Quoted from ulbuilder

Drill a .040 hole near the end of the SHCS so you can install a washer and cotter pin. This ensures the head of the SHCS can slip through the bracket only when you allow it.  

Ulbuilder, Thanks for the tip. Though I guess the original design should work well,  I too felt a little uncomfortable while looking at the root / tip hinge. This cotter pin idea is great. I will see if I can drill a neat hole. If I cannot handle that without messing up the SHCS, alternatively I was thinking of making slightly wider bushings ( 5/16 instead of 3/16) for tip and root, so the SHCS head sticks out farther outwards from the steel strap ( bearing bracket). I wonder if there is adequate clearance of fuselage from wing root to take this added 1/8 protrusion.

Edit: I meant longer bushings ( not wider bushings )

On my airplane the SHCS barely clears the fuselage fabric at the root.

I also got slightly longer drilled head bolts that hold the brackets to the wing.
This way I can safety wire them and the bolts the plans say to use are actually too short.
https://ulbuilder.wordpress.com/2016/10/25/bolt-length/

I just ordered  '1/4"-28 x 2" (PT) Fine Thread Socket Head Cap Screw (Alloy Steel Black Oxide) Pk of 25(MOQ) from ASMC Industrial. I could not locate it at Aircraft Spruce or Wicks aircraft. This cost me $10.55 with free shipping. Let me check for quality after I receive it, because obviously this is industrial hardware.

IMHO, if they can hold industrial machinery together they will have no problem holding your stick and fabric aileron in place.

Picture of drilled SHCS with cotter pin:
http://www.lonesomebuzzards.co.....ron+bolt+drill/#num2

As you can see the hole for the pin needs to be very close to the edge. The only tricky part to drilling it is to line up the bolt so the drill bit is perpendicular to the inside flat part of the SHCS.

This:
===(|==|)===>
Not this (unless you enjoy breaking drill bits):
===(\==\)===>

Quoted from Keith103

I just ordered  '1/4"-28 x 2" (PT) Fine Thread Socket Head Cap Screw (Alloy Steel Black Oxide) Pk of 25(MOQ) from ASMC Industrial. I could not locate it at Aircraft Spruce or Wicks aircraft. This cost me $10.55 with free shipping. Let me check for quality after I receive it, because obviously this is industrial hardware.

There you go....you can still lose 1 of the bolts in the package and still have enough to build 5 more MiniMAXs    ulbuilder is right, in my opinion. The bolts should be just fine. They're probably just like the bolts that are holding the ailerons on most of the other 1000's of MiniMAXs out there. In reality, all they're doing is holding the busings in place on which the ailerons pivot. I takes a lot of force to shear off a 1/4" bolt. #370# per bolt according to this chart, and that's on a Grade 2 bolt.  http://dodgeram.org/tech/specs/bolts/SAE_bolt_strength.html

Lynn

UlBuilder and Lynn, Thanks for sharing your valuable insight.

I have a question on building the spar, about gluing the spar frame on to the spar web. I saw an earlier post about how after the glue dried up, a builder's spar frame did not contact the spar web at all points, and he had to build a new spar. ( Not sure if it was on this forum or else where. )

Any suggestions on how to ensure good, uniform  contact between the spar caps and spar web along the full length of the spar ?

I am deciding between one of the options below while the glue cures.

   1. Spar web below, spar frame on top of that and a cover ply sheet on the frame  and then distributed weight on top.

   2. Same as 1 above, except the web is above frame.

   3. Same as 1 or 2, but web is stapled to frame at 2 or 3 inch intervals, and then weight placed on top.

   or some other combination.



My table top is reasonably straight / level,  and will not by itself create pockets of non contact.

Thanks

I used staples, the downside is removing the staples once the epoxy is dry.

Lots of clamps.  You can always use clamps.

Tom

Staple the web on top of the spar caps every 1-2 inches, 2-3 inch spacing is too much in my opinion.  This prevents using too much clamping pressure with weights or clamps.  Butter both surfaces to be joined with glue to prevent dry spots. Leave the staples in if you want.  Once stapled, you can move the spar all you want to clean up glue squeeze out or clear the work surface for the next assembly, not true with weights.

