|Feb 21, 2009, 06:54 AM|
glass n glue vs roofing cloth
gotboosted . .
With one of these mixed material wings (EPP LE and White Foam main structure) you need to be careful of your choice of glues.
Spray 90 works great on EPP BUT does not play nice with the white foam, for this build you would need to use Spray 77 exactly the same way you used your spray 90.
It takes a few more days to cure to the point that Spray 90 does and yields a little more flexibility than the spray 90 from what I have found so far.
If you read the 48" MCW build you can see the technique I used and the weights before and after the drying process.
the spray 90 and Henry's 183 is bullet proof for all intensive purposes but it is heavy, almost 3X - compared to the glass cloth and wbpu and you still have to cover it with monocoat or other materials, cloth and wbpu can be painted with many of the household sprays.
You are correct, the glass cloth and WPBU does tend to be far more brittle than the Henry's 183 with spray 90 and does not render the plane indstructible...my observation is that from a normal flying perspective, it provides plently of strength for the everyday flying folks, although I would use .75 cloth the next time (the .56 cloth is expensive in relation to the readily available .75oz cloth and gives a little more substance, those flying this as a slope flyer or looking for a little more emat can easily up to 1.5oz cloth with little change as the WPBU fills nicely and will stick it far easier than the old epoxy method . . .
those looking for a far more durable method can always shift to my favorite finish of years gone by -- Bob Smith or Sig "finish cure" epoxy with 1 oz cloth. This is probably on par with the weight of the Henry's 183 and spray 77/90 but you do not need to cover it, just sand lightly and paint.
but then again, you have to ask yourself what you want from the build...
On the mid motor beta, I am shooting for a strong air frame with light wing load ... lots of power but mid speed range.
With the 8X8 prop and the AXI I am shooting for somewhere in the 70-80 mph range on a 3s 2100 mah 20- 30C pack.
On the rear motor set up (more or less confirming the alpha build with the mods discussed and original motor choice) I am shooting for a higher speed model that will be abused by the loads and speed, hence the choice of the kellys and spray 77.
I love the Rite way .. This will be the 5th plane I have built using the Henry's 183 and spray method and love everything but the messyness and stench of the Spray glues..reminds me of polyester resin... To give you an idea of "beater ability of this method I offer this . . .I accidentally shut my 48 MCW in the car with the wing sticking out about 10" . .(trying to chase the kids into the car and not paying attention to the task at hand!) I shut the door firmly and the door pushed the wing across my front seat and wedged it between the door and the steering wheel bending both tips up on 15 and 30 degree angles outside of the spar ends.
I really thought I was done . . no more 48!
I took the plane home, got out my heatgun and began to slowly warm the tips while rubbing them back in place. I kept them warm . . not hot!
When I was finished getting them back into place, I let it sit overnight. They stayed where they were and all I needed to do was take the wrinkles out of the ultracoat to finish the job!
I was amazed ...and sold on this building method!
No matter how sold I was, there are some applications that it just does not fit, especially when you want something that will be light and strong. For this, there is nothing that fits better and easier than the cloth and WPBU.
I can monocoat a tennis ball if I need to (thanks to many reads of Jeff troy's covering and finish books) but I really would prefer not to - esp over the foam ..just me but . .. I just have never really been happy with the results.
After flying the heck out of the Alpha build of the starfire, I found the cloth and WBPU to be increadibly resiliant to all but the last crash . .and I really could not have expected either method to have stood up to that hit! The hit was at full power from 100' up and straight in . . .like a lawn dart...
The upside to the cloth/wbpu method is that you can see what you have and access cracks and stress spots with some gorilla glue or if they are deep, you can rub thinned epoxy in there and place a light patch of glass cloth over it . .sand and go fly!..
The spray 77 method with Henry's 183 would have yielded a bag of foam flakes aft of the epp, I do not believe it would have been as repairable as the alpha build has ended up being..Yes it cracked, but it only tore a short distance. The cloth stopped the progression.
The one change I may make this time is to place an oval shaped piece over the motor and prop cut out to add a litte more meat to the area to resist the vibration and torque of the mount. I found that after a few days of flying with the flight testing (many hits until we found the correct CG), anywhere there was a 90 degree cut out, there was some stress cracking. Simply adding a little extra cloth over these areas would prevent this as well as making cut outs with a slight radius to spread the loads and sheer.
I think the WPBU yields a pretty finish and opens the door to the ability to paint rather than going nuts cutting out monocoat trim sheets. I prersonally like the painting so . .. .one to be covered and one to be painted!
|Feb 21, 2009, 07:36 AM|
pics no words
sorry for the delay in this build as well as the pics with no explanations.
Have had a slew of computer problems over the past few weeks and had to upload my camera from my wife's computer . . .text to come in the next few days . .
|Mar 08, 2009, 09:28 AM|
beta one motor mounting
the only change between pics and actual was:
motor mounting material made 3/8 X 3/8 from sheet of 6X12 aircraft grade ply
notch cut to go over spar DOES NOT have a complete loop around the spar, I was worried about the impact pushing or pulling the mount and crushing the CF spar (I used ultra light 6mm tubes for this build) I notched the rear out and gave the spar 1/32 clearance on the front and top . . mount is well supported in wing and should not shift . . but not willing to take that chance!
|Mar 08, 2009, 09:45 AM|
short sheeted in the servo lead department
short sheeted in the servo lead department!
The servo leads on all servos are just too short to fit the design, so a little fix is required.
I picked up servo wire from my local hobby shop, soldering it onto the original lead. This gives me any length. You can place small heat shrink over the solder joints and gently press them into the slot but remember that you will need to slightly enlarge the servo wire trench where the joint sits.
You need to make usre you use the lightest amount of solder on these wires. Too much solder (huge blobs) seem to cause interference.
If you feel uncomfortable soldering. You can also purchase extension cables that will bring you to the receiver trench. remember that you need quite a large slot to accommodate the connecting plugs. It is fine to use these.
I have heard some say that you need to use a choke on an extension longer than 24", I have not found this with my soldered extensions up to 30" long but I may start looking in this direction with anything longer than these..we are only looking at about an 20" stretch here so . . .
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