motortommy

Yes that`s also my thinking. I´d love to buy from the factory (spar $195) but packing & freight add another $1420 Plus the risk that something stupid could happen during the long journey...
@Manu: Thanks! will check ULM Tech   

might be an option, but to be honest I like to go `genuine factory` with my rebuild. I have already a sleeve I want to get rid of...
 

Hi Skelly,
I´m in need of only one for a mk4, means without extruded stiffener...
Thanks.
 

So was it worth the effort? Yes and No!

For the spent money (materials, tools, …) I could have bought likely a set of factory tips, including horrific transatlantic shipping cost. Further it took me roughly 3 months (sure not fulltime) from scratch to finished part, but:

-        my wingtips were in desolate condition, badly repaired and way too heavy (left 2.3kgs/right 2.7kgs)

-        even the modern style tips I borrowed still weighed 1.5/1.7kgs

-        my new parts weigh 1.5 per set, means only by replacing the tips I saved 3.5kgs including preferred new look for free!  

-        I wanted to try, if I´m still able and willing to work with fiberglass (after having 25years break) as my planning is to touch seatpan, cowling, wingtanks, panel,… as well

Finally after tearing the whole plane down for months finding more and more issues I didn`t like, it was mentally important to create something gaining strength to proceed with the project. These wingtips were the first new homemade parts I made for my plane…

OMG it´s difficult to express…hope you get my point.

Thanks for reading!

Part4
vacuum process was successful! 
honeycomb bonds perfect w/o bubbles or unglued spots. Next was some grinding to get a nice fit and smooth transitions...

 
...test fitting the molds together to check fot both clearance an space for glue. The honeycomb offers a nice surface for a strong bond.

Then again into the vacuum bag after the inner top layer was applied. coffeetime!

 
Now the sandwich is ready, including both inner and outer layers enclosing the honeycomb. Cutting protrusions and preparing for bonding. 

 
Finally the halves were glued together using additional 1" reinforcing tape covering seam and edges. Now it`s getting hot! Both wingtips, still in their molds went into a heated box for tempering the epoxy resin for about 8 hours @ 75 deg. C.
l
 
Exciting moment. Final demolding! No trouble, no damage! YES!!!  

 
Even slightly better than calculated. Final part is 730grams means 1.6lbs?! Further only 40grams variation between left and right part. That is marginal for homemade handcrafted production

 
 
Finished part, ready for paint preparation

End of story 

Part3

So after cleaning the molds were polished and coated carefully several times using release agent. Finally first parts were made. I decided to go with a sandwich construction consisting of only 3 very thin layers of fiberglass enclosing an aramide honeycomb core. Each wingtip is made up of two halves which were glued together later using a reinforcement tape.

 Some may ask why no carbon fiber?
I wanted to have both lightweight but also robust wingtips. To achieve this with pure carbon layup, more layers soaking lots of resin (=weight) would be needed. Pricy and IMHO no advantage here.

 Further, I wanted to try a sandwich construction using vacuum technique anyway in view of future components like cowling, seatpan, etc., I`m planning to do. 



All four waxed molds have gelcoat and first layer of 80gram on - let it set.

 If proceed w/o wait following vacuum pressing would cause imprint on top surface… 
 

Next is matching/cutting the honeycomb core. Nice material easy to work with, though expensive. The uncovered area will later touch the aluminum stripe attached to the outer rib.

 

Honeycomb is glued in a wet bed of an underneath additional 80gram layer. Covered by perforated film (blue) absorber fleece (white) and a peel ply stripe. Afterwards the package was carefully put into a poly bag. A vacuum pump will soak excess resin through the foil into the absorber. Less resin means less weight!

 

Pump is working at least until resin has set (better 5h). Check for leaks!

Time for beer or coffee!

 
To be continued…

John. Thanks! I immediate saved your .pdf via Facebook. I also spent nights studying cub-style landing gear. As both commercial options (groove and cabane gear) are out of scope, I probably also will end up making my own...Thanks again for your time creating the file.
Question regarding the bungee. Is your planing to go with the wraps? What about using fabricated rings? Both options: How to determine correct force/tension?

Part2

See how the black resin molding compound faded more and more as the fiberglass layup builds. I decided to make a strong mold which also can handle tempering. Maybe overkill, but I need to make at least 2 sets



Exciting moment. Will the top half release? Original part unscathed? As with 2-piece molds it is better not to demold until finish both halves, I could not withstand to ckeck. If something would have gone wrong only one surface would be damaged…



As everything turned out as expected, I continued. Lower half (removed parting) and certainly opposite wingtip.



Almost ready. Some trimming and bolts to secure alignment added. No need for ground board anymore...



Finished mold righthand, white is original wingtip (still with insert)

stains are residues of release agent, I forgot to remove before photoshoot



 
Next. Let`s make parts…

To be continued…

Jim. I followed your rebuild closely. Lots of valuable input there. Thanks!