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Author Topic: Fibreglassing centre section - profile models  (Read 2029 times)

Offline Mike Quinn

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Fibreglassing centre section - profile models
« on: September 20, 2023, 09:28:59 AM »
Hi

Finally getting round to finishing my DickSarpolus Challenger after flying 3rd hand hand me downs.

On profile models like this and say Brodak Cardinal etc, would you recommend glassing the centre section for strength?  I used a suspended bell crank so not exactly per plan.  The bell crank is suspended between top and bottom 1/16 play plates that extend out 3 rib bays wach side so some strength there.  Would you still glass a strip  down the centre section?

Cheers

Mike
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Offline Steve Berry

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Re: Fibreglassing centre section - profile models
« Reply #1 on: September 20, 2023, 12:34:08 PM »
Yes, that would be a tremendous way to add strength without much of a weight penalty. If you can afford the weight, do 2 layers with one a 45° bias.

Steve

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Online Ken Culbertson

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Re: Fibreglassing centre section - profile models
« Reply #2 on: September 20, 2023, 06:05:51 PM »
Quote from: Mike Quinn on September 20, 2023, 09:28:59 AM
Hi

Finally getting round to finishing my DickSarpolus Challenger after flying 3rd hand hand me downs.

On profile models like this and say Brodak Cardinal etc, would you recommend glassing the centre section for strength?  I used a suspended bell crank so not exactly per plan.  The bell crank is suspended between top and bottom 1/16 play plates that extend out 3 rib bays wach side so some strength there.  Would you still glass a strip  down the centre section?

Cheers

Mike
If the 1/16" caps are glued to the center section planking, then I see no need to glass the entire center section.  I am old school and still double plank the center section.   I glue the wing in balsa to balsa then put a 1" strip of glass around the LE back to just past the bellcrank.  I had a Cardinal wing on a profile a couple of years back and had zero issues.  I am also a fan of very large balsa fillets for the wing joint.

Ken
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Offline Dwayne Donnelly

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Re: Fibreglassing centre section - profile models
« Reply #3 on: September 21, 2023, 07:22:51 AM »
Not 100% necessary but certainly can't hurt and if it gives you peace of mind go for it.  :) 
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Online Dan McEntee

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Re: Fibreglassing centre section - profile models
« Reply #4 on: September 21, 2023, 01:42:17 PM »
  The Challenger wing is essentially a SIG Chipmunk wing and I think he spells that out in the construction article. It's a pretty large wing and plenty strong. The Challenger has a lot of fuselage area, and in a profile that can add a lot of weight. I would get the fuselage built and see where things weigh. Most of these that I have seen guys build and required nose weight, so if you can plan and build a built up profile fuselage that can help you keep the tail light, that will help a lot. I don't feel that glass is necessary for this model but if you decide to glass it, use the lightest that you can find and apply the resin as thing as possible to help keep weight under control.
  Type at you later,
    Dan McEntee
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Offline Mike Quinn

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Re: Fibreglassing centre section - profile models
« Reply #5 on: October 02, 2023, 03:35:56 PM »
Hi

Well i applied some lightweight glass cloth as it only added about 5g.  Nearly there.  Wings covered in Oracover.  Fuselage is glassed and primed.  Will spray in matching Oracolor.  Will be pretty yellow 🤣 but using up what I have from a glass fuse/Oracolor and Oracover wing F3A Pattern model I’m completing.  Price of things these days can’t afford to not use left overs!  Fortunately Oracolor and Klasskote spray OK onto Oracover so should be able to add some trim colours similar to the original Dick Sarpolus Challenger pics I have. 

Weight should come out at around 52oz for 570ish square inches with an OS 46LA.  I reckon I could have built lighter but didnt want to use my 4-6Ib stash on a model that might not last very long given my current abilities at CL.

Cheers

Mike
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Offline Dwayne Donnelly

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Re: Fibreglassing centre section - profile models
« Reply #6 on: October 03, 2023, 06:20:35 AM »
 Looking good, I've built 3 so far, really like they way they fly.
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Offline Mike Quinn

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Re: Fibreglassing centre section - profile models
« Reply #7 on: October 03, 2023, 07:00:50 AM »
Hello Dwayne

Been I while since we talked about this model.  It ended up on the back burner whilst I was learning on some hand me downs.  I figure I’m safe enough to fly my own model model now (badly 🤣).  How much do your models weigh?

