Blue Pearl 450

[Sandgroper]

Hi all,

the latest design to get my carbon fiber tube spar and fuselage treatment is this Pearl 450 powered by a OS15 buggy motor I converted for free flight a few years ago. I already had templates for the wing and tail sections from the Clarkson Trainer open power model and seeing as they were very similar to the original ribs I used them instead of making new ones, ditto for the dihedral keepers. The wingspan is 55.2" flat,the chord is 8.45" and the wing area is 466 sq inches. The spiral wound carbon fiber main spars are 12mm diameter and 0.5 mm thick,the fishing pole sections were 40mm short for my wing so I added 10mm diameter sections at the tips to make up the difference. The wing panels are all flat apart from 3/16" wash in on the right inboard,the engine has 1/8" left thrust measured at the prop nut and one degree of down thrust built in. The wing joiners are 2mm carbon fiber board faced with hard 5mm balsa sanded round to fit the tubes and then epoxied in. The tailplane is standard size but the Clarkson section is slightly thinner, it has a single 5mm diameter carbon spar and it is stiffer than the multi spar version I built for the Slow 520. The tail moment is slightly longer than standard at 22 inches. I was trying to make the model up to F1C weight so I used lots of spruce and heavier covering than I would normally use so I was quite happy when the total weight came out at 25.6 oz (730g) which gives me a little left for a tracker and electronic timer rc d/t setup if I ever want to make up the numbers in F1C.

Phil

[Scottl0413]

Phil, I have a question about the method used to put the holes in the wing/stab ribs? Could you let me know what method you used? Also I'm interested in the buggy engine conversion???

Thks, Scott

[Sandgroper]

Hi Scott,

I have tried a few different ways to drill the holes in the ribs but the best tool I have found are these cheap diamond coated hole saws from China. I pin and tape the ribs together, mark the hole using my rib template and stack drill as many ribs as the tool will handle. I use the slowest speed on my pedestal drill but I don't think the cutting speed is very important.
https://www.banggood.com/10pcs-5-22mm-Diamond-Hole-Saw-Drill-Bit-Set-Tile-Ceramic-Glass-Porcelain-Marble-Drill-Bits-p-1116959.html?rmmds=detail-top-buytogether&cur_warehouse=CN

The OS 15 CV-R(P)-T buggy motor was a limited edition engine with a turbo plug head insert and an alloy back plate instead of a pull starter. I cut the cooling fins off the head on a bandsaw first and then machined it into a clamp ring in the lathe.  The spinner assembly is off a MDS -UCTKAM 15  piped C/L speed engine, the Cox Conquest assemble fits OK but I found you need a OS 15 LA end float shim behind the prop driver to stop the bearings from being preloaded. I had to machine up an adapter to secure the spinner to the crank with a 3mm bolt and the stepped propnut is a modified OS part , I machined up the venturi myself and the needle valve is a Brodak unit.
If you do not have access to a lathe and want a little horsepower there is always the NOVAROSSI RFX15TV at US$219 already kitted up for FF. http://www.novarossidirect.com/RFX15TV_p_3273.html


Phil

[Sandgroper]

Here are a couple of construction shots.The fin was built as a "T" with the main three inch piece of balsa sheet going through a slot cut in the carbon tube first and the top rear section of fin added latter. To preserve structural integrity and avoid putting glued joints under stress it is best not to slot to the end of cf tubes because they spring apart. I found using bean tins and packets of jelly crystals to keep the pylon square and in line with the fin when I glued it on made the job easy.
The kitchen bench is the right height for my back but those square edges are very hard on the balsa so I can see why rolled edges on laminate are so popular

[Scottl0413]

Phil, thanks for the info. on the miniature hole saws and the Mod's you made to the O.S. buggy engine. I've already ordered the hole saws.

Thk, Scott

[Sandgroper]

I have found the handle section of the blue handled fishing poles I gave an e bay link to a while back are only black fiberglass and not carbon fiber as advertised,the tubes also have a heavy coat of black paint that is hard work to get off so this brand could be better, you need to buy two poles for left and right spars.
https://www.ebay.com.au/itm/2-7-7-2M-Ultra-Light-Carbon-Fiber-Fishing-Rod-Telescopic-Hand-Pole-Portable/263294675308?_trkparms=aid%3D222007%26algo%3DSIM.MBE%26ao%3D2%26asc%3D20140106155344%26meid%3Ddf34a58aca574d52b1e9cea35768a14b%26pid%3D100005%26rk%3D5%26rkt%3D6%26sd%3D332313580888&_trksid=p2047675.c100005.m1851