Tom, mine is a non-standard work bench, the ply edges stick out from the stud frame by 5 inches along the length on either side.  I used to clamp one edge of the piece to be glued, along the edge of my work table, but there was no way to clamp the other edge. ( pic below )

I can elevate the spar itself by 6 inches on the work bench for wiggle room for the clamps on either side. But elevating the spar and not having the table surface to support it to make sure it is straight in one plane, is also a challenge. That may lead to warp along the spar, unless I make sure the spar itself is exactly in one plane. Does anyone have a picture of how they clamped the spar?

Ulbuilder, thanks. I was keeping the stapling method as one option.

Quoted from Bob Daly

Staple the web on top of the spar caps every 1-2 inches, 2-3 inch spacing is too much in my opinion.  This prevents using too much clamping pressure with weights or clamps.  Butter both surfaces to be joined with glue to prevent dry spots. Leave the staples in if you want.  Once stapled, you can move the spar all you want to clean up glue squeeze out, not true with weights.

Thanks Bob, copied.
I am leaning towards just stapling the whole length about every 2 inches. I think the construction manual has left this procedure slightly hazy.

I stapled the web to the structure when I built my MiniMAX spars. Staple spacing was about 2", I'd suppose. I glued web to structure in the same jig I used to make sure the structure (ladder?) was straight and flat when I built it, to make sure the spar had no bow or twist built in.

When I recently did another set of spars for a RW-2 Special biplane, I decided to use weights so I didn't have to pull all of those staples. Personally, I wouldn't even think of leaving the staples in. I borrowed about 2 dozen bricks from a bricklayer friend of mine and used them for the weights along the spar caps. I glued up each ~48" wide web section strip and let it cure before doing the next one. I placed a few staples on the intercoastals to hold the web in place and used a relatively thin, narrow strip of wood directly over the spar caps, and on top of the spar web plywood, to evenly spread out the weight of the bricks on top of that strip. The glue "squeeze out" on the inside corners was a nice fillet, and the outer edge I trimmed with a laminate cutter on my router table.

Lots of ways to do things, I suppose, and that's how I did mine.

Lynn  

"Personally, I wouldn't even think of leaving the staples in."

People say this all the time.  I have no idea why.  I suppose it has to do with corrosion of the staples.  Or the weight of the staples.  Regarding the weight, a box of 1000 staples weighs about 3 oz. I think I used 3 boxes so that's about a half-pound of staples or 0.2% of the empty weight of my plane. As for corrosion, it needs air and water, same as rot, so I varnished.  Metal embedded in wood with a moisture content less than 15% (atmospheric relative humidity <75%) will not corrode. Kept dry, wood and wood-embedded fasteners can last for centuries.  But let's imagine the staples corroded nevertheless, so what?  The epoxy is still there, holding the plane together.  Corrosion of the metal staples will degrade the immediate surrounding wood slightly because the process produces a tiny amount of acid.  

But pulling staples is not that much extra work either.  I pulled those that would come in contact with fabric.

Keith,

I'm about to build another jig.  This time for ribs for the "Epic Sport".  I'm just waiting for answers to a couple of questions I've asked David about.  Depending on what one is building if you want to clamp everything you can either set the jig on uniform depth blocks to allow the clamps to reach both sides or, if appropriate to the particular operation and type of clamps, the actual table top can be made of strips so that there is always a gap you can put a clamp through.  Of course as Bob Daly says, it isn't that hard to pull staples.

Tom

Bob....I have the utmost respect for your insight and would merely point out that you mentioned all of the reasons I would not leave staples in.

1) They aren't that hard to remove.
2) There is a potential downside of corrosion follows a staple into the wood. Potential, probably minimal, but it is a possiblility.
3) Extra weight.....yes, VERY minimal, but never the less the weight is some tiny part of the total, and it all adds up. People are weight conscious for various reasons I suppose. Legal requirements, performance, pride, and there's probably more.....some fickle, perhaps, but they are personal reasons.
4) Appearance. To some the appearance of staples left in is not an issue, much less when it's hidden from view on the finished plane. To others, including myself, a staple left in gives the appearance of a job partially completed.