Cheers

 Mike
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Online Ken Culbertson

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Re: Fibreglassing centre section - profile models
« Reply #8 on: October 03, 2023, 08:22:26 AM »
Quote from: Mike Quinn on October 03, 2023, 07:00:50 AM
How much do your models weigh?
With modern power I have found a good range rule of thumb - Wing area / 12 to wing area / 10.  That would be a range of 47 to 51 for your plane.  The OS46 is a powerful engine but not as powerful as it's modern counterparts or electric so try for the lower end.  Personally I fly on the upper end of that scale.  I like line tension and wind penetration but that is 100% a personal thing.

Ken
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Offline Mike Quinn

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Re: Fibreglassing centre section - profile models
« Reply #9 on: October 03, 2023, 10:09:02 AM »
Quote from: Ken Culbertson on October 03, 2023, 08:22:26 AM
With modern power I have found a good range rule of thumb - Wing area / 12 to wing area / 10.  That would be a range of 47 to 51 for your plane.  The OS46 is a powerful engine but not as powerful as it's modern counterparts or electric so try for the lower end.  Personally I fly on the upper end of that scale.  I like line tension and wind penetration but that is 100% a personal thing.

Ken

Hi Ken

I guess it will be good with the OS 46 LA
In general though, what would be a modern counterpart IC wise to a 46 LA.
I mean CL wise.  I’ve got OS 46/55 SFs, FXs, AXs but they are all RC motors per se.

Stalker 46?

Thanks

Mike
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Offline Dwayne Donnelly

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Re: Fibreglassing centre section - profile models
« Reply #10 on: October 03, 2023, 11:34:50 AM »
Quote from: Mike Quinn on October 03, 2023, 07:00:50 AM
Hello Dwayne

Been I while since we talked about this model.  It ended up on the back burner whilst I was learning on some hand me downs.  I figure I’m safe enough to fly my own model model now (badly 🤣).  How much do your models weigh?

Cheers

 Mike

Hi Mike, sorry it's bean so long I didn't realize who was posting..lol Good to hear from you so glad you're finishing her, all mine were powered with LA 46's at around 46-47 oz.
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Offline Mike Quinn

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Re: Fibreglassing centre section - profile models
« Reply #11 on: October 03, 2023, 11:45:29 AM »
Hi Dwayne

Just looked through my messqges.  Some good info from you there.  Thanks.  Mike 😀
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Online Ken Culbertson

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Re: Fibreglassing centre section - profile models
« Reply #12 on: October 03, 2023, 12:54:39 PM »
Quote from: Mike Quinn on October 03, 2023, 10:09:02 AM
Hi Ken

I guess it will be good with the OS 46 LA
In general though, what would be a modern counterpart IC wise to a 46 LA.
I mean CL wise.  I’ve got OS 46/55 SFs, FXs, AXs but they are all RC motors per se.

Stalker 46?

Thanks

Mike
I am far from an expert on IC motors but most of the piped engines in the 40 class are going to outperform the 46LA, and, they would be far more than you need.  The only one in that group that you mentioned is the 46FX.  It runs well for stunt but it is just too much for what you have and pretty heavy.  To give you reference, I had a 58oz profile 675 sq" wing that I flew for years on my 46LA.  5.4 laps with a solid fast 4, never went 2 cycle.  I had originally bult the plane for the FX and I had mounting holes for it so one day I tried it.  4.2 was as slow as I could get it to go on 63' lines.  Hell of a motor though.

Ken
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Offline Colin McRae

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Re: Fibreglassing centre section - profile models
« Reply #13 on: November 24, 2023, 06:37:52 PM »
Just my 2 cents but you might consider an Evolution 36 NT. I run one on a Brodak P40 and it runs as well as any OS LA I have used. Power will be equal to or better than a 46LA. Plus, it is a bit lighter. The EVO 36 is a higher compression engine (compared to the OS LA's) and with a BB supported crank.
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Offline Paul Smith

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Re: Fibreglassing centre section - profile models
« Reply #14 on: November 26, 2023, 10:06:16 AM »
On my last build I fiberglassed the center section using lightweight cloth and 30-minute epoxy.  I glued the wing to the body with same epoxy, thereby making a rock solid bond.

I trusted the 'glass and saved a little weight on the structure, thereby making the weight difference nil or maybe a savings with a gain strength.
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Offline Mike Griffin

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Re: Fibreglassing centre section - profile models
« Reply #15 on: November 28, 2023, 06:31:34 PM »
Mike, this tip would not apply to this build because it looks like you used Mono or Ultracote to cover with, but if you ever use Polyspan, overlap the center sheeting so you have a double layer in that area.  It adds a lot of strength.  I picked this up from Tom Morris.

Mike
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