Airframe's Mid BEC LMP
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Author:  airframefixer [ January 15, 2017, 4:20 pm ]
Post subject:  Re: Airframe's Mid BEC LMP

GonzoRacer wrote:
a.moore wrote:
Where do you get your foam?
It is delivered directly to him by a Heavenly Host of Angels... Well, OK, I don't really know, but it wouldn't surprise me if that were true... :mrgreen:

Thanks guys.

We have a local fiberglass supply in town I source from. Divinycell is a specific composite product so chances are you won't find it in any other type of store. A marine supply store may be worth a look too.


Author:  Warren Nethercote [ January 15, 2017, 9:22 pm ]
Post subject:  Re: Airframe's Mid BEC LMP

Aircraft Spruce also stocks Divinycel foam.

Author:  airframefixer [ February 23, 2017, 11:20 am ]
Post subject:  Re: Airframe's Mid BEC LMP

Warren Nethercote wrote:
Aircraft Spruce also stocks Divinycel foam.

Yes they do and also honeycomb but only in narrow thickness... Aircraft spruce is a problem for me.. I suffer from "Well Im paying for shipping anyway, might as well stock up"... it gets expensive.

No more excuses for slow progress.. Its just life happening, but here's what I am doing..

Originally the radiator intake was going to be composite due to the angles and compound curves desired for flow. I'm avoiding fiberglass work until the weather improves but I want to move on. Thought about a sheet metal intake from thin aluminum but I didn't want to make it from my dwindling supply of sheet stock 2024-t3.. Its expense and no one has any surplus around here.. that I can find.. I don't like solid riveting 6061-t6 as it deforms during the riveting process unless you can squeeze every rivet...."Hey wait a minute, I just bought a TIG welder and I have a few large pieces of 5052, Ill just make it from that".... Well I made two. The first one warped the mounting flange as I was butt welding on one of the last flanges... aluminum really expands when welding.. that one got punted out of the shop into a snow bank in frustration.. I've been through 2 design changes and 2 material changes this should be that hard.

Onto version two.. went even thinner on the material which I ended up buying. simple and see it to be effective. I may end up adding some vanes to better direct airflow. in the end.. This radiator is more than double the size of the bike radiator so there is excess cooling capacity built into the system.. I may modify the exit if it proves inadequate.

The mounting flange will be riveted to the lower metal sidepod wall and the shroud/intake will be bolted/screwed to that. The flange was made from some surplus 7075-t651 bulbed extrusion. It was pretty oxidized with some minor filiform corrosion.. cleanup and primed.. This aluminum is hard like steel and you'd think your drilling butter when you drill some 6061-t6 after drilling 7075.. neat stuff but prone to corrosion.. not need to prime the 5052.. its pretty corrosion resistant.

Pics and grammar/spelling correction to follow.

Author:  airframefixer [ February 23, 2017, 11:51 am ]
Post subject:  Re: Airframe's Mid BEC LMP


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Author:  airframefixer [ February 23, 2017, 11:57 am ]
Post subject:  Re: Airframe's Mid BEC LMP


Overall I think its kinda fugs, I might make a new one later, a wider bending brake would help too.


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Author:  ckouba [ February 23, 2017, 2:47 pm ]
Post subject:  Re: Airframe's Mid BEC LMP

airframefixer wrote:
Overall I think its kinda fugs,

I know a few people who would be happy to call that theirs. I'll say nice work!

Author:  airframefixer [ February 24, 2017, 11:51 am ]
Post subject:  Re: Airframe's Mid BEC LMP

ckouba wrote:
airframefixer wrote:
Overall I think its kinda fugs,

I know a few people who would be happy to call that theirs. I'll say nice work!

Thank you you but I should clarify, I don't admire my design on this one, but I can see now that making negative commentary on my work whether design or fabrication doesn't contribute to the spirit of the forum.

On to building. Mirror mounts.

The mirrors I'm using are from a hyabusa and have integrated turn signals. Unfortunately I don't see hem as a bolt on. The angle is just not ideal for mounting on the body work so I had to make custom brackets. Started with welding a washer into the end of some tubing. It was cut it off at the angle needed and welded it to some larger square tubing, then cut off the amount needed. This is my second attempt at these as I ended up with a warped part when attempting to make this from sheet stock. Letting things cool and cutting out the part you need when done yields a nicer more accurate part than making it small and hoping it doesn't warp.

These will bolt to the underside of the bodywork and be secure with bolts to nut plates on the brackets themselves. An observation lately with my nutplate drill jig is that the drill bushing is either getting worn out or was never that accurately sized for a #40 drill. If you use these you know the pita when flipping it around to drill the other hole and it doesnt fit without a fight. My solution is to mark the holes with a large #38 drill and finish the holes with a #40 which is final size for -3 solid rivets. Lesson, don't buy cheap import nut plate drill jig next time

Ill need to get different hardware.. Ideally a banjo bolt Ill drill through so I can pass the wiring through and use the factory caps.


