I would like to make a few hatch covers of clear plastic, if possible.
Is it possible to do? I have some scraps from plastic packaging, and some large bottles of fruit juice ( like Twister.) Would that work? I would probably use a heatgun to heat the plastic on a plywood slab until soft, then place it over the radio box or hatch combing, then use a hairdryer or paintbrush/tool to mold the plastic around the shape.
I could probably use the technique to make both convex and concave covers.
I used to make hatch covers similar to the ones you intend to take a crack at. I used sheet vinyl (often used in vacu-forming), heated to soft with a heat gun, and pressed over an acrylic mold. I used a strong ring with slightly chamfered sides to press the plastic down over the male mold so that the sides conformed to the mold shape. This is a necessary step because the plastic will drape but not conform tightly to the mold contours on its own.
Just forming the plastic cover doesn’t make a waterproof seal. I molded hatch combing rims to compliment the covers that I heat formed. These were really just channels that surrounded the hatch opening. Into these channels I applied silicone bathtub sealer (GE is the best for this) and pressed my hatch cover into the sealer (apply mold release like wax or a spray release specifically formulated for use with silicone to the cover first). If you don’t have access to the underside of the combing make sure to put tape tabs (I use strapping tape) on the cover before you apply the mold release so that you can remove it from the silicone once the silicone has cured.
One additional thing, clear hatch covers tend to increase heat build up inside your hull, much like a greenhouse. The increase in condensation in your hull might put your electronics at risk as well as heat effecting your battery performance. This is compounded when your boat is made from carbon fiber as carbon is conductive and black, and heats up quickly. A friend of mine had his carbon M in the back of his station wagon on a warm summer day. We noticed that all these small bubbles had formed along the length of the hull. The greenhouse effect inside the car and the carbon fiber had literally boiled the epoxy resin causing it to bubble and weaken.
So I would recommend using white plastic for your covers and a white towel to cover your boat (no matter what its made from) when its exposed to summer sun.
I’m not trying to make watertight covers, just ones to fit on the hatches. I will use tape to seal them, so they don’t have to fit that well. On some, they won’t even have to fit over the hatch combing, so just a square piece would do, but I’d like to form it to fit into the hole some.
If you are just looking for something to cover the approx. size of the hatches, why not just use clear tape? you can sorta make a “patch” of tape, and just stick it on… or, what i use, it a little piece of sailcloth, stretched the length of the hatch, and held with double-stick… just thoughts…!
Tomo - I have also used coffee can lids for hatch covers. The combing rims for these lids are not hard to make. The weight of the average lid is comparatively light (about 4 grams), on par with heat formed covers.
To make rims for a coffee can lid (or any size round can lid) you need to start out with the coffee can and matching lid, a G-10 fiberglass or 1/32nd aircraft ply strip roughly 1/2 inch wide, some Ca glue, dacron line, and a strip of paper the same width as the material strip.
The basic idea is to use the inside of the coffee can as a mold to constrain the strip of fiberglass or ply into a ring shape. By first placing the strip of paper into the can the length you’ll need of fiberglass or ply strip can be determined and marked. The paper forms a pattern for the length of the fiberglass or ply strip. Ideally, the strip of fiberglass or ply should resist being placed into the can, otherwise the ring formed will have flat spots. Once the fiberglass or ply strip is forced into the can with the ends butting a piece of the same material (a cutoff of the strip perhaps) an inch or inch and a quarter long, overlapping evenly, can be Ca glued in place to connect the ends and retain the curve. Try not to get Ca on the can. If you do its not the end of the world, Ca does not bond very well to metal so you should be able to pop it free, carefully. This is the basic rim shape.
The coffee can has a lip around its edge which creates it’s freshness seal. To make the lip around the new hatch cover rim the rim needs to be slid up until it extends over the edge of the can the same vertical distance as the thickness of the can’s lip. The dacron line should be carefully tacked with a dab of Ca to the fiberglass or ply rim right above the edge of the coffee can. Then the line should be wrapped around the hatch combing rim until it is flush with the outside edge of the coffee can’s lip. You should tack the line in place as you go so that it doesn’t slip about too much. Next remove the rim from the can and flood the line with Ca to make the lip permanent.
When the dacron line lip is no longer tacky place the new hatch combing back into the coffee can so that the lower edge of the rim’s lip rests on the lipped edge of the coffee can. You may find the the dacron lip has swelled after being flooded with the Ca. The dacron lip should be sanded back until it is flush with the can’s lip. If you sand into the line it will fuzz up. Not to worry, more Ca applied to the fuzz will harden it so that it can be sanded further. Repeat as often as required. Matching the coffee can’s lip is important to create a waterproof seal between the lid and the combing rim.
Your rim is now completed and the coffee can lid should fit snugly in place over it. When mounting the combing rim into your boat leave enough room to get your fingernails underneath the lid so you can remove it easily.
If you make this type of hatch combing I suggest you use the same brand of coffee for a while to collect backup lids.
