Laser cutting change

[Mike Griffin]

Today I called Eric Rule to cut one of my Shark 35 profile kits.  The profile fuselage is cut from two pieces of 1/4" X 4" that is laminated together by the builder to form your 1/2" wide fuselage....Normally up until now.  Because of the shortage of 4" wide boards, Eric is having to cut the profile out of 3" stock and this means there has to be joints vertically whereas when we had 4" wide material this was not necessary.  We are joining these pieces in a staggered configuration so a stress riser is not created. 

This is the first adjustment that is being made due to shortages, and it looks like more adjustments will coming down the road.

Mike

[ericrule]

Mike is correct.

There is a real problem obtaining contest grade balsa in 4" wide boards. This is caused by the worldwide demand for balsa caused by the makers of wind turbine blades switching from foam centers to balsa centers. Because of this increased demand the balsa growers have stripped the forests near the shores of balsa. They are being forced to go further into the bush for trees. In addition to this they are harvesting trees before they achieve decent growth. This has resulted in less and less 4" wide stock available.

It is of some concern that I have seen a number of balsa wholesalers starting to change their definitions for contest balsa from a 6 pound maximum weight to 7 pound. In addition to this I have been informed by my major balsa suppliers that we can anticipate increased prices for contest balsa in the very near future. Since the last major price increase in 2009 saw a jump of 40% for contest balsa all I can say is that we have been purchasing as much balsa as we can afford and stocking it so that we can maintain our current kit pricing as long as possible.

Since RSM currently produces over 91 kits and most of them use 4" wide balsa for fuselage sides we are being forced to modify almost all of our kit laser cut files. Where 4" fuselage sides were used we are being forced to modify the parts to allow 3" balsa sheets to be used. This makes us create a glue joint in the fuselage side. Since glue joints can be weak points and subject to failure due to flight stresses we also have to create notches in the formers of all of the built up models to allow for a balsa strip to be laid behind the new glue joint in order to provide additional strength in that area. For profiles where  we use two 1/4" balsa laminations we need to create glue joints that do not mirror each other. This means we have to set glue joints apart. Needless to say this is a very large job and will require untold hours of AutoCAD time to make the changes.

[Howard Rush]

Why not glue sheets together yourself, then cut the parts?

[Fredvon4]

LASER cutting does NOT like glue joints

Mike Pratt does a good job of this issue for his Profile fuselages

Personally I think 4 to 5 inch wide stock can be sourced and NOT worry about hardness or density

A profile fuselage is less than half the volume or weight of a 35"~60" in airplane

and a tall Profile Fuselage has a LOT of area to reduce weight by coring and filling

....I might consider the heavier and more dense 36 X 4 or 5 Inch blanks may actually be a benefit in a 1/2 to 3/4 inch fuse.....Miky Pratt and others have very well designed stiff PROFILE techniques....

so lack of 36 x 3 (or 4") x 1/2 light balsa...MEH...grin

[Howard Rush]

LASER cutting does NOT like glue joints

Contentious person that I am, I would like to go to my shop and try lasering some, but I’m laid up with a new knee, boo hoo. 

[john e. holliday]

Well at least you have a doctor that will/or did take care of your knee.   Mine just gives me pain pills and says it is artritous.