Author:  airframefixer [ February 24, 2017, 11:57 am ]
Post subject:  Re: Airframe's Mid BEC LMP


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Author:  airframefixer [ February 24, 2017, 12:00 pm ]
Post subject:  Re: Airframe's Mid BEC LMP


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Author:  airframefixer [ February 28, 2017, 1:06 pm ]
Post subject:  Re: Airframe's Mid BEC LMP

Had a good day yesterday... finally a shop day.. my wife and I were sick all last week so little got done.

Took off the right lower side pods to install the rad intake mount flange. I ran over something in the shop as there was some bad rash on the panel and a few torn off rivet heads.

The flange fitting was straight forward other than not having the correct length nas1097 reduced shear head rivets.. so I has to cut about 50 to length. Installed wet with sealant, and the opening routered out.

Did more sanding on the rear body work and made a tail pipe from the header stock I had left over.

Pics to follow

Author:  airframefixer [ February 28, 2017, 3:57 pm ]
Post subject:  Re: Airframe's Mid BEC LMP


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Author:  jaf [ February 28, 2017, 8:00 pm ]
Post subject:  Re: Airframe's Mid BEC LMP

I'll take the bait.............pic #4. Is that a tool that cuts solid rivet to the correct grip length? I could have used that.

Author:  airframefixer [ February 28, 2017, 9:35 pm ]
Post subject:  Re: Airframe's Mid BEC LMP

jaf wrote:
I'll take the bait.............pic #4. Is that a tool that cuts solid rivet to the correct grip length? I could have used that.

It sure is.. the downside of doing things with AN/MS hardware is the 1/16 grip range variance of each fastener necessitating stocking multiple lengths.


Author:  airframefixer [ March 30, 2017, 8:04 am ]
Post subject:  Re: Airframe's Mid BEC LMP

Small update.

Remember how I said sanding of the composite parts was going faster than expected.... well I take that back.

Remember how I said that it would be easier to reinforce the rear most section of body work rather than make a new wing mount.. well I decided that I would do that as well.

Kinda a boring month of sanding and filling and repairing thin cracked pieces of fiberglass in the body parts.. they are prototypes really like everything on the car that is revision 2 or 3.. there is little that I have gotten right the first time around. But the designing and building is the fun part for me, the driving will have to wait longer, and I'm OK with that.

I'm using an epoxy fairing compound, it's not like polyester filler where it's sandable in short time. This stuff takes a day or so to become hard enough to sand without gumming up sandpaper. Why so much sanding and filling... I used 7781 cloth or 8 harness satin weave... it is so tightly woven that air doesn't pass easily.. you can briefly heat the resin with a heat gun to reduce viscosity for wet out, but that will release more air in the lower plies, which won't pass through the 7781. Had I had used plain weave, I doubt I would have the pin holes and pockets.. the upper side pods are a great example of what I should have done. Revision 2 will be much lighter.

The wing mount is simple, bulky and I feel there is room for improvement. It doesn't allow the rear body to be removed without taking off the wing. Version 2 will be better executed. As opposed to making it from angle stock, I'm cutting out sections of aluminum from a large 4x4 section. I'm tying in the corners where loads pass with additional material and fasteners transferring loads.

Regarding fasteners. It's difficult to engineer this, as I have yet to see a rivet bearing strength chart for 6061-t6. I don't like using solid AN rivets for this grade of aluminum and I find the radially expansion forces enlarge the hole diameter and dent the sheet slightly when driving them.. That leads me to bolts.. subject to loosening. Hiloks are ideal but I only have them in smaller sizes and grip ranges. So for the wing mount and some other structure in the rear of the car I will be using huck c6l lock bolts. All the benefits of a rivet and a bolt in one fastener.

Assuming for the design and testing off the wing mount. I figured the wing will generate a 200lbs down load at 100mph. I'll go conservative and say the wing will generate the same drag.. I know I can stand on the wing and observe little to no deflection. That tells me I over built it and there is room to strategically remove excess material. It will also be subject to routine inspection. If anything on the car were to depart, I fear this would have the potential to cause damage to other vehicles... so this is getting a little more attention.

Why not weld it?
Didn't just buy a tight welder in the fall? Aluminum looses 30 percent of its strength when welded. So that's out as well. There's a good read in the chassis section about welding aluminum for those interested..

Other small tasks were welding heat sheild mounts to the tail pipe, which runs close to the underside of the body work and I'd rather not cook the bodywork. I'll need some thin stainless to make the shield. Note the blind rivets holding the nuplates , they are monel and have a 100 degree countersunk as opposed to the razor thin 120 degree countersink on most other blind rivets. Cherry N MSC-3-2 is the part number. I wouldn't be scared of these, you commonly see these in aircraft construction, only for nuplates and trim though.

Pics to follow

Author:  airframefixer [ March 30, 2017, 8:19 am ]
Post subject:  Re: Airframe's Mid BEC LMP


Rear body almost ready for topcoat... nevermind the ugly weld beside the heat shield mount... I tried pulsing over an old mig weld. Beginnings of the new wing mount... huck c6l lock bolts.. fiberglass repair to underbelly section.

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