I usually hang on to any flat plastic stuff, especially the clear plastic packaging- the kind with large flat panels. They make great material for tracing engine parts to make patterns for gaskets and such.
I cut the hatch cover out of the coffe can lid to fit the combing and just tape it in place.
I’m still going to see if I can make a cover from zip-lok material somehow. The trick, IMO, is to find some bags with a heavy enough closure so it can be curved ( (for rounded corners) without kinking. Maybe I could glue the zip-lok ‘zipper’ to the coffe can lid?
Some of us are thinking about building Footys and I am looking around for good ideas. I’m uncomfortable with taping a hatch cover down and want something a little easier. That’s when my young nubile mind happened upon an idea while pondering left-over bachelor choices in my fridge. I saw a couple of those cheap reusable plastic storage containers that have a nice fitting watertight covers. There are several different brands in the grocery store… Well I thought, wouldn’t be neat if the container bottom was cut off leaving the nice rim and cover. The rim could be glued on the deck and since the material is semi-flexible the deck wouldn’t even have to be flat. I measured the outside dimensions on the 22 oz. container and it measured 6.25" x 4.75". It sure would be fast and easy and watertight and cheap - but would it work? What do all you experts think about something like this?
well, if it is 6.25" wide then it won’t fit into the measurement box… if you are planning on putting it the other way, so that the long end is oriented bow-stern i suppose that would work, you could just have to make sure that the boat was wide enough at all points… in my humble opinion a hatch that long is too long. when you think about it, it is over half the boat’s length. Also, cutting off the rim, then gluing it down to the deck seems like a lot of work. as i said in my post earlier, i just double-sticky-back tape my hatches to the deck. it works like a charm, and stays watertight even during full rollovers. besides, the weight savings is nice. that said, its not as re-usable as top with a rim… for me, that is not enough to make me go to the extra effort, but as i said, thats just my .02, the great thing about footys is that its really up to you!
best of luck!
Here is a combination hatch set up I am trying. The forward hatch covers the servos and receiver and will be covered with a ‘Fablon’ (sticky back plastic) cover or similar. This cover will not need to be disturbed very often. The rear hatch gives access to the batteries and switch. As the easy access cover can now be smaller I am using a ‘Pringles’ tube cover. The frame is two rings of 3mm Liteply which works nicely but I will be experimenting with a different ring combination so that the cover will slip up a little before the inner ledge hits the upper (wider) ring. This will make removal easier. As the rings are varnished the fit will tighten so I expect to be able to create a good seal.
Once I have the sizes finalised I will have the rings laser cut so that I can knock these up more quickly.
Tomo - You don’t need anything fancy like magnets and such. I have used the type of setup that Graham is developing for years, all-be-it with composites for the rim, not Liteply. I described my method on an earlier post for all you guys with long memories.
This system is simple, reasonably light, waterproof, and removable. And in Graham’s case a replacement hatch cover is just a snack session away. The Pringles lid is one of the more lightweight plastic tops around weighing in at 3 grams.
Graham’s new setup satisfies part of my objection to sticky back cloth hatch covers, that they make it harder to swap out batteries or r/c gear if something goes wrong and then reseal the hatch when the deck is wet. I have never had a breakdown in sunny, warm, dry weather, they only come in inclement conditions for me. Having a hatch that I can remove to get at the problem and then replace when I am done while my hands are numb with cold is worth the small weight penalty. Once you have traveled a long distance to race in bad weather and had that major breakdown that sidelines you for the event the value of what I’ve laid out here will hit home.
I have used magnets succesully on powerboat and 1M hatches, and if you can make them small enough, they might work on a Footy. If the Pringles cover won’t pop off on its own, then I’m for that. I also like to avoid anything sticky because as soon as you get a drop of water on it or the deck, you need an hour to dry it off.
What about making a small lip around the circumference using some thin wire, to simulate the top of the Pringles can?
Thanks Neil, it was indeed your earlier post which inspired my thought process that a home made rim could work with a commercial snap top. I chose the Pringles top in particular because it is an international standard :rolleyes:
Your comment previously about needing a 1/16" or so gap to get a nail under is very true. The next prototype will have different rings to allow for that lift.
A wire would work Tomo as indeed would a cyano soaked thread as Neil described. One thing that I have to do differenly though is to think about any parts production and ease of repeatability in a production kit. This does force me to do things differently from what I would on a one off for myself. Hence my use of laser cut ply rings which makes the construction relatively simple and very repeatable in accuracy.
Incidentally the Pringle covered hole is large enough to get a flat battery box and cells out easily, also the 2-up 2-down battery packs often used. Thanks for the comments…
I am looking forward to meeting the Northern Variant Harpy at Sheboygan Greg! The hull in the photos above is a Harpy core hull with the deck sliced at an angle to reduce the transom height and the rather nice curved transom added. Sufficiently different to be re-named I think. The Harpy will remain as is because the shape is easier to build from the plan alone. Thanks for noticing.