It is on it's way.

PT-40 manual, he’s asking about step 9 on page 32 and all of page 33
http://manuals.hobbico.com/gpm/gpma0...anual-v1_2.pdf

Because the jigs automatically build the washout into the panel it is possible raising the panel up 5" one end at a time will still build the washout in, but I would like some opinions first.

Thank you.

Basically what he is proposing to do is raise one wing panel up 5" with the jig while the other panel is laying flat on the board, glue the sheeting in place on one panel (not sure if he is gluing the sheeting on the raised panel or the panel laying flat). Then place the jig at the reverse end of the wing and do the same.

Is it possible that if he applies the sheeting in place on the raised panel, and then reverse sides and do the same to the opposite panel, will the washout still be built in?

OK, after looking at the manual, he doesn't need to make a 5" jig. As long as he has the dhideral correct, he can just weight the center per the manual and work one wing half with the stock jigs. When he has finished the first side, slide the wing over so the center is on the other edge of the table and then do the other side. The only down side to doing it this was is if the center of the wing doesn't touch the table when the wing is suspended between the jigs. It's hard to tell from the photos, but it looks as if the wing will settle so the root is firm on the table. If this is the case, then doing as I suggested will work just fine. The 5" height may be a bit aquward to work with and the last thing you want is things shifting halfway through a glue step.


In fact, using the 5" moified jig will give different results on the second side as you will have the washout built into the "down" side and it will not lay flat to the table like the first side did. Just use the stock jigs and hang one wing pannel off the table.

Don

I'm just a painter, what do I know, but it seems to me that since the jig is designed to build a certain amount of washout into the wing using a certain dihedral, wouldn't changing the dihedral by raising one side change the washout you got from that jig? Otherwise why jig both wings at one time so that they were an equal distance from the table top?

If his table isn't long enough, wouldn't it be better to measure the table top from the floor and let the other wing over hang that height plus the 2.5". Otherwords, if the table top is 36" above the floor, let one wing hang over the table 38.5" above the floor. Weight it down (pin it, clamp it, what ever) in the center so it didn't move and go for it. At least that way he could do one side at a time while the dihedral was correct. Then switch the wing and do the other side. I don't know, I think I'd probably find a floor and clear the dog off of it and use that instead. Then you could be sure. Just my thoughts.

For $30.00 or less, one can buy a hollow core door at the big box stores. I clamped a 36 x 80 inch door onto the top of my table saw. Now, I have a great, wide and lightweight (easily removable) work-table. I can leave it up all of the time, but if one could not do that, it would fit nicely behind a door and be available only when needed. Rich

p.s. I saw a sale on the doors over the weekend for under $20.00 . Scratch and dented doors might even be cheaper.

The dihedral if fixed by the diherral brace. At the point you using the jigs, the dhidral has been established. What you are doing is putting a twist into the wing so angle of attack decreases as you progress to the wing tip. The method used in this kit is basicly to give you one setup and let you put the top sheeting on without changing the setup. As you are working basicly using the root ribs pinned to the table and the tips raised, you are only working one pannel at a time. The relationship you are establishing is from the root rib to the tip, not tip to tip. The dihedral was established on page 30 of the manual. These jigs will not change it, but only put the twist in. If you could setup the jig correctly, you could accomplish this task with the wing vertical vs laying on table.

Don

I didnt' mean to elude to the dihedral changing by laying one wing flat while the other is elevated. I understand that the dihedral is what it is at this point. What I meant was that if the jig was built to provide the correct amount of washout with the wing placed on the table the way the plans show, and you change the way the wing is placed from the plans, in affect you change the dihedral in relation to the jig inadvertantly and without changing the jig, could it possibly change the amount of washout you build into it. Perhaps it would be insignificant since the other wing would be done in similar manor afterwards, but why chance it when there are other options?

Like I said, I'm a painter not an engineer. I just figured that if you change an angle of something you have jigged, then you most likely change other angles associated with that.

I'd still find an open floor (or other suitable surface) and use that if I didn't have a big enough table. That's why I'm a painter!

Paul

I am the friend that’s building the wing.
Campgems :

You are correct about the dihedral is set on the previous step with epoxy and 6 hard wood joiners it’s not going to change. The washout jigs are angled as to put a twist on the wing they don’t set or change the dihedral. If the root is pined to the table why should it make any difference if the wing is 1”. 3” or 5” from the table the washout angel will not change.

You just summed up what I was trying to get across. It's all relationship between the tip and the root. the height above the table doesn't matter. Keep it as short as possible to make the work eaiser.

Don