So, I would submit that there may not be a single justified reason that staples should be removed or need not be removed, to me personally the sum of the reasons to remove them outweighs the time and effort to remove them.

Sorry for my un-solicited epistle, so I'll now go back under my rock  

Lynn

Tom, Yes that is a possibility, of removing the table top temporarily or moving it to one side and working with a narrow plywood strip of 12 ft length and  9 inches width. That will give clamping room on both sides. Let me figure which is easier - whether pulling all those staples or making a temporary table top strip.

Lynn, thanks for your thoughts. For placing weight while gluing the tip ribs , I just stole Bigbrixx Brian's idea of deploying gallon paint cans which I have plenty lying around. Unfortunately some of them are not full, so alternatively I am also using gallon milk cans filled with water. These work great too, except that these plastic jugs are very thin walled, so can easily be punctured by any of the sharp tools lying around, possibly causing a deluge. Not wanting to make a sea-plane, at least not yet, I am a bit attentive while moving these about.

Yes it is going got be some tedious work pulling a little more than 1000 staples ( at 8 to 9 staples per running foot ), but I really have no choice not to pull them,  since I am trying to make Pt 103.

Also if I go stapling, I thought it may be better to start at the center of the spar and proceed towards the tips, so the spar web is fully stretched out and taut.

Thanks again

As I am just making my front spar, a question that I have is,
how do I make sure the spars align correctly with the attachment points inside the fuselage.
If everything is measured correctly and made per plans, they ought to line up for sure,
but is there any way to know this ahead ? I have not attached the
carry through bracket on the spar so there is still some scope for minor adjustment
to make the spars align exactly on to the fuselage receiving points.
The distance between spars is dictated by the rib which is already made,
and this is 27 and 7/16 inches on my ribs. I guess this should match
with the distance between the stations on the fuselage where they go in.
It looks like this is not a very critical aspect, but since there was a mention
on another thread by Bill that his wings are a tight fit, I got thinking about it.

The final adjustment for that distance is made by position of the front aluminum carry through channel , it is described later on in the rigging instructions.  

George, That surely helps. Appreciate your response.

This cross section is of an RS-9 piece that came with the kit. I used it for one of the vertical members in the spar. There was no other visual defect or knots etc. (The grain pattern looks like the EKG of the spruce tree.). Seriously, I hope it is not a defect in the wood.

The end grain shown here does not indicate a defect.

Tom

Thanks, Tom.  
The page below gives some information on this type of grain formation ( indented grain), but I was not sure about the strength characteristics.

http://www.hobbithouseinc.com/personal/woodpics/_indented_and_bearclaw.htm

I found measuring 3 degrees dihedral on the spar build, a little tricky.
So here is an alternate way to mark out 3 degrees without using a protractor.
Correct me if the calculation is flawed.

I have a question about the spar webs:  The Max 103 kit from Team has the front spar web stock, cut so as to butt joint at 2 places, but the rear spar webs are cut, so as to scarf joint at 2 places. The construction manual just states that the spar webs are to be butt jointed.

Does any one recollect having scarf-jointed the rear spar web ? Mine is a very old kit, so I am using new ply wood stock from ACS for the front spar, but plan to use the old kit stock for the rear spar web.

Thanks

My kit and manual both spars are butt joint.
Got my kit in 2014

I built fro scratch and unless I missed something in the build manual, I just did butt joints at the 3/4" X 3/4" (RS-9?) intercoastals of the spar "ladder". I'd imagine scarf joints would be stronger, if done well, but probably not worth the extra effort, given the application....but that's just my opinion. If you make use of the parts that are already cut for the scarf joint (and I think you said you weren't) I'd still do the overlap at the larger intercoastals.

Lynn

ULBuilder, My kit is of 1997 vintage ( see image below ). Sl # is 975.

The manual clearly says to butt joint the web for both spars, but they sent out the scarfed pre-cut plywood only for the rear spar web. Probably may have been an experiment at that time to see if spar webs should be scarf jointed. Hard to know for sure after so many years.

Thanks for the clarification.

Lynn, Appreciate your help. I will check to see if the scarf joints align with the thicker vertical stock (RS-9). If not, I will simply use new plywood and butt joint them at the 3/4 inch